Chondrocranial Anatomy and Skeletogenesis in Dendrobates auratus

Abstract

-The larval chondrocranium and visceral skeleton of Dendrobates auratus is described and compared with those of other dendrobatids. Four characters, i.e, lack of fusion between orbital cartilages and otic capsules, wide processus muscularis palatoquadrati, lack of processus pseudopterygoideus, and lack of processus anterolateralis hyalis, represent derived conditions for Dendrobates within Dendrobatidae. Cranial and postcranial ossification sequences are reported for D. auratus and Epipedobates tricolor. Skeletogenesis is earlier in E. tricolor, but the overall pattern of ossification is similar in the two species. RESUMEN.-Se describe el condrocraneo y esqueleto visceral de Dendrobates auratus comparandolo con el de otros dendrobatidos Cuatro caracteristicas-no fusion de cartilagos orbitales con capsulas oticas, proceso muscular del palatocuadrado ancho, ausencia de proceso pseudopterigoideo, y ausencia de proceso anterolateral hyalis-representan estados derivados para Dendrobates. Se reportan la secuencia de osificaci6n cranial y post-cranial para D. auratus y Epipedobates tricolor. La osificacio6n es mas temprano en E. tricolor, pero el patr6n general de osificacion es similar en las dos especies. The family Dendrobatidae consists of approximately 157 recognized species clustered in six genera (Frost, 1985; Ford, 1993). The genus Dendrobates comprises 47 recognized species whose combined distribution extends from southern Nicaragua throughout South America, reaching Bolivia and Peru. Dendrobates auratus (Girard, 1855) is found from southern Nicaragua to Colombia at elevations of 0-800 m. Chondrocranial anatomy has been reported for only seven species of Dendrobatidae (Haas, 1995), representing about 4% of known species of dendrobatids. Data on skeletogenesis has not been reported for any species in the Dendrobatidae. Herein, we describe the chondrocranial anatomy and ossification sequence of Dendrobates auratus. Skeletal development of D. auratus is compared with that of Epipedobates tricolor. MATERIALS AND METHODS Tadpoles were staged following Gosner's table (1960). Specimens were cleared and doublestained for bone and cartilage using Alizarin Red S and Alcian blue respectively, following the technique of Dingerkus and Uhler (1977). A total of 26 tadpoles of Dendrobates auratus (stages 29-44, and one juvenile) and 28 tadpoles of Epipedobates tricolor (stages 29-46) were examined. Specimens are deposited in the National Museum of Natural History, Washington D.C. (Dendrobates auratus USNM 509456-509482; Epipedobates tricolor USNM 509483-509510). The chondrocranium of Dendrobates auratus is described based on a stage 32 tadpole, this corresponds to the latest larval stage before cranial ossification was observed. Terminology follows that of de Sa (1988) and Haas (1995). Observations and illustrations were made using a Wild MC3 stereomicroscope with the aid of a camera lucida attachment.