Early Development of the Clingfish, Gobiesox strumosus Cope

Abstract

Descriptions and illustrations of the egg, early larval stages, and young of the clingfish,Gobiesox strumosus, are presented for the first time. The eggs and early larvae are compared briefly with those of ecologically similar species. Morphometric and meristic data are also provided for 95 specimens ranging from 2.85 to 50 mm total length (T.L.). Skeletal drawings of stained and cleared specimens show propression of ossification. The eggs of the clingfish are laid in empty oyster shells and are distinguished from other ecologically similar species in upper Chesapeake Bay area by their ovate shape. The egg number per cluster ranges from about 300 to 2500. A single cluster may contain eggs in several different developmental stages. The diagnostic feature of the pre-hatching embryo is lack of pigment on the yolk and head and heavy pigmentation on the trunk. Eggs hatch within five to seven days. Chances of survival are much greater for eggs tended by an adult fish throughout the incubation period. The average hatching length of larvae is between 3.4–3.8 mm T.L. with yolk already absorbed, but artificial conditions may cause the embryo to hatch between 2.8–3.4 mm with yolk still present. Diagnostic features include a broad head and laterally compressed body with spatulate tail; large, heavily-pigmented eyes; 10–15 stellate melanophore saddles: and the absence of pigment on the posterior 30 per cent of the body. By 12 mm T.L. the young clingfish, is essentially similar to the adult in appearance, although some osseous structures are still incomplete and pigmentation has not yet developed into the definitive reticulated patterns of the adult. By 40 mm T.L. the clingfish can properly be considered an adult. When measured against standard length, the dependent variables of head length, snout-to-anus length, eye length, disc length, and greatest body depth are seen to be proportional in their rate of growth. The head increases while the eye decreases, relative to body growth.