A peer-reviewed open-access journal ZooKeys 504:Status 11–58 of (2015)Exosphaeroma amplicauda (Stimpson, 1857), E. aphrodita (Boone, 1923)... 11 doi: 10.3897/zookeys.504.8049 RESEARCH ARTICLE http://zookeys.pensoft.net Launched to accelerate biodiversity research Status of Exosphaeroma amplicauda (Stimpson, 1857), E. aphrodita (Boone, 1923) and description of three new species (Crustacea, Isopoda, Sphaeromatidae) from the north-eastern Pacific Adam R. Wall1, Niel L. Bruce2,3, Regina Wetzer1 1 Research and Collections Branch, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007 USA 2 Museum of Tropical Queensland and School of Marine and Tropical Biology, James Cook University; 70–102 Flinders Street, Townsville, 4810 Australia 3 Water Research Group (Ecology), Unit for Environmental Sciences and Management, North West University, Potchefstroom, 2520, South Africa Corresponding author: Adam R. Wall ([email protected]) Academic editor: S. Taiti | Received 6 June 2014 | Accepted 11 February 2015 | Published 18 May 2015 http://zoobank.org/4BD71172-7F03-44B7-9C60-09DEC6109817 Citation: Wall AR, Bruce NL, Wetzer R (2015) Status of Exosphaeroma amplicauda (Stimpson, 1857), E. aphrodita (Boone, 1923) and description of three new species (Crustacea, Isopoda, Sphaeromatidae) from the north-eastern Pacific. ZooKeys 504: 11–58. doi: 10.3897/zookeys.504.8049 Abstract Exosphaeroma amplicauda (Stimpson, 1857) from the west coast of North America is reviewed and redescribed and revealed to be a group of closely related species. A neotype is designated and the species redescribed based on the neotype and topotypic specimens. Exosphaeroma amplicauda is known only from the coast of California, at Marin, Sonoma and San Mateo Counties. E. aphrodita (Boone, 1923), type locality La Jolla, California and previously considered nomen dubium is taken out of synonymy and re-validated. A further three species: E. paydenae sp. n., E. russellhansoni sp. n., and E. pentcheffi sp. n. are described herein. Sphaeroma octonctum Richardson, 1899 is placed into junior synonymy with Exosphaeroma amplicauda. A key to the Pacific West Coast Exosphaeroma is provided. Keywords Isopoda, Sphaeromatidae, Exosphaeroma, Alaska, Washington, California, intertidal Copyright Adam R. Wall et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 12 Adam R. Wall et al. / ZooKeys 504: 11–58 (2015) Table of contents Introduction ............................................................................................................. 2 Abbreviations ..................................................................................................... 3 Material and methods............................................................................................... 3 Taxonomy ................................................................................................................ 4 Exosphaeroma Stebbing, 1900 ............................................................................. 5 Exosphaeroma amplicauda (Stimpson, 1857) ....................................................... 7 Exosphaeroma paydenae sp. n. ........................................................................... 12 Exosphaeroma russellhansoni sp. n...................................................................... 18 Exosphaeroma pentcheffi sp. n. ........................................................................... 23 Exosphaeroma aphrodita Boone, 1923 ............................................................... 29 Acknowledgements ................................................................................................. 41 References .............................................................................................................. 42 Appendix 1 ............................................................................................................. 47 Introduction The Sphaeromatidae is a large family, currently with 99 accepted genera (WoRMS, World Register of Marine Species, Bruce and Schotte 2013) and nearly 700 species. The phylogenetic relationships of the Sphaeromatidea were reviewed by Wetzer et al. 2013, but no family-wide treatment since the time of Hansen (1905) and the much later key of Harrison and Ellis (1991) are available. The most recent comprehensive treatment for the United States is Richardson’s (1905) monograph, which to a degree was updated by Kensley and Schotte (1989). The number of described species and genera of North American Sphaeromatidae have slowly increased over the 20th century but many species remain poorly known and attributed to inappropriate genera. At last count, marine and freshwater sphaeromatids in North America included 21 genera with a total of 67 species (seven species inquirenda, incertae sedis or both). The North American western coast lies within the East Pacific biogeographic zone, and the Sphaeromatidae are represented by 37 species in 11 genera, six of these regarded as species inquirenda and incertae sedis (see Appendix 1). While some western coast United States species have been described in detail (e.g. Bruce and Wetzer 2004; Carvacho and Haasmann 1984; Espinosa-Pérez and Hendrickx 2002; Hendrickx and Espinosa-Pérez 1998; Wetzer and Bruce 2007) many others remain poorly described, and unrecognizable by modern standards (see Appendix 1). One such poorly-known North American species is Exosphaeroma amplicauda (Stimpson, 1857). The original description ofExosphaeroma amplicauda is brief with a single postage-stamp sized (1.5×2.0 cm) figure of the dorsum taken from specimens “found adhering to fragments of star-fishes picked up on the beach of Tomales Bay by Mr. Samuels, 6.4 mm long and deposited at the Smithsonian” (Stimpson 1857). Stimpson (1858) later provided a paragraph-long description without additional details. Status of Exosphaeroma amplicauda (Stimpson, 1857), E. aphrodita (Boone, 1923)... 13 The species was redescribed by Kussakin (1979) based on material collected from Amchitka Island, Alaska, some 2000 kilometers north of the type locality. Differences between Kussakin’s (1979) description and fresh material of what appeared to be E. amplicauda from California, including the type location, prompted a re-evaluation of the species. Reviewing morphological and molecular data, we realize that there is a ‘species flock’ of five morphologically similar species on the western coast of North America. Such ‘species flocks’ have been reported for other sphaeromatid genera (e.g. Paracassidina – see Bruce 1994; Oxinasphaera – see Bruce 1997) and other families (e.g. Cymothoidae, see Bruce 1986; Cirolanidae, see Bruce 2004; Aegidae, see Bruce 2004, 2009; Serolidae, see Poore 1987), but this is the first such example in the East Pacific. We redescribe Exosphaeroma amplicauda from the type locality Tomales Bay (central California coast) and E. aphrodita from San Diego, and describe three new closely related species: E. paydenae sp. n., Aleutians; E. russellhansoni sp. n., Puget Sound, E. pentcheffi sp. n., Palos Verdes Peninsula. Abbreviations LACM–Natural History Museum of Los Angeles County; USNM–United States Na- tional Museum, Smithsonian Institution; BM–British Museum; MCZ–Museum of Comparative Zoology Harvard; ANSP–Academy of Natural Sciences Philadelphia; UAF–University of Alaska, Fairbanks; AM–Amherst College, Massachusetts; PM– Yale Peabody Museum, Connecticut; RS–robust seta/e; PMS–plumose marginal setae; SEM–scanning electron microscopy; SCAMIT–Southern California Association of Marine Invertebrate Taxonomists. Latitudes and longitudes denoted with “~” are ap- proximate and estimated from Google Earth. Material and methods Descriptions are based on the male holotype, female allotype, and topotypic paratypes. Specimens examined have been assigned a USNM or LACM catalog/type numbers. Num- bers preceded by “RW” are field and station numbers. Species descriptions were prepared using DELTA (Dallwitz et al. 1997). Setal terminology broadly follows Watling (1989). Specimens prepared for SEM were cleaned for 10–20 seconds in a Branson 1200 ultrasonic cleaner in a weak solution of Branson GP jewelry soap and distilled water. Specimens were then dehydrated with 100% ethanol. Specimens were placed in solu- tions of pure ethanol and distilled water in the ratios 2:1, 1:1, 1:2, and finally into 100% ethanol (20 minutes per treatment). Once dehydrated and in 100% ethanol, hexamethyldisilzane (HMDS) was used to replace the ethanol in the specimens. Speci- mens were transferred through ethanol and HMDS solutions in the following ratios 2:1, 1:1, 1:2 and finally into 100% HMDS (20 minutes per treatment). Specimens were transferred from the final 100% HMDS to fresh HMDS and allowed to evapo- 14 Adam R. Wall et al. / ZooKeys 504: 11–58 (2015) rate overnight. Specimens were mounted on carbon conductive tabs and coated with gold/palladium using an Emitech K550x sputter coater (Quorum Technologies, LTD, Kent, UK) and imaged using a Hitachi S-3000N variable pressure SEM (Hitachi, Troy, MI) at the LACM. Drawings were made with the aid of a camera lucida and illustrations were elec- tronically “inked” with Adobe Illustrator CS6. Whole body illustrations were made with a Wild M5D stereo dissecting scope. Appendages were illustrated by dissecting off the appendage and placing them in