Chelonian Eggs Research Articles

Consumption of wildlife-origin products by local residents at the largest wildlife market of Amazonian Peru: is there scope for demand reduction?

Wildlife and wildlife-origin products are illegally traded across Peru, with negative consequences for animal welfare, conservation, human health and livelihoods. We surveyed residents of Iquitos who regularly shop at Belén Market, the largest open-air market selling wildlife in the Peruvian Amazon. We wished to assess what proportion of the local population purchases wildlife for personal use, to determine the involvement of the local population in the wider national trade of Peruvian wildlife, and to assess whether information campaigns could reduce demand for these products among local consumers. We derived 265 responses. The principal purchases were meat from domesticated animals, and fish: 89.4% of respondents bought these on every or most visits. By comparison 75.1% purchased bushmeat, but only 3.0% did so frequently, and 58.1% purchased chelonian eggs, with < 1% doing so frequently. Percentages purchasing wildlife pets, and wildlife-origin artefacts and remedies were low (all under 14.7% of respondents). There was no evidence that respondents were selling wildlife or wildlife-origin products into the national wildlife trade. Over 90% of respondents held negative views of both animal welfare and conservation impacts of the capture of wildlife for sale, with lower proportions expressing negative views of issues surrounding zoonotic disease risks and illegality. When shown statements detailing these impacts, 51.3% of respondents stated they would be less likely to buy wildlife-origin products in the future. When asked to state which aspects of the Belén Market they would change, however, only six respondents referenced the sale of wildlife, with the vast majority (>95%) referencing levels of orderliness, hygiene or personal security at the market. Despite widespread consumption of bushmeat – albeit relatively infrequently - among respondents in Iquitos, many respondents to our questionnaire disliked the associated negative impacts, sufficient that making such impacts salient through repeated demand-reduction messaging might be expected to lower the likelihood of such purchases in the future. Such interventions should, however, be accompanied by action to address structural issues within the market.

Parataxonomy and palaeobiogeographic significance of dinosaur eggshell fragments from the Upper Cretaceous strata of the Cauvery Basin, South India

In the past, fossilised dinosaur eggshells have been extensively documented from the Upper Cretaceous Lameta Formation of Central India and as many as nine oospecies are known at present from this formation. Compared to this, only one dinosaur oospecies has been described from the Cretaceous succession of the Cauvery Basin. However, the first fossil egg from India, identified as a chelonian egg, was documented from the Aptian – Albian Karai Formation of the Cauvery Basin in 1957. Following this, a solitary titanosaurid dinosaur egg was described from the Upper Cretaceous (Lower Maastrichtian) Kallankuruchhi Formation, Cauvery Basin in 1996. More recently, we have recovered isolated eggshell fragments from the marine part of the Upper Cretaceous (Late Maastrichtian) Kallamedu Formation. Based on eggshell morphology, microstructure and ultrastructure, these eggshell fragments are assigned to the oospecies Fusioolithus baghensis. The new find from the Cauvery Basin is important from palaeobiogeographic point of view as the oofamily Fusioolithidae is found in the Upper Cretaceous strata of India, France, Argentina and Morocco. Based on the common occurrence of similar oospecies in South America, Africa, Europe and India, a Late Cretaceous palaeobiogeographic connection between India and South America as well as Europe via Africa is suggested.

A new approach for measuring temperature inside turtle eggs.

For turtles, the thermal environment experienced during development plays critical roles in many biological processes. While the temperature inside an egg is assumed to match the substrate temperature, many factors such as evaporative cooling, metabolic heating and the insulating properties of extra-embryonic components can lead to thermal differences. However, no method developed to date has allowed for measurement of the embryonic temperature in live chelonian eggs. We designed a thermocouple-based technique to measure embryonic temperature, achieving 94% survival in Trachemys scripta This methodology may be applicable to other reptile species. We found that, while the temperature in the substrate adjacent to the eggshell accurately reflects the internal egg temperature, it differs from air temperature (∼2°C) in a moisture-dependent manner. Our results demonstrate that external egg temperature, but not air temperature, is suitable for assessing the effects of temperature on biological processes, which could be critical when considering that processes such as temperature-dependent sex determination in turtles occurs within a 4°C window.

Chelonian perivitelline membrane-bound sperm detection: A new breeding management tool

Perivitelline membrane (PVM)-bound sperm detection has recently been incorporated into avian breeding programs to assess egg fertility, confirm successful copulation, and to evaluate male reproductive status and pair compatibility. Due to the similarities between avian and chelonian egg structure and development, and because fertility determination in chelonian eggs lacking embryonic growth is equally challenging, PVM-bound sperm detection may also be a promising tool for the reproductive management of turtles and tortoises. This study is the first to successfully demonstrate the use of PVM-bound sperm detection in chelonian eggs. Recovered membranes were stained with Hoechst 33342 and examined for sperm presence using fluorescence microscopy. Sperm were positively identified for up to 206 days post-oviposition, following storage, diapause, and/or incubation, in 52 opportunistically collected eggs representing 12 species. However, advanced microbial infection frequently hindered the ability to detect membrane-bound sperm. Fertile Centrochelys sulcata, Manouria emys, and Stigmochelys pardalis eggs were used to evaluate the impact of incubation and storage on the ability to detect sperm. Storage at -20°C or in formalin were found to be the best methods for egg preservation prior to sperm detection. Additionally, sperm-derived mtDNA was isolated and PCR amplified from Astrochelys radiata, C. sulcata, and S. pardalis eggs. PVM-bound sperm detection has the potential to substantially improve studies of artificial incubation and sperm storage, and could be used to evaluate the success of artificial insemination in chelonian species. Mitochondrial DNA from PVM-bound sperm has applications for parentage analysis, the study of sperm competition, and potentially species identification.

New turtle egg fossil from the Upper Cretaceous of the Laiyang Basin, Shandong Province, China

A new type of turtle egg fossil was established: Emydoolithus laiyangensis oogen. et oosp. nov.. Based on its elliptical morphological shape, rigid eggshells, and eggshell characteristics, it is different from other types of round chelonian egg fossils. It is the second chelonian egg fossil found in Cretaceous in China. This discovery shows the Laiyang ecosystem in Late Cretaceous is more diversified than previously thought.

First chelonian eggs and carapace fragments from the Pliocene of Rhodes, Greece

Well-preserved fossil eggs and eggshell fragments from the Pliocene Apolakkia Formation of Rhodes (Greece) are described. The eggs were found in-situ in a clutch. They are sub- spherical with lengths of 53-60 mm and widths of about 40 mm. All eggs are diagenetically compressed and their original diameters are estimated at 45-50 mm. The eggshells are 0.3-0.5 mm thick, partly re-crystallized, but widely still aragonitic. They consist of needle-like crystals that form individual shell units. A few pores are preserved between these shell units. This shell-structure allows assignment to chelonian eggs in the oofamily Testudoolithidae and the oogenus Testudolithus. The external morphology, microstructure and mineralogical composition of the eggshells show close resemblance to eggs of the extant tortoise Geochelone elephantopus. Together with a small association of turtle carapace fragments from the same formation, the clutch represents the first discovery of turtle and reptilian remains from the Pliocene of the island of Rhodes. (Less)

Influence of the Hydric Environment on Water Exchange and Hatchlings of Rigid‐Shelled Turtle Eggs

To examine the possible influence of incubation substrate water potential on rigid-shelled chelonian eggs and hatchlings, rigid-shelled eggs from four clutches of Brisbane River turtle (Emydura signata) were incubated buried in vermiculite at water potentials of approximately -100, -350, and -850 kPa, and patterns of egg mass change and hatchling attributes were examined. All eggs hatched successfully, and there was no apparent effect of water potential on incubation period, fresh hatchling mass, hatchling water content, or hatchling size. Clutch of origin also had no apparent effect on these attributes when initial egg mass was used as a covariate. However, clutch of origin affected initial egg mass, and clutch of origin and incubation water potential influenced the amount of water exchanged between the eggs and their environment during incubation and the amount of residual yolk found in hatchlings. Substrate water potential has little effect on hatchling outcomes other than the proportion of yolk converted to hatchling tissue during incubation in the rigid-shelled eggs of E. signata. It would appear that in general, the substrate water potential during incubation affects the quality of chelonian hatchlings by influencing the amount of yolk converted to hatchling tissue during embryonic development and that this influence is stronger in flexible-shelled eggs than in rigid-shelled eggs.

Chelonian eggshells from the Lower Cretaceous Kuwajima Formation of the Tetori Group, Central Japan

ABSTRACT Chelonian eggshell fossils from the Lower Cretaceous Kuwajima Formation of the Tetori Group are described. The eggs were originally spherical or ellipsoidal in shape. The eggshells consist of a single layer of spherulitic shell units composed of needle-like crystallites originating from a nucleation center. This corresponds to modern rigid-shelled chelonian eggs. The eggshell fragments are commonly found buried together and are known from deposits of subaerial environments, such as vegetated swamps. In contrast, the vast majority of turtle remains are known primarily from nearby shallow lake deposits, indicating that they are aquatic; no terrestrial turtles are known from this formation. These taphonomic settings suggest that the eggs were laid on land by lacustrine turtles in a process still apparent today.

Maternal Plasma and Egg Yolk Testosterone Concentrations during Embryonic Development in Green Anoles (Anolis carolinensis)

Sex steroids of presumably maternal origin have been found in avian, crocodilian, and chelonian egg yolks, and they can affect offspring morphology and behavior. The present study reports testosterone (T) levels to which embryos are potentially exposed in the green anole (Anolis carolinensis), a lizard with genotypic sex determination. We documented plasma and yolk T concentrations in adult females, in their developing follicles and eggs, and in freshly oviposited and incubating eggs. Plasma T was higher in reproductively active than in reproductively inactive females. Within reproductively active females, those with a single, large yolking follicle had higher plasma T than those that had one or more shelling, oviductal eggs. Individual females contributed different amounts of T to their yolks, but within females, more mature follicles or eggs consistently had higher yolk T concentrations than did less mature follicles or eggs. Similar to previous research, yolk T concentrations at oviposition were higher in male eggs than in female eggs. However, T levels during incubation did not differ by embryo sex, but rather increased in both male and female eggs. These results suggest that T plays a role in the reproductive physiology of females and potentially in the phenotypic development of their offspring. Furthermore, whereas the yolk T increase observed during follicular maturation is clearly a maternal influence, it remains unclear whether that observed during egg development (i.e., postfertilization) results from a lack of T uptake by the embryo as yolk is absorbed, from embryonic production of T that diffuses into the yolk, or from some combination of these processes. Because lizard embryos are comparatively well developed at oviposition, the assumption that yolk steroids are strictly of maternal origin may require modification, and the possibility that embryos are modulating their own steroid environment needs to be explored.

Concentrations of Steroid Hormones in Layers and Biopsies of Chelonian Egg Yolks

The actions of circulating hormones, although relatively well understood for adults, are largely unknown for their developing embryos. Transfer of maternal hormones to the egg is known to occur in oviparous species, and recently the presence of hormonally heterogeneous yolk layers has been described in two avian species. To investigate the possibility of a similar phenomenon occurring in chelonian species, egg yolk layers were analyzed in the painted turtle (Chrysemys picta marginata) and the red-eared slider turtle (Trachemys scripta elegans), two species that exhibit temperature-dependent sex determination. There was a similar pattern of hormonally heterogeneous yolk layers in both species: concentrations of progesterone and testosterone were significantly higher in the external yolk layer while concentrations of 17β-estradiol were significantly higher in the intermediate and internal layers. This pattern of hormone deposition concurs with previously published studies of plasma hormone profiles from females of temperate-zone turtle species. Yolks of freshly laid eggs were also sampled using a biopsy technique to examine the concordance of early yolk hormone concentrations and offspring sex. No relationship was found between yolk hormone concentrations and individual offspring sex. Previous work showing that maternally derived yolk estradiol concentrations are correlated with female-biased sex ratios was, however, replicated. These findings suggest that offspring sex is influenced, in part, by the maternal hormone environment.

A possible chelonian egg from the Brazilian late cretaceous

This paper describes a possible fossil egg proceeding from the Bauru Group, Late Cretaceous of Paraná Basin, Brazil. External morphology, dimensions, texture and shell ornamentation examined under electron microscopy show close resemblance to the Recent podocnemidid chelonian eggs. Association with bony material in the outcrop suggests that it is related to a species of Podocnemis. Computerized tomography reveals a high density outer region corresponding to the shell component layers, and successive layers with decreasing density towards the nucleus. An area of high density in the central region may represent remains of an embryo.

Water Relations of Chelonian Eggs and Embryos: Is Wetter Better?

The exchange of water between a chelonian egg and its subterranean environment is influenced by numerous factors, the most important of which are (1) structure of the calcareous layer of the eggshell, (2) water potential and temperature in the nest, and (3) fraction of the eggshell that actually contacts soil in the nest cavity. Eggs with relatively porous shells tend to absorb large quantities of water from cool, moist environments and to lose large amounts of water to warm, dry ones. Net water-exchange by such eggs also tends to be more favorable (= positive) when soil contacts the entire eggshell than when a large fraction of the shell is exposed to air trapped inside the nest cavity. In contrast, eggs with relatively impermeable shells usually exchange only small amounts of water with their environment, regardless of the physical conditions that prevail inside the nest. The pattern of net water-exchange, together with size (and water content) of the freshly laid egg, determines the amount of water that is available to sustain the embryo. An embryo having access to a relatively large reserve of water will consume more of its yolk and grow to larger size before hatching than will an embryo having access to a smaller reserve of water. Large, well-hydrated hatchlings may survive better than small, dehydrated animals during the trek overland from nest to water. If so, a cooler, wetter nest will also be a better nest.

Parataxonomic classification of fossil chelonian and gecko eggs

ABSTRACT The probability of fossil preservation of eggs with a soft or pliable shell or of small eggs with a thin hard shell layer is very poor. As result, their structural and parataxonomic classification has been almost non-existant. To fill this gap, the following parataxonomic groups have been established: 1) for chelonian eggs two oofamilies Testudoolithidae and Testudoflexoolithidae with the oogenera Testudoolithus and Testudoflexoolithus and three oospecies, and 2) for gecko eggs one oofamily Gekkoolithidae, with the oogenus Gekkoolithus and one oospecies. This paper also provides some condensed background information about amniote eggshell, its identification, structural and parataxonomical classification, and the potential of eggshell to fossilize.

Fossile Schildkröteneier aus dem Miozän von Saint- Gérand-le-Puy (Frankreich)

Fossile Schildkröteneier aus dem Miozän von Saint- Gérand-le-Puy (Frankreich)

A chelonian egg from the Vraconian of South East France, Paleogeographic implications

An egg has been discovered in the Vraconian of South-East France. Its morphology, size and ornamentation allow us to attribute it to a Chelonian. It is associated with a littoral fauna (essentially oysters). The egg is complete and well preserved, and as reptile laying sites are always subaerial, it has not undergone sizeable reworking from the laying site. An episode close to emersion is thus detected in a series which was believed to be marine.

Pliocene chelonian fossil eggs from Gran Canaria, Canary Islands

ABSTRACT Thirty years ago Macau-Vilar (1958) reported chelonian eggs from Gran Canaria. Analysis of the microstructure of these eggs corroborates this identification. Field studies show that these eggs, which were originally thought to be Miocene in age, are from Pliocene pyroclastic sediments about 3.5–4.5 my old.

Morphology of shell formation in eggs of the turtle Kinosternon flavescens.

Shells from eggs of the turtle Kinosternon flavescens were examined during different stages of development with light and scanning electron microscopy. Prior to initiation of the calcareous layer, organic spheres or cores appear on the outer surface of the shell membrane. Presumably, these cores nucleate deposition of the mineral layer of the eggshell. Growing shell units of the mineral layer are rounded and nodular in shape, crystallites of adjacent shell units do not interlock, and numerous spaces occur between shell units. As growth continues, most of the spaces between shell units are obliterated, and shell units become more elongate in form. The calcareous layer of partially shelled eggs resembles the calcareous layer of flexible-shelled eggs of emydids and chelydrids. Eggshells assume the morphology typical of rigidshelled chelonian eggs only at an advanced stage of shell formation. These observations indicate that rigid and flexible eggshells may form by fundamentally similar mechanisms, with length of shell growth being the primary determinant of whether shells are flexible or rigid.

Structure of the shell from eggs of the tuatara, Sphenodon punctatus.

Shells from eggs of the tuatara (Sphenodon punctatus) are 0.2 mm thick and are composed of a layer of calcite and a multi-layered, fibrous shell membrane. Most of the calcareous layer is composed of roughly circular columns of crystalline material that extend deep into the shell membrane. The crystalline matrix of the columns is interwoven with fibers of the shell membrane except near the outer surface of the eggshell, where the calcareous material is more compact. Overlying the columns is a granular layer composed of blocks of crystalline material of random size, shape, and orientation. Disruption of this granular layer, perhaps through swelling of the eggs or as a result of environmental factors, gives the outer surface of the eggshell a coarse, weathered appearance. Removal of the calcareous material with a decalcifying agent shows that the outer surface of the shell membrane is composed of a meshwork of small fibers bound together by an amorphous matrix. No matrix was observed in inner layers of the shell membrane, and the fibers of these inner layers are arranged somewhat more regularly than the outer fibers. No structure comparable to the central cores of avian and certain chelonian eggs was observed in eggshells of the tuatara.

Water Relations of Chelonian Eggs

Eggs of painted turtles (Chrysemys picta) absorb water across that portion of the eggshell in contact with the substrate and simultaneously lose water by transpiration from that part of the eggshell exposed to air inside the nest chamber. Depending upon the rates of influx and efflux, eggs may experience increases or decreases in mass during incubation, or mass may remain essentially constant between oviposition and hatching. Water exchanges are especially sensitive to such factors as substrate water potential, relative surface exposed to the nest atmosphere, hydraulic conductance of the eggshell, and conductance of the eggshell to water vapor. Hatchlings emerging from eggs absorbing and storing large quantities of water are heavier than hatchlings emerging from eggs taking up smaller quantities of water from the substrate. Furthermore, water absorption equal to, or in excess of, water loss by transpiration assures that the original shape of the egg will be preserved, thereby guaranteeing that sufficient space is available within the egg for normal development of the embryo.

Impression Tonometry of Chelonian Eggs (Reptilia, Testudines), a Guide to Internal Pressure and Membrane Phenomena

The weighted SchiOtz tonometer, an instrument used in ophthalmology for estimation of intraocular pressure through measurement of ocular tension, was used in studies on internal pressure and shell-membrane characteristics of freshwater turtle eggs of five species. The descriptive value of graphic profiles of egg tension portrayed by tonometry was demonstrated. Correlated tonometric and manometric studies on the same eggs provided a means of giving pressure values to tonometer readings, and of differentiating structural and pressure factors in tonometer measurement of egg tension. Impression tonometry is suggested as a technique for both field and laboratory monitoring of physical changes in reptilian eggs.