The microanatomy of the central nervous system and brain of the Indo-Pacific seahorse, Hippocampus barbouri, during development

The central nervous system (CNS) of Teleostei is a complex system of self-governance and its morphology is reflected in the physiological and reproductive behaviors. The Indo-Pacific seahorse, Hippocampus barbouri Jordan & Richardson, 1908, is a new candidate species for aquaculture in Thailand. In this study, we investigated the brain morphology of H. barbouri across various developmental windows. Light microscopic observations of adult brains revealed a large optic tectum in the mesencephalon, whereas the cerebral hemispheres and the cerebellum are of medium size. The detailed brain structures were generally similar to those of other teleosts; however, only five distinct layers were present in the optic tectum, including the stratum marginale, stratum opticum, stratum album central, stratum griseum central, and stratum periventriculae, versus six layers observed in other fish. One day after birth (1 DAB) the brain was a packed structure without any clear sub-structures. The number of capillaries in the optic tectum began to increase at 6 DAB, and at 14 DAB several features, including small blood vessels in the optic tectum and Purkinje cells, became noticeable. By 35 DAB, the optic tectum became highly vascularized and included five layers. Additionally, large Purkinje cells were developed in the cerebellum. Based on the brain development pattern, we speculate that the predatory ability of this fish starts to develop from 6 to 14 days after birth

Histopathological observation and health status of the zebra-snout seahorse Hippocampus barbouri Jordan & Richardson, 1908 in captivity

The health status of the zebra-snout seahorse, Hippocampus barbouri in captivity has been required for approval for aquaculture. In this study, we investigated the histopathological appearance of three vital organs including gill, kidney and liver in captive H. barbouri during its juvenile and adult stages, by using histological techniques. In juveniles from stage 14-days (100% prevalence) towards stage 30-days adults (100% prevalence), the gills exhibited intraepithelial edema and necrosis while hepatic tissue showed evidence of intracytoplasmic vacuoles. In addition, histological alteration to renal tissues was observed the degeneration of renal tubules, the presence of melanomacrophage, and the infection of trematode parasites. The parasites were found in stage 30-days adult fish in the kidney (33.3 % prevalence). Taken together, this study highlights the issue of health in captive rearing of H. barbouri, in particular histopathological alterations in gill, liver and kidney tissues, suggesting that aquaculture of this seahorse species requires improved methods and protocols for maintenance and preventing infection

The microanatomy of the central nervous system and brain of the Indo-Pacific seahorse, Hippocampus barbouri, during development

The central nervous system (CNS) of Teleostei is a complex system of self-governance and its morphology is reflected in the physiological and reproductive behaviors. The Indo-Pacific seahorse, Hippocampus barbouri Jordan & Richardson, 1908, is a new candidate species for aquaculture in Thailand. In this study, we investigated the brain morphology of H. barbouri across various developmental windows. Light microscopic observations of adult brains revealed a large optic tectum in the mesencephalon, whereas the cerebral hemispheres and the cerebellum are of medium size. The detailed brain structures were generally similar to those of other teleosts; however, only five distinct layers were present in the optic tectum, including the stratum marginale, stratum opticum, stratum album central, stratum griseum central, and stratum periventriculae, versus six layers observed in other fish. One day after birth (1 DAB) the brain was a packed structure without any clear sub-structures. The number of capillaries in the optic tectum began to increase at 6 DAB, and at 14 DAB several features, including small blood vessels in the optic tectum and Purkinje cells, became noticeable. By 35 DAB, the optic tectum became highly vascularized and included five layers. Additionally, large Purkinje cells were developed in the cerebellum. Based on the brain development pattern, we speculate that the predatory ability of this fish starts to develop from 6 to 14 days after birth