scholarly journals Magnetic orientation by hatchling loggerhead sea turtles (Caretta caretta)

1991 ◽  
Vol 155 (1) ◽  
pp. 37-49 ◽  
Author(s):  
K. J. Lohmann
Keyword(s):  
Magnetic Field ◽  
Laboratory Experiments ◽  
Caretta Caretta ◽  
Sea Turtle ◽  
Magnetic Orientation ◽  
Complete Darkness ◽  
Loggerhead Sea Turtles ◽  
Loggerhead Sea Turtle ◽  
The Earth ◽  
The Magnetic Field

Laboratory experiments were conducted to test the ability of loggerhead sea turtle hatchlings (Caretta caretta L.) to orient using the magnetic field of the earth. Hatchlings were tethered to a rotatable lever-arm apparatus which tracked swimming orientation in complete darkness. Hatchlings tested in the earth's magnetic field were nonrandomly oriented with a mean angle of 42 degrees; those tested under an earth-strength field with a reversed horizontal component were also nonrandomly oriented, but with a mean angle of 196 degrees. The distributions under the two magnetic field conditions were significantly different, indicating that loggerhead sea turtle hatchlings can detect the magnetic field of the earth and use it as a cue in orientation.

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.

Assessing the Impacts of Human Activities on Nesting of Loggerhead Sea-turtles (Caretta caretta L.) on Zákynthos Island, Western Greece

1988 ◽  
Vol 15 (4) ◽  
pp. 327-334 ◽  
Author(s):  
Margarita Arianoutsou
Keyword(s):  
Human Activities ◽  
Caretta Caretta ◽  
Sea Turtle ◽  
Loggerhead Sea Turtles ◽  
Loggerhead Sea Turtle ◽  
Marine Park ◽  
Sound Management ◽  
Unique Species ◽  
Western Greece ◽  
Beach Use

The island of Zákynthos, in western Greece, supports the most important nesting biotope of the endangered Loggerhead Sea-turtle (Caretta caretta) within Europe. The evaluation of the impacts of human activities, such as beach-use by people, lights, noise, and traffic, on its nesting habitats revealed that they are running out of time under the pressure of rapid and massive tourist development. It is therefore essential for the protection of this unique species to conserve its nesting biotope. This implies adequate, ecologically sound management, which might well be ensured through the establishment of a Marine Park.

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.

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.

The widely occurring brittlestar Ophiactis savignyi (Amphilepidida: Ophiactidae) as an epibiont on loggerhead sea turtle, Caretta caretta

Zootaxa ◽  
2019 ◽  
Vol 4695 (5) ◽  
pp. 497-500
Author(s):  
RYOTA HAYASHI ◽  
MASANORI OKANISHI
Keyword(s):  
New Species ◽  
Sea Turtles ◽  
Caretta Caretta ◽  
Sea Turtle ◽  
The Novel ◽  
Loggerhead Sea Turtles ◽  
Loggerhead Sea Turtle ◽  
First Occurrence

We describe the first occurrence of the widely occurring brittlestar Ophiactis savignyi (Müller & Troschel, 1842) as epibionts on Caretta caretta (Linnaeus, 1758), the loggerhead sea turtles. On the sea turtle epibionts, the coronulid barnacles were well studied as listed in Hayashi (2013), and recently some crustaceans were collected from loggerhead sea turtles and described as new species (Tanabe et al. 2017; Tanaka and Hayashi 2019). In contrast, echinoderm epibionts listed from sea turtles are poorly understood (Table 1) and this study represents the novel discovery of an ophiuroid, which was not previously known to occur on the surface of this species. 

scholarly journals Record of the Loggerhead Sea Turtle, Caretta caretta (Testudines, Cheloniidae), in the Black Sea with the Review of the Species Occurrence in the Region

Zoodiversity ◽  
2021 ◽  
Vol 55 (2) ◽  
pp. 127-132
Author(s):  
O. Zinenko ◽  
K. A. Vishnyakova ◽  
L. Stoyanov ◽  
P. E. Gol’din
Keyword(s):  
Black Sea ◽  
Sea Turtles ◽  
Caretta Caretta ◽  
First Record ◽  
Sea Turtle ◽  
The Black Sea ◽  
Loggerhead Sea Turtles ◽  
Loggerhead Sea Turtle ◽  
The North ◽  
North Western

A rare live record of the loggerhead sea turtle Caretta caretta (Linnaeus, 1758) is reported from the Dzharylgach Gulf in the north-western Black Sea. This is the first record from Ukrainian waters since 1962 and the northernmost record of the species in the Black Sea. The loggerhead sea turtles of the east Mediterranean origin are increasingly often seen in the Marmara and the Black Sea during the latest decade, which is an evidence for potential expansion of this species range, at least partly due to climate changes. Key words: sea turtles, Caretta caretta, Black Sea, Ukraine, range expansion.

MAGNETIC FIELD REVERSALS OF THE EARTH: A TWO–DISK RIKITAKE DYNAMO MODEL

2009 ◽  
Vol 23 (28n29) ◽  
pp. 5492-5503 ◽  
Author(s):  
SANDRO DONATO ◽  
DOMENICO MEDURI ◽  
FABIO LEPRETI
Keyword(s):  
Magnetic Field ◽  
Laboratory Experiments ◽  
Dynamo Model ◽  
The Sun ◽  
The Earth ◽  
Simulation Based ◽  
Dynamical Regimes ◽  
Polarity Reversals ◽  
Disk Dynamo ◽  
The Magnetic Field

The Sun and the Earth possess dipolar magnetic fields that exhibit polarity reversals. Recent works, based on numerical simulations and laboratory experiments, found similar dynamical behaviours. We present results of a statistical analysis of a numerical simulation based on a generalized two–disk dynamo model. From a first investigation, we found that the dynamics of the system is controlled by the variations of the ratio of the torques and we observed different dynamical regimes characterized either by bursts or reversals, which can be periodic or random, of the magnetic field.

scholarly journals The geomagnetic environment in which sea turtle eggs incubate affects subsequent magnetic navigation behaviour of hatchlings

2014 ◽  
Vol 281 (1791) ◽  
pp. 20141218 ◽  
Author(s):  
Matthew J. Fuxjager ◽  
Kyla R. Davidoff ◽  
Lisa A. Mangiamele ◽  
Kenneth J. Lohmann
Keyword(s):  
Magnetic Field ◽  
Sea Turtle ◽  
Northern Coast ◽  
Magnetic Orientation ◽  
Loggerhead Sea Turtle ◽  
Orientation Behaviour ◽  
Migratory Route ◽  
First Time ◽  
Northeastern Atlantic

Loggerhead sea turtle hatchlings ( Caretta caretta ) use regional magnetic fields as open-ocean navigational markers during trans-oceanic migrations. Little is known, however, about the ontogeny of this behaviour. As a first step towards investigating whether the magnetic environment in which hatchlings develop affects subsequent magnetic orientation behaviour, eggs deposited by nesting female loggerheads were permitted to develop in situ either in the natural ambient magnetic field or in a magnetic field distorted by magnets placed around the nest. In orientation experiments, hatchlings that developed in the normal ambient field oriented approximately south when exposed to a field that exists near the northern coast of Portugal, a direction consistent with their migratory route in the northeastern Atlantic. By contrast, hatchlings that developed in a distorted magnetic field had orientation indistinguishable from random when tested in the same north Portugal field. No differences existed between the two groups in orientation assays involving responses to orbital movements of waves or sea-finding, neither of which involves magnetic field perception. These findings, to our knowledge, demonstrate for the first time that the magnetic environment present during early development can influence the magnetic orientation behaviour of a neonatal migratory animal.

scholarly journals Nesting Patterns of Loggerhead Sea Turtles (Caretta caretta): Development of a Multiple Regression Model Tested in North Carolina, USA

2018 ◽  
Vol 7 (9) ◽  
pp. 348 ◽  
Author(s):  
Joanne Halls ◽  
Alyssa Randall
Keyword(s):  
North Carolina ◽  
Negative Binomial ◽  
Management Strategies ◽  
Temporal Trends ◽  
Caretta Caretta ◽  
Sea Turtle ◽  
Multiple Regression Model ◽  
Loggerhead Sea Turtles ◽  
Loggerhead Sea Turtle ◽  
Nesting Patterns

Numerous environmental conditions may influence when a female Loggerhead sea turtle (Caretta caretta) selects a nesting site. Limited research has used Geographic Information Systems (GIS) and statistical analysis to study sea turtle spatial patterns and temporal trends. Therefore, the goals of this research were to identify areas that were most prevalent for nesting and to test social and environmental variables to create a nesting suitability predictive model. Data were analyzed at all barrier island beaches in North Carolina, USA (515 km) and several variables were statistically significant: distance to hardened structures, beach nourishment, house density, distance to inlets, and beach elevation, slope, and width. Interestingly, variables that were not significant were population density, proximity to the Gulf Stream, and beach aspect. Several statistical techniques were tested and Negative Binomial Distribution produced good regional results while Geographically Weighted Regression models successfully predicted the number of nests with an average of 75% of the variance explained. Therefore, the combination of traditional and spatial statistics provided insightful predictive modeling results that may be incorporated into management strategies and may have important implications for the designation of critical Loggerhead nesting habitats.

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