Comparative morphology of blood cells of Ambassis nalua, A. vachelli, and Inegocia japonica

Hematological investigation is an essential tool for monitoring fish health. This research compared morphometric traits and blood cell characteristics between two representative pelagic fish species (Ambassis nalua and A. vachelli) and one benthic species (Inegocia japonica) collected from seagrass meadows off Libong Island in Thailand, where they coexist with human activity. Blood samples were collected and prepared using the smear technique. The erythrocytes of all observed specimens had elliptical or oval shapes. The benthic fish I. japonica significantly outperformed both pelagic fish in terms of the mean size of many erythrocyte features. However, more erythrocyte nuclear abnormalities were found in I. japonica, along with A. nalua. Lymphocytes made up the highest proportion of leukocytes in I. japonica, followed by neutrophils. The morphometric erythrocyte data of I. japonica possibly indicated the greater oxygen requirement of fish living in demersal habitats. The baseline parameters from the hematological data of the sampled fish will be used to monitor environmental quality.