Histological evidence of the heart and ovarian vessels in the short mackerel, Rastrelliger brachysoma

Background: Limited research has been reported in the basic information about the structural organizations of heart and ovarian vessel. Hence, produced herein is the first report on the heart, aortas, ovarian blood vessel and blood cells of the short mackerel Rastrelliger brachysoma. Material and Methods: All fish were collected in the upper Gulf of Thailand and then they were elucidated under histological techniques. Results: The results revealed that the heart structure contained four parts including the sinus venosus, the atrium, the ventricle and the bulbus arteriosus. Several vessels including arteriole, capillary, small vein and lymphatic vessel were also commonly seen among oogenic stages of the R. brachysoma. Within capillaries, according to ultrastructural levels, various blood cells including red blood cell, eosinophil and lymphocyte were also seen. The systematic ovarian vessels especially arterial system could be classified into two patterns according to different seasons. During the nonbreeding season, the arteriole at each ovigerous fold protruded in to the ovigerous fold and gradually changed into numerous capillaries. All vessel types increased in both amount and size, especially in capillaries, where their dilation contained various red blood cells that appeared closely around the vitellogenic stage in the breeding season. Nevertheless, the systematic venous vessel was not easily observed in ovarian tissue under the light microscopic analysis. Conclusions: The hearth with consisting of four chambers including the sinus venosus, the soft atrium, the muscular ventricle and the bulbus arteriosus as well as the ovarian vessels throughout the systematic ovarian vessels were present in the R. brachysoma.