Some aspects of the taxonomy and biology of the fish family Teraponidae

Some aspects of the taxonomy and biology of the fish family Teraponidae Detailed studies of sagittal structure, with scanning electron micrographs, have produced a familial definition, 11 generic diagnoses and comprehensive specific descriptions as well as diagnoses for sagittal series of 19 teraponid species. Substantial intraspecific variation in shape, sulcal features and marginal ornamentation has been observed but suggested plesiomorph features are: an elliptical shape; short ostium and longer narrow cauda with a short gradual ventral posterior curvature; minimal marginal ornamentation. Numeric analyses of phenetic structural variation in sagittae of six berycoids, one scorpaenoid, 21 outgroup percoids and the teraponids have not clarified interor intrafamilial relation­ ships to any degree, but some interesting points have been raised. Leiopotherapon unioolor and Pelsartia humeralis are repeatedly demonstrated to be divergent from each other and from other teraponids; Bidyanus 3 two Scortum and Pingalla species are closely associated but Soortum barooo appears more similar to Hephaestus fuliginosus. As no conspicuous distinguishing attributes have been elucidated it has been impossible to compile workable generic or specific sagittal keys so the utilization of sagittal structure for species delineation in Teraponidae is considered limited. Electrophoretic testing for genetic variation in seven teraponid species shows that allele fixation is high and heterozygosity values relatively low; polymorphism levels are comparable to those in other fishes. Distance values duplicate sagittal phenetic similarity grouping Hephaestus ̂ Bidyanus and Seortum species; very slight divergence separates Seortum hillii and Seortum parviceps whereas 5. bareoo is more distinct and grouped with H. fuliginosus. Investigations of morphometric, meristic, chromatophore and alimentary canal features of two Hephaestus and four Seortum species indicate that Hephaestus suavis is not valid, that the synonomy status of Seortum ogilbyi should be changed and that the postulated designation of S. bareoo is correct. Hephaestus earbo and H. suavis populations cannot be separated; it is concluded that the latter species has been described from juvenile H. earbo specimens and should be placed in synonomy. North-east Coast S. hillii and S. parvieeps are shown to be distinct both from each other and from Gulf Seortum ogilbyi and Lake Eyre S. bareoo populations; however, the last two pop­ ulations cannot be separated and the specific epithet "ogilbyi" should therefore be placed in S. bareoo synonomy. Intestinal convolution pattern and dentition confirm the assignation of "bareoo" to Seortum. A possible geological-topographical pattern for initial invasion, dispersal, isolation and sub­ sequent divergence of Seortum stocks is suggested. Reproduction in the family is demonstrated to be relatively unspecialised; reasons for this situation resulting from past conditions, current stream conditions and wide physio­ logical tolerance are briefly discussed. Teraponids are dioecious and oviparous with minimal sexual dimorphism; urogenital papilla enlargement in L. unicolor3 H. fuliginosus and Bidyanus bidyanus is considered to be a requisite secondary sex character. The external fertilization generally involves large numbers of demersal non-adhesive, demersal adhesive or semi-pelagic eggs; the only fluviatile species with the latter egg type represent the more derived Bidyanus and Scovtum groups, largely restricted to one stream type. There is no parental care and development is rapid: incubation takes between 24 and 50 h; postlarval development commences after four to six days; metamorphosis occurs three to four weeks after spawning. Some marine species appear to spend extended periods in freshwaters but no anadromy or catadromy has been developed. Marine species apparently need relatively shallow waters, temperatures exceeding 20°C, substantial salinities and rocks or cover for successful spawning; some local migration to river mouths or estuarine shallows occurs. Australian fluviatile species require limited temperature ranges, fluct­ uating water levels, flow, specified photoperiodicity, food abundance and a chemical associated with soil. Prespawning migrations of varying magnitude occur and spawning involves schools of 50-100 adults in protracted activities. The annual spawning season may be brief or extended and may involve two or more partial spawnings during the warmer months. The only reproductive specialization detected is the apparent reaction to soil chemicals by 3. bidyanus. The existence of an olfactory mechanism in teraponid reproduction is postulated. Possible origins of natural soil-associated chemical stimuli are discussed; three types of chemical mechanism involving long and short term changes in soil compound concentrations and endogenous short range pheromones are suggested.