Atypical Red Blood Cells Are Prevalent in California Sea Lion Pups Born during Anomalous Sea Surface Temperature Events

Abstract

To date, there is limited knowledge of the effects that abnormal sea surface temperature (SST) can have on the physiology of neonate pinnipeds. However, maternal nutritional deficiencies driven by alimentary restrictions would expectedly impact pinniped development and fitness, as an adequate supply of nutrients is essential for growth and proper functioning of all body systems, including red blood cell synthesis and clearance. Here, we investigated red blood cell morphology of California sea lion (CSL) pups from the San Benito Archipelago born during the 2014 and 2015 anomalously high SST events recorded in the northeastern Pacific Ocean. We examined whether atypical erythrocyte morphologies were more common in 2015, when the high SST event was more pronounced, and whether the stable isotope signature of pup fur, as an indicator of maternal feeding strategies, accounted for the number of atypical cells. Various atypical erythrocyte morphologies were more prevalent and more abundant than reference values. Evidence of iron deficiency was found in both years, and only pups born in 2014 showed evidence of active erythropoiesis. Microcytes and reticulocytes were more common in pups with higher isotopic δC and lower δN values, suggesting a probable relationship between maternal feeding strategies and the effect of climatic anomalies on red blood cell physiology of their pups. As developing pinnipeds require increased oxygen storage capacity for diving and foraging, the presence of atypical erythrocytes could be relevant to CSL pup fitness if the underlying cause is not reverted. This study is a first step to explore the effects that climatic alterations in the marine environment can have on the blood physiology of developing individuals.

Climate variability and life history impact stress, thyroid, and immune markers in California sea lions (Zalophus californianus) during El Niño conditions

“…When forced to increase foraging effort, nursing adult female sea lions have difficulty in allocating resources towards pup development (Ono et al , 1987). Additionally, body condition and glucose-dependent immune markers, IgG and IgA (Palmer et al , 2015), were reduced in dependent CSL pups born during anomalous conditions of high SST in 2015 (Banuet-Martínez et al , 2017), and also showed abnormalities to erythrocytes, which can further impact nutrient uptake (Flores-Morán et al , 2017). This extended period presented a unique opportunity to investigate the effects of sustained stressors on CSL facing abnormally high energetic demands.…”

Guadalupe fur seal alopecia: a metabolic syndrome associated to climatic anomalies?

“…Loss of fur will demand more energetic resources to maintain thermal homeostasis [47], in turn reducing the available resources for other costly physiological processes [48,49]. This has already been shown for other pinniped species (namely, the California sea lion, Zalophus californianus) that inhabit the same region, where individuals impacted by temperature-related dietary shifts had reduced inflammatory responses and antibody levels [50] and red blood cell membrane alterations [51].…”

The demographic decline of a sea lion population followed multi-decadal sea surface warming

“…Abrupt or sustained changes of temperature affect the abundance and diversity of plankton communities (Bronikowski and Promislow, 2005), pelagic fishes (Chavez, 2003), and marine mammals (Laake et al, 2018; Simmonds and Isaac, 2007). The latter typically respond with alterations in foraging habits (Elorriaga-Verplancken et al, 2016; McClatchie et al, 2016), key physiological processes (Banuet-Martínez et al, 2017; Flores-Morán et al, 2017), reproductive success, and survival (Melin et al, 2012). Although many marine mammal populations can withstand and recover from short-term sea surface warming conditions (e.g.…”