Identification and Development of Larval and JuvenileUrophycis chuss,U. tenuisandPhycis chesteri(Pisces, Gadidae) from the Northwest Atlantic

Abstract

Pelagic stages of Urophycis chuss, Urophycis tenuis and Phycis chesteri from the Northwest Atlantic were identified by differences in caudal fin-ray and epibranchial gillraker counts, body depth and pigmentation. The adult complement of caudal fin rays in U. chuss (28-34, mean 31.5) and U. tenuis (33-39, mean 36.5) distinguished larvae greater than 7-8 mm SL (standard length). Caudal fin-ray counts in P. chesteri (32-35, mean 33.3) overlapped those of the two Urophycis species. The adult complement of epibranchial gillrakers in U. chuss (3), U. tenuis (2) and P. chesteri (4-5) developed at 12-14 mm in Urophycis and at 16-·18 mm in P. chesteri. Phycis chesteri was deeper-bodied (24.4% SL) than U. tenuis (21.3% SL) which in turn was deeper-bodied than U. chuss (19.3% SL). Pelagic larvae and juveniles of the three species had 3 pelvic fin rays. A size-dependent key to pelagic stages of these species is presented.Black pigment on pelvic fins of pelagic Urophycis and Phycis was absent in newly-demersal specimens. Differences in pigmentation on the midline, pectoral fin base, dorsa-lateral trunk and caudal peduncle helped to separate 5-10 mm Urophycis larvae. Ossification generally occurred at a smaller size in U. ctiuss than in either U. tenuis or P. chesteri for most ofthe structures examined. The mandibular arch, dentary, premaxilla, precaudal vertebrae, branchiostegals, cleithra and parasphenoid ossified first. Pelvic fins were the first fins to develop. The first dorsal fin and the pectoral fins developed last.

Genetic and Morphological Variation of the Forkbeard, Phycis phycis (Pisces, Phycidae): Evidence of Panmixia and Recent Population Expansion along Its Distribution Area

“…Moreover, and taking into account the existence of unique haplotypes in the Northeast Atlantic and the Mediterranean, recent gene flow between populations from these groups is unlikely to occur or, if present, occurs at low levels. Although larval behaviour of the forkbeard is unknown, other species of the genus Phycis present pelagic larvae for several months [79, 80] and, thus, long distance dispersal may occur during forkbeard larval phase. The putative absence or reduction of current larval dispersion of the forkbeard between the Northeast Atlantic and the Mediterranean suggests the presence of significant barriers to gene flow in this species.…”

Updated Morphological Descriptions of the Larval Stage of Urophycis (Family: Phycidae) from the Northeast United States Continental Shelf

“…Larvae of Urophycis are morphologically similar, and previous descriptions did not produce reliable identifying characteristics at the species level for small larvae. Individual species have been described in detail based on reared larvae from known adults (U. chuss: Miller and Marak, 1959; U. regia: Barans andBarans, 1972 andSerebryakov, 1978), but comparisons among the common species relied heavily on characters that are unavailable at the small sizes common in plankton tows (,6 mm) or characters that could be misleading (i.e., the presence of pelvic filament pigment is unreliable; Methven, 1985;Comyns and Grant, 1993;Comyns and Bond, 2002;Fahay, 2007).…”