The “Chitons” are marine inhabitants that are geographically distributed from Ecuador to Chile. Their value as bioindicators and biological controllers is highlighted since they feed on algae and colonial animals. This study aims to describe the gonadal histology of females and males of Chiton granosus (Frembly, 1827), Enoplochiton niger (Barnes, 1824), and Acanthopleura echinata (Barnes, 1824) by recognizing oogenesis and spermatogenesis. The gonad was extracted from five individuals for each species by dissecting the dorsal area of the body and the Histological Technique with Hematoxylin- Eosin (H-E) staining was applied. The common structures identified in females and males are germ tissue and gonadal wall. About oogenesis, the following were observed: oogonia, in contact with the germ tissue; previtellogenic oocytes with a highly vacuolated or granulous cytoplasm presenting an ac...

The main objective of tissue preservation with the use of fixatives is to maintain the histology of an organ identical to its natural state for subsequent study. The most common fixatives used in histology are alcohol, formaldehyde, and Bouin's solution. Recent studies on the application of fixative substances in histological processes indicate the need to guarantee the quality of the relationship: type of fixator-sample. For this reason, the purpose of this work is to compare the fixation quality of alcohol, formaldehyde and Bouin's solution at the tissue level of the trachea and small intestine of Mus musculus (Linnaeus, 1758) "albino mouse". To do this, the animal was slaughtered using an anesthetic, then the samples were dissected, extracted and fixed, which were placed in vials containing ethyl alcohol, 10% formaldehyde and Bouin's solution for a week; Subsequently, the histological...