Larvae of Enchelyurus ater (Günther, 1877) and E. kraussi (Klunzinger, 1871) (Pisces: Blenniidae: Omobranchini)
Abstract
The omobranchinin blenniid, Enchelyurus ater, ranges across the islands of the south Pacific Ocean, and E. kraussi ranges from the Red Sea to the Mariana Islands and eastern Australia. The planktonic larvae of these blennies were identified by establishing developmental series up to large larvae identifiable to species using morphological and meristic characters and geographic location. Larvae of both species are similar in appearance, hatch at about 1.52.5 mm length, and undergo notochord flexion at about 4.55.5 mm. Enchelyurus ater probably is near 12 mm, and E. kraussi probably nearer 15 mm, at settlement from the plankton. Larvae of both species have a rounded head, a short, coiled gut, an elongate, compressed tail, and about 34 myomeres. Small spines are present on the posterior preopercular margin at, or soon after, hatching. The spine at the preopercular angle becomes largest, reaching about 25% of head length in the postflexion stage. First the pectoral-fin rays, then principal caudal-fin rays, dorsaland anal-fin anlagen, and pelvic-fin buds begin to form during the preflexion stage. All principal caudal rays are present by the end of the flexion stage. Pelvic-fin rays and all segmented dorsal- and anal-fin rays are present by mid-postflexion stage. Dorsal-fin spines and procurrent caudal-fin rays form during the postflexion stage. Larvae of both species initially are pigmented dorsally on the head and gut, posteriorly on the ventral margin of the tail, and on the mesial surface of the pectoral-fin base. Pigmentation gradually increases on the head and gut in both and on the pectoral fin in E. kraussi, and decreases on the ventral margin of the tail in both. Enchelyurus ater, E. kraussi, and the Hawaiian endemic, E. brunneolus, are a monophyletic group with unknown sister-species relationships. Larval characters suggest the hypothesis that E. ater is the sister species to E. brunneolus, and E. kraussi is the sister species to the other two.
