Histological Characteristics and Regional Adaptations Study of the Climbing Perch (

The climbing perch (Anabas testudineus) is a freshwater fish native to Indonesia that is known for its high adaptability to extreme and fluctuating aquatic habitats. Despite its ecological importance, histological information about its integument remains limited. The aim of this study was to characterise the histological structure of the integument and identify regional variations that could contribute to adaptive functions. Four specimens were collected from the Progo River in Yogyakarta, Indonesia. Integument samples from the cranial, medial and caudal areas were treated with haematoxylin-eosin staining and observed under light and stereomicroscopes. The integument consisted of a thin epidermis and a thicker dermis, with significant regional differences in thickness. The cranial region had the thickest epidermal and dermal layers, suggesting enhanced mechanical protection, while the caudal region had thinner layers associated with the mobility of the musculoskeletal system. The epidermis contained mucous cells, club cells and pigment cells, suggesting a role in protection, chemical defence and interaction with the environment. These results show that regional histological variations in the integument support functional adaptations that enable A. testudineus to thrive in diverse and challenging environments.