Spawning behaviour and early development in the naked dragonfish Gymnodraco acuticeps

Abstract

Nesting sites of the naked dragonfish Gymnodraco acuticeps have been identified in 15-35 m water under fast ice adjacent to McMurdo Station, making it possible to examine embryonic development and early larval growth. Egg-laying (predominantly in October) is preceded by a distinctive whirling behavioural pattern driven by the male prodding the side of the female's abdomen. The eggs (3.42 ± 0.19 mm in diameter) are laid on rocks as a single adherent layer (c. 2500 per patch). Development is unusually protracted, the first cleavage occurring after about 24 hr at about -1.9ºC. Hatching occurs about 10 months post-fertilization, beginning soon after the sun rises above the horizon. During this period one of the parents may act as a guard in an attempt to keep predators at bay. Upon hatching, the larvae (12.09 ± 0.36 mm long) swim towards the surface ice where they presumably seek refuge. Yolk absorption is complete in about 15 days. Larvae (grown in aquaria at a density of 0.7 larvae l -1 ) display an average daily growth rate of 0.42% over nine weeks. Hatching in aquaria can occur up to 100 days in advance of that seen in the field, suggesting that under natural conditions hatching may be delayed until an appropriate stimulus (such as the return of the sun) is received.

Freezing resistance of antifreeze-deficient larval Antarctic fish

“…However, by the time of hatching the TH exhibited by whole larvae homogenates is less than half of that of the newly spawned eggs, and the FPs of hatchling G. acuticeps sera and intestinal fluids are more than 0.5°C higher than the ambient water temperature (-1.91°C, Table·1, Fig.·5). Paradoxically, larval G. acuticeps have been observed to seek out the iciest surface waters upon hatching (Evans et al, 2005). For aquarium-reared G. acuticeps, the yolk is completely absorbed by about 15·d.p.h.…”

“…In early to mid-September of 2002 and 2003 divers collected ready-to-hatch Gymnodraco acuticeps Boulenger 1902 eggs from rocks at depths of 15-35·m near the saltwater intake jetty of McMurdo Station. Spawning occurs in mid-October, with larvae hatching in early September of the following year (Evans et al, 2005). Eggs were transferred to tanks with flow-through seawater (-1.3°C to -1.6°C) at McMurdo Station, where all viable larvae hatched within 24·h.…”

“…To enhance larval survival, in 2003 the larvae were fed fresh plankton immediately after hatching and regularly for the duration of the sampling period. A description of spawning behavior and larval development is provided in Evans et al (2005).…”

“…The eggs collected near the saltwater intake jetty of McMurdo Station were identified as those of G. acuticeps by the presence of nest-guarding adults, and the eventual development of adult morphological features in the aquariumreared larvae (Evans et al, 2005). The identities of the other two newly hatched larvae were tentatively designated as P. antarcticum (Terra Nova Bay) and P. borchgrevinki (Cape Evans iceberg) based on morphological characteristics, but verification awaited DNA sequence analysis.…”

Isolation and characterization of the mitochondrial genome ofGymnodraco acuticeps(Perciformes: Bathydraconidae) with phylogenetic consideration

“…The common name of G. acuticeps is the naked dragonfish, which stems from its body feature such as lack of scales, the dragon-like form of its head, a protruding lower jaw bearing prominent, and the exposed canines. They are the predators in Antarctic food web, feeding on a variety of organisms including some fish, amphipods and polychaetes (Evans et al 2005). Some regions of the mitochondrial genome were thought to be the ideal markers for studies on population genetic diversity, molecular phylogeny, and species identification due to the high mutation rate, simple structure, abundant distribution and maternal inheritance.…”