The Global Diversity of Parasitic Isopods Associated with Crustacean Hosts (Isopoda: Bopyroidea and Cryptoniscoidea)

Parasitic isopods of Bopyroidea and Cryptoniscoidea (commonly referred to as epicarideans) are unique in using crustaceans as both intermediate and definitive hosts. In total, 795 epicarideans are known, representing ∼7.7% of described isopods. The rate of description of parasitic species has not matched that of free-living isopods and this disparity will likely continue due to the more cryptic nature of these parasites. Distribution patterns of epicarideans are influenced by a combination of their definitive (both benthic and pelagic species) and intermediate (pelagic copepod) host distributions, although host specificity is poorly known for most species. Among epicarideans, nearly all species in Bopyroidea are ectoparasitic on decapod hosts. Bopyrids are the most diverse taxon (605 species), with their highest diversity in the North West Pacific (139 species), East Asian Sea (120 species), and Central Indian Ocean (44 species). The diversity patterns of Cryptoniscoidea (99 species, endoparasites of a diverse assemblage of crustacean hosts) are distinct from bopyrids, with the greatest diversity of cryptoniscoids in the North East Atlantic (18 species) followed by the Antarctic, Mediterranean, and Arctic regions (13, 12, and 8 species, respectively). Dajidae (54 species, ectoparasites of shrimp, mysids, and euphausids) exhibits highest diversity in the Antarctic (7 species) with 14 species in the Arctic and North East Atlantic regions combined. Entoniscidae (37 species, endoparasites within anomuran, brachyuran and shrimp hosts) show highest diversity in the North West Pacific (10 species) and North East Atlantic (8 species). Most epicarideans are known from relatively shallow waters, although some bopyrids are known from depths below 4000 m. Lack of parasitic groups in certain geographic areas is likely a sampling artifact and we predict that the Central Indian Ocean and East Asian Sea (in particular, the Indo-Malay-Philippines Archipelago) hold a wealth of undescribed species, reflecting our knowledge of host diversity patterns

Ecomorphological plasticity of juvenile fall-run chinook salmon (Oncorhynchus tshawytscha) in perennial and ephemeral streams

In the Central Valley of California, environmental characteristics differ between perennial and ephemeral stream types and therefore present different challenges for rearing salmonids with respect to water discharge, water temperature, food availability, and habitat complexity. Body shape of juvenile fall-run Chinook salmon (Oncorhynchus tshawytscha) reared in a perennial stream environment was compared to juveniles reared in an ephemeral stream environment. Using geometric morphometrics and multivariate analyses, this study presents morphological differences of rearing juvenile Chinook salmon both within and between ephemeral and perennial stream types. We found that shape differences between stream types were primarily associated with expansion of the mid-body region relative to differences in body length. Specifically, juvenile Chinook salmon reared in the ephemeral stream expressed increased body depth dominated by dorsal-ventral elongation of the dorsal, adipose, and anal fins. Eye position and gill opercula-body insertion points also were anteriorly shifted in the juvenile body shape of the ephemeral stream. Our findings support that juvenile Chinook salmon are morphologically flexible and can express habitat-specific developmental differences