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Belg. J. Zool., 131 (1): 43-55 January 2001 Checklist of isopods (Crustacea : Peracarida : Isopoda) from the Eastern Tropical Pacific Maria del Carmen Espinosa-Pérez and Michel E. Hendrickx Laboratorio de Invertebrados Bentónicos, Estación Mazatlán UNAM, P.O. Box 811, Mazatlán, 82000 Sinaloa, Mexico ABSTRACT. Literature dealing with isopods from the east Pacific is reviewed. Marine and brackish water species reported at least once in the Eastern Tropical Pacific zoogeographic subregion, which extends from Magdalena Bay, on the west coast of Southern Baja California, Mexico, to Paita, in northern Peru, are listed, and their ranges along the Pacific coast of America are provided. Unpublished records, based on material kept in the collections of the authors, were also considered, to modify previously published distribution ranges within the study area. A total of 124 species, belonging to 68 genera, is included in the checklist and new records or new distribution data are provided for 19 species. A list of names of species and subspecies currently recognized as invalid for the area is also included. KEY WORDS : Isopoda, Eastern Tropical Pacific, Checklist, Distribution. INTRODUCTION of species ofCymothoa and Lironeca) (B r u s c a , 1980; 1981 ; B r u sc a & Iv e r s o n , 1985). Isopods belong to the superorder Peracarida, which The high diversity and ecological success of this group represents approximately 50% of all described crus are reflected by their presence in a great variety of marine taceans. The order Isopoda contains about 9500 species and brackish water habitats. They are virtually found that inhabit marine, fresh water and terrestrial ecosystems everywhere in the seas and oceans, from the supralittoral (B r u s c a , pers. comm., April 2000). As in other ecosys zone (e.g., Ligia species) to abyssal depths (e.g., species tems where they occur, marine isopods play an important of the suborder Asellota). They live in a wide variety of role in the food web, in particular in removing decaying habitats, including mangrove roots(R ib i, 1 9 8 1 ; E l l iso n material from natural or altered environments. Isopods & Fa r n s w o r t h , 1990), mixed and soft bottoms(T a y l o r also represent an important factor of economic unbalance. & M o o r e , 1995), seagrasses(K a n g & Y u n , 1988), coral Some species (e.g., Limnoria lignorum Rathke, 1799) are reefs (D e l a n e y , 1984) and rocky and sandy beaches wood-burrowing species which damage wooden marine (S c h u l t z , 1961; D e x t e r , 1972; 1974; 1976). structures (e.g., docks, ships, piers, etc.), although they also contribute to the initial breakdown of woody detritus As in other tropical marine regions of the world, the in natural shallow waters ecosystems (S c h m it t , 1965; isopods of the Eastern Tropical Pacific (ETP) include a S c h u l t z , 1969; B r u s c a , 1980). Species ofSphaeroma, wide variety of forms, contained in many families from known to affect red mangrove roots (e.g.,S. peruvianum different habitats and sites. Although generally rather Richardson, 1910; see P e r r y & B r u s c a , 1989) have also small, Sphaeromatidae are among the most obvious been observed boring into sandstone and chalk(S c h m it t , marine isopods as they live in intertidal or shallow waters, 1965). Other species are parasites on commercially hence they are easy to observe or collect. They occur important fishes and crustaceans (B r u s c a , 1981; under rocks but also in high numbers among intertidal M a r k h a m , 1985) and can cause damage to gills (e.g., algae, within the chambers of sponges and with other males of species of Livoneca), skin (e.g., species of encrusting animals such as bryozoans. Aegidae and Rocinela and Nerocila), or within the mouth (e.g., females Cymothoidae are temporary and obligatory parasites in fishes, sometimes with a very low host specificity; Nerocila acuminata Schiödte & Meinert, 1881, for instance, has been observed on as many as 40 species of Corresponding author: M. Hendrickx, e-mail:[email protected] fishes (families Engraulidae, Atherinidae, Serranidae, 44 Maria del Carmen Espinosa-Pérez and Michel E. Elendrickx Mugilidae and Embiotocidae). Predaceous species of the porcellain crabs and caridean shrimps (e.g., Upogebia family Cirolanidae are found in many habitats (e.g., in dawsoni Williams, 1986; Upogebia macginitieorum algae and mussel beds, under rocks and among intertidal Williams, 1986; Munida refulgens Faxon, 1893; animals, on sandy beaches) of the intertidal zone and shal Pleuroncodes planipes Stimpson, 1860; Parapagurodes low waters. Anthuridae are often small and usually do not laurentae McLaughlin & Haig, 1973; Parapagurodes occur in large numbers. Hence, anthurids are relatively makarovi McLaughlin & Haig, 1973; Petrolisthes hians rare in collections although they share a wide variety of Nobili, 1901; Glyphocrangon spinulosa Faxon, 1893; intertidal and shallow water habitats with more common Hyppolyte californiensis Holmes, 1895;Thor algicola species. Anthurids usually build burrows or are associated Wicksten, 1987)(H a n s e n , 1897;N ie r s t r a s z & B r e n d e r with encrusting organisms, which might be the major rea À B r a n d is , 1929; M a r k h a m , 1975;C a m p o s -G o n z á l e z son for their scarcity in collections. Idoteidae are usually & C a m p o y -Fa v e l a , 1987; Sa l a z a r -V a l l e jo & L e ija - solitary animals with a clear preference for seaweed, T r is t á n , 1989). The other epicaridean family known in although they occupy other habitats as well (e.g., mussel the area, Dajidae, is represented in the ETP by one species beds, muddy substrates). Due to their mimetic capacity, only, an ectoparasite of euphausiacean shrimps(S h ie l d s idoteids are difficult to spot while they grasp to algal & G ó m e z-G u t ié r r e z , 1996). leaves and stems. Corallanidae include free-living and The earliest works specifically related to isopods of the temporary parasitic species, mostly on fishes, turtles and east Pacific were published at the end of last century shrimps. They are wide-spread marine, brackish water (H a n s e n , 1890, 1897). A few years later Harriet and fresh water organisms, found from the intertidal zone Richardson presented her Monograph of the North to the upper shelf fringe in virtually every type of habitat America Isopods (R ic h a r d s o n , 1905), which still repre (B r u s c a , 1980; 1981; B r u s c a & I v e r s o n , 1985; sents to date the most complete monograph on isopods D e l a n e y , 1989; S c h u l t z , 1961). from the American continent. Many papers have been Other families are represented in the ETP by only one produced since then, most by American scientists (see or two species. Oniscidae are found on rocky and sandy M e n z ie s , 1962; S c h u l t z , 1969; B o w m a n , 1977; beaches, generally along the upper tidal limit where the N u n o m u r a , 1978). In the mid 70’s a very important series substrate remains humid and detritus offers food and shel of taxonomic, ecological and zoogeographic works were ter. Members of the family Serolidae are rarely found in presented by a group of Californian scientists under the the Gulf of California. Tylidae contains one genus only, leadership of Richard C. Brusca. Their most relevant with terrestrial habits. Found at the upper limit of the tides works were a review of the species known from the Gulf on sandy beaches, they feed on all kinds of organic detri of California(B r u s c a , 1980), a review of the families tus, especially seaweeds. The families Microcerberidae Cymothoidae (B r u sc a 1978a, 1978b, 1981), Aegidae and Munnidae (with at least one undescribed species for (B r u s c a , 1983) and Idoteidae (B r u sc a & W a l l e r s t e in , the area) are poorly known and only a few records are 1979a; 1979b), a monograph on isopods of the Pacific available. Gnathiidae are known from all depths. coast of Costa Rica(B r u sc a & Iv e r s o n , 1985) and a Gnathiids are a poorly known group, with the taxonomy review of the Cirolanidae of the Eastern Tropical Pacific almost entirely based on the morphology of males due to (ETP) (B r u sc a et al., 1995). For more complete lists of the similarity among female specimens. Arcturidae are recent literature on marine isopods of the ETP see papers among the most bizarre isopods species. Often associated by B r u sc a (1980), D e l a n e y (1984) and B r u sc a et al. with seagrass and crinoids, they feature striking adapta (1995). tions of pereopods related to their clinging habits. Jaeropsidae, Janiridae, Paramunnidae, and Gnathostene METHODS troididae are represented in the area by a single species each; maximum size is usually of the order of 2 mm or Records in the checklist were derived from a review of less, making these animals difficult to spot and collect; the literature dealing with Eastern Tropical Pacific there might be numerous undescribed species present isopods, combined with unpublished data obtained during along the ETP coast.

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