Immaculate Conception, Incubation Protocols, and Egg Characteristics of the Ganges Softshell Turtle (Aspideretes Gangeticus) (original) (raw)
Related papers
Aquaculture, 2007
Understanding the effects of incubation temperature on embryos and hatchlings may have important implications for husbandry and conservation in turtles. Unfortunately, such knowledge is deficient for most Asian turtles. We incubated eggs of the Chinese three-keeled pond turtle (Chinemys reevesii) at 6 constant temperatures (24, 26, 28, 30, 32 and 34°C) to test for the effects of embryonic thermal environment on incubation duration, hatching success, hatchling size and mass, sex ratio and post-hatching growth. Incubation duration (ID) decreased nonlinearly as the temperature (T) increased, and could be estimated by the equation: ID = 42.74 ⁎ exp (4.30 / (T − 17.28). Eggs incubated at 32°C and 34°C had lower hatching success than those at 24°C, 26°C and 28°C. The turtle showed a Male-Female pattern of temperature-dependent sex determination (MF or TSDIa), with male bias at low temperatures (24°C and 26°C), and female bias at high temperatures (30°C, 32°C, and 34°C). The relationship between sex ratio (SR) and temperature (T) could be estimated by a nonlinear equation, SR = 0.025 + 0.923 / (1 + exp (− (T − 30.03) / 0.009)) 0.006. Hatchlings from eggs incubated at 24, 26 and 28°C were larger and heavier than their counterparts at 30°C, 32°C and 34°C. However, the temperature influence on hatchling size disappeared when the turtles were 3 months old, while most hatchlings from eggs incubated at 34°C did not survive. After 3 months, female turtles from 30°C and 32°C grew faster than did male turtles from 24°C and 26°C; females from 28°C grew significantly faster than males from the same temperature. In contrast, there was no difference in growth rate either within females or within males from different temperatures. The dichotomy of growth rate between turtles from high vs low temperatures are thus largely attributed to between-sex difference rather than temperature effects. Taken together, our results indicate that the temperatures ranging from 28 to 30°C are most suitable for egg incubation in C. reevesii, because of the high hatchability and post-hatching survival, and the fastest growth of hatchlings in these thermal regimes. Small hatchling turtles may catch up in the subsequent post-hatching growth if provided with a suitable husbandry environment, given that turtle size at hatching is not a determinant of growth in this species.
Clutch Size and Incubation Temperatures of Green Turtle Eggs
Since clutch size of sea turtle eggs, through metabolic heating, can affect incubation temperatures. a study was conducted on Redang Island, Malaysia to look into the magnitude of this effect and its possible influence on sex determination of hatchlings. Miniature self-recording temperature loggers were used to monitor the incubation temperatures of relocated green turtle nests with 0, 5, 25, 50, 75, and 100 eggs at 60cm depth. Incubation temperatures were not constant but changed depending on weather, season, period of incubation and clutch size. The differential effects of metabolic heating on nest temperature due to clutch size only became evident after the first-th ird of incubation. These effects increase as the incubation progresses until hatching. Metabolic heating effects were greater in larger clutches compared to smaller clutch sizes. Incubation temperature reached its maximum after approximately 45 days of incubation. Clutch size can have a significant impact on incubation temperature through metabolic heating but may not necessarily influence significantly the sex ratio output of hatchlings.
Aquaculture, 2007
Incubation of northern snake-necked turtle (Chelodina rugosa) eggs and subsequent sale of hatchlings for the pet industry has the potential to provide culturally suitable employment for indigenous communities in northern Australia. Developmental arrest in response to egg inundation is unique to C. rugosa. Eggs can be stored under water for up to 10 weeks without appreciable impact on egg or embryo survival, allowing the transport and sale of eggs into niche markets without high levels of mortality, and permitting eggs to accumulate in diapause until there are sufficient numbers to incubate as batches. Eggs that are not inundated or inundated for short periods experience similar survival rates to eggs inundated for lengthy periods. Incubation temperature influences embryo survival and development period in C. rugosa. Embryonic survival is greatest at 26°C, steadily declining as temperature increases to 32°C. A similar increase in incubation temperature decreases incubation period by approximately 40 days, however almost half of this variation is attributed to the increase in incubation temperature from 26 to 28°C. Hatchling growth in C. rugosa is characterized by two phases. There is an initial phase of relatively slow growth under the partial influence of initial egg size and incubation duration, followed by a second phase of relatively rapid growth under the partial influence of water temperature and mass at hatching. Posthatching survival is negatively correlated with duration of egg inundation and water temperature. Evidence suggests that inundation of C. rugosa eggs for 6 weeks, incubation of embryos at 28°C and raising hatchlings in 28°C water will yield the best overall outcomes.
Some analyses of artificially incubated eggs and hatchlings of Green and Loggerhead sea turtles
Journal of Zoology, 1969
Eggs of the Green sea turtle (Chefonia mydas) and the Loggerhead sea turtle (Caretta carettu) were incubated in coral sand or silica sand moistened with distilled water. The eggs and hatchlings were analysed for calcium, magnesium and phosphorus. There was less magnesium but more calcium in the hatchlings than in the original egg contents but this was not influenced by the type of sand used during incubation. The results are interpreted as indicating that the eggshell is the major source of calcium for the developing embryos. The Loggerhead sea turtle shows a greater efficiency in the incorporation of yolk magnesium and phosphorus into the embryo than does the Green sea turtle.
Conservation …, 2010
Although widespread in South America, the yellow-headed sideneck turtle Podocnemis unifilis is considered 'Vulnerable' in Venezuela. A large proportion of eggs of this riverine species may be lost due to predation (including collection by humans) and flooding. As a technique to enhance reproductive success, transfer of wild-laid eggs to protected zones for incubation has been successfully carried out. This study undertaken in 2009, evaluated the hatch success of clutches transferred to artificial nest chambers at protected locations compared with natural clutches left in situ along stretches of the Cojedes and Manapire rivers (Venezuela). Along the Cojedes River, 78 turtle nests were located, 27 of which were excavated and eggs transferred for incubation. In the Manapire River, 87 nests were located, eggs from 13 of which were transferred for incubation. In the Cojedes River, 28.2% of study clutches (n=22) were lost due to predation and flooding; in the Manapire River, 85% of nests (n=74) were lost due to predation (humans and other animals). At Cojedes River, hatching success of eggs in artificial nests was 88.2% and 63.2% in natural nests. At Manapire River, hatching success of eggs in artificial nests was 42% and 0% in natural nests.
The study is a pioneering effort for sea turtle research and conservation in Karwar, Karnataka, India. I conducted this study as part of my Masters dissertation in Marine Biology between the years 2000 and 2002.The nesting species found through our field survey was the olive ridley turtle.Our first sighting was during a night survey along the Devbag beach of Karwar, and a clutch of 64 eggs was found laid by the turtle near the ipomea-pes-caprae. From a conservation perspective-as these are consumed by the local community- the 64 eggs, and several other clutches salvaged from the fish market, were relocated into a hatchery on the Devbag beach. Low hatching rates from these clutches resulted in the investigation of environmental factors that influenced the hatching success.The environmental variables included temperature(soil), nest depth, moisture, and sand type. The hatchlings that emerged from the clutches were also reared for three months both from a research and conservation perspective. Feeding patterns, behavior towards light during release, and other parameters (not detailed in the paper) were recorded in this study. To date there have been just few studies of sea turtles along Karnataka's coast, and this has been an important study. Although the paper could not afford detailed acknowledgements due to limits prescribed for text size, I would like to acknowledge a few names here: Mr.B.K Dikshit-District Forest Officer of Karwar, and RFO, Mr.D 'Souza, who I sought permission for work on turtles (the permission was granted despite the fact they had no evidence if sea turtles visited Karwar coast). Eventually as I submitted proof of sea turtle eggs on sale in the Karwar market, and the nesting turtle on Devbag beach, they joined in the effort enthusiastically, by offering facilities such as a hatchery for relocation of turtle nests, and a steel tank to raise hatchlings. There were also other staff who were extremely helpful with my work ; Dr.Rajgopalan, a sea turtle researcher himself,and Senior Scientist from the Central Marine Fisheries, in 2003, allowed me the privilege of being a resource person, and presenting my work during the GOI-UNDP-WII-CMFRI organized turtle workshop in Cochin, happening after a gap of 20 years, since the last held in the 1980's. After my presentation in the workshop, Dr. Kartik Shanker who was a participant and resource person, invited me to share this work in his publication- Kachhappa. Dr. Shanker took much pains to review the report, and got it to good shape, the form you are now reading :). This study was a major beginning in my turtle story, and the support and nurturing efforts provided by these wonderful people have come a long way in sustaining my turtle career until today.
Basic and Applied Herpetology, 2013
We monitored reproductive females of Emys orbicularis and Mauremys leprosa during the summer of 2001 in Doñana National Park. Radiographs revealed that females of both species may lay at least two clutches from May to July. We recorded incubation temperatures in one nest of each species, and found them to be 24.7ºC in E. orbicularis and 28.7ºC in M. leprosa. Egg incubation lasted 83 days in E. orbicularis, with all the hatchlings remaining in the nest until we extracted them in October, and 46-53 days in M. leprosa, with three hatchlings emerging one to 12 days after hatching, and three hatchlings remaining in the nest. We detected M. leprosa hatchlings in their first trip to the pond from late August to early October and E. orbicularis hatchlings from September 18 th to September 23 rd .
A captive breeding program for the critically endangered Chitra chitra (Testudines: Trionychidae) at Kanchanaburi Inland Fisheries Development Center (KIFDC), Thailand, produced 710 hatchlings between 2000 and 2004, with eggs being incubated in shaded areas only. Thirty-one captive bred C. chitra that died during rearing were dissected and their gonads examined histologically and microscopically to determined if they were ovaries or testes. Of the 29 samples that could be sexed, 23 were males and 6 were females (79% males). The male biased sex ratio in captive-bred C. chitra indicates that the incubation conditions at KIFDC, which are likely to be cooler than in natural nests on sun exposed river sand banks, may have had a masculinising effect on hatchlings. This is potentially contrary to the generally accepted wisdom that softshell turtles have genotypic sex determination and that incubation temperature has no effect on hatchling sex ratios. Although we cannot formally rule out di...