scholarly journals Orientation and open-sea navigation in sea turtles

1996 ◽  
Vol 199 (1) ◽  
pp. 73-81 ◽  
Author(s):  
K Lohmann ◽  
C Lohmann
Keyword(s):  
Magnetic Field ◽  
Visual Cues ◽  
Sea Turtles ◽  
Positional Information ◽  
Sea Turtle ◽  
Compass Orientation ◽  
Loggerhead Sea Turtle ◽  
Open Sea ◽  
Nesting Beaches ◽  
Field Inclination

Loggerhead sea turtle hatchlings (Caretta caretta L.) emerge from underground nests, scramble to the sea and begin a transoceanic migration by swimming away from their natal beach and into the open ocean. Evidence suggests that hatchlings sequentially use three different sets of cues to maintain orientation during their initial migration offshore. While on the beach, hatchlings find the ocean by crawling towards the lower, brighter seaward horizon and away from the dark, elevated silhouettes of vegetation and dunes. Upon entering the ocean, turtles initially orient seawards by swimming into waves, which can be detected as orbital movements from under water. Laboratory experiments have demonstrated that turtles can transfer a course initiated on the basis of waves or visual cues to a course mediated by a magnetic compass. Thus, by setting a magnetic course on the basis of nearshore cues that indicate the seaward direction, hatchlings may continue on offshore headings after entering deep water beyond sight of land. Sea turtles may use the earth's magnetic field not only as a cue for compass orientation but also as a source of world-wide positional information. Recent experiments have demonstrated that loggerheads can detect subtle differences in magnetic field inclination and intensity, two geomagnetic features that vary across the surface of the earth. Because most nesting beaches and oceanic regions are marked by a unique combination of these features, these findings raise the possibility that adult sea turtles navigate using a bicoordinate magnetic map.

scholarly journals ACQUISITION OF MAGNETIC DIRECTIONAL PREFERENCE IN HATCHLING LOGGERHEAD SEA TURTLES

1994 ◽  
Vol 190 (1) ◽  
pp. 1-8 ◽  
Author(s):  
K Lohmann ◽  
C Lohmann
Keyword(s):  
Magnetic Field ◽  
Visual Cues ◽  
Laboratory Experiments ◽  
Sea Turtles ◽  
Magnetic Orientation ◽  
Loggerhead Sea Turtles ◽  
Preferred Direction ◽  
Open Sea ◽  
Directional Preference ◽  
The Magnetic Field

During their natal migration, hatchling loggerhead sea turtles (Caretta caretta L.) establish courses towards the open ocean and maintain them after swimming beyond sight of land. Laboratory experiments have demonstrated that swimming hatchlings can orient using the earth's magnetic field. For the magnetic compass to function in guiding the offshore migration, however, hatchlings must inherit or acquire a magnetic directional preference that reliably leads them towards the open sea. On land, hatchlings find the ocean using light cues associated with the seaward horizon. To determine whether turtles might acquire a preference for a specific magnetic direction on the basis of such cues, we studied the magnetic orientation of turtles initially exposed to light from either magnetic east or west. Hatchlings that had been exposed to light in the east subsequently oriented eastward when tested in darkness, whereas those that had been exposed to light in the west swam westward. Reversing the magnetic field resulted in a corresponding shift in orientation, indicating that the turtles were orienting to the ambient magnetic field. These results demonstrate that light cues can set the preferred direction of magnetic orientation by loggerhead hatchlings. We therefore hypothesize that hatchlings initially establish a seaward course using visual cues available on or near land, then maintain the course using magnetic cues as they migrate into the open sea.

scholarly journals First report of the scavenging isopod Natatolana neglecta (Crustacea: Isopoda: Cirolanidae) feeding on a sea turtle

2019 ◽  
Vol 20 (2) ◽  
pp. 297
Author(s):  
OHIANA REVUELTA ◽  
FRANCESC DOMÈNECH ◽  
STEPHEN KEABLE ◽  
RAÚL MÍGUEZ-LOZANO
Keyword(s):  
Sea Turtles ◽  
Caretta Caretta ◽  
Sea Turtle ◽  
Dead Sea ◽  
Mediterranean Coast ◽  
Gut Contents ◽  
Post Mortem ◽  
Juvenile Male ◽  
Coelomic Cavity ◽  
Loggerhead Sea Turtle

A juvenile male loggerhead sea turtle (Caretta caretta) was found dead in April 2015, entangled in a trammel net on the Mediterranean coast of Spain. Post-mortem examination revealed the presence of ninety-five isopods dispersed in the coelomic cavity, and inside the oesophagus and skull. All individuals found scavenging on the sea turtle were identified as Natatolana neglecta (Hansen, 1890) (Isopoda: Cirolanidae). Genetic analysis of the isopod gut contents showed that they were feeding on turtle tissue, confirming that N. neglecta can also attack dead sea turtles. This study shows the value of cirolanids as potential indicators of the cause of death in stranded sea turtles.

scholarly journals DETECTION OF MAGNETIC INCLINATION ANGLE BY SEA TURTLES: A POSSIBLE MECHANISM FOR DETERMINING LATITUDE

1994 ◽  
Vol 194 (1) ◽  
pp. 23-32 ◽  
Author(s):  
K Lohmann ◽  
C Lohmann
Keyword(s):  
Inclination Angle ◽  
Sea Turtles ◽  
Positional Information ◽  
Compass Orientation ◽  
Loggerhead Sea Turtles ◽  
Southern Boundary ◽  
The North ◽  
Magnetic Inclination ◽  
Inclination Angles ◽  
Field Lines

For animals that migrate long distances, the magnetic field of the earth provides not only a possible cue for compass orientation, but a potential source of world-wide positional information. At each location on the globe, the geomagnetic field lines intersect the earth's surface at a specific angle of inclination. Because inclination angles vary with latitude, an animal able to distinguish between different field inclinations might, in principle, determine its approximate latitude. Such an ability, however, has never been demonstrated in any animal. We studied the magnetic orientation behavior of hatchling loggerhead sea turtles (Caretta caretta L.) exposed to earth-strength magnetic fields of different inclinations. Hatchlings exposed to the natural field of their natal beach swam eastward, as they normally do during their offshore migration. In contrast, those subjected to an inclination angle found on the northern boundary of the North Atlantic gyre (their presumed migratory path) swam south-southwest. Hatchlings exposed to an inclination angle found near the southern boundary of the gyre swam in a northeasterly direction, and those exposed to inclination angles they do not normally encounter, or to a field inclination found well within the northern and southern extremes of the gyre, were not significantly oriented. These results demonstrate that sea turtles can distinguish between different magnetic inclination angles and perhaps derive from them an approximation of latitude. Most sea turtles nest on coastlines that are aligned approximately north­south, so that each region of nesting beach has a unique inclination angle associated with it. We therefore hypothesize that the ability to recognize specific inclination angles may largely explain how adult sea turtles can identify their natal beaches after years at sea.

Transplastron Enterocentesis to Manage Buoyancy Disorder in an Adult Loggerhead Sea Turtle (Caretta caretta)

2021 ◽  
Author(s):  
Brittany L Liguori ◽  
MAXIMILIAN POLYAK ◽  
Samantha A Clark ◽  
Ashley N Sabater ◽  
Taylor B Clasen ◽  
...  
Keyword(s):  
Gastrointestinal Tract ◽  
Medical Therapy ◽  
Sea Turtles ◽  
Systemic Disease ◽  
Caretta Caretta ◽  
Sea Turtle ◽  
Loggerhead Sea Turtle ◽  
Gas Accumulation ◽  
In The Wild ◽  
Patient Size

Buoyancy disorder in sea turtles is a common condition that contributes to increased morbidity and mortality in the wild and because of this, is often encountered in rehabilitation facilities. The pathological gas accumulation that is a sequelae of this disorder can create challenges in treatment of this disease, especially when concurrent systemic disease is present. These challenges increase with patient size, as anatomy and location of pathology makes gas evacuation more difficult utilizing conventional methods when medical therapy alone is unsuccessful. This report discusses a novel technique utilizing ultrasonic-guided transplastron enterocentesis of the proximal gastrointestinal tract in an adult loggerhead sea turtle ( Caretta caretta ) with suspected intestinal obstruction. The sea turtle presented with positive buoyancy and routine workup revealed gas accumulation in the gastrointestinal tract, as well as concurrent pneumonia. Medical therapy alone did not diminish the positive buoyancy or gastrointestinal distension. Ultrasonic-guided transplastron enterocentesis was performed via the connective tissue lateral to the 3rd inframarginal scute while the turtle was positioned with its left side raised, allowing any gas-filled intestine to be positioned laterally. Approximately 10.3 L of gas were evacuated from the proximal gastrointestinal lumen and within 15 mins, the turtle was neutrally buoyant. It continued to exhibit normal surfacing, diving, and resting behavior. The turtle was released 111 days after enterocentesis in order to allow treatment of the concurrent pneumonia. The technique discussed in this report has implications for improving treatment of buoyancy disorder in large adult sea turtles and increasing likelihood of release.

scholarly journals Relative abundance of oceanic juvenile loggerhead sea turtles in relation to nest production at source rookeries: implications for recruitment dynamics

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Frederic Vandeperre ◽  
Hugo Parra ◽  
Christopher K. Pham ◽  
Miguel Machete ◽  
Marco Santos ◽  
...  
Keyword(s):  
Relative Abundance ◽  
Sea Turtles ◽  
Climatic Variability ◽  
Sea Turtle ◽  
Loggerhead Sea Turtles ◽  
Turtle Species ◽  
Stage Juvenile ◽  
Reproductive Females ◽  
Nesting Beaches ◽  
Nest Abundance

Abstract After hatching, juveniles of most sea turtle species undertake long migrations across ocean basins and remain in oceanic habitats for several years. Assessing population abundance and demographic parameters during this oceanic stage is challenging. Two long-recognized deficiencies in population assessment are (i) reliance on trends in numbers of nests or reproductive females at nesting beaches and (ii) ignorance of factors regulating recruitment to the early oceanic stage. To address these critical gaps, we examined 15 years of standardized loggerhead sighting data collected opportunistically by fisheries observers in the Azores archipelago. From 2001 to 2015, 429 loggerheads were sighted during 67,922 km of survey effort. We used a model-based approach to evaluate the influence of environmental factors and present the first estimates of relative abundance of oceanic-stage juvenile sea turtles. During this period, relative abundance of loggerheads in the Azores tracked annual nest abundance at source rookeries in Florida when adjusted for a 3-year lag. This concurrence of abundance patterns indicates that recruitment to the oceanic stage is more dependent on nest abundance at source rookeries than on stochastic processes derived from short term climatic variability, as previously believed.

Intraerythrocytic inclusion bodies in the loggerhead sea turtle Caretta caretta from Madeira

2000 ◽  
Vol 80 (5) ◽  
pp. 957-958 ◽  
Author(s):  
J.C. Eiras ◽  
T. Dellinger ◽  
A.J. Davies ◽  
G. Costa ◽  
A.P. Alves de Matos
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Inclusion Bodies ◽  
Sea Turtles ◽  
Caretta Caretta ◽  
Sea Turtle ◽  
Loggerhead Sea Turtles ◽  
Loggerhead Sea Turtle ◽  
Intracytoplasmic Inclusion ◽  
Intracytoplasmic Inclusion Bodies

Intracytoplasmic inclusion bodies were detected in the mature red blood cells of twenty juvenile loggerhead sea turtles, Caretta caretta, captured in Madeira. The bodies were mostly single, round to oval, frequently irregular in outline, and their diameter varied from 0.5 to 2.0 μm. Most bodies were associated with small granular areas, often in the form of a tail or projection. In some cells, only granular areas were apparent. The nuclei of most erythrocytes were irregular in outline but degeneration of red blood cells was not observed. The identity of these intraerythrocytic structures is not clear but they may be viral or rickettsial in nature.

A cleaning association between the oceanic crab Planes minutus and the loggerhead sea turtle Caretta caretta

1994 ◽  
Vol 74 (3) ◽  
pp. 735-737 ◽  
Author(s):  
John Davenport
Keyword(s):  
Sea Turtles ◽  
Caretta Caretta ◽  
Sea Turtle ◽  
Loggerhead Sea Turtle ◽  
General Acceptance

Columbus crabs, Planes minutus (L.) (Crustacea: Brachyura) are often found on the postero-ventral surfaces of sea turtles, particularly the loggerhead Caretta caretta (L.) (Testudines: Cheloniidae). There has been a general acceptance of a hypothesis that the crabs feed upon turtle faeces. However, evidence is presented here to demonstrate that Planes has a ‘cleaning’ role, feeding on other epibionts (e.g. barnacle cyprids, parasitic amphipods) during daylight hours. At night it is likely that the crabs feed on neustonic animals (e.g. euphausids). The species is also cannibalistic.

scholarly journals Threatened Sea Turtles in Hawaii Losing Ground to Rising Oceans

Eos ◽  
2017 ◽  
Author(s):  
Alex Fox
Keyword(s):  
Sea Turtles ◽  
Sea Turtle ◽  
Green Sea Turtle ◽  
Nesting Beaches

By midcentury, the Hawaiian green sea turtle could lose nesting beaches of increasing importance on Oahu, the most populous island in the chain.

scholarly journals First record of loggerhead sea turtles Caretta caretta in Sebastián Vizcaíno Bay, Baja California Peninsula, Mexico

2020 ◽  
Vol 48 (1) ◽  
pp. 146-149
Author(s):  
Helena Fernández-Sanz ◽  
Fabián Castillo Romero ◽  
Joaquín Rivera Rodríguez ◽  
Noé López Paz ◽  
Gabriel Arturo Zaragoza Aguilar ◽  
...  
Keyword(s):  
Baja California ◽  
Sea Turtles ◽  
Chelonia Mydas ◽  
Caretta Caretta ◽  
First Record ◽  
Sea Turtle ◽  
Baja California Peninsula ◽  
Loggerhead Sea Turtles ◽  
Biometric Data ◽  
Loggerhead Sea Turtle

The loggerhead sea turtle (Caretta caretta) is an endangered species which distributes around the west coast of the Baja California Peninsula. In Baja California Sur, the conservation efforts for this species were focused in the Gulf of Ulloa; however, within the Pacific coast of the Baja California Peninsula, Sebastián Vizcaíno Bay (SVB) biological active center suit the optimal conditions for the presence of loggerheads. This study aimed to investigate SVB as a potential foraging area for loggerheads. Between July and August 2018, three prospective surveys were conducted, in search of marine turtles in SVB. A total of three loggerhead turtles and one eastern Pacific green turtle (Chelonia mydas) were captured; biometric data were recorded, and organisms were classified as juveniles. This is the first report of the loggerhead sea turtles in the SVB and given the oceanographic characteristics of the bay, it is a potential foraging and development area for the species.

scholarly journals Helminth Infection of the Loggerhead Sea Turtle Caretta caretta along the Coasts of Sicily and the North West Adriatic Sea

Animals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1408
Author(s):  
Antonino Gentile ◽  
Tullia Amato ◽  
Andrea Gustinelli ◽  
Maria Letizia Fioravanti ◽  
Delia Gambino ◽  
...  
Keyword(s):  
Adriatic Sea ◽  
Sea Turtles ◽  
Single Species ◽  
Caretta Caretta ◽  
Sea Turtle ◽  
Helminth Parasites ◽  
Loggerhead Sea Turtles ◽  
Loggerhead Sea Turtle ◽  
North West ◽  
The North

We provide new data on the presence of helminth parasites in 64 individual loggerhead sea turtles Caretta caretta stranded along the coasts of Sicily and the northwest Adriatic Sea between June 2014 and August 2016. The necropsy examination revealed 31 individuals (48.4%) positive for endoparasites, showing a greater prevalence of trematodes than nematodes. In particular, seven species and a single genus of Trematoda (Hapalotrema) and a single species and genus of Nematoda (Kathlania) were identified. Among the Digenea flukes the species with the highest prevalence of infection were Rhytidodes gelatinosus (34.6%) and Hapalotrema sp. (33.3%), while among the Nematoda they were Kathlania sp. (33.3%) and Sulcascaris sulcata (33.3%). Analysis of variance (ANOVA) was applied among the recovery sites of the stranded loggerhead sea turtles and prevalence of endoparasites was used to highlight any relationship between the parasites and the origin of the hosts. ANOVA showed significant differences (p < 0.001) among the data used.

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