Histochemical characteristics of macrophages of butterfly splitfin ameca splendens

Abstract

The butterfly splitfin (Ameca splendens) is a fish species that belongs to the Goodeidae family. The biology of this species, which is today at risk of extinction in its natural habitats, has not been fully explored. The objective of the present study was to characterize melanomacrophages (MMs) and the melanomacrophage centers (MMCs) that they form, associated with the immunological system of butterfly splitfin. Butterfly splitfin is a potential new model species with a placenta for scientific research. In addition, knowledge about the location and characteristics of MMCs will allow the effective development of a conservation strategy for this species and monitoring of the natural environment. The results of histological analyses show that the immune system of fish aged 1 dph was completely developed. Single MMs were observed in hepatic sinusoids and in head kidney and their agglomerations were noticed in the exocrine pancreas and in the spleen. Hemosiderin was detected in single MMs in the head kidney of fish aged 1 dph, and in the spleen, exocrine pancreas and liver of older fish. Furthermore, histological analyses of older fish revealed the presence of lipofuscin in the head kidney, exocrine pancreas and spleen in melanomacrophages. The localization and size of MMCs may be an indicator of the health status of fish and may be a biomarker of their immune system activation. The obtained results will allow effective monitoring of the populations of this species. Furthermore our results demonstrate the contribution of liver in the iron homeostasis in fish, as evidenced by enhanced deposition of hemosiderin during butterfly splitfin ontogenesis.