Sandra Hochscheid

First records of dive durations for a hibernating sea turtle.

The first published record, from the early 1970s, of hibernation in sea turtles is based on the reports of the indigenous Indians and fishermen from Mexico, who hunted dormant green turtles (Chelonia mydas) in the Gulf of California. However, there were no successful attempts to investigate the biology of this particular behaviour further. Hence, data such as the exact duration and energetic requirements of dormant winter submergences are lacking. We used new satellite relay data loggers to obtain the first records of up to 7 h long dives of a loggerhead turtle (Caretta caretta) overwintering in Greek waters. These represent the longest dives ever reported for a diving marine vertebrate. There is strong evidence that the dives were aerobic, because the turtle surfaced only for short intervals and before the calculated oxygen stores were depleted. This evidence suggests that the common belief that sea turtles hibernate underwater, as some freshwater turtles do, is incorrect.

When surfacers do not dive: multiple significance of extended surface times in marine turtles

SUMMARY Marine turtles spend more than 90% of their life underwater and have been termed surfacers as opposed to divers. Nonetheless turtles have been reported occasionally to float motionless at the surface but the reasons for this behaviour are not clear. We investigated the location, timing and duration of extended surface times (ESTs) in 10 free-ranging loggerhead turtles (Caretta caretta) and the possible relationship to water temperature and diving activity recorded via satellite relay data loggers for 101–450 days. For one turtle that dived only in offshore areas, ESTs contributed 12% of the time whereas for the other turtles ESTs contributed 0.4–1.8% of the time. ESTs lasted on average 90 min but were mostly infrequent and irregular, excluding the involvement of a fundamental regulatory function. However, 82% of the ESTs occurred during daylight, mostly around noon, suggesting a dependence on solar radiation. For three turtles, there was an appreciable (7°C to 10.5°C) temperature decrease with depth for dives during periods when ESTs occurred frequently, suggesting a re-warming function of EST to compensate for decreased body temperatures, possibly to enhance digestive efficiency. A positive correlation between body mass and EST duration supported this explanation. By contrast, night-active turtles that exceeded their calculated aerobic dive limits in 7.6–16% of the dives engaged in nocturnal ESTs, probably for lactate clearance. This is the first evidence that loggerhead turtles may refrain from diving for at least two reasons, either to absorb solar radiation or to recover from anaerobic activity.

Long‐Term Cold Acclimation Leads to High Q10 Effects on Oxygen Consumption of Loggerhead Sea Turtles Caretta caretta

We monitored oxygen consumption (V̇o2, body temperatures (Tb), submersion intervals, and circadian rhythms of V̇o2 in nine loggerhead turtles during a 6‐mo period. The turtles originated from the Tyrhennian Sea, South Italy (40°51′N, 14°17′E) and were kept in indoor tanks at constant photoperiod while being subject to the seasonal decline in water temperature (Tw = 27.1° to 15.3°C). From summer to winter, all turtles underwent profound reductions in V̇o2 (Q10 = 5.4). Simultaneously, their activity was greatly reduced and submergence intervals increased. Over 24‐h periods, however, the turtles showed no circadian rhythm in activity or V̇o2. However, there was a significant positive correlation between the proportion of a day spent actively swimming and V̇o2. Tbs were not significantly different from Tw and followed the same seasonal decline. A second experiment was conducted to establish the effect of short‐term exposure to various temperatures on V̇o2. Tb equilibrated with the experimental Tw within 3 h. The metabolic responses were again positively correlated with changes in Tw , but this time the corresponding Q10 was only 1.3. On the basis of the range of body masses of the turtles used in this study (2–60 kg), the intraspecific scaling exponent for V̇o2 was 0.353.

Regional Blood Flow in Sea Turtles: Implications for Heat Exchange in an Aquatic Ectotherm

Despite substantial knowledge on thermoregulation in reptiles, the mechanisms involved in heat exchange of sea turtles have not been investigated in detail. We studied blood flow in the front flippers of two green turtles, Chelonia mydas, and four loggerhead turtles, Caretta caretta, using Doppler ultrasound to assess the importance of regional blood flow in temperature regulation. Mean blood flow velocity and heart rate were determined for the water temperature at which the turtles were acclimated (19.3°– 22.5°C) and for several experimental water temperatures (17°–32°C) to which the turtles were exposed for a short time. Flipper circulation increased with increasing water temperature, whereas during cooling, flipper circulation was greatly reduced. Heart rate was also positively correlated with water temperature; however, there were large variations between individual heart rate responses. Body temperatures, which were additionally determined for the two green turtles and six loggerhead turtles, increased faster during heating than during cooling. Heating rates were positively correlated with the difference between acclimation and experimental temperature and negatively correlated with body mass. Our data suggest that by varying circulation of the front flippers, turtles are capable of either transporting heat quickly into the body or retaining heat inside the body, depending on the prevailing thermal demands.

Black and white under the South African sun: are juvenile Cape gannets heat stressed?

(1) We measured dorsal surface temperature (Td), skin temperature (Ts) and body temperature (Tb) of adult (white plumage) and juvenile (black plumage) Cape gannets, Morus capensis, subject to high ambient temperatures. (2) Mean Td and Tb of juveniles were significantly elevated compared to those of adults. (3) Mean Ts of older juveniles, which had down beneath their body feathers, were significantly lower than Ts of younger juveniles, indicating that the down provided insulation. (4) Juveniles spent a significantly greater proportion of time thermoregulating via evaporative cooling than adults. (5) The high thermal load of the dark plumage is presumably associated with major costs for the thermal and water balance of juveniles.

The first report of a loggerhead turtle Caretta caretta nest on the central Tyrrhenian coast (western Mediterranean)

Here we report for the first time on a loggerhead turtle, Caretta caretta, which laid 92 eggs on the south-west Italian coast on 11 July 2002. During the 64 day incubation period the nest was threatened by inundation and hence, it was transferred on the 28th day. The hatching success was 49.4% and all live hatchlings entered the sea. Unhatched eggs were opened to determine at which developmental stage embryonic death occurred. This analysis confirmed that most of the embryos died in the first few days after laying and that the transfer of the nest did not affect embryonic development. This was the third of three unusual nesting events in the western Mediterranean in the years 2001–2002.

Seasonal heterogeneity of ocean warming: a mortality sink for ectotherm colonizers.

Distribution shifts are a common adaptive response of marine ectotherms to climate change but the pace of redistribution depends on species-specific traits that may promote or hamper expansion to northern habitats. Here we show that recently, the loggerhead turtle (Caretta caretta) has begun to nest steadily beyond the northern edge of the species’ range in the Mediterranean basin. This range expansion is associated with a significant warming of spring and summer sea surface temperature (SST) that offers a wider thermal window suitable for nesting. However, we found that post-hatchlings departing from this location experience low winter SST that may affect their survival and thus hamper the stabilization of the site by self-recruitment. The inspection of the Intergovernmental Panel on Climate Change model projections and observational data on SST trends shows that, despite the annual warming for this century, winter SST show little or no trends. Therefore, thermal constraints during the early developmental phase may limit the chance of population growth at this location also in the near future, despite increasingly favourable conditions at the nesting sites. Quantifying and understanding the interplay between dispersal and environmental changes at all life stages is critical for predicting ectotherm range expansion with climate warming.

Discovery of the northernmost loggerhead sea turtle ( Caretta caretta ) nest

A loggerhead turtle nest was accidentally discovered during the raking of a beach at St Tropez, France, on 18 July 2006. This is the northernmost loggerhead nest so far in the Mediterranean and in the world. The clutch was deposited close to the sea in a sand-soil-pebbles mixture and became partially inundated in September. In total there were 141 eggs, none of which hatched. Only 24% of the eggs contained embryos, while 107 eggs contained yolk but no visible embryo. The failure to hatch was probably the result of the non-suitable nest environment, the low mean incubation temperatures and the inundation. Further observations of beaches are recommended to establish other nesting occurrences of loggerhead turtles in this region.

Detection and Partial Characterization of Herpesviruses from Egyptian Tortoises (Testudo kleinmanni) Imported into Italy from Libya

Abstract A group of approximately 370 Egyptian tortoises (Testudo kleinmanni) and 36 spur-thighed tortoises (Testudo graeca) were illegally imported into Italy from Libya. Within 6 mo of their entry into Italy, all but 40 of the Egyptian tortoises had died with signs of severe stomatitis. Herpesviruses were detected from the tongues of seven Egyptian tortoises by polymerase chain reaction (PCR) and virus isolation. Sequencing of a portion of the UL39 homologue of the herpesviruses from three different tortoises demonstrated that the viruses were identical to one another and identical to a herpesvirus isolated from a Hermanns tortoise (Testudo hermanni) in Germany. This is the first description of the detection of a herpesvirus from diseased Egyptian tortoises. That these animals were imported into Europe from Libya provides circumstantial evidence for the presence of herpesviruses among tortoises in northern Africa.

Parallel use of a shared genomic island of speciation in clinal and mosaic hybrid zones between cryptic seahorse lineages

Diverging semi-isolated lineages either meet in narrow clinal hybrid zones, or have a mosaic distribution associated with environmental variation. Intrinsic reproductive isolation is often emphasized in the former and local adaptation in the latter, although both can contribute to isolation. Rarely these two patterns of spatial distribution are reported in the same study system, while this could provide fundamental information on the endless debate about the relative contribution of intrinsic reproductive isolation and local adaptation on the speciation process. Here we report that the low diversity long-snouted seahorse Hippocampus guttulatus is genetically subdivided into five cryptic semi-isolated lineages. Along the Atlantic coasts, northern and southern lineages meet and coexist with little hybridization in the southwest of France, forming a clinal hybrid zone. In the Mediterranean Sea, two lineages have a mosaic distribution associated with lagoon-like and marine habitats. A fifth lineage was identified in the Black Sea. Genetic homogeneity over large spatial scales within each lineage, together with among-locus variance in differentiation levels between lineages and spatial patterns of introgression provide evidence that partial reproductive isolation is maintaining the divergence. Surprisingly, the North Atlantic and the Mediterranean lagoon lineages are genetically similar for a single chromosome-wide island showing parallel genetic differentiation among regions. Since Atlantic lineages distribution lacks association with habitat variation, genetic parallelism suggests that a shared genomic barrier contributes to reproductive isolation in contrasted contexts - i.e. spatial vs. ecological. We discuss how a genomic hotspot of parallel differentiation could have evolved and become associated either with space or with a patchy environment in a single study system.Diverging semi-isolated lineages either meet in narrow clinal hybrid zones, or have a mosaic distribution associated with environmental variation. Intrinsic reproductive isolation is often emphasized in the former and local adaptation in the latter, although both can contribute to isolation. Rarely these two patterns of spatial distribution are reported in the same study system. Here we report that the long-snouted seahorse Hippocampus guttulatus is subdivided into discrete panmictic entities by both types of hybrid zones. Along the European Atlantic coasts, a northern and a southern lineage meet in the southwest of France where they coexist in sympatry with little hybridization. In the Mediterranean Sea, two lineages have a mosaic distribution, associated with lagoon-like and marine habitats. A fifth lineage was identified in the Black Sea. Genetic homogeneity over large spatial scales contrasts with isolation maintained in sympatry or close parapatry at a fine scale. A high variation in locus-specific introgression rates provides additional evidence that partial reproductive isolation must be maintaining the divergence. Surprisingly, fixed differences between lagoon and marine populations in the Mediterranean Sea belong to the most differentiated SNPs between the two Atlantic lineages, against the genome-wide pattern of structure. These parallel outlier SNPs cluster on a single chromosome-wide island of differentiation. Since Atlantic lineages do not match the lagoon-sea habitat variation, genetic parallelism at the genomic island suggests a shared genetic barrier contributes to reproductive isolation in contrasting contexts -i.e. spatial vs. ecological. We discuss how a genomic hotspot of parallel differentiation could have evolved and become associated either with space or with a patchy environment in a single study system.