DEVELOPMENTAL-CHANGES IN LARVAL MOUTHPARTS AND FOREGUT IN THE RED FROG CRAB, RANINA-RANINA (DECAPODA, RANINIDAE)

Organic development of the zoeal and megalopal stages of Ranina ranina Linnaeus was examined in the mouthparts and foregut. The gnathal lobe of the mandible consists of the incisor and molar portions in the zoe a, whereas the latter degenerates in the megalopa. Lubrication of the mouthparts is considered to be low in the early instars, because of th e reduced number and limited distribution of tegumental glands. In the zoea and megalopa, the proventriculus is composed of cardiac and pylo ric portions, which were divided by calcified median and lateral teeth , and a cardiopyloric valve. The proventriculus of instar I zoea was s mall and the median tooth was poorly developed, but the cardiac portio n enlarged and the masticatory function of the teeth and valve develop ed with each instar. A setal screen in the cardiac proventriculus deve loped at instar IV. The structure of the mandible and proventriculus i ndicates that small suspended organic matter is suitable for the early instar zoea whereas solid benthic organisms can be eaten by the megal opa.