Ecotoxicological and histopathological aspects of stranded cetaceans in the Philippines

Polychlorinated biphenyls (PCBs) are a group of synthetic organic chemicals that enrich the food chain via biomagnification where the highest levels have been detected in cetaceans. While several studies have reported cetaceans as sentinels of environmental pollution, information on the contamination status of PCBs in cetaceans found stranded along Philippine coasts has been very limited over the past decades. An important contributory factor to this paucity is the challenging analytical method for the analysis of PCBs in lipid-rich biological tissues due to lipid interferences that can affect gas chromatographic systems especially column efficiency and lifetime. Thus, a modified method consisting of a series of three cleanup steps-involving isolation column chromatography, gel permeation chromatography (GPC), and solid-phase extraction (SPE) using silica gel following Soxhlet extraction, plus macro-and micro-concentration prior to gas chromatographic/mass spectrometric analyses-was used. Recovery of added analytes corresponding to appropriate concentration ranges and repeatability of data values were excellent as values obtained were within the established performance criteria of 40-120% recovery, including a 106% mean recovery for the QC material (FAPAS T05100QC-Oily Fish) and < 30% RSD for an analyte concentration of 1 µg kg-1. Thus, the modified cleanup technique in conjunction with GC/MS detection is proven suitable for its intended use. Thirty-eight (38) congeners (and-209) were detected in cetacean blubber (n = 15) ranging from 21.7 ng g-1 lipid weight (in an adult female dwarf sperm whale (Kogia sima) found in Camarines Sur) to 1460 ng g-1 lipid weight (in an adult male rough-toothed dolphin (Steno bredanensis) found in Zambales.

The spinner dolphin (Stenella longirostris) is one of the smallest odontocetes that commonly strands in the Philippines. Despite its apparent abundance and cosmopolitan distribution, there is no published data on the haematological and serum chemical reference values for this species. This limitation greatly affects the ability of veterinarians and marine mammal rehabilitators to make informed decisions in the diagnosis and treatment of diseases, and the formulation of action plans when individuals of this species strand alive. This study used blood samples from two subadult female spinner dolphins that were successfully rehabilitated after stranding in 2014 to establish haematological and serum chemistry reference values for the species. The overall resulting values of the blood parameters recorded such as the WBC (5.01-10.45 10 3 /μL), RBC (4.23-6.18 10 6 /μL), and PCV (42-50%) generally demonstrated narrow ranges and were close to the published reference values for other similar conspeci c odontocetes. Although there were only two individuals of the species used in this study, the data gathered serves as a valuable reference tool for future cases of spinner dolphin strandings in the Philippines.

Stranded marine mammals may serve as opportunities for probing scientific queries. This study subjected formalin-fixed tissues of two cetaceans, Mesoplodon densirostris (Blainville’s beaked whale) and Kogia sima (dwarf sperm whale), found stranded in Region 11 (Davao) of the Philippines between April and July 2014 to histopathological analyses following necropsy and hematological evaluations. Lesions observed in 2 of 2 animals (100%) were congested hepatic sinusoids, hemorrhages, hemosiderosis, parasitic disease, and pulmonary edema. Other lesions (1 of 2, 50%) were seen in the (1) gastrointestinal tract (congestion, Lieberkhun mononuclear cell infiltrations, villi blunting and adhesion), (2) kidney (blood sludging, membranous glomerulopathy, tubular cell atrophy), and (3) lungs (fungal granuloma, pneumonia). M. densirostris showed severe iron deficiency and thrombocytopenia but with lymphocytosis. K. sima revealed low white blood cell count and neutropenia but with thrombocytosis and hemoconcentration. This study suggests that systemic infection for both animals with (1) membranous glomerulopathy and endoparasitism-associated pneumonia (in M. densirostris) and (2) microthrombi formation (in K. sima) were the major causes of their deaths. Presented results, however limited, may serve as baseline data underpinning cetacean clinicopathological research in the Philippines.