Island-finding ability of marine turtles

Abstract

Traditionally, two types of rib are distinguished in gnathostomes: dorsal (upper) and ventral (lower, pleural) ribs. They are defined according to their position in the connective tissue system of the body: dorsal ribs develop at the intersection of the serially arranged myosepta with the horizontal septum that separates epaxial from hypaxial musculature, whereas ventral ribs develop at the intersection of myosepta with the peritoneum and usually encircle the body cavity. Distribution of rib types among gnathostomes has traditionally been reported as follows: elasmobranchs have dorsal ribs; all Actinopterygii have only ventral ribs with the exception of polypterids, and two subgroups of teleosts, which supposedly also have dorsal ribs; within Sarcopterygii tetrapods have dorsal ribs, whereas dipnoans have ventral ribs. Here, we report the development of ribs in polypterids, a taxon playing a crucial role in discussions on rib homology. We demonstrate that putative dorsal ribs of polypterids have a unique ontogeny and represent an autapomorphy of this taxon. We discuss previous hypotheses of rib homology and offer a more plausible (i.e. more parsimonious) alternative to the conventional interpretation. We conclude that dorsal ribs do not exist and that ribs of gnathostomes are ventral ribs.

Perception of airborne odors by loggerhead sea turtles

“…Additional cues are also likely to be involved, however, especially when turtles have arrived in the general vicinity of target areas and need to pinpoint islands, nesting areas or other specific locations (Lohmann et al, 1999;Putman and Lohmann, 2008). Airborne odorants have been proposed to play a role in helping turtles locate islands at the end of long migrations (Luschi et al, 2001;Hays et al, 2003;Lohmann et al, 2008b). Our results confirm for the first time that sea turtles can indeed perceive airborne odors, suggesting that the use of airborne chemical cues in navigation might be plausible.…”

“…First, turtles navigating into the vicinity of remote islands, used as nesting sites, might be able to perceive the targets from considerable distances downwind if they are able to detect volatile chemicals associated with the island (Luschi et al, 2001;Hays et al, 2003;Lohmann et al, 2008b). Second, volatile chemicals such as dimethyl sulfide (DMS) emanate from oceanic regions in which productivity is high (Andreae and Raemdonck, 1983).…”

From chemotaxis to the cognitive map: The function of olfaction

“…Sea turtles orient to magnetic fields and to a map-like representation of such fields, adjusting their heading in response to simulated ocean locations in the laboratory (66,67). In the field, sea turtles may also use windborne odorants to locate their natal beach by orienting upwind (68), but as secondarily aquatic vertebrates, sea turtles have a smaller relative OB size and fewer OR genes than land turtles (69). Thus, living and extinct reptiles appear to show predictable heterogeneity and plasticity in the components of the OS system, in concordance with the OS hypothesis.…”

Orientation behaviour of leatherback sea turtles within the North Atlantic subtropical gyre

“…Travel adjacent to oceanic fronts has also been hypothesized [33,34]. Additional studies point to a 'multifactor navigation system' in turtles [35] that may include a combination of visual and magnetic cues [36], currents [37] and, possibly, olfactory cues over shorter distances [38,39]. Sea turtles may rely on a combination of orientation cues in different situations (i.e.…”