Abstract

As diving mammals subjected to routine dramatic pressure changes, marine mammals produce large erythrocytes with comparatively higher oxygen-carrying capacity and blood volume than terrestrial species; however, marine mammal hematopoiesis has been minimally investigated to date. Bone marrow evaluation is critical in the assessment of hematopoiesis and the optimal collection site varies among species based on anatomic and physiologic differences and safety. We sought to determine optimal bone marrow sampling site(s) and to cytologically and histopathologically characterize this tissue in pinnipeds. Bone marrow aspirates and biopsies were collected from the dorsal iliac crest and tibial crest from two clinically ill otariids while under anesthesia; and at time of euthanasia (12 otariids; one phocid) using an 11-gauge Jamshidi™ needle and/or 14-, 16-, or 18-gauge needles. Pinnipeds euthanized due to severe disease included animals with neoplasia, leptospirosis, domoic acid intoxication, or congenital abnormality; sampling sites from euthanized animals were evaluated at necropsy to assess techniques. Samples were collected into EDTA or heparin and slides were prepared immediately from full aspiration samples and/or aspiration of bone spicules from a Petri dish. Aspirates showed systemic inflammatory responses in the myeloid cell line (n=11), bacterial infection (n=3), lymphoid and/or plasma cell infiltrates (n=7), erythroid cell line changes (n=2), assessment of megakaryocytes (n=15), and occasional presence of microfilaria (n=9). Superior quality samples were obtained with a ratio of 3 ml EDTA to 1 ml bone marrow. These results provide valuable information on bone marrow collection techniques and cytologic and histopathologic evaluation methods in pinniped species.

Acknowledgments

The authors thank the staff and volunteers of The Marine Mammal Center for their dedicated animal care.