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

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 valves 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.

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

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 valves 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.(AU)

Morfología comparada del esqueleto axial en la familia de cangrejos de agua dulce Trichodactylidae (Crustacea: Decapoda: Brachyura)

El esqueleto axial es una estructura compleja de origen cuticular, formada a partir de las láminas esclerotizadas de los esternitos y pleuritos torácicos así como por sus invaginaciones internas. Los caracteres de la parte ventral del esqueleto axial, que se reflejan externamente en las líneas de sutura del esternón torácico, son criterios importantes en el actual sistema de supragenerico de Trichodactylidae: (Trichodactylinae y Dilocarcininae (Dilocarcinini + Valdiviini)). Con el objetivo de probar esa hipótesis de clasificación fue realizado el estudio anatómico del esqueleto axial de 43 individuos adultos, tanto machos como hembras, pertenecientes a 17 especies de 10 géneros de Trichodactylidae. Para la preparación del material, los individuos fueron diseccionados y sus esqueletos sumergidos, por un periodo de 24 a 48 horas, en una solución caliente de Hidróxido de Potasio (KOH). El análisis anatómico permitió describir un grupo de variaciones en la forma, orientación y conformación del esternón torácico, techo pleural, fragmas ventrales y dorsales, así como de la lámina de unión. De acuerdo con esas características las especies estudiadas fueron reunidas en tres grupos, siendo esas agrupaciones consistentes con la actual propuesta de clasificación de Trichodactylidae en subfamilias y tribus. El presente trabajo resalta la importancia informativa de la morfología del esqueleto axial para la taxonomía de Trichodactylidae.

The axial skeleton is a complex structure of cuticular origin, formed by sclerotic plates of thoracic sternite and pleurites as well as its internal invaginations. The ventral characters of the axial skeleton, reflected externally in the suture lines of the thoracic sternum, are an important classification criteria for the current suprageneric system of Trichodactylidae: (Trichodactylinae & Dilocarcininae (Dilocarcinini + Valdiviini)). In order to test this hypothesis, the internal and external characters of the axial skeleton of 42 adult crabs belonging to 17 species and 10 genera were examined. For the material preparation the crabs were dissected and their skeletons submerged in a hot solution of potassium hydroxide (KOH) for a period of 24 to 48 hours. Variations in the shape, orientation and conformation of the thoracic sternum, pleural roof, ventral and dorsal phragmas and junction plate were described from anatomical preparations. Based on these characteristics, the species were separated into three groups, which are consistent with the proposed classification of Trichodactylidae into subfamilies and tribes. This study highlights the importance of the morphological characteristics of the axial skeleton for Trichodactylidae taxonomy.

Morfología comparada del esqueleto axial en la familia de cangrejos de agua dulce Trichodactylidae (Crustacea: Decapoda: Brachyura)

El esqueleto axial es una estructura compleja de origen cuticular, formada a partir de las láminas esclerotizadas de los esternitos y pleuritos torácicos así como por sus invaginaciones internas. Los caracteres de la parte ventral del esqueleto axial, que se reflejan externamente en las líneas de sutura del esternón torácico, son criterios importantes en el actual sistema de supragenerico de Trichodactylidae: (Trichodactylinae y Dilocarcininae (Dilocarcinini + Valdiviini)). Con el objetivo de probar esa hipótesis de clasificación fue realizado el estudio anatómico del esqueleto axial de 43 individuos adultos, tanto machos como hembras, pertenecientes a 17 especies de 10 géneros de Trichodactylidae. Para la preparación del material, los individuos fueron diseccionados y sus esqueletos sumergidos, por un periodo de 24 a 48 horas, en una solución caliente de Hidróxido de Potasio (KOH). El análisis anatómico permitió describir un grupo de variaciones en la forma, orientación y conformación del esternón torácico, techo pleural, fragmas ventrales y dorsales, así como de la lámina de unión. De acuerdo con esas características las especies estudiadas fueron reunidas en tres grupos, siendo esas agrupaciones consistentes con la actual propuesta de clasificación de Trichodactylidae en subfamilias y tribus. El presente trabajo resalta la importancia informativa de la morfología del esqueleto axial para la taxonomía de Trichodactylidae.(AU)

The axial skeleton is a complex structure of cuticular origin, formed by sclerotic plates of thoracic sternite and pleurites as well as its internal invaginations. The ventral characters of the axial skeleton, reflected externally in the suture lines of the thoracic sternum, are an important classification criteria for the current suprageneric system of Trichodactylidae: (Trichodactylinae & Dilocarcininae (Dilocarcinini + Valdiviini)). In order to test this hypothesis, the internal and external characters of the axial skeleton of 42 adult crabs belonging to 17 species and 10 genera were examined. For the material preparation the crabs were dissected and their skeletons submerged in a hot solution of potassium hydroxide (KOH) for a period of 24 to 48 hours. Variations in the shape, orientation and conformation of the thoracic sternum, pleural roof, ventral and dorsal phragmas and junction plate were described from anatomical preparations. Based on these characteristics, the species were separated into three groups, which are consistent with the proposed classification of Trichodactylidae into subfamilies and tribes. This study highlights the importance of the morphological characteristics of the axial skeleton for Trichodactylidae taxonomy.(AU)