Morphological and developmental studies on the eggs of four <I>Coryphopterus</I> species (Actinopterygii: Gobiidae) in the caribbean sea

Currently, the gobiid genus Coryphopterus Gill, 1863 includes 13 western Atlantic species (Victor 2008). The sand dwelling species have been reported to live in similar habitats and therefore the question arises in how far they differ in ecological aspects such as their reproductive biology. No information has been presented on that topic, in particular their egg morphology, mode of attachment and development of eggs. This study investigates the morphology of eggs as well as aspects of their development and compares the results within the genus and to other gobiids. Eggs of Coryphopterus venezuelae Cervigon, 1966; Coryphopterus dicrus Bohlke et Robins, 1960; Coryphopterus eidolon Bohlke et Robins, 1960; and Coryphopterus thrix Bohlke et Robins, 1960 were collected under laboratory conditions and studied under a scanning electron microscope (SEM). These species are of similar size, with a maximum length of 5–7 cm and live associated with coral reefs. Eggs are deposited under stones or rocks and guarded by the male till hatching (Thresher 1984). The eggshell is called zona radiata or chorion and has been reported to vary in thickness, surface structure, and adhesive filaments. In many cases the zona radiata can be used to identify species (Riehl 1995, Riehl and Patzner 1998, Giulianini and Ferrero 2000). Its main function is to protect the embryo from mechanical forces. Normally it measures between 5 and 15 μm in thickness, but may reach up to 100 μm in species like Agonus cataphractus (L.) (Actinopterygii: Agonidae), which deposit their eggs in tidal wave zones (Riehl 1995). Typically gobiid fishes lay their eggs in a dense patch of single layers on the underside of a solid structure e.g., stones, rocks or shells and the male guards them until they hatch (Miller 1984, Thresher 1984). A characteristic feature of gobiid eggs is the formation of a layer of filaments between the follicle granulosa and the zona radiata. These filaments are arranged around the micropylar pole to provide a mode of attachment for these demersal eggs (Miller 1984). Giulianini et al. (2001) have proved that spermatozoa can pass through ACTA ICHTHYOLOGICA ET PISCATORIA (2008) 38 (2): 97–102 DOI: 10.3750/AIP2008.38.2.03