Biodiversity Data Journal 3: e4912 doi: 10.3897/BDJ.3.e4912 General Article Collecting and Preserving Marine and Freshwater Isopoda (Crustacea: Peracarida) Regina Wetzer ‡ ‡ Natural History Museum of Los Angeles County, Los Angeles, United States of America Corresponding author: Regina Wetzer ([email protected]) Academic editor: Niamh Kilgallen Received: 17 Mar 2015 | Accepted: 07 May 2015 | Published: 12 May 2015 Citation: Wetzer R (2015) Collecting and Preserving Marine and Freshwater Isopoda (Crustacea: Peracarida). Biodiversity Data Journal 3: e4912. doi: 10.3897/BDJ.3.e4912 Abstract Background Isopoda are the most diverse Crustacea. In order to encourage the study of isopod crustaceans and their use in biodiversity studies, systematics, ecology, physiology and more, one needs to know who the isopods are and where to find them. New information This is a short “how to” guide focusing on the free-living marine and freshwater isopods: where they live and how to collect and preserve them. The tools and techniques described here are simple, but invaluable in accessing the natural history of these remarkable creatures. Keywords habitat, trap, night light, net, sieve, dredge, box core, ethanol, storage © Wetzer R. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), $hich permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. ' Wetzer R Introduction In terms of body shape, size (0.5 – 500 mm), and the habitats in which they occur, the Isopoda are the most diverse Crustacea. They inhabit shallow water and live in the deep- sea. Some are pelagic, while others occur in interstitial spaces between grains of sand. Most are free-living, others are temporary or permanent parasites. Some live on land in leaf litter, others in underground waters, anchialine caves, wells, or thermal springs, and a few are even adapted to life in deserts. Approximately half of all isopod species live on land; the other half are aquatic. Of the aquatic species roughly 6,250 are marine (Poore and Bruce 2012Williams and Boyko 2012, Wetzer et al. 2013, Boyko et al. 2012, Boyko et al. 2013, Smit et al. 2014) and 500 species are associated with freshwater. With approximately 10,000 described species and a fossil record dating back to at least the Carboniferous (300 mya), isopod diversity and persistence is truly remarkable. Eleven suborders are recognized. The Cymothoida and Sphaeromatidea are the replacement taxa for the paraphyletic Flabellifera (see Brandt and Poore 2003, Wetzer et al. 2013). The Cymothoida are most diverse in the tropics, with most members of the plesiomorphic and speciose family Cirolanidae living as active predators. Derived families (e.g., Aegidae, Cymothoidae, Corallanidae, Tridentellidae, Gnathiidae) are often temporary or permanent ectoparasites and micro-predators on fishes and other crustaceans. Anthuroidea are marine free-living or tube-dwelling, long, slender isopods commonly inhabiting offshore, soft-bottom environments. The Epicaridea, now recognized as two superfamilies Bopyroidea and Cryptoniscoidea, are exclusively parasites on other crustaceans (see Boyko et al. 2013). The Sphaeromatoidea includes the speciose family Sphaeromatidae, the families Serolidae, Basserolidae, Plakarthriidae, Bathynatallidae, the incerta sedis genus Paravireia , and the extinct Schweglerellidae. The closely related Valvifera and Sphaeromatoidea are benthic herbivores common on marine shorelines worldwide whose pleopods are restricted to a branchial chamber for respiration rather than both locomotion and respiration as in most Cymothoida. A few sphaeromatids occur in freshwater. All Valvifera are marine. The Limnoriidea (families Limnoriidae, Keuphyliidae, and Hadromastacidae) are herbivores with the largest family, the Limnoriidae, predominately tropical borers of wood, mangroves, and other hard substrates. The sole species of Phoratopidea is marine, rare, and we know little about its ecology. The Asellota occur in both freshwater and marine environments and are the predominant deep-sea (>500 m) isopod taxon. They have radiated widely, with some re-emerging into shallower water, while others occur in freshwater habitats including caves and ground water. Microcerberidea inhabit coastal ground waters or are interstitial. Calabozoida are known only from freshwater springs in Venezuela and Brazilian karst. Tainisopidea occur in freshwater relictual habitats. Although the Phreatoicidea fossil record indicates a globally- distributed marine past, today all Phreatoicidea species occur exclusively in freshwater of Australia, Tasmania, New Zealand, South Africa, and India. Phreatoicidea occur in groundwater habitats, ponds, pools, moist puddles, occasionally burrows, mosses, and Collecting and Preserving Marine and Freshwater Isopoda (Crustacea: Peracarida) - moist habitats with very little water. The Oniscidea have diversified based on the isopod attribute of direct development (there are no free-living larval stages in isopods except in Epicaridea), and they are fully terrestrial. Insects aside, oniscids (also known as rolly polies, pill bugs, sow bugs, and woodlice) are the most diverse crustacean group to invade land. Collecting techniques applicable to oniscids are more similar to those employed by entomologists than those used by marine biologists and are not further addressed here. Discussion Habitats Most isopods hide, presumably to avoid predation. The iconic Bathynomus, at nearly a half meter long, may hold its own, although healed scars on museum specimens indicate they too sometimes tangle with predators. Only a few species, such as the pelagic species of Anuropus (Anuropidae) and some mid-water asellotans, occur in open water. Some Cirolanidae, Corallanidae, and occasionally juvenile Aegidae and Cymothoidae can occur in the water column and can be lured to light or baited traps. Most isopods live in benthic habitats under rocks, in rock crevices and rock rubble, and amongst rocks and shells previously bored by sponges, mollusks, and worms. They are commonly found in coral rubble, dead coral heads, coarse shelly sand, and loose conglomerate rubble. Some live in algal holdfasts or on algal blades and stipes. Others occur in algal turf, sea grasses, gorgonians, and the interstices of live sponges. They can inhabit dead barnacle tests, abandoned worm tubes, and even the tunics of tunicates. Some marine asellotans, microcerberids, and a few sphaeromatids are so small they can be considered meiofaunal. Limnorids and some sphaeromatids bore holes into mangrove prop roots, kelp stipes, dead logs and tree stumps, wooden pier pilings and boats, and mud and rock banks. Cymothoids, aegiids, tridentellids, corallanids, gnathiids, and some cirolanids are temporary or permanent parasites or micro-predators on the skin of fish with some species having specific body preferences. Some cymothoids exclusively inhabit the mouths of fish, while others exist only in the gill chambers. Some cymothoids and aegiids are associated with specific fish species, others have less specific host requirements. Some cirolanids are extreme scavengers and in large numbers can denude caged fish and dead humans of flesh in a very short time, functioning as the marine equivalent of dermestid beetles. Some gnathiids (juvenile praniza life stage) are readily collected from fish gills and external body surfaces; adult gnathiids are free-living. Anthurids commonly live in tubes or burrows and within holdfasts and in rubble and so are rarely collected in large numbers. Aquatic Phreatoicidea live in freshwater springs and underground aquifers, but some occur in roadside ditches, cow patties, and crayfish burrows. Freshwater sphaeromatids, cirolanids, and asellotans occur in ground water, springs, and caves. Wetzer R Most marine isopod taxa are well represented in the tropics where they also achieve their greatest diversity. Valviferans are the exception, as they are more diverse in the temperate regions of the world. Serolids are most speciose in the cold Southern Hemisphere marine environments, especially in the waters surrounding Antarctica. In general, species of all isopod taxa are larger in temperate and polar regions and smaller in the tropics. There are few habitats isopods have not exploited. Few isopods inhabit mud flats with fine silty sediments. They are seldom found in disturbed habitats or in poorly circulating water. They never occur in temporary ponds. They are also rare in live coral. Once removed from their natural habitats many succumb quickly as they have difficulty keeping debris from fouling their pleopods and bodies. Maintaining marine and freshwater isopods, although successfully accomplished by some, is usually not a lackadaisical affair and requires well established and maintained aquaria. Sphaeroma serratum is an exception to this rule. It lives in mud burrows and uses the long setae on its pereopods to collect bacteria and detritus. The author has successfully maintained these in the lab in a collecting tray covered with only moistened newspaper covering the mud for months. Isopod families and some large genera are largely ubiquitous with very low endemism. Isopod species, unlike amphipods and some other peracarids, have high regional endemicity and hence some previously understudied areas are full of new species. Isopods inhabit the deep-sea, intertidal rocky shores, algal beds, coral reefs, sand beaches, and subtidal sediments.