title: Development and ossification of the feeding apparatus in the larvae of two co-occurring species of kob (Sciaenidae), Argyrosomus japonicus and Argyrosomus inodorus, in South Africa.
abstract: The teeth of the oral jaws of two sympatric species of Argyrosomus, Argyrosomus japonicus and Argyrosomus inodorus, found along the South African coast developed first on the premaxilla and then on the dentary of the lower jaw. Teeth were observed on the premaxilla of A. inodorus [head length (LH) = 1·0 mm; notochord length (LN) = 2·7 mm] at a smaller size than in A. japonicus (LH = 1·2 mm; LN = 4·7 mm). The ventral elements of the gill arches (hypo- and basibranchials) were not ossified by the end of preflexion. The fifth ceratobranchial began ossifying and possessed pharyngeal teeth by 1·2 mm LH (LN = 4·7 mm) in A. japonicus and 1·1 mm LH (LN = 3·2 mm) in A. inodorus. To complement the osteological data, stomach contents were also analysed as a proxy for feeding apparatus functionality. Prey were first present in the stomach of A. japonicus at 1·2 mm LH (LN = 4·7 mm) and only 22% of the stomachs contained no prey suggesting that A. japonicus is already actively foraging by preflexion. In comparison, 83% of the stomachs of A. inodorus contained no prey and a single prey item was present in the largest examined specimen (LH = 1·6 mm; LN = 5·4 mm). Elements of the feeding apparatus begin to ossify early during ontogeny. While the overall pattern of ossification is similar between the two species, A. japonicus may be able to begin feeding at smaller head lengths relative to A. inodorus in their nursery habitats.
authors.affiliation: Department of Coastal Sciences, Gulf Coast Research Laboratory, University of Southern Mississippi, 703 East Beach Drive, Ocean Springs, MS 39564, U.S.A.
authors.forename: A L
authors.initials: AL
authors.lastname: Deary
authors.affiliation: South African Institute for Aquatic Biodiversity (SAIAB), Private Bag 1015, Grahamstown 6140, South Africa.
authors.forename: P
authors.initials: P
authors.lastname: Pattrick
authors.affiliation: Department of Zoology, Nelson Mandela Metropolitan University, P. O. Box 77000, Port Elizabeth 6031, South Africa.
authors.forename: N A
authors.initials: NA
authors.lastname: Strydom
mesh_terms: D000818:Animals; D005880:Gills; D007568:Jaw; D007814:Larva / Q000254:growth & development; D008445:Maxillofacial Development; D010012:Osteogenesis; D010473:Perciformes / Q000145:classification / Q000254:growth & development*; D013019:South Africa; D014070:Tooth / Q000254:growth & development*
keywords: drum; functional morphology; jaw; meagre; ontogeny; osteology