Early Life History of the Nurseryfish, Kurtus gulliveri (Perciformes: Kurtidae), from Northern Australia
Eggs and larvae of nurseryfish, Kurtus gulliveri, one of two known species of Kurtidae, are described and illustrated for the first time using material collected in two rivers of Australia's Northern Territory. Nurseryfish are unique among fishes in that males carry a cluster of fertilized eggs on a bony hook projecting from their foreheads. No brooding males were captured during this study, although one partial egg cluster was found adjacent to a male caught in a gill net. Three clusters found attached to gill nets without associated males had approximately 900–1300, slightly elliptical, 2.1–2.5 mm diameter, eggs, each with multiple oil droplets and a single, relatively thick chorionic filamentous strand at opposite poles. Larvae are pelagic and hatch at approximately 5-mm body length (BL) at the flexion stage possessing a large yolk sac, forming dorsal, caudal, and anal fins, and little pigment. Notochord flexion and yolk-sac resorption are complete by 6.9 mm. Post–yolk-sac larvae resemble adults in having a hatchet-shaped body that is almost transparent in life, including a large head with relatively small eyes, preopercular spines and a prominent, inflated gas bladder. Larval length data obtained fortnightly from August to November 2001 suggests that breeding occurs during northern Australia's dry season (May to November) and that larvae leave the pelagic environment at about 25 mm.Abstract
(A) Male (behind) and female (front) Kurtus gulliveri photographed live in an aquarium at the Northern Territory Wildlife Park (photo by T. M. Berra); (B) partial egg mass obtained in a gill net immediately adjacent to a 224 mm SL male K. gulliveri in the Adelaide River on 20 June 2001; note yolk-sac larva almost dislodged from egg mass; top right inset: head of a 190-mm SL male with eggs captured from Ajkwa Estuary near Timika (Papua Province, Irian Jaya) in 2000 (photo by K. Hortle). (C) Antero-dorsal region of a cleared-and-stained 20-mm postflexion K. gulliveri larva from the Wildman River showing the serrated supraoccipital crest (SO), the three serrated supraneurals, and Y-shaped first spine-bearing pterygiophore (I)
(A) 2.5-mm diameter late-stage egg and (B–E) larval stages of Kurtus gulliveri from rivers of Australia's Northern Territory. Egg in (A) and 5.9 mm flexion larva with large yolk sac in (B) were removed from partial egg mass collected in the Adelaide River on 20 June 2001; note forming dorsal, caudal, and anal fin rays; (C) 6.7 mm; note developing pectoral fin rays and pelvic fin; (D) 12.6 mm; (E) 24.1 mm; (C–E) were collected in the Wildman River in May 1998 (S14644–005). Illustrated by F. J. Neira
Length-frequency distributions (body length, mm) of larval Kurtus gulliveri caught in surface waters (∼1 m) of the Adelaide River fortnightly between 7 August and 13 November 2001