The developmental ontogeny and morphology of the eggs, larvae and early juveniles of the endangered Nannoperca oxleyana is described based on collections of preserved wild fish, and preserved and live captive specimens reared at 25 ± 1° C. Eggs are telolecithal, spherical, average 1.02 ± 0.004 (± S.E.) mm in diameter, have a smooth, slightly adhesive chorion without filaments, a translucent homogeneous yolk, display meroblastic cell division and follow the general pattern of teleost embryogenesis. Early, middle and late stages of embryonic development were completed on average at 16, 28 and 50 hours post fertilisation. The larvae have generalised perciform morphological development with no apparent larval specialisations. The body is moderately deep bodied and compressed laterally. Head spination is limited to the development of an opercular spine in postflexion larvae. Pigmentation is relatively heavy and uniform over the head and body. Large melanophores occur on the dorsal, lateral and ventral midlines. Squamation commenced in postflexion larvae from 7.5 mm preserved body length (BL) and was complete in all specimens greater than 10.3 mm. Live captive, translucent larvae become pale green within two days of hatching and then light brown during the preflexion and postflexion stages. Juveniles are typically light brown laterally, darker dorsally and have a silvery-white belly. Growth of live, captive larvae and juveniles up to 6-months post hatching was described by the equation: Log10 live BL = 0.6043 + 0.0042A (r2 = 0.917, P<0.00l, n = 323). Ranges for body length and age (days post hatch) of live captive fish were: preflexion 2.80-6.70 mm, 0-40 days; flexion: 6.35-7.70 mm, 21-61 days; postflexion: 6.40-10.30 mm, 43-118 days; and juveniles: 9.60-20.60 mm, 70-188 days. Live captive larvae commenced exogenous feeding at five days post hatching. Comparisons of N. oxleyana early developmental ontogeny and morphology are made with related percichthyids and sympatric species and implications for the conservation of the species are discussed.
Research Article| October 20 2011
Early development of the endangered Oxleyan pygmy perch Nannoperca oxleyana Whitley (Percichthyidae)
Australian Zoologist (2011) 35 (3): 895–909.
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James Knight, Thomas Trnski; Early development of the endangered Oxleyan pygmy perch Nannoperca oxleyana Whitley (Percichthyidae). Australian Zoologist 1 January 2011; 35 (3): 895–909. doi: https://doi.org/10.7882/AZ.2011.044
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