Retia mirabilia: Protecting the cetacean brain from locomotion-generated blood pressure pulses.

Cetaceans have massive vascular plexuses (retia mirabilia) whose function is unknown. All cerebral blood flow passes through these retia, and we hypothesize that they protect cetacean brains from locomotion-generated pulsatile blood pressures. We propose that cetaceans have evolved a pulse-transfer mechanism that minimizes pulsatility in cerebral arterial-to-venous pressure differentials without dampening the pressure pulses themselves. We tested this hypothesis using a computational model based on morphology from 11 species and found that the large arterial capacitance in the retia, coupled with the small extravascular capacitance in the cranium and vertebral canal, could protect the cerebral vasculature from 97% of systemic pulsatility. Evolution of the retial complex in cetaceans-likely linked to the development of dorsoventral fluking-offers a distinctive solution to adverse locomotion-generated vascular pulsatility.

Immune status and function in harbor seal pups during the course of rehabilitation.

Routine hematological and serum chemistry parameters are important tools for the evaluation of health and the treatment of marine mammals admitted to rehabilitation centers. The evaluation of phagocytosis, oxidative burst and immunoglobulin G (IgG), as markers of immune system function, and haptoglobin (Hp), as a stress marker, were evaluated alongside routine hematology and chemistry as potentially informative diagnostic tools for marine mammal health assessments. Blood samples from harbor seal pups (Phoca vitulina) admitted to (n=46), and released from (n=28), the Vancouver Aquarium's Marine Mammal Rescue Center (VAMMRC) were collected (1) to perform routine and novel functional approaches to evaluate the health of pups at admission; (2) to determine how these parameters changed during the rehabilitation process; and (3) to generate baseline values for reference purposes. Sodium was the only blood parameter which differed between seal pups that survived and those that died, with the surviving pups exhibiting higher levels on admission diagnostics. Positive correlations between total protein concentrations, IgG and Hp levels were observed with globulin concentrations of seal pups. Changes in serum chemistry values between admission and release included a decrease in red blood cells (RBCs), glucose, bicarbonate, total bilirubin, γ-glutamyltransferase (GGT) levels, and an increase in mean cell volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), lymphocytes, eosinophils, urea, potassium, anion gap, calcium, phosphorus, total protein, albumin, globulin and osmolality levels. During the rehabilitation process, phagocytosis decreased, while Hp levels increased. Age and improved health appeared to underlie changes in these parameters during the rehabilitation period.

Intestinal volvulus in cetaceans.

Intestinal volvulus was recognized as the cause of death in 18 cetaceans, including 8 species of toothed whales (suborder Odontoceti). Cases originated from 11 institutions from around the world and included both captive (n = 9) and free-ranging (n = 9) animals. When the clinical history was available (n = 9), animals consistently demonstrated acute dullness 1 to 5 days prior to death. In 3 of these animals (33%), there was a history of chronic gastrointestinal illness. The pathological findings were similar to those described in other animal species and humans, and consisted of intestinal volvulus and a well-demarcated segment of distended, congested, and edematous intestine with gas and bloody fluid contents. Associated lesions included congested and edematous mesentery and mesenteric lymph nodes, and often serofibrinous or hemorrhagic abdominal effusion. The volvulus involved the cranial part of the intestines in 85% (11 of 13). Potential predisposing causes were recognized in most cases (13 of 18, 72%) but were variable. Further studies investigating predisposing factors are necessary to help prevent occurrence and enhance early clinical diagnosis and management of the condition.

Pathology and epidemiology of phocid herpesvirus-1 in wild and rehabilitating harbor seals (Phoca vitulina richardsi) in the northeastern Pacific.

Phocid herpesvirus-1 (PhHV-1, subfamily Alphaherpesvirinae) was isolated from harbor seals (Phoca vitulina vitulina) in the Netherlands in 1985, and was subsequently identified in Pacific harbor seals (Phoca vitulina richardsi) from California, USA in the 1990s. PhHV-1-associated pathology was first recognized in harbor seal carcasses submitted to a veterinary diagnostic laboratory in Abbotsford, British Columbia, Canada in 2000, and 63 cases were identified by 2008. A review of these cases indicated that PhHV-1-associated disease is widespread in harbor seals in the wild and within rehabilitation facilities in the coastal northeastern Pacific (including British Columbia, Canada, and Washington, USA). Morbidity and mortality occurred primarily in neonatal and weanling seal pups, and was due to PhHV-1 alone, or in combination with other disease processes. All cases occurred between July and October, corresponding to the pupping and weaning seasons in this area. Although previous publications have described the prevalence of antibody to PhHV-1 in harbor seals from British Columbia, Canada and Washington, USA this is the first study to focus on the epidemiology and pathology of the virus in this region.