Ossículos do moinho gástrico de cinco espécies de trichodactylidae (crustacea: decapoda: brachyura)

Abstract

The stomach of decapod crustaceans is divided into three regions: esophagus, cardiac chamber and pyloric chamber, and has a complex muscular and nervous systems in which a set of striated muscle performs the movements of skeletal elements called the gastric mill. This gastric mill consists of a set of calcified skeletal elements and a set of striated muscles which work together to grind and break down large particles of food in the stomach of the heart chamber. This set consists of the following skeletal ossicles: mesocardiac, pterocardiac, pyloric, exopyloric, zygocardiac, propyloric and urocardiac. In order to test if the current suprageneric classification hypothesis of the family Trichodactylidae can be corroborated by the stomach morphology, the gastric mill ossicles were described based on 25 individuals, including males, females and young adults belonging to five species: Trichodactylus fluviatilis (Trichodactylinae), and Dilocarcinus pagei Moreirocarcinus laevifrons (Dilocarcinini), and Sylviocarcinus pictus and Valdivia serrata (Valdiviini). The ossicles were prepared by dissecting and submersion of the stomach for 24 hours in formalin, then boiled at 100 ◦C for 60 minutes in a solution of potassium hydroxide (KOH), and red-alizarin for macerate all the stomach tissue and purpose the ossicles, respectively. The analysis was performed with the aid of optical stereoscope, and the illustrations of ossicles and their stomachs were individually made with the aid of camera lucida coupled to optical stereoscope. It was possible to recognize 48 ossicles in the five species studied, and among them were able to identify significant differences in nine ossicles: zygocardiac, prepectineal, pectineal, subdentate, urocardiac, posterior mesopyloric, anterior inferior pyloric, pyloric e propyloric. According to characteristics of certain regions of these nine ossicles, it was found that the resulting clusters are consistent with the proposed current classification of Trichodactylidae. The description of internal morphological characters may contribute to a more thorough picture of intrafamilial relationships, as well as to obtain a more precise delimitation of the systematic position of Trichodactylidae.