scholarly journals Strong male‐biased operational sex ratio in a breeding population of loggerhead turtles ( Caretta caretta ) inferred by paternal genotype reconstruction analysis

2013 ◽  
Vol 3 (14) ◽  
pp. 4736-4747 ◽  
Author(s):  
Jacob A. Lasala ◽  
J. Scott Harrison ◽  
Kris L. Williams ◽  
David C. Rostal
Keyword(s):  
Sex Ratio ◽  
Caretta Caretta ◽  
Breeding Population ◽  
Operational Sex Ratio ◽  
Loggerhead Turtles ◽  
Paternal Genotype

Validation of incubation duration as an index of the sex ratio of hatchling sea turtles

1999 ◽  
Vol 77 (5) ◽  
pp. 831-835 ◽  
Author(s):  
N Mrosovsky ◽  
Cecília Baptistotte ◽  
Matthew H Godfrey
Keyword(s):  
Sex Ratio ◽  
High Temperatures ◽  
Low Temperatures ◽  
Sea Turtles ◽  
Sex Ratios ◽  
Caretta Caretta ◽  
Turtle Species ◽  
Loggerhead Turtles ◽  
Incubation Duration

One method of estimating the sex ratio of hatchling sea turtles is to use the incubation duration. Long and short durations imply low and high temperatures, respectively. In turtle species whose sex is determined by temperature, males are produced at low temperatures and females at high temperatures. This study assesses the validity of using incubation duration to estimate the sex ratio. Samples of hatchling loggerhead turtles (Caretta caretta) were collected from nests with known incubation durations, and sex was ascertained by means of histology. The sex ratio of groups of nests determined by histology was compared with that predicted from previous relationships between incubation duration and sex ratio. For conditions causing relatively long or relatively short incubation durations, the sex ratio could be predicted with considerable accuracy. For conditions causing durations nearer to the pivotal duration (that which gives 50% of each sex), predictions could be off by 10%, depending on the distribution of incubation durations, but it was still possible to determine whether ratios were highly skewed or approximately balanced. Estimating sex ratios of hatchling sea turtles from incubation durations is simple, cheap, and can be used retrospectively.

Estimating sex ratios of loggerhead turtles in Brazil from pivotal incubation durations

1997 ◽  
Vol 75 (5) ◽  
pp. 755-770 ◽  
Author(s):  
Maria Ângela Marcovaldi ◽  
Matthew H. Godfrey ◽  
N. Mrosovsky
Keyword(s):  
Sex Ratio ◽  
Sexual Differentiation ◽  
Sex Ratios ◽  
Caretta Caretta ◽  
Temperature Dependent ◽  
Loggerhead Turtles ◽  
Biased Sex Ratio ◽  
Nesting Beaches

A method of estimating natural sex ratios of hatchlings of species with temperature-dependent sexual differentiation from data on incubation durations is described. The method was applied to loggerhead turtles (Caretta caretta) nesting in Brazil. Data on incubation durations were collected from 11 nesting beaches monitored for up to six seasons. It was estimated that 82.5% of the loggerhead hatchlings produced were female. The strongly female-biased sex ratio in Brazil is similar to that found previously for loggerheads using beaches in the eastern U.S.A. This suggests that a female-biased hatchling sex ratio may be a feature of loggerhead populations.

scholarly journals Large-scale movement patterns of male loggerhead sea turtles (Caretta caretta) in Shark Bay, Australia

2012 ◽  
Vol 63 (11) ◽  
pp. 1108 ◽  
Author(s):  
Erica L. Olson ◽  
Anne K. Salomon ◽  
Aaron J. Wirsing ◽  
Michael R. Heithaus
Keyword(s):  
Breeding Season ◽  
Large Scale ◽  
Sea Turtles ◽  
Spatial Scales ◽  
Management Strategies ◽  
Caretta Caretta ◽  
Breeding Population ◽  
Loggerhead Sea Turtles ◽  
Shark Bay ◽  
Loggerhead Turtles

Large marine vertebrates are particularly susceptible to anthropogenic threats because they tend to be long-lived, late to mature and wide-ranging. Loggerhead sea turtles (Caretta caretta) are characterised by such life history traits and are listed as ‘Endangered’ by The World Conservation Union. Although juvenile movements and at-sea behaviour of adult females are relatively well studied, little is known about the movements of males and their subsequent exposure to threats. Shark Bay, Western Australia, is home to the largest breeding population of loggerhead turtles in Australia. We assessed the large-scale movements of nine adult male loggerhead turtles, with the goal of aiding conservation and management policies. During 7 months outside the breeding season, all nine turtles stayed within the Shark Bay World Heritage Area, with most showing fidelity to small coastal foraging areas. Several turtles, however, showed relatively large movements between core foraging areas. None of the four turtles that continued transmitting through the breeding season exhibited obvious movements towards nesting beaches, suggesting that mating may occur on foraging grounds or that males are not mating every year. Quantifying male loggerhead movements assists conservation planning by identifying biologically relevant spatial scales at which research and management strategies should be designed.

Sex ratio of hatchling loggerhead sea turtles: data and estimates from a 5-year study

1992 ◽  
Vol 70 (3) ◽  
pp. 530-538 ◽  
Author(s):  
N. Mrosovsky ◽  
Jane Provancha
Keyword(s):  
Global Warming ◽  
Sex Ratio ◽  
Sea Turtles ◽  
Sex Ratios ◽  
Caretta Caretta ◽  
Loggerhead Sea Turtles ◽  
Loggerhead Turtles ◽  
Biased Sex Ratio ◽  
Nesting Season

Hatchling loggerhead sea turtles (Caretta caretta) were collected over three nesting seasons from a rookery at Cape Canaveral, Florida. From data on the distribution of nests over the season, we estimated that 92.6–96.7, 94.7–99.9, and 87.0–89.0% of the hatchlings produced on this beach in 1986, 1987, and 1988, respectively, were females. These skewed sex ratios were consistent with the fact that for most of the season, sand temperatures were above the pivotal level for loggerhead turtles. The present results show that the female-biased sex ratio reported previously by these authors for the 1986 nesting season at this site was not an isolated, atypical event. In addition to a total of 3 years of sampling for sex ratio, measurements of beach temperatures at the depth of turtle nests were extended to cover 5 years. These temperatures were commonly above the pivotal level. The strongly female-biased hatchling sex ratio found in this population of loggerhead turtles poses theoretical challenges. It may also complicate conservation efforts, since global warming might be expected to skew the sex ratio still further toward females.

Male-Biased Sex Ratio of Adult-Sized Loggerhead Turtles (Caretta caretta) Migrating to High-Latitude Summer-Restricted Foraging Grounds in the Northwest Pacific1

2020 ◽  
Vol 74 (2) ◽  
Author(s):  
Shohei Kobayashi ◽  
Takuya Fukuoka ◽  
Chihiro Kinoshita ◽  
Katsufumi Sato ◽  
Katsuhiko Arai ◽  
...  
Keyword(s):  
Sex Ratio ◽  
High Latitude ◽  
Caretta Caretta ◽  
Loggerhead Turtles ◽  
Biased Sex Ratio

scholarly journals Reproduction and food habits of the lined seahorse, Hippocampus erectus (Teleostei: Syngnathidae) of Chesapeake Bay, Virginia

2001 ◽  
Vol 61 (1) ◽  
pp. 79-90 ◽  
Author(s):  
R. L. TEIXEIRA ◽  
J. A. MUSICK
Keyword(s):  
Sex Ratio ◽  
Chesapeake Bay ◽  
Breeding Population ◽  
Brood Pouch ◽  
Operational Sex Ratio ◽  
Gammarus Mucronatus ◽  
Turbid Waters ◽  
Hippocampus Erectus ◽  
Mouth Size ◽  
Size Limits

The reproductive and feeding biology of the lined seahorse, Hippocampus erectus, was studied in Chesapeake Bay. Seahorses are monogamous, and males incubate the eggs received from females in a closed brood pouch (= marsupium). Females do not play any parental care after mating. Total sex ratio and the operational sex ratio was strongly skewed toward females. Males and females had similar number of eggs/embryos and hydrated oocytes, respectively. The number of eggs/embryos found in the male brood pouch varied from 97 to 1,552 (fish from 80 to 126 mm TL), whereas the number of hydrated oocytes in female varied from 90 to 1,313 (fish from 60 to 123 mm TL). Both, the number of eggs/embryos and hydrated oocytes were better linearly correlated to total weight than to total length. The small snout and mouth size limits the feeding of the lined seahorse to small prey size. Amphypods were the predominant food items found in the guts, especially Ampithoe longimana, Gammarus mucronatus, and Caprella penantis. The lined seahorse is not abundant in Chesapeake Bay, but keeps a breeding population which is probably brought inside the bay by currents on drifting vegetation. Chances to find a partner may be difficult because of its low abundance, due to turbid waters, and its sedentary behavior.

Sex ratio of loggerhead sea turtles hatching on a Florida beach

1989 ◽  
Vol 67 (10) ◽  
pp. 2533-2539 ◽  
Author(s):  
N. Mrosovsky ◽  
Jane Provancha
Keyword(s):  
Global Warming ◽  
Sex Ratio ◽  
Sea Turtles ◽  
Caretta Caretta ◽  
Loggerhead Sea Turtles ◽  
Histological Criteria ◽  
The Future ◽  
Loggerhead Turtles ◽  
Nesting Season

Hatchling loggerhead sea turtles (Caretta caretta) were collected over the summer nesting season from a major rookery at Cape Canaveral, Florida, in 1986. Sex was assessed using histological criteria. From data on the distribution of nests over the season, we estimated that in 1986, > 93% of the hatchlings produced on this beach were females. This huge bias toward females is consistent with sand temperatures at the depth of turtle nests; for most of the season these temperatures were above the pivotal level for loggerhead turtles. The results suggest that in the future, turtles in this area will encounter difficulty in overcoming the feminizing effect of global warming and that biologists should pay more attention to the beaches at the northern end of the loggerhead's nesting range.

scholarly journals Sex Chromosome Meiotic Drive in Stalk-Eyed Flies

Genetics ◽  
1997 ◽  
Vol 147 (3) ◽  
pp. 1169-1180 ◽  
Author(s):  
Daven C Presgraves ◽  
Emily Severance ◽  
Gerald S Willrinson
Keyword(s):  
Sex Ratio ◽  
Sex Chromosome ◽  
Sex Ratios ◽  
Natural Populations ◽  
Meiotic Drive ◽  
Operational Sex Ratio ◽  
Genetic Modifiers ◽  
Ratio Distortion ◽  
The Impact ◽  
Sex Ratio Distortion

Meiotically driven sex chromosomes can quickly spread to fixation and cause population extinction unless balanced by selection or suppressed by genetic modifiers. We report results of genetic analyses that demonstrate that extreme female-biased sex ratios in two sister species of stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei, are due to a meiotic drive element on the X chromosome (Xd). Relatively high frequencies of Xd in C. dalmanni and C. whitei (13–17% and 29%, respectively) cause female-biased sex ratios in natural populations of both species. Sex ratio distortion is associated with spermatid degeneration in male carriers of Xd. Variation in sex ratios is caused by Y-linked and autosomal factors that decrease the intensity of meiotic drive. Y-linked polymorphism for resistance to drive exists in C. dalmanni in which a resistant Y chromosome reduces the intensity and reverses the direction of meiotic drive. When paired with Xd, modifying Y chromosomes (Ym) cause the transmission of predominantly Y-bearing sperm, and on average, production of 63% male progeny. The absence of sex ratio distortion in closely related monomorphic outgroup species suggests that this meiotic drive system may predate the origin of C. whitei and C. dalmanni. We discuss factors likely to be involved in the persistence of these sex-linked polymorphisms and consider the impact of Xd on the operational sex ratio and the intensity of sexual selection in these extremely sexually dimorphic flies.

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