Funding was provided by the US National Science Foundation (NSF OCE&#160;2023420 and DEB 2231250, P. Sikkel PI). We thank the municipality of Dumaguete City, Negros Oriental, Philippines, for permission to conduct this study. We also thank the many volunteers for their field assistance and the staff and our colleagues at the Silliman University Institute for Environmental and Marine Sciences for their support.

Collection of samples was permitted by the Department of Agriculture-Bureau of Fisheries and Aquatic Resources (0154-18 DA-BFAR) in accordance with Philippine laws and regulations (RA 9147; FAO 233) and approved by the Silliman University (SU) animal ethics committee.
1. Light Traps
<ol>
	<li>Construction
	<ol>
		<li>Construct light traps from commercial polyvinyl chloride (PVC) tubes originally designed for plumbing. Use 10-15&#160;cm diameter PVC cut to 30-40 cm length (Figure 1).</li>
		<li>To both ends of the tubes, add PVC &#34;caps&#34; with a transparent acrylic funnel inserted in the center of the opening and glue in place with transparent epoxy glue (Figure 1). Let it dry.</li>
		<li>Ensure that one end of the tube has a screw-on or otherwise removable lid and that both ends are water-tight when the trap is &#34;closed&#34; (e.g., with the addition of an O-ring).</li>
	</ol>
	</li>
	<li>Light source
	<ol>
		<li>Before deployment, turn on an underwater light/torch (see Table of Materials) and place it in the tube, facing one of the transparent funnels, such that the light from the underwater torch illuminates the area in front of one side of the tube. If necessary, chemical glow sticks can be used in place of underwater torches, although their light intensity is lower. 
		NOTE: The light attracts a variety of small nocturnal organisms31, including gnathiids, and drives them to swim into the tube through the clear funnel. Once they have entered the tube, they are unable to escape due to the geometry of the light trap (small funnel opening) and the continued presence of a light source.</li>
	</ol>
	</li>
	<li>Placement
	<ol>
		<li>When in the water at the deployment site, fill light traps, with the light turned on, with seawater, and secure both ends. To ensure that the torch is not below or blocking the funnel tip, tilt the &#34;front&#34; of the tube upward to allow the torch to slide back away from the funnel.</li>
		<li>Place traps on the seafloor, in the sand or rubble, next to coral heads or other complex structures known to attract fish. Focus the light cone &#34;inwards&#34;, towards areas where fish aggregate. 
		NOTE: In shallow water, traps can be placed by breath-hold diving. Deeper deployment requires scuba.</li>
	</ol>
	</li>
	<li>Retrieval
	<ol>
		<li>Immediately prior to retrieving the trap, seal the openings of both the funnels (on either end of the tube) with a piece of modeling clay or rubber stopper sealing, keeping all the seawater and the contained organisms inside. 
		NOTE: The organisms will remain in the trap once the batteries of the lights have expired and the light is no longer illuminated. This provides flexibility when the traps are retrieved (&#34;soak time&#34;). Factors to consider when deciding on soak time are presented below (see Discussion).</li>
	</ol>
	</li>
	<li>Transport
	<ol>
		<li>Once the traps have been retrieved from the bottom, carry them to a boat, or swim ashore.</li>
		<li>Maintain traps close to ambient seawater temperature once removed from the ocean.</li>
		<li>Transport them to the laboratory for processing as soon as possible since no gas or water exchange will take place once removed from the ocean.</li>
	</ol>
	</li>
</ol>
2 Laboratory processing
<ol>
	<li>Storing and filtering of the samples
	<ol>
		<li>Once the light traps are removed from the ocean and brought back to the lab, empty their contents into buckets with fresh seawater.</li>
		<li>Add aeration to keep organisms alive until filtering.</li>
		<li>Filter the contents of the bucket by pouring through a funnel lined with 50-100 &#181;m plankton mesh, then empty the contents into a 100 mL container of fresh seawater.</li>
		<li>Use a pipette to draw from this smaller container to place aliquots of the sample into a Petri dish for microscopy. Repeat until the entire sample has been processed.</li>
	</ol>
	</li>
	<li>Gnathiid isopod identification and rearing
	<ol>
		<li>Because light trap samples attract multiple species of small invertebrates, carefully screen the samples to identify and remove gnathiid isopods. 10-20x magnification is the best for this task (Figure 2). 
		NOTE: Identifying gnathiids at the family level does not require living specimens. However, adult gnathiids, which are seldom caught in light traps, are needed for morphological species identification and breeding (see reference1,3,9 for a methodology for breeding and rearing gnathiids in captivity).</li>
		<li>In cases where gnathiids need to be kept alive for rearing, gently remove them with a pipette and place them in small plastic containers of fresh seawater.</li>
	</ol>
	</li>
</ol>

<ol>
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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=First+record+and+molecular+characterisation+of+two+Gnathia+species+(Crustacea,+Isopoda,+Gnathiidae)+from+Philippine+coral+reefs,+including+a+summary+of+all+Central-Indo+Pacific+Gnathia+species.">First record and molecular characterisation of two Gnathia species (Crustacea, Isopoda, Gnathiidae) from Philippine coral reefs, including a summary of all Central-Indo Pacific Gnathia species.</a> International Journal for Parasitology: Parasites and Wildlife. 14, 355-367 (2021).</li><li>Losey, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cleaning+symbiosis+in+Puerto+Rico+with+comparison+to+the+tropical+Pacific.">Cleaning symbiosis in Puerto Rico with comparison to the tropical Pacific.</a> 4 (4), 960-970 (1974).</li><li>Grutter, A. 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K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diel+infestation+dynamics+of+gnathiid+isopod+larvae+parasitic+on+Caribbean+reef+fish.">Diel infestation dynamics of gnathiid isopod larvae parasitic on Caribbean reef fish.</a> Coral Reefs. 25, 683-689 (2006).</li><li>Santos, T. R. N., Sikkel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Habitat+associations+of+fish-parasitic+gnathiid+isopods+in+a+shallow+reef+system+in+the+central+Philippines.">Habitat associations of fish-parasitic gnathiid isopods in a shallow reef system in the central Philippines.</a> Marine Biodiversity. 4, 83-96 (2019).</li><li>Nagel, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+vision+in+host-finding+behaviour+of+the+ectoparasite+Gnathia+falcipenis+(Crustacea).">The role of vision in host-finding behaviour of the ectoparasite Gnathia falcipenis (Crustacea).</a> Isopoda). Marine and Freshwater Behaviour and Physiology. 42 (1), 31-42 (2009).</li><li>Sikkel, P. C., Sears, W. T., Weldon, B., Tuttle, B. 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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parasite+infection+rather+than+tactile+stimulation+is+the+proximate+cause+of+cleaning+behaviour+in+reef+fish.">Parasite infection rather than tactile stimulation is the proximate cause of cleaning behaviour in reef fish.</a> Proceedings of the Royal Society of London. Series B: Biological Sciences. 268 (1474), 1361-1365 (2001).</li><li>Sikkel, P. C., Cheney, K. L., C&#244;t&#233;, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+evidence+for+ectoparasites+as+a+proximate+cause+of+cleaning+interactions+in+reef+fish.">In situ evidence for ectoparasites as a proximate cause of cleaning interactions in reef fish.</a> Animal Behaviour. 68 (2), 241-247 (2004).</li><li>Sikkel, P. C., Herzlieb, S. E., Kramer, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compensatory+cleaner-seeking+behavior+following+spawning+in+female+yellowtail+damselfish.">Compensatory cleaner-seeking behavior following spawning in female yellowtail damselfish.</a> Marine Ecology Progress Series. , 1-11 (2005).</li><li>Triki, Z., Grutter, A. S., Bshary, R., Ros, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+short-term+exposure+to+ectoparasites+on+fish+cortisol+and+hematocrit+levels.">Effects of short-term exposure to ectoparasites on fish cortisol and hematocrit levels.</a> Marine Biology. 163, 1-6 (2016).</li><li>Hayes, P. M., Smit, N. J., Grutter, A. S., Davies, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unexpected+response+of+a+captive+blackeye+thicklip,+Hemigymnus+melapterus+(Bloch),+from+Lizard+Island,+Australia,+exposed+to+juvenile+isopods+Gnathia+aureamaculosa+Ferreira+&amp;+Smit.">Unexpected response of a captive blackeye thicklip, Hemigymnus melapterus (Bloch), from Lizard Island, Australia, exposed to juvenile isopods Gnathia aureamaculosa Ferreira &amp; Smit.</a> Journal of Fish Diseases. 34 (7), 563-566 (2011).</li><li>Grutter, A. S., Pickering, J. L., McCallum, H., McCormick, M. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+micropredatory+gnathiid+isopods+on+young+coral+reef+fishes.">Impact of micropredatory gnathiid isopods on young coral reef fishes.</a> Coral Reefs. 27 (3), 655-661 (2008).</li><li>Artim, J. M., Sellers, J. C., Sikkel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micropredation+by+gnathiid+isopods+on+settlement-stage+reef+fish+in+the+eastern+Caribbean+Sea.">Micropredation by gnathiid isopods on settlement-stage reef fish in the eastern Caribbean Sea.</a> Bulletin of Marine Science. 91 (4), 479-487 (2015).</li><li>Sellers, J. C., Holstein, D. M., Botha, T. L., Sikkel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lethal+and+sublethal+impacts+of+a+micropredator+on+post-settlement+Caribbean+reef+fishes.">Lethal and sublethal impacts of a micropredator on post-settlement Caribbean reef fishes.</a> Oecologia. 189, 293-305 (2019).</li><li>Allan, B. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parasite+infection+directly+impacts+escape+response+and+stress+levels+in+fish.">Parasite infection directly impacts escape response and stress levels in fish.</a> Journal of Experimental Biology. 223 (16), (2020).</li><li>Spitzer, C. A., Anderson, T. W., Sikkel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Habitat+associations+and+impacts+on+a+juvenile+fish+host+by+a+temperate+gnathiid+isopod.">Habitat associations and impacts on a juvenile fish host by a temperate gnathiid isopod.</a> International Journal for Parasitology: Parasites and Wildlife. 17, 65-73 (2022).</li><li>Sikkel, P. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nocturnal+migration+reduces+exposure+to+micropredation+in+a+coral+reef+fish.">Nocturnal migration reduces exposure to micropredation in a coral reef fish.</a> Bulletin of Marine Science. 93 (2), 475-489 (2017).</li><li>Artim, J. M., Hook, A., Grippo, R. S., Sikkel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predation+on+parasitic+gnathiid+isopods+on+coral+reefs:+a+comparison+of+Caribbean+cleaning+gobies+with+non-cleaning+microcarnivores.">Predation on parasitic gnathiid isopods on coral reefs: a comparison of Caribbean cleaning gobies with non-cleaning microcarnivores.</a> Coral Reefs. 36, 1213-1223 (2017).</li><li>Artim, J. M., Sikkel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Live+coral+repels+a+common+reef+fish+ectoparasite.">Live coral repels a common reef fish ectoparasite.</a> Coral Reefs. 32, 487-494 (2013).</li><li>Paula, J. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+corals+on+the+abundance+of+a+fish+ectoparasite+in+the+Great+Barrier+Reef.">The role of corals on the abundance of a fish ectoparasite in the Great Barrier Reef.</a> Coral Reefs. 40, 535-542 (2021).</li><li>Sikkel, P. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+abundance+of+fish-parasitic+gnathiid+isopods+associated+with+warm-water+bleaching+events+on+the+northern+Great+Barrier+Reef.">Changes in abundance of fish-parasitic gnathiid isopods associated with warm-water bleaching events on the northern Great Barrier Reef.</a> Coral Reefs. 38 (4), 721-730 (2019).</li><li>Shodipo, M. O., Duong, B., Graba-Landry, A., Grutter, A. S., Sikkel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+acute+seawater+temperature+increase+on+the+survival+of+a+fish+ectoparasite.">Effect of acute seawater temperature increase on the survival of a fish ectoparasite.</a> In Oceans. 1 (4), (2020).</li><li>Artim, J. M., Nicholson, M. D., Hendrick, G. C., Brandt, M., Smith, T. B., Sikkel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Abundance+of+a+cryptic+generalist+parasite+reflects+degradation+of+an+ecosystem.">Abundance of a cryptic generalist parasite reflects degradation of an ecosystem.</a> Ecosphere. 11 (10), (2020).</li><li>Richardson, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+continuous+plankton+recorder+data.">Using continuous plankton recorder data.</a> Progress in Oceanography. 68 (1), 27-74 (2006).</li><li>McLeod, L. E., Costello, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+traps+for+sampling+marine+biodiversity.">Light traps for sampling marine biodiversity.</a> Helgoland Marine Research. 71 (1), 1-8 (2017).</li><li>Artim, J. M., Sikkel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+sampling+methodologies+and+estimation+of+population+parameters+for+a+temporary+fish+ectoparasite.">Comparison of sampling methodologies and estimation of population parameters for a temporary fish ectoparasite.</a> International Journal for Parasitology: Parasites and Wildlife. 5 (2), 145-157 (2016).</li><li>Pag&#225;n, J. A., Ver&#237;ssimo, A., Sikkel, P. C., Xavier, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hurricane-induced+disturbance+increases+genetic+diversity+and+population+admixture+of+the+direct-brooding+isopod,+Gnathia+marleyi.">Hurricane-induced disturbance increases genetic diversity and population admixture of the direct-brooding isopod, Gnathia marleyi.</a> Scientific reports. 10 (1), (2020).</li><li>Doherty, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light-traps:+selective+but+useful+devices+for+quantifying+the+distributions+and+abundances+of+larval+fishes.">Light-traps: selective but useful devices for quantifying the distributions and abundances of larval fishes.</a> Bulletin of Marine Science. 41, 423-431 (1987).</li><li>Jones, C. M., Nagel, L., Hughes, G. L., Cribb, T. H., Grutter, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Host+specificity+of+two+species+of+Gnathia+(Isopoda)+determined+by+DNA+sequencing+blood+meals.">Host specificity of two species of Gnathia (Isopoda) determined by DNA sequencing blood meals.</a> International Journal for Parasitology. 37 (8-9), 927-935 (2007).</li><li>Hendrick, G. C., Dolan, M. C., McKay, T., Sikkel, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Host+DNA+integrity+within+blood+meals+of+hematophagous+larval+gnathiid+isopods+(Crustacea).">Host DNA integrity within blood meals of hematophagous larval gnathiid isopods (Crustacea).</a> Isopoda, Gnathiidae). Parasites &amp; Vectors. 12 (1), 1-9 (2019).</li></ol>

The authors declare no disclosures to make.

Traditional light traps, such as those used for collecting larval fishes, are large and are suspended in water column34. In contrast, the light traps described here are small and deployed on the sea bottom. These traps can be easily transported and rapidly deployed. They can be placed by breath-hold (free)-diving in shallow sites (as in this study) or on scuba in deeper sites, and attract both fed and unfed 
juvenile stages.
Variations of the benthic light traps described here for studying gnathiids have been used for a variety of purposes by our team and collaborators, and modifications can be made in the design or protocol, depending on the specific purpose (Figure 3). These are described below.
Some studies require live gnathiids. These include studies identifying the source (fish species) of blood meals35,36, or studies that require rearing. The light traps in this study were 30 cm long, with a 10.16&#160;cm diameter, and hence a volume of ~1.3 L. When they become overly crowded with organisms, the oxygen demand inside the tube can surpass the delivery of oxygen via the ports, causing organisms to die and exacerbating the problem. To avoid this, the trap can be deployed for shorter periods or modified by increasing its volume (larger diameter PVC) or adding additional holes covered with plankton mesh9,29,32. Note that while larger diameter PVC can be used to increase the volume, this is done at the cost of lower portability, resulting in the transport of fewer traps to the field site. This is of particular concern when the transport involves extended surface swims and/or the use of small boats with limited storage space.
Alternatively, or in addition, the trap can be deployed for a shorter duration. A major advantage of this design is that while the trap will only collect organisms at night (when the light is effective), it can be set at any time and retrieved at any time. To collect as many gnathiids as possible, we set traps before sunset and retrieved them shortly after sunrise the following day. However, to maximize the number of live gnathiids, we limit deployment to 3-4 hours of darkness. A short set time also reduces the amount of &#34;bycatch&#34; that must be sorted through to extract the gnathiids.
The traps described here lie horizontally, with the beam of the light pointing in one direction. Thus, the stimulus signal extends as far as the light will shine, usually traversing multiple substrate types, and some light is emitted from the rear funnel as well. In order to focus sampling on a particular substrate at a short distance from the trap, the trap can be modified to sit vertically, with the light pointing downward (Figure 3). This is accomplished by adding &#34;legs&#34; to form a tripod29,32. However, this type of light trap is useful only in low-current situations.
The torch we used (see materials table) takes four (4) AAA batteries. We use rechargeable batteries to reduce cost and waste. The burn time for these lights is approximately 12 hours, which allows them to function overnight. However, a suitable substitute is &#34;glowsticks&#34;. These are particularly useful when setting in deeper water, such as mesophotic reefs.
While the light traps described here attract a wide range of small, mobile invertebrates, the composition of this bycatch is highly variable. However, when set in a habitat that includes rubble and fish, gnathiids are caught consistently. Although this demonstration study focused on sites in the Philippines, traps of similar design have also been used successfully for studies at sites in the Caribbean region and the Great Barrier Reef.

Parasitic crustaceans are important in the ecology and life histories of reef fishes. The biomass and energy they remove from their hosts are considerable and influence behavior, physiology, and survivorship1. Gnathiid isopod crustaceans represent the most prominent group of fish parasites in tropical and subtropical reef systems, where they are both abundant and diverse2,3 and are the primary food item of cleaner fishes4,5. Gnathiids are generally 1-3 mm in size. They have unusual life histories in which only the three juvenile stages feed on the blood and body fluids of fishes6,7. They are most active at night8,9, and while vision appears to play some role, host-finding10 relies heavily on olfactory cues to find hosts11,12. Each of the three juvenile feeding stages feeds on a single host fish, with each feed separated by a molting phase. After the final feed, third-stage larvae metamorphose into non-feeding adults, which reproduce and then die. Given that feeding requires only brief association with the host, while each inter-feeding interval lasts days, gnathiids spend most of their life free-living in the benthos.
Gnathiids impact hosts in multiple ways1. Aside from their role as drivers of interactions between cleaner fish and clients13,14,15, gnathiids can increase cortisol levels and decrease hematocrit in adult fish hosts16 and in high numbers, can even cause death17. For juvenile fish, even a single gnathiid can be fatal18,19,20, and even if the fish survives, its ability to compete for space and escape predators is compromised20,21,22. Avoiding gnathiids may even constitute one of the benefits of nocturnal migration in some reef fishes23.
In addition to cleaner fishes, gnathiid populations can be impacted by other micro carnivorous fishes24, as well as corals25,26. Ocean warming and the associated loss of live corals appear to have opposing impacts on gnathiids27,28,29.
Given their clear ecological importance and the likely influence of anthropogenic environmental change on their populations, there are compelling reasons to include them in ecological studies of coral reefs. However, their unique life history and the small number of researchers who study them create a barrier to the development, implementation, and dissemination of reliable, reproducible sampling methods to collect them for research.
Light traps have long been used to collect small marine organisms at night30,31. They take advantage of and are based on the fact that many nocturnally active organisms, including arthropods, are attracted to light. Traditionally they have been used to collect planktonic organisms in the water column30. However, the basic principles can be applied to collecting free-swimming organisms that are active near the benthos. Here we present a light trapping method adapted for collecting free-living stages of gnathiid isopods near the ocean bottom in remote coral reef environments such as the Philippines. For collecting in remote areas, these light traps (Figure 1) offer some advantages over other methods developed for collecting these organisms32. They are highly portable and durable, requiring only three parts, which are easily obtainable and inexpensive. They are also negatively buoyant, as when deployed, they are completely filled with seawater. Because they depend on light for attraction, they are only effective at night for collecting nocturnally active species. They also attract more than the target species, requiring sorting of the samples under a dissecting scope to obtain the target organisms. Three methods have thus far been used by our team and collaborators to collect gnathiids in coral reef systems throughout the world32. These include emergence traps, live fish-baited traps, and light traps, each with advantages and limitations.

<table><tbody><tr><td>Buckets, small sample containers</td><td></td><td>hardware store</td><td></td></tr><tr><td>Funnels</td><td>Supplier No. 2209-03</td><td>Funnels: AMERICAN SCIENTIFIC LLC SE&amp;nbsp;-&amp;nbsp;75 mm (3&amp;rdquo;)&amp;nbsp;</td><td>https://us.vwr.com/store/product/8884369/plastic-funnels</td></tr><tr><td>Main body of light traps (made from commercially available PVC sanitarty pipes)</td><td>(SKU 145640)&amp;nbsp;</td><td>Alasco Sanitary uPVC Pipes Series 1000 107mm/4&#039;&amp;nbsp;</td><td>https://alascopvcpipes.com/product/alasco-standard-sanitary-upvc-pipe-series-1000/.&amp;nbsp; This brand can be found in the Philippines. Other simular brands can also be used</td></tr><tr><td>Modeling clay&amp;nbsp;</td><td></td><td>Can be found in art suppliy and childreans toy stores</td><td>To seal the funnel after retreival</td></tr><tr><td>Plankton mesh (50-100 &amp;micro;m)</td><td></td><td>any reputable brand and source</td><td>https://www.adkinstruments.in/products/plankton-nets-in-various-mesh-size-1633936883</td></tr><tr><td>Screw on lids for the light trap</td><td></td><td>Alasco&amp;nbsp; Sanitary &amp;nbsp;Clean-Out&amp;nbsp; 4&quot;</td><td>https://alascopvcpipes.com/product/alasco-standard-sanitary-upvc-clean-out/. This brand can be found in the Philippines. Other simular brands can also be used</td></tr><tr><td>Scuba/snorkel equipment</td><td></td><td>any reputable brand and source</td><td></td></tr><tr><td>Stereo-microscopes</td><td></td><td>Scientific suppliers</td><td></td></tr><tr><td>Underwater touches</td><td></td><td>Princeton Tec Ecoflare or&amp;nbsp;Fantasea Nanospotter 6023</td><td></td></tr></tbody></table>

collecting marine gnathiid isopod fish parasites with light traps

A method to collect marine gnathiid isopod fish parasites with the use of light traps is presented. Gnathiid isopods are a major group of marine fish parasites that feed on blood and fluid from host fishes, mostly at night. Like ticks and mosquitos on land, they associate only temporarily with their host and spend most of their life free-living in the benthos. Given their high mobility and transient and predominantly nocturnal association with hosts, they cannot easily be collected by capturing free-living hosts. However, they are readily attracted to underwater light sources, creating the opportunity to collect them in light traps. Here the design and individual steps involved in the deployment and processing of specially adapted light traps for collecting free-living stages of gnathiid isopods are outlined. Sample results and possible modifications of the basic protocol for a variety of different sampling needs are presented and discussed.

For sampling in the central Philippines, the outlined trap design (Figure 1) was used. When 36 traps were set overnight (in one site), 1 to 1343 gnathiids per trap (275 &#177; 54) were collected. These included both fed and unfed juvenile stages (Figure 2; Table 1, 2). These results demonstrate the effectiveness of light traps for collecting gnathiid isopods under the study conditions. Figure 3 shows the placement of the trap underwater.
This method for gnathiid collection is effective and sufficiently flexible for various field sites and scientific questions. For example, reference29&#160;used light traps to quantify the effects of coral cover and fish biomass on gnathiid abundance (Figure 4), and reference33 used similar traps to quantify the effects of hurricanes on genetic haplotypes (Figure 5). While other techniques have been developed and used for collecting gnathiids32, this technique is particularly efficient (Table 3). Emergence traps, &#34;tents&#34; made of plankton mesh32 require large platforms to transport, are difficult to deploy, and tear easily, requiring continual repair. Moreover, they rarely collect fed juvenile stages. Traps baited with live fish32 (necessary because gnathiids will not feed on dead fish), require capture and housing of live fish. This makes their use more difficult in remote places. Moreover, their effectiveness relies on olfactory cues11,12, which are influenced by the size of the fish, the size of the openings of the trap, and water currents. They tend to collect fewer gnathiids, are more difficult to retrieve than light traps, and only collect fed stages.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65059/65059fig1v2.jpg" /> 
Figure 1: Light trap PVC tubes. Right: top view, with the translucent funnel glued into the tube with acrylic glue, visible. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65059/65059fig1v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/65059/65059fig02.jpg" /> 
Figure 2: A gnathiid isopod in a Petri dish after capture. Note the transparent body fluid of the fish and brownish red fish blood in the gnathiid&#39;s gut. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65059/65059fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/65059/65059fig03.jpg" /> 
Figure 3: A modified light trap (foreground) in which the light is directed down. This design can be used in calm sea conditions to sample more directly the substrate below the trap. Emergence traps are shown in the background. This figure is reprinted with permission from reference32. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65059/65059fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/65059/65059fig04.jpg" /> 
Figure 4: Boxplots showing differences in the distribution. Boxplots showing differences in the distribution (A) of first-stage gnathiid abundance, (B) first-stage hyperabundance, (C) total abundance, and (D) blood volume extracted per fish biomass. The sample size for each subgroup is shown in parentheses under each subgroup mean. Boxes display first- and third-quartile edges, while whiskers show the third quartile plus 1.5 times the interquartile range. For (C), hinges are an approximation of the 95% confidence interval. Differences seen at (A), (B), and (C) are significant; see Appendix S1: Table S7 in reference29. This figure is reprinted with permission from reference29. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65059/65059fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/65059/65059fig05.jpg" /> 
Figure 5: Haplotype networks representing the genetic diversity of Gnathia marleyi and its spatial distribution before and after the 2017 hurricanes. Pre- and post-hurricane datasets are indicated in panels I and II, respectively. The haplotypes found in both pre- and post-hurricane datasets are indicated by haplotype number. Haplogroups A, B, and C are indicated by dashed boxes. This figure is reprinted with permission from reference33. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65059/65059fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Gnathiid count</td>
			<td>Light traps (n)</td>
			<td>Total count</td>
			<td>Mean</td>
			<td>Median</td>
			<td>Minimum (per trap)</td>
			<td>Maximum (per trap)</td>
			<td>Standard Error (+-)</td>
		</tr>
		<tr>
			<td>Total</td>
			<td>34</td>
			<td>9336</td>
			<td>275</td>
			<td>191</td>
			<td>1</td>
			<td>1343</td>
			<td>54</td>
		</tr>
		<tr>
			<td>Live</td>
			<td>34</td>
			<td>6605</td>
			<td>206</td>
			<td>114</td>
			<td>4</td>
			<td>1226</td>
			<td>46</td>
		</tr>
		<tr>
			<td>Dead</td>
			<td>34</td>
			<td>2667</td>
			<td>86</td>
			<td>42</td>
			<td>1</td>
			<td>659</td>
			<td>24</td>
		</tr>
	</tbody>
</table>
Table 1: Summary statistics for gnathiid counts from 36 light traps deployed by breath-hold diving overnight in the Bantayan coral reef, Philippines, from July - September 2017. The numerical value in the Live column refers to gnathiids from the light trap that were alive at the time of counting, the Dead column refers to gnathiids that were dead, and the Total column is the sum total of the dead and live gnathiid counts.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Gnathiid count</td>
			<td>N</td>
			<td>Total count</td>
			<td>Mean</td>
		</tr>
		<tr>
			<td>Total</td>
			<td>10</td>
			<td>434</td>
			<td>43</td>
		</tr>
	</tbody>
</table>
Table 2: Summary statistics for gnathiid counts from light traps deployed for 3 hours in Bantayan coral reef, Negros Oriental province, Philippines, from July-August 2022.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td rowspan="2">Trap type</td>
			<td rowspan="2">Median count</td>
			<td colspan="2">95% CI</td>
		</tr>
		<tr>
			<td>Lower</td>
			<td>Upper</td>
		</tr>
		<tr>
			<td>Un-baited Emergence</td>
			<td>0.31</td>
			<td>0.04</td>
			<td>0.81</td>
		</tr>
		<tr>
			<td>Fish-baited Emergence</td>
			<td>0.42</td>
			<td>0.19</td>
			<td>0.69</td>
		</tr>
		<tr>
			<td>Fish-baited Tripod</td>
			<td>0.92</td>
			<td>0.46</td>
			<td>1.46</td>
		</tr>
		<tr>
			<td>Open-mesh Fish-baited</td>
			<td>1.5</td>
			<td>0.35</td>
			<td>3.54</td>
		</tr>
		<tr>
			<td>Lighted Plankton Trap</td>
			<td>5.69</td>
			<td>2.69</td>
			<td>9.58</td>
		</tr>
	</tbody>
</table>
Table 3: The performance of different trap designs, including light traps, in the Caribbean were compared. Estimates of median count per sample and 95% confidence intervals for each trap design were evaluated in the multi-trap comparison. Estimates were derived from 10,000 bootstrapping iterations drawing with replacement from the 26 sample counts for each trap type. This table is adapted with permission from reference32.

Watch this Scientific Journal Video about Collecting Marine Gnathiid Isopod Fish Parasites with Light Traps at JoVE.com

Collecting Marine Gnathiid Isopod Fish Parasites with Light Traps

We present a method to collect marine gnathiid isopod fish parasites using light traps placed at field sites via breath-hold diving or scuba diving.

A method to collect marine gnathiid isopod fish parasites with the use of light traps is presented. Gnathiid isopods are a major group of marine fish ...

collecting-marine-gnathiid-isopod-fish-parasites-with-light-traps

Nanyang Technological University

Research

JoVE Journal

Biology

1.3K Views.  Silliman University. Parasitaire schaaldieren zijn belangrijke factoren in de ecologie en levensgeschiedenis van rifvissen. De biomassa en energie die ze van hun gastheren verwijderden, waren aanzienlijk en beïnvloedden gedrag, fysiologie en overleving. Gnathiid isopod schaaldieren vertegenwoordigen de meest prominente groep visparasieten in tropische en subtropische rifsystemen, waar ze zowel overvloedig als divers zijn en het primaire voedselproduct zijn van schonere vissen.Gnathiiden hebben ongewone le...

Video: Collecting Marine Gnathiid Isopod Fish Parasites with Light Traps

Helminth Collection and Identification from Wildlife

Wild animals are commonly parasitized by a wide range of helminths. The four major types of helminths are &#34;roundworms&#34; (nematodes), &#34;thorny-headed worms&#34; (acanthocephalans), &#34;flukes&#34; (trematodes), and &#34;tapeworms&#34; (cestodes). The optimum method for collecting helminths is to examine a host that has been dead less than 4-6 hr since most helminths will still be alive. A thorough necropsy should be conducted and all major organs examined. Organs are washed over a 106 &#956;m sieve under running water and contents examined under a stereo microscope. All helminths are counted and a representative number are fixed (either in 70% ethanol, 10% buffered formalin, or alcohol-formalin-acetic acid). For species identification, helminths are either cleared in lactophenol (nematodes and small acanthocephalans) or stained (trematodes, cestodes, and large acanthocephalans) using Harris&#39; hematoxylin or Semichon&#39;s carmine. Helminths are keyed to species by examining different structures (e.g. male spicules in nematodes or the rostellum in cestodes). The protocols outlined here can be applied to any vertebrate animal. They require some expertise on recognizing the different organs and being able to differentiate helminths from other tissue debris or gut contents. Collection, preservation, and staining are straightforward techniques that require minimal equipment and reagents. Taxonomic identification, especially to species, can be very time consuming and might require the submission of specimens to an expert or DNA analysis.

Wild animals are commonly parasitized by a wide range of helminths.&#160; The four major types of helminths are &#8220;roundworms&#8221; (nematodes), &#8220;thorny-headed worms&#8221; (acanthocephalans), &#8220;flukes&#8221; (trematodes), and &#8220;tapeworms&#8221; (cestodes).&#160; Here we describe how helminths are collected from a vertebrate animal and how they are preserved and taxonomically identified.&#160;

Wild animals are commonly parasitized by a wide range of helminths. The four major types of helminths are &#34;roundworms&#34; (nematodes), ...

Environment

Assaying Predatory Feeding Behaviors in Pristionchus and Other Nematodes

This protocol provides multiple methods for the analysis and quantification of predatory feeding behaviors in nematodes. Many nematode species including Pristionchus pacificus display complex behaviors, the most striking of which is the predation of other nematode larvae. However, as these behaviors are absent in the model organism Caenorhabditis elegans, they have thus far only recently been described in detail along with the development of reliable behavioral assays 1. These predatory behaviors are dependent upon phenotypically plastic but fixed mouth morphs making the correct identification and categorization of these animals essential. In P. pacificus there are two mouth types, the stenostomatous and eurystomatous morphs 2, with only the wide mouthed eurystomatous containing an extra tooth and being capable of killing other nematode larvae. Through the isolation of an abundance of size matched prey larvae and subsequent exposure to predatory nematodes, assays including both "corpse assays" and "bite assays" on correctly identified mouth morph nematodes are possible. These assays provide a means to rapidly quantify predation success rates and provide a detailed behavioral analysis of individual nematodes engaged in predatory feeding activities. In addition, with the use of a high-speed camera, visualization of changes in pharyngeal activity including tooth and pumping dynamics are also possible.

Assaying Predatory Feeding Behaviors in Pristionchus and Other Nematodes

Behavioral assays provide powerful tools for understanding neuronal function. Here we present several protocols for quantifying predatory feeding behavior found in the model nematode Pristionchus pacificus and its relatives. Additionally, we provide methods for analyzing predatory feeding adaptations including mouth structures and teeth.

This protocol provides multiple methods for the analysis and quantification of predatory feeding behaviors in nematodes. Many nematode species including ...

Fatty Acid 13C Isotopologue Profiling Provides Insight into Trophic Carbon Transfer and Lipid Metabolism of Invertebrate Consumers

Fatty acids (FAs) are useful biomarkers in food web ecology because they are typically assimilated as a complete molecule and transferred into consumer tissue with minor or no modification, allowing the dietary routing between different trophic levels. However, the FA trophic marker approach is still hampered by the limited knowledge in lipid metabolism of the soil fauna. This study used entirely labelled palmitic acid (13C16:0, 99 atom%) as a tracer in fatty acid metabolism pathways of two widespread soil Collembola, Protaphorura fimata and Heteromurus nitidus. In order to investigate the fate and metabolic modifications of this precursor, a method of isotopologue profiling is presented, performed by mass spectrometry using single ion monitoring. Moreover, the upstream laboratory feeding experiment is described, as well as the extraction and methylation of dominant lipid fractions (neutral lipids, phospholipids) and the related formula and calculations. Isotopologue profiling does not only yield the overall 13C enrichment in fatty acids derived from the 13C labeled precursor but also produces the pattern of isotopologues exceeding the mass of the parent ion (i.e., the FA molecular ion M+) of each labeled FA by one or more mass units (M+1, M+2, M+3, etc.). This knowledge allows conclusions on the ratio of dietary routing of an entirely consumed FA in comparison to de novo biosynthesis. The isotopologue profiling is suggested as a useful tool for evaluation of fatty acid metabolism in soil animals to disentangle trophic interactions.

Fatty Acid 13C Isotopologue Profiling Provides Insight into Trophic Carbon Transfer and Lipid Metabolism of Invertebrate Consumers

The fatty acid trophic marker approach, i.e., the assimilation of fatty acids as entire molecule and transfer into consumer tissue with no or minor modification, is hampered by knowledge gaps in fatty acid metabolism of small soil invertebrates. Isotopologue profiling is provided as a valuable tool to disentangle trophic interactions.

Fatty acids (FAs) are useful biomarkers in food web ecology because they are typically assimilated as a complete molecule and transferred into consumer ...

Biochemistry

An Ultra-clean Multilayer Apparatus for Collecting Size Fractionated Marine Plankton and Suspended Particles

The distributions of many trace elements in the ocean are strongly associated with the growth, death, and re-mineralization of marine plankton and those of suspended/sinking particles. Here, we present an all plastic (Polypropylene and Polycarbonate), multi-layer filtration system for collection of suspended particulate matter (SPM) at sea. This ultra-clean sampling device has been designed and developed specifically for trace element studies. Meticulous selection of all non-metallic materials and utilization of an in-line flow-through procedure minimizes any possible metal contamination during sampling. This system has been successfully tested and tweaked for determining trace metals (e.g., Fe, Al, Mn, Cd, Cu, Ni) on particles of varying size in coastal and open ocean waters. Results from the South China Sea at the South East Asia Time-Series (SEATS) station indicate that diurnal variations and spatial distribution of plankton in the euphotic zone can be easily resolved and recognized. Chemical analysis of size-fractionated particles in surface waters of the Taiwan Strait suggests that the larger particles (&#62;153 &#181;m) were mostly biologically derived, while the smaller particles (10 - 63 &#181;m) were mostly composed of inorganic matter. Apart from Cd, the concentrations of metals (Fe, Al, Mn, Cu, Ni) decreased with increasing size.

Plankton and suspended particles play a major role in the biogeochemical cycles in the ocean. Here, we provide an ultra-clean, low stress method for the collection of various sizes of particles and plankton at sea with the capability of handling large volumes of seawater.

The distributions of many trace elements in the ocean are strongly associated with the growth, death, and re-mineralization of marine plankton and those ...

The Identification of Sea Lamprey Pheromones Using Bioassay-Guided Fractionation

Bioassay-guided fractionation is an iterative approach that uses the results of physiological and behavioral bioassays to guide the isolation and identification of an active pheromone compound. This method has resulted in the successful characterization of the chemical signals that function as pheromones in a wide range of animal species. Sea lampreys rely on olfaction to detect pheromones that mediate behavioral or physiological responses. We use this knowledge of fish biology to posit functions of putative pheromones and to guide the isolation and identification of active pheromone components. Chromatography is used to extract, concentrate, and separate compounds from the conditioned water. Electro-olfactogram (EOG) recordings are conducted to determine which fractions elicit olfactory responses. Two-choice maze behavioral assays are then used to determine if any of the odorous fractions are also behaviorally active and induce a preference. Spectrometric and spectroscopic methods provide the molecular weight and structural information to assist with the structure elucidation. The bioactivity of the pure compounds is confirmed with EOG and behavioral assays. The behavioral responses observed in the maze should ultimately be validated in a field setting to confirm their function in a natural stream setting. These bioassays play a dual role to 1) guide the fractionation process and 2) confirm and further define the bioactivity of isolated components. Here, we report the representative results of a sea lamprey pheromone identification that exemplify the utility of the bioassay-guided fractionation approach. The identification of sea lamprey pheromones is particularly important because a modulation of its pheromone communication system is among the options considered to control the invasive sea lamprey in the Laurentian Great Lakes. This method can be readily adapted to characterize the chemical communication in a broad array of taxa and shed light on waterborne chemical ecology.

Here, we present a protocol to isolate and characterize the structure, olfactory potency, and behavioral response of putative pheromone compounds of sea lampreys.

Bioassay-guided fractionation is an iterative approach that uses the results of physiological and behavioral bioassays to guide the isolation and ...

The Barnacle Balanus improvisus as a Marine Model - Culturing and Gene Expression

Barnacles are marine crustaceans with a sessile adult and free-swimming, planktonic larvae. The barnacle Balanus (Amphibalanus) improvisus is particularly relevant as a model for the studies of osmoregulatory mechanisms because of its extreme tolerance to low salinity. It is also widely used as a model of settling biology, in particular in relation to antifouling research. However, natural seasonal spawning yields an unpredictable supply of cyprid larvae for studies. A protocol for the all-year-round culturing of B. improvisus has been developed and a detailed description of all steps in the production line is outlined (i.e., the establishment of adult cultures on panels, the collection and rearing of barnacle larvae, and the administration of feed for adults and larvae). The description also provides guidance on troubleshooting and discusses critical parameters (e.g., the removal of contamination, the production of high-quality feed, the manpower needed, and the importance of high-quality seawater). Each batch from the culturing system maximally yields roughly 12,000 nauplii and can deliver four batches in a week, so up to almost 50,000 larvae per week can be produced. The method used to culture B. improvisus is, probably, to a large extent also applicable to other marine invertebrates with free-swimminglarvae. Protocols are presented for the dissection of various tissues from adults as well as the production of high-quality RNA for studies on gene expression. It is also described how cultured adults and reared cyprids can be utilized in a wide array of experimental designs for examining gene expression in relation to external factors. The use of cultured barnacles in gene expression is illustrated with studies of possible osmoregulatory roles of Na+/K+ ATPase and aquaporins.

The Barnacle Balanus improvisus as a Marine Model - Culturing and Gene Expression

The barnacle Balanus (Amphibalanus) improvisus is a model for studying osmoregulation and antifouling. However, natural seasonal spawning yields an unpredictable supply of cyprid larvae. Here, a protocol for the all-year-round culturing of B. improvisus is described, including the production of larvae. The use of cultured barnacles in gene expression studies is illustrated.

Barnacles are marine crustaceans with a sessile adult and free-swimming, planktonic larvae. The barnacle Balanus (Amphibalanus) improvisus is particularly ...

Fluorescently Labeled Bacteria as a Tracer to Reveal Novel Pathways of Organic Carbon Flow in Aquatic Ecosystems

Elucidating trophic interactions, such as predation and its effects, is a frequent task for many researchers in ecology. The study of microbial communities has many limitations, and determining a predator, prey, and predatory rates is often difficult. Presented here is an optimized method based on the addition of fluorescently labelled prey as a tracer, which allows for reliable quantitation of the grazing rates in aquatic predatory eukaryotes and estimation of nutrient transfer to higher trophic levels.

Presented here is a protocol for a single-cell, epifluorescence microscopy-based technique to quantify grazing rates in aquatic predatory eukaryotes with high precision and taxonomic resolution.

Elucidating trophic interactions, such as predation and its effects, is a frequent task for many researchers in ecology. The study of microbial ...

Modeling the Size Spectrum for Macroinvertebrates and Fishes in Stream Ecosystems

The size spectrum is an inverse, allometric scaling relationship between average body mass (M) and the density (D) of individuals within an ecological community or food web. Importantly, the size spectrum assumes that individual size, rather than species&#8217; behavioral or life history characteristics, is the primary determinant of abundance within an ecosystem. Thus, unlike traditional allometric relationships that focus on species-level data (e.g., mean species&#8217; body size vs. population density), size spectra analyses are &#8216;ataxic&#8217; &#8211; individual specimens are identified only by their size, without consideration of taxonomic identity. Size spectra models are efficient representations of traditional, complex food webs and can be used in descriptive as well as predictive contexts (e.g., predicting responses of large consumers to changes in basal resources). Empirical studies from diverse aquatic ecosystems have also reported moderate to high levels of similarity in size spectra slopes, suggesting that common processes may regulate the abundances of small and large organisms in very different settings. This is a protocol to model the community-level size spectrum in wadable streams. The protocol consists of three main steps. First, collect quantitative benthic fish and invertebrate samples that can be used to estimate local densities. Second, standardize the fish and invertebrate data by converting all individuals to ataxic units (i.e., individuals identified by size, irrespective of taxonomic identity), and summing individuals within log2 size bins. Third, use linear regression to model the relationship between ataxic M and D estimates. Detailed instructions are provided herein to complete each of these steps, including custom software to facilitate D estimation and size spectra modeling.

This is a protocol to model the size spectrum (scaling relationship between individual mass and population density) for combined fish and invertebrate data from wadable streams and rivers. Methods include: field techniques to collect quantitative fish and invertebrate samples; lab methods to standardize the field data; and statistical data analysis.

The size spectrum is an inverse, allometric scaling relationship between average body mass (M) and the density (D) of individuals within an ecological ...

Streamlined Sampling and Cultivation of the Pelagic Cosmopolitan Larvacean, Oikopleura dioica

Oikopleura dioica is a planktonic chordate with exceptional filter-feeding ability, rapid generation time, conserved early development, and a compact genome. For these reasons, it is considered a useful model organism for marine ecological studies, evolutionary developmental biology, and genomics. As research often requires a steady supply of animal resources, it is useful to establish a reliable, low-maintenance culture system. Here we describe a step-by-step method for establishing an O. dioica culture. We describe how to select potential sampling sites, collection methods, target animal identification, and the set-up of the culturing system. We provide troubleshooting advice based on our own experiences. We also highlight critical factors that help sustain a robust culture system. Although the culture protocol provided here is optimized for O. dioica, we hope our sampling technique and culture setup will inspire new ideas for maintaining other fragile pelagic invertebrates.

Streamlined Sampling and Cultivation of the Pelagic Cosmopolitan Larvacean, Oikopleura dioica

Oikopleura dioica is a tunicate model organism in various fields of biology. We describe sampling methods, species identification, culturing setup, and culturing protocols for the animals and algal feed. We highlight key factors that helped strengthen the culture system and discuss the possible problems and resolutions.

Oikopleura dioica is a planktonic chordate with exceptional filter-feeding ability, rapid generation time, conserved early development, and a compact ...

Rapid Testing of Resistance of Timber to Biodegradation by Marine Wood-Boring Crustaceans

Wood-boring invertebrates rapidly destroy marine timbers and wooden coastal infrastructure, causing billions of dollars of damage around the globe every year. As treatments of wood with broad spectrum biocides, such as creosote and chromated copper arsenate (CCA), are now restricted in marine use by legislation, naturally durable timber species and novel preservation methods of wood are required. These methods undergo testing in order to meet regulatory standards, such as the European standard for testing wood preservatives against marine borers, EN 275. Initial investigation of durable timbers species or wood preservative treatments can be achieved quickly and inexpensively through laboratory testing, which offers many advantages over marine field trials that are typically costly, long-term endeavours. Many species of Limnoria (gribble) are marine wood-boring crustaceans. Limnoria are ideal for use in laboratory testing of biodegradation of wood by marine wood-borers, due to the practicality of rearing them in aquaria and the ease of measuring their feeding rates on wood. Herein, we outline a standardizable laboratory test for assessing wood biodegradation using gribble.

This protocol presents a method for assessing the feeding rate of the wood-boring crustacean, Limnoria, by measuring faecal pellet production. This method is designed for use in non-specialist labs and has potential for incorporation into standard testing protocols, to evaluate enhanced wood durability under marine conditions.

Wood-boring invertebrates rapidly destroy marine timbers and wooden coastal infrastructure, causing billions of dollars of damage around the globe every ...

Collecting Marine Gnathiid Isopod Fish Parasites with Light Traps

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