Effects of Oceanic Salinity on Body Condition in Sea Snakes

Abstract

Since the transition from terrestrial to marine environments poses strong osmoregulatory and energetic challenges, temporal and spatial fluctuations in oceanic salinity might influence salt and water balance (and hence, body condition) in marine tetrapods. We assessed the effects of salinity on three species of sea snakes studied by mark-recapture in coral-reef habitats in the Neo-Caledonian Lagoon. These three species include one fully aquatic hydrophiine (Emydocephalus annulatus), one primarily aquatic laticaudine (Laticauda laticaudata), and one frequently terrestrial laticaudine (Laticauda saintgironsi). We explored how oceanic salinity affected the snakes' body condition across various temporal and spatial scales relevant to each species' ecology, using linear mixed models and multimodel inference. Mean annual salinity exerted a consistent and negative effect on the body condition of all three snake species. The most terrestrial taxon (L. saintgironsi) was sensitive to salinity over a short temporal scale, corresponding to the duration of a typical marine foraging trip for this species. In contrast, links between oceanic salinity and body condition in the fully aquatic E. annulatus and the highly aquatic L. laticaudata were strongest at a long-term (annual) scale. The sophisticated salt-excreting systems of sea snakes allow them to exploit marine environments, but do not completely overcome the osmoregulatory challenges posed by oceanic conditions. Future studies could usefully explore such effects in other secondarily marine taxa such as seabirds, turtles, and marine mammals.

Hypernatremia in Dice Snakes (Natrix tessellata) from a Coastal Population: Implications for Osmoregulation in Marine Snake Prototypes

“…However, this hypothesis seems unlikely as we did not find any relationship between plasma sodium and BCI (see above) or haematocrit (Spearman rank correlation, r s  = 0.20, p >0.05), two parameters known to correlate with hydration state [17], [48]. Our results rather suggest that free-ranging N. tessellata gained salt during their day-to-day activities.…”

“…Specifically, the most detailed studies performed on marine snakes have shown that species having a functional salt gland cannot equilibrate their hydromineral balance without access to fresh water [12], [16]. Dehydration in seawater has been shown to occur in amphibious sea snakes (Laticaudine sea kraits) as well as in fully marine species (Hydrophine sea snakes) [12], [16], [17]. In addition, elevated plasmatic sodium concentrations have been measured in various marine snake species [18]–[25].…”

Natural and anthropogenic alterations of the soil affect body condition of the fossorial amphisbaenian Trogonophis wiegamnni in North Africa

“…Body condition indexes are used as proxies of health state in many animals (e.g. SchulteHostedde et al, 2001;Amo et al, 2006Amo et al, , 2007Wikelski and Cooke, 2006;Hickman and Swan, 2010;Brischoux et al, 2012).…”

“…Na, Cl). Thus, for example, even sea snakes that are adapted to living in salt water have lower body condition during periods of high oceanic salinity (Brischoux et al, 2012). In addition, soil salinity restricts the abundance and diversity of vegetation and invertebrate prey of amphisbaenians (García et al, 1993;McKenzie et al, 2003).…”

Do researchers impact their study populations? Assessing the effect of field procedures in a long term population monitoring of sea kraits

“…On one hand, this research yielded substantial results regarding sea snake foraging ecology Brischoux, Bonnet and Shine, 2009), physiology (Brischoux et al, 2012), prey community (Ineich et al, 2007;Brischoux and Bonnet, 2008), conservation issues Brischoux, Bonnet and Pinaud, 2009;Bonnet, 2012), and others ). On the other hand, we inevitably perturbed a very large number of individuals with a potential impact on the populations.…”