eDNA metabarcoding for diet analyses of green sea turtles (Chelonia mydas)

AbstractUnderstanding sea turtle diets can help conservation planning, but their trophic ecology is complex due to life history characteristics such as ontogenetic shifts and large foraging ranges. Studying sea turtle diet is challenging, particularly where ecological foraging observations are not possible. Here, we test a new minimally invasive method for the identification of diet items in sea turtles. We fingerprinted diet content using DNA from esophageal and cloacal swab samples by metabarcoding the 18S rRNA gene. This approach was tested on samples collected from green turtles (Chelonia mydas) from a juvenile foraging aggregation in the Bijagós archipelago in Guinea-Bissau. Esophagus samples (n = 6) exhibited a higher dietary richness (11 ± 5 amplicon sequence variants (ASVs) per sample; average ± SD) than cloacal ones (n = 5; 8 ± 2 ASVs). Overall, the diet was dominated by red macroalgae (Rhodophyta; 48.2 ± 16.3% of all ASVs), with the main food item in the esophagus and cloaca being a red alga belonging to the Rhodymeniophycidae subclass (35.1 ± 27.2%), followed by diatoms (Bacillariophyceae; 7.5 ± 7.3%), which were presumably consumed incidentally. Seagrass and some invertebrates were also present. Feeding on red algae was corroborated by field observations and barcoding of food items available in the benthic habitat, validating the approach for identifying diet content. We conclude that identification of food items using metabarcoding of esophageal swabs is useful for a better understanding of the relationships between the feeding behavior of sea turtles and their environment.

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Chelonocytherois omutai gen. et sp. nov. (Crustacea: Ostracoda) from the back of loggerhead sea turtles

Zootaxa ◽

10.11646/zootaxa.4624.4.4 ◽

2019 ◽

Vol 4624 (4) ◽

pp. 507-522 ◽

Cited By ~ 1

Author(s):

HAYATO TANAKA ◽

RYOTA HAYASHI

Keyword(s):

New Genus ◽

Sea Turtles ◽

Sea Turtle ◽

18S Rrna Gene ◽

Rrna Gene ◽

Long Distance ◽

Loggerhead Sea Turtles ◽

Yakushima Island ◽

Molecular Phylogenetic ◽

Dispersal Vector

Chelonocytherois omutai gen. et sp. nov., is found on the back of female loggerhead sea turtles on the nesting beach of the Yakushima Island, Kagoshima Prefecture, Japan. The present study provides the first species-level identification and description of Ostracoda as sea turtle epibionts. The new genus and species, which belongs to the family Paradoxostomatidae Brady and Norman, 1889, can clearly be distinguished from other genera by the morphology of the carapace and the appendages. Especially, the quite large sieve structure on the pore system of the carapace is characteristic to this genus. Although a similar structure is also found in the commensal ostracod genus Redekea de Vos, 1953, the new genus has distinctive mandibular and maxillular morphologies. From examination of the appendages, C. omutai gen. et sp. nov. seems to be an epibiotic species associated with sea turtles, but not a strictly commensal species. Additionally, the nearly complete 18S rRNA gene sequence is determined for C. omutai gen. et sp. nov. for future molecular phylogenetic studies. Since the sea turtles migrate across the oceans in their ontogenetic stages, they may play a role as a long-distance dispersal vector for C. omutai gen. et sp. nov.

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Red blood cell osmotic fragility in healthy loggerhead and green sea turtles

Journal of Veterinary Diagnostic Investigation ◽

10.1177/1040638720957117 ◽

2020 ◽

Vol 32 (6) ◽

pp. 908-911

Author(s):

Rebecca Radisic ◽

Sean D. Owens ◽

Charles A. Manire ◽

Nicole Montgomery ◽

Doug Mader ◽

...

Keyword(s):

Blood Cell ◽

Red Blood Cell ◽

Sea Turtles ◽

Osmotic Fragility ◽

Chelonia Mydas ◽

Sea Turtle ◽

Green Sea Turtles ◽

Nacl Concentration ◽

Life Threatening ◽

Rehabilitation Facilities

Loggerhead ( Caretta caretta; Cc) and green sea ( Chelonia mydas; Cm) turtles admitted to rehabilitation facilities may require blood transfusions for supportive treatment of disorders resulting in life-threatening anemia, but, considering the unique erythrocyte chemistry of sea turtles, standardized donor red blood cell (RBC) storage protocols have not been established. Prolonged cold storage and the effects of various anticoagulant-preservative solutions have been associated with increased RBC osmotic fragility across a broad range of species. Increased RBC fragility in stored RBC products has been associated with acute transfusion reactions. The osmotic fragility test is used to measure erythrocyte resistance to hemolysis while being exposed to a series of dilutions of a saline solution. We obtained baseline measurements for osmotic fragility in healthy Cc and Cm. Osmotic fragility testing was performed on samples from 10 Cc to 10 Cm. Fifty percent (50%) RBC hemolysis was identified at a mean NaCl concentration of 0.38% in both species. Results of our study will help guide future studies evaluating optimal storage solutions for sea turtle blood products.

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Predation on green sea turtle, Chelonia mydas, hatchlings by invasive rats

Pacific Conservation Biology ◽

10.1071/pc18087 ◽

2019 ◽

Vol 25 (4) ◽

pp. 423 ◽

Cited By ~ 2

Author(s):

Markus Gronwald ◽

Quentin Genet ◽

Margaux Touron

Keyword(s):

Food Source ◽

Sea Turtles ◽

Rattus Rattus ◽

Chelonia Mydas ◽

Sea Turtle ◽

French Polynesia ◽

Camera Traps ◽

Green Sea Turtle ◽

Green Sea Turtles ◽

Invasive Rats

We used camera traps to identify invasive Rattus rattus as predators at a green sea turtle, Chelonia mydas, nest in French Polynesia. The footage shows that the hatchlings are a familiar food source for rats and that the control of invasive rats has to be considered for the protection of endangered green sea turtles.

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Estimating past and present sex ratios of sea turtles in Suriname

Canadian Journal of Zoology ◽

10.1139/z96-033 ◽

1996 ◽

Vol 74 (2) ◽

pp. 267-277 ◽

Cited By ~ 86

Author(s):

Matthew H. Godfrey ◽

N. Mrosovsky ◽

R. Barreto

Keyword(s):

Sea Turtles ◽

Sex Ratios ◽

Negative Relationship ◽

Chelonia Mydas ◽

Sea Turtle ◽

Dermochelys Coriacea ◽

Green Turtles ◽

Sand Temperature ◽

Turtle Conservation ◽

Sea Turtle Conservation

Leatherback (Dermochelys coriacea) and green (Chelonia mydas) sea turtles in Suriname lay eggs over several months of the year. During this nesting season, changes in rainfall produce changes in sand temperature, which in turn influence the sexual differentiation of incubating sea turtle embryos. The overall sex ratio of leatherback and green sea turtle hatchlings produced at Matapica beach in Suriname was investigated. Estimates of the sex ratios of these turtles in 1993 (green turtles 63.8% female, leatherbacks 69.4% female) were roughly 10% more female-biased than those from an earlier study in 1982. For both species, a significant negative relationship was found between monthly rainfall and monthly sex ratios. Using this relationship and data on rainfall in the past, it was possible to estimate overall sex ratios for an additional 12 years. These estimates varied considerably among different years, ranging from 20 to 90% female in the case of green turtles. Nevertheless, males tended to be produced primarily in April and May, while some females were produced in all months. Such seasonal patterns of production of turtles of different sexes have implications for sea turtle conservation programs that involve manipulating or harvesting eggs.

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Incidental capture of sea turtles by industrial bottom trawl fishery in the Tropical South-western Atlantic

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315417000352 ◽

2017 ◽

Vol 98 (6) ◽

pp. 1525-1531 ◽

Cited By ~ 5

Author(s):

Suzana Machado Guimarães ◽

Davi Castro Tavares ◽

Cassiano Monteiro-Neto

Keyword(s):

Sea Turtles ◽

Action Plan ◽

Chelonia Mydas ◽

Sea Turtle ◽

Bottom Trawl ◽

Conservation Strategies ◽

Future Research ◽

Olive Ridley ◽

Western Atlantic ◽

Turtle Species

The five sea turtle species occurring in Brazilian waters are susceptible to threats, including incidental catches by fisheries. Studies on incidental captures in fishing gears are the main focus of several conservation actions due to high sea turtle fishery mortality worldwide. This study provides the first evaluation of incidental sea turtle catches by industrial bottom trawl fisheries operating in Brazilian waters. Four twin-trawler vessels were monitored between July 2010 and December 2011 by captains who voluntarily completed logbooks. Forty-four turtles were captured during the 1996 tows (8313 fishing hours), resulting in a catch of 5.3 ± 0.8 turtles per 1000 h per unit effort. Captured species included the loggerhead turtle (Caretta caretta, 22 individuals), olive ridley turtles (Lepidochelys olivacea, 21 individuals) and one green turtle (Chelonia mydas). Water depth was the only variable that significantly affected sea turtle captures according to Generalized Linear Models. The capture rates reported in this study ranked sixth in relation to other published studies of similar fisheries occurring worldwide. Considering the importance of this region for sea turtles, the increasing evidence of sea turtle mortality and the goals of the National Action Plan for Conservation of Sea Turtles in Brazil, it is essential to identify the main threats towards these animals and propose mitigating solutions to reduce sea turtle mortality induced by fishing activities. This study provides results that may guide future research and goals in meeting sea turtle conservation strategies.

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Population dynamic between vulnerable coastal jaguars (Panthera onca) and endangered green sea turtles (Chelonia mydas) in Tortuguero National Park, Costa Rica.

10.7287/peerj.preprints.26915 ◽

2018 ◽

Author(s):

Stephanie Butera ◽

Jaime Restrepo

Keyword(s):

National Park ◽

Sea Turtles ◽

Chelonia Mydas ◽

Sea Turtle ◽

Predator Prey ◽

Green Sea Turtles ◽

Turtle Population ◽

Nest Depredation ◽

The Impact ◽

Nest Predators

New-born sea turtles face a number of predators between the time the mothers lay eggs on the beach to when the hatchlings grow into larger juveniles. Nest depredation impacts reproductive success of nesting sea turtles, reducing the number of new turtles that make it to the sea. On Tortuguero beach nest predators include; dogs, coati, and raccoons. Nest depredation within Tortuguero National Park (TNP) has decreased dramatically since 1979. This decrease in nest depredation is linked to the increased jaguar population within TNP as the aforementioned species are considered the jaguars natural prey. Although jaguars prey on nesting turtles, they also control the populations of nest predators. Even more, jaguars have been demonstrated to change their behaviour to suit their preference in prey species therefore the nest predator distribution in TNP was examined to investigate whether changes in jaguar prey preference had an effect. Nest predation and the number of adult turtles lost to jaguar depredation were examined to determine the significance of the threat jaguars pose to the sea turtle population. This study investigates the predator prey relationship between jaguars, nest predators, and nesting female sea turtles; aiming to assessing the impact that jaguars have on the turtle's population.

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Revealing Sea Turtle Behavior in Relation to Fishing Gear Using Color-Coded Spatiotemporal Motion Patterns With Deep Neural Networks

Frontiers in Marine Science ◽

10.3389/fmars.2021.785357 ◽

2021 ◽

Vol 8 ◽

Author(s):

Janie L. Reavis ◽

H. Seckin Demir ◽

Blair E. Witherington ◽

Michael J. Bresette ◽

Jennifer Blain Christen ◽

...

Keyword(s):

Sea Turtles ◽

Marine Species ◽

Chelonia Mydas ◽

Sea Turtle ◽

Time Frame ◽

Visual Object ◽

Fishing Gear ◽

Motion Patterns ◽

Incidental Capture ◽

Marine Megafauna

Incidental capture, or bycatch, of marine species is a global conservation concern. Interactions with fishing gear can cause mortality in air-breathing marine megafauna, including sea turtles. Despite this, interactions between sea turtles and fishing gear—from a behavior standpoint—are not sufficiently documented or described in the literature. Understanding sea turtle behavior in relation to fishing gear is key to discovering how they become entangled or entrapped in gear. This information can also be used to reduce fisheries interactions. However, recording and analyzing these behaviors is difficult and time intensive. In this study, we present a machine learning-based sea turtle behavior recognition scheme. The proposed method utilizes visual object tracking and orientation estimation tasks to extract important features that are used for recognizing behaviors of interest with green turtles (Chelonia mydas) as the study subject. Then, these features are combined in a color-coded feature image that represents the turtle behaviors occurring in a limited time frame. These spatiotemporal feature images are used along a deep convolutional neural network model to recognize the desired behaviors, specifically evasive behaviors which we have labeled “reversal” and “U-turn.” Experimental results show that the proposed method achieves an average F1 score of 85% in recognizing the target behavior patterns. This method is intended to be a tool for discovering why sea turtles become entangled in gillnet fishing gear.

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Occurrence of sea turtles during seismic surveys in Northeastern Brazil

Biota Neotropica ◽

10.1590/s1676-06032006000100004 ◽

2006 ◽

Vol 6 (1) ◽

Cited By ~ 5

Author(s):

Cristiano Leite Parente ◽

Juliana Doyle Lontra ◽

Maria Elisabeth de Araújo

Keyword(s):

Sea Turtles ◽

Low Frequency ◽

Chelonia Mydas ◽

Sea Turtle ◽

Reproductive Period ◽

Northeastern Brazil ◽

Seismic Survey ◽

Shallow Waters ◽

Seismic Surveys ◽

Lepidochelys Olivacea

There are seven species of sea turtles around the world. Among these, five visit the northeast coast of Brazil to reproduce and feed. These sea turtles are impacted by human activity and need conservation measures. The seismic survey is one of these activities due to its high intensity and low frequency sound emissions in the marine environment. Records of sea turtles during seismic surveys in shallow waters of the northeast of Brazil between 2002 and 2003 are presented in this study with some discussion about the effectiveness of the monitoring procedures. Three species of sea turtle were recorded within the seismic survey areas. The Chelonia mydas species was the most commonly sighted turtle. There was only one record of Caretta caretta and Lepidochelys olivacea. The presence of sea turtles in Sergipe state was linked to the reproductive period while this pattern was not observed in Ceará state. The absence of information about distribution and abundance of sea turtles in the surveyed areas previous to and after the seismic surveys, as well as numerous incomplete data make it hard to identify the effect of seismic surveys on those factors and also sea turtle behaviors.

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Lipid profiling suggests species specificity and minimal seasonal variation in Pacific Green and Hawksbill Turtle plasma

PLoS ONE ◽

10.1371/journal.pone.0253916 ◽

2021 ◽

Vol 16 (7) ◽

pp. e0253916

Author(s):

Chelsea E. Clyde-Brockway ◽

Christina R. Ferreira ◽

Elizabeth A. Flaherty ◽

Frank V. Paladino

Keyword(s):

Sea Turtles ◽

Multiple Reaction Monitoring ◽

Chelonia Mydas ◽

Sea Turtle ◽

Lipid Classes ◽

Plasma Samples ◽

Lipid Profiling ◽

Eretmochelys Imbricata ◽

Species Specific ◽

Hawksbill Turtles

In this study, we applied multiple reaction monitoring (MRM)-profiling to explore the relative ion intensity of lipid classes in plasma samples from sea turtles in order to profile lipids relevant to sea turtle physiology and investigate how dynamic ocean environments affect these profiles. We collected plasma samples from foraging green (Chelonia mydas, n = 28) and hawksbill (Eretmochelys imbricata, n = 16) turtles live captured in North Pacific Costa Rica in 2017. From these samples, we identified 623 MRMs belonging to 10 lipid classes (sphingomyelin, phosphatidylcholine, free fatty acid, cholesteryl ester, phosphatidylserine, phosphatidylinositol, phosphatidylglycerol, phosphatidylethanolamine, ceramide, and triacylglyceride) and one metabolite group (acyl-carnitine) present in sea turtle plasma. The relative ion intensities of most lipids (80%) were consistent between species, across seasons, and were not correlated to body size or estimated sex. Of the differences we observed, the most pronounced was the differences in relative ion intensity between species. We identified 123 lipids that had species-specific relative ion intensities. While some of this variability is likely due to green and hawksbill turtles consuming different food items, we found indications of a phylogenetic component as well. Of these, we identified 47 lipids that varied by season, most belonging to the structural phospholipid classes. Overall, more lipids (n = 39) had higher relative ion intensity in the upwelling (colder) season compared to the non-upwelling season (n = 8). Further, we found more variability in hawksbill turtles than green turtles. Here, we provide the framework in which to apply future lipid profiling in the assessment of health, physiology, and behavior in endangered sea turtles.

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West Florida Shelf pipeline serves as sea turtle benthic habitat based on in situ towed camera observations

Aquatic Biology ◽

10.3354/ab00722 ◽

2019 ◽

Vol 29 ◽

pp. 17-31 ◽

Cited By ~ 1

Author(s):

HA Broadbent ◽

SE Grasty ◽

RF Hardy ◽

MM Lamont ◽

KM Hart ◽

...

Keyword(s):

Habitat Use ◽

Sea Turtles ◽

Sea Turtle ◽

Environmental Data ◽

Benthic Habitat ◽

West Florida Shelf ◽

Benthic Habitats ◽

Florida Shelf ◽

Turtle Species

The use of marine offshore benthic habitats by sea turtles is poorly characterized due to the difficulty of obtaining in situ data. Understanding benthic habitat use that is important to the species’ reproduction, foraging, and migrations is critical for guiding management decisions. A towed camera-based assessment survey system (C-BASS) equipped with environmental sensors was used to characterize and assess benthic habitats on the West Florida Shelf (WFS) from 2014 to 2018. During these cruises, sea turtles were opportunistically observed during the surveys, and critical in situ data such as spatiotemporal information, species identification, habitat use, behavior, and environmental data were collected and evaluated. In total, 79 sea turtles were observed during 97 transects of approximately 2700 km of seafloor, which was recorded on 380 h of video. Several sea turtle species were spotted within the WFS, including loggerhead Caretta caretta, Kemp’s ridley Lepidochelys kempii, and green turtles Chelonia mydas. These opportunistic sightings revealed an area of high use on the WFS, an anthropogenic structure known as the Gulfstream natural gas pipeline (GSPL). C-BASS survey results suggest that 2 sea turtle species (C. caretta and L. kempii) utilize this artificial structure primarily as a resting area. We emphasize the importance of combining habitat mapping techniques (towed underwater video and multibeam bathymetry/backscatter) with tracking technology to better understand the fine-scale habitat use of sea turtles.

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