Regional and Age-Related Variations in Haptoglobin Concentrations in Steller Sea Lions (Eumetopias Jubatus) From Alaska, Usa

Abstract

Varying concentrations of the highly conserved acute phase response protein, haptoglobin, can indicate changes to the health and disease status of mammals, including the Steller sea lion ( Eumetopias jubatus; SSL). To better understand factors relating to acute phase response in SSLs, circulating haptoglobin concentrations (Hp) were quantified in plasma collected from 1,272 individuals sampled near rookeries and haulouts off the coast of Alaska. We compared Hp in SSLs between sexes and among different age classes (young pups, young-of-the-year, yearlings, subadults, and adults) sampled within distinct regions in Alaska (Aleutian Islands, Gulf of Alaska, Southeast Alaska). Regional and age-related differences were observed, particularly in younger SSLs. No sex-related differences were detected. We identified weakly significant relationships between Hp and hematology measurements including white blood cell counts (WBC) and hematocrit (Hct) in young pups from the Aleutian Islands and Southeast Alaska. No relationship between Hp and body condition was found. Lastly, a nonlinear relationship of plasma Hp and whole blood total mercury concentrations (THg) was observed in SSLs from the endangered western distinct population segment in Alaska. These results demonstrated that regional variation in Hp, especially in younger SSLs, may reflect regional differences in health and circulating THg.

Erythrocyte sedimentation rate and hemoglobin-binding protein in free-living box turtles (Terrapene spp.)

“…It is possible that reproductive differences would emerge if turtles were sampled at more time points during the active season. Seasonal differences in HBP concentrations have been identified in Pyrenean chamois (Rubricapra pyrenaica pyrenaica) and site differences have been detected in Steller sea lions, indicating the potential need for season and population-specific reference intervals [10,91,94]. All HBP measurements in the present study came from a single box turtle population that was serially sampled over the course of three years, and the potential for seasonal and population-level variability in this analyte is unknown.…”

Acute phase reactants in nondomesticated mammals—A veterinary clinical pathology perspective

“…Full assay validation has not been performed for any APR assay in nondomesticated mammal species, and some studies provide no information about assay validation 16–18,20–29 . When validation has been performed, this usually only includes imprecision and linearity experiments, 22,30–38 sometimes with additional recovery or limit of detection studies 13,39–46 (Tables 1‐4).…”

“…Haptoglobin has been proposed as a bioindicator, but a lack of attention to assay validation and the use of varying methods confounds the interpretation of results. For example, two studies measured haptoglobin in the same population of Steller sea lions and harbor seals in the Gulf of Alaska 25,29 . Populations in the western portion of this ecosystem were declining and were considered endangered, while populations in the eastern portion were stable.…”

Total Mercury, Total Selenium, and Monomethylmercury Relationships in Multiple Age Cohorts and Tissues of Steller Sea Lions (Eumetopias jubatus)

“…Many factors have been implicated in the lack of recovery (Atkinson et al, 2008); studies reporting relatively high and spatially dependent concentrations of total mercury ([THg]) in wDPS Steller sea lion tissues (Correa et al, 2014; Rea et al, 2020) raise concern about the potential for Hg‐associated biological effects. Similar to other marine mammals (Dietz et al, 2019), recent studies of Steller sea lions have reported Hg‐associated effects on immunological parameters (Kennedy et al, 2019; Levin et al, 2020), although direct cause and effect in wild populations can be difficult to assess. Archived tissues can be a valuable resource for assessing Hg and selenium (Se) in wild populations, but interpretation requires an understanding of organotropism across age cohorts.…”