Microanatomical characterization and histochemistry of the Siamese dwarf rasbora, Trigonostigma somphongsi (Meinken, 1958), a critically endangered species in Thailand: Implicating to the conservative biology.

The fundamental organization of fish tissue is crucial to bridge the fields of histopathology and physiology throughout research on biology. This study examines tissue examination of the Siamese dwarf rasbora, Trigonostigma somphongsi (Meinken, 1958), a critically endangered freshwater fish in Thailand. All fish were obtained from the freshwater area in Nakhon Nayok Province, Thailand, and were then processed using the standard histological and histochemical methods. Our observation clearly provides a detailed histological pattern of the major systems. Interestingly, the oral cavity had three distinct regions based on the presence of a taste bud, a mucous secreting cell and a longitudinal fold in the anterior, middle and posterior regions, referring to the digestive function. Moreover, the mature gonads (mature oocytes and spermatozoa) from all fishes indicate the adult stage. It is noted that this is a foundation of reproductive success under a biological life history, which is implicated to protect the area-based conservation during the rainy season. This study uses a histological approach to provide information related to the systematic functional and anatomical phenomenon of T. somphongsi throughout the basic information for the effective area-based conservation.