Blood oxygen stores of olive ridley sea turtles, Lepidochelys olivacea are highly variable among individuals during arribada nesting

Abstract

Sea turtles are mostly pelagic, air-breathing divers that can become neritic during nesting season. Sea turtles dive with a full lung of air and these O2 stores are supplemented by O 2 stored in blood. Olive ridley sea turtles exhibit polymorphic nesting behavior; mass nesting behavior called arribada, where up to 25,000 turtles will nest at once, and solitary nesting behavior. As mostly pelagic and highly migratory species, we hypothesize that newly arrived turtles, nesting in arribadas, will exhibit increased blood oxygen stores as compared to solitary nesting towards the end of the season, where turtles have likely become neritic. We measured blood volume and associated variables to estimate total blood O2 stores including hematocrit and blood hemoglobin content. There were no significant differences in mean values between nesting periods, but arribada nesting individuals were more variable than those performing solitary nesting. Mass specific plasma volume was relatively invariant among individuals but mass specific blood volume and blood oxygen stores varied widely, 2-fold and 3-fold, respectively. Blood O2 stores represented 32% of total body O2 stores. Under typical mean diving conditions of 26°C and high levels of activity, blood stores confer ~14 min to aerobic dive times and are likely critical for the long duration, deep diving exhibited by the species. Individual differences in blood O2 stores strongly impact estimated aerobic dive limits and may constrain the ability of individuals to respond to changes on ocean climate.

Oxidative stress is a potential cost of synchronous nesting in olive ridley sea turtles

“…In a previous study conducted in the same individuals we showed that arribada nesters have higher circulating corticosterone and glucose levels than solitary nesters [32]. Here, we found that arribada nesters are bigger and have higher thyroid hormone levels than solitary nesters.…”

“…While neither TG nor NEFA levels were different between nesting modes (TG: solitary 14.46 ± 9.52 vs arribada 20.47 ± 10.03 mg/mL, t=1.94, p=0.07; NEFA: solitary 0.93 ± 0.22 vs arribada 1.08 ± 0.55 mM, t=0.445, p=0.66), arribada nesters were heavier than solitary nesters (29.20 ± 5.20 vs 24.76 ± 4.37 kg, t=2.17, p=0.042). We then conducted correlation analyses between hormones and metabolites including those (corticosterone, glucose and lactate) measured in samples from the same individuals in a previous study [32]. We found a positive correlation between corticosterone and glucose (ρ=0.87, p<0.0001; Figure 3A ), corticosterone and lactate (ρ=0.73, p=0.005; Figure 3B ), glucose and lactate (r=0.85, p=0.0003; Figure 3C ), and TG and NEFA (r=0.82, p=0.0005; Figure 3D ) in arribada but not in solitary nesters.…”

“…A nominal logistic regression was used to analyze 4-HNE data since the response variable was binary. Correlation analyses between hormones, mass, and metabolites including those measured in samples from the same animals in a previous study [32], were conducted by calculating Pearson or Spearman coefficients (for corticosterone non-parametric data). Data are expressed as mean ± SD unless otherwise indicated.…”

Influence of Season, Environment, and Sex on Selected Blood Parameters of Geoffroy's Side-Necked Turtles, Phrynops Geoffroanus (Schweigger, 1812)

“…60 No correlation was also found between BM and size and PCV and MHCH in Lepidochelys olivacea from Mexico and only a weak positive relationship with Hb. 6 Although, in hatchlings of Dermochelys coriacea from Florida, there was a significant negative relationship between hatchling BM and WBC and absolute mature Het, and the authors inferred that higher WBC counts and higher mature Het in smaller turtles could be indicative of subclinical active inflammation during development. 43…”

Ecological and life‐history correlates of erythrocyte size and shape in Lepidosauria

“…Similarly, reptiles use a range of physiological mechanisms, including bradycardia, prolonged apnoea, cardiac shunts and Bohr effects, to support diving behaviour (Anderson, 1966; Millard & Johansen, 1974; Seymour & Webster, 1975). In diving turtles, oxygen is stored both in the lungs and blood (Arango et al, 2021; Lutz & Bentley, 1985), and blood oxygen stores are thought to be important in some squamates (Ferguson & Thornton, 1984). Marine snakes have significantly higher haematocrit levels (Brischoux et al, 2011; Feder, 1980), with the file snake Acrochordus granulatus , the species with the largest recorded erythrocytes, having the largest blood oxygen stores of any reptile (Feder, 1980).…”