Studies on the Development and Osteology of Some New Zealand Inshore Fishes

Abstract

This study deals principally with the problems involved in the identification of the early stages of tripterygiid, clinid and gobiesocid fish in the Cook Strait region, New Zealand. The nomenclature of 7 tripterygiid and 4 clinid species is reviewed to assist in the identification of the developmental stages. Those species reviewed are preceded by an asterisk in the list included later in this abstract. The adult osteology of Forsterygion varium (Forster in Bloch and Schneider, 1801) is described and illustrated in detail, together with the osteology of the larvae and prejuveniles at different stages of development. The adult osteology is compared with that of other blennioid fishes. In F. varium the skeletal elements begin to form over a wide range of larval sizes and full adult osteological characters are acquired at a variable time after prejuvenile development is reached. Functionally related elements tend to attain their adult form at about the same size. There is no correlation between the size at initial ossification and the endochondral or dermal origin of a bone. Elements of the vertebral column and median fins develop sequentially and therefore provide (in tripterygiids) an index of development which is useful in comparing the larval stages of different species. The embryological stages of 5 tripterygiid and 3 gobiesocid fish are described and illustrated in detail. Species studied are: Forsterygion capito (Tripterygion capito) (Jenyns, 1842), Forsterygion nigripenne (Tripterygion robustum) (Valenciennes in Cuvier and Valenciennes, 1836), Forsterygion varium (Forster in Bloch and Schneider, 180I), Gilloblennius decemdigitatus (Clarke, 1879), G. tripennis (Forster in Bloch and Schneider, 1801), Trachelochisnus melobesia Phillipps, 1927, T. pinnulatus (Forster in Bloch and Schneider, 1801), Diplocrepis puniceus (Richardson, 1846). The eggs of all species are laid on submerged objects in clusters of 20-3000 eggs in shallow coastal water. Eggs are attended by an adult fish until hatching occurs. Prolarvae are well developed with fully pigmented eyes, functional jaws and reduced yolk-sacs, and are therefore useful in linking later larval stages with adults. An assessment of the general problems encountered in the identification of larvae and prejuveniles is presented with attention given to the fish in this study. The larval and prejuvenile stages of 1O tripterygiid, 4 clinid and 9 gobiesocid species are described and illustrated in detail. Those described are -Tripterygiidae:*Forsterygion variun (Forster in Bloch and Schneider, 1801), *F. nigripenne (Valenciennes in Cuvier and Valenciennes, 1836), *F. capito (Jenyns, 1842), *Tripterygion segmentatum McCulloch and Phillipps, 1923, *Gilloblennius decemdigitatus (Clarke, 1879), *G. tripennis (Forster in Bloch and Schneider, 1801), *Helcogramma medium (in part Günther, 1861), two Helcogramma species, new tripterygiid species (genus not certain); Clinidae: *Notoclinus compressus (Hutton, 1872), *N. fenestratus (Forster in Bloch and Schneider, 1801), *Ericentrusrubrus (Hutton, 1872), *Cologrammus flavescens (Hutton, 1872); Gobiesocidae: Trachelochismus melobesia Phillipps, 1927, T. pinnulatus (Forster in Bloch and Schneider, 1801), Diplocrepis puniceus (Richardson, 1846), Diplocrepis puniceus (South Island form), Gastroscyphus hectoris (Günther, 1876), Gastroscyphus species, Gastrocyathus gracilis Briggs, 1955, Dellichthys morelandi Briggs, 1955, Haplocylix littoreus (Forster in Bloch and Schneider, 1801). A key to the larvae and prejuveniles of the above species is included. Closely related tripterygiid species with very similar larval stages were identified mainly, by considering myomere counts and by consistent differences in size (standard length) at given stages of development. In contrast clinid and gobiesocid larvae from unrelated adults were readily distinguished by a wide range of characteristics. Larvae and prejuveniles were collected using standard equipment such as nylon mesh plankton nets and light-traps. A light-trap designed specifically for collecting larvae is described in detail in the appendix. An annotated bibliography of New Zealand teleost eggs and larvae is presented in the appendix with reference to 70 marine and freshwater species.