ABSTRACT
Adult bathysaurids are characteristic inhabitants of waters >1000 m deep, but larvae apparently develop within a few hundred meters of the surface. Eggs are unknown. The elongate larvae have long precocious fins, anteriorly positioned dorsal and pelvic fins, a preanal length about 75% BL, and lack head spination and convoluted muscular bands along the hindgut. They have vertical bars laterally along the trunk and tail and may have several uniserial spots along the gut, but lack the prominent bilateral peritoneal gut pigment of synodontids and aulopids. Bathysaurids attain a large size before transformation, with the smallest known benthic juvenile about 60 mm SL (Sulak et al. 1985). Changes that accompany metamorphosis include: reduction in fin length, expansion of the mouth gape, rearward migration of the dorsal fin, and darkening of the body surface, oral cavity and peritoneum (Okiyama 1984). Bathysaurus ferox lose the adipose fin during metamorphosis, whereas B. mollis retain the adipose fin as an adult. ELH stages of several taxa formerly described as “Macristium” are actually B. ferox (Regan 1911; Marshall 1961; Rosen 1971; Porteiro et al. 1998) or B. mollis (Ida & Tominaga 1971; Johnson 1974). Species accounts and illustrations are provided and meristics are given in Table Bathysauridae 1.
