Description of ten additional ossicles in the foregut of the freshwater crabs Sylviocarcinus pictus and Valdivia serrata (Decapoda: Trichodactylidae)

Abstract

ABSTRACT. The morphology of stomach ossicles of decapod crustaceans provides valuable information on their phylogeny and biology. We herein described ten new ossicles in the foreguts of two trichodactylid crabs, Sylviocarcinus pictus (H. Milne-Edwards, 1853) and Valdivia serrata White, 1847, in addition to previously described 38 ossicles, which are also recognized and listed. Five specimens each of S. pictus and V. serrata were selected for morphological analysis of gastric ossicles. The stomachs were obtained after removing the carapace, and they were fixed in 10% formalin for 24 hours. After this procedure, the stomachs were immersed in a solution of 10% Potassium Hydroxide (KOH) and heated to 100 °C during 60 minutes for tissue maceration. At this point, the clean skeletons were colored by adding 1% Alizarin Red to the KOH solution in order to facilitate visualization of the internal structures such as the setae and ossicles. The ten new ossicles are: dorsomedial cardiac plate; dorsolateral cardiac plate; suprapectineal lateral ossicle; inferior cardiac valve; lateral mesopyloric ossicle; ampullary roof-medium portion ossicle; process of the ampullary roof-upper portion; lateral-inferior post-ampullary plate; pleuro-pyloric valve's ossicle; and lateral pleuro-pyloric plate. Some ossicles are thin plates that together with the main ossicles assist in the structure and support of the stomach, which are similar in the two species studied herein. The current knowledge on gastric ossicles will be useful in establishing taxonomic characters, which can evaluate phylogenetic relationships among brachyuran crabs.

Comparative morphology of the stomach ossicles of four freshwater crabs species of Dilocarcinini (Crustacea, Decapoda, Trichodactylidae)

“…Thus, Lima (2010) considered these ossicles as new. Lima-Gomes et al (2017) also recognized these plates in V. serrata and S. pictus and, similarly, we observed them in all four species studied herein. Nevertheless, Alves et al (2010) did not recognize these plates in D. septemdentatus.…”

“…1C, 2C, 3C, 4C). Lima-Gomes et al (2017) observed this ossicle to be partially fused in V. serrata and S. pictus.…”

“…Thus, it is probable that the lateral mesopyloric and posterior uropyloric ossicles are indeed present in O. gaudichaudii and O. cursor and possibly due to their low degree of calcification Brösing (2010) did not regonize them. Lima-Gomes et al (2017) also recognized these ossicles in V. serrata and S. pictus. These two ossicles that were proposed as new by Lima (2010) are clearly visible in the four species analyzed in this study (Figs.…”

“…Lima 2010observed and proposed as new, the lateral-inferior post-ampullary plate. Lima-Gomes et al (2017) also recognized it in V. serrata and S. pictus, although always as a slightly calcified piece. This plate is also present in the species studied herein, and always slightly calcificated (Figs.…”

“…The proposal of this ossicle as new was based on the frequency in which this ossicle was found to be moderately calcified and was observed by Lima (2010) in Cardisoma Latreille in Latreille, Le Peletier, Serville and Guérin, 1828, Discoplax A. Milne-Edwards, 1867, Ucides and others. Lima-Gomes et al (2017) also adopted the proposed division of the ossicles into three portions in their study. This ossicle was present in all species studied by us (Figs.…”