Hormone-induced spawning and development of artificially reared larvae of the West Australian dhufish, Glaucosoma hebraicum (Glaucosomatidae)

Abstract

Hormone-induced spawning of the West Australian dhufish, Glaucosoma hebraicum (Glaucosomatidae) is reported, and the artificially-reared eggs and larvae are described. Hormones tested were hCG, Ovaprim and LHRH analogue, the last both as implants and in a saline solution. Late-stage fertilized eggs are spherical (960–1200 µm), possess a pigmented oil globule (210–273 µm) anteriorly on the unsegmented yolk, and hatch in about 32 hours at ~23˚C. Newly hatched larvae (1.75–2.10 mm) have a prominent yolk sac which is resorbed after 3.3 days. The mouth becomes functional from Day 3, first feeding occurs from Day 3.5 and the inflated gas bladder is first observed from Day 4.3. Larvae examined (1.75–8.13 mm) have a moderately deep body, 24–25 myomeres, early-forming pelvic fins that are heavily pigmented by the postflexion stage, small to moderate head spination, no gap between anus and anal-fin origin, and a distinct pattern of pigmentation. Notochord flexion occurs between 3.42 (15 days) and 4.83 mm (25 days), and the transition to the juvenile stage starts from ~8 mm (45–46 days). Comparisons with taxa with similar larvae show that Glaucosoma larvae share some similarities with pempherid larvae, although the evidence is not sufficient to strengthen the view that both groups are closely related.