Histology Atlas and Systematic Approach to Postmortem Examination of the Queen Conch Lobatus gigas

Abstract

The queen conch Lobatus gigas is the second largest commercial fishery in the Caribbean, and overharvesting has resulted in significant population declines. Depleted populations are at greater risk of stochastic events, including disease epidemics; however, disease diagnosis in L. gigas has been limited by the lack of standard procedure and histological reference material. This manual outlines a systematic technique for postmortemexamination and compiles a comprehensive histology atlas to facilitate research regarding the pathology of L. gigas. Methods for euthanasia, dissection, sampling, and fixation are described, which produced optimal presentation and preservation of tissues. The recommended approach includes anesthesia with magnesium sulphate, extraction from shell, and euthanasia by incision through ganglia posterior to the buccal mass, followed by exposure of all tissues using four incisions. Anatomy is described for both sexes and standard sample locations are established. Tissue fixation is optimal using Davidson's formula. A histological reference for 16 tissues, nine of which were described for the first time in this species, is presented, including the anus, columellar muscle, digestive gland, esophagus, foot, ganglia and nerves, gill, gonad, heart, hypobranchial gland, kidney, mantle, nephridial gland, osphradium, small intestine and rectum. This manual is the first necropsy guide and histology atlas for L. gigas, a baseline resource for researchers monitoring health and disease in the species.