"Georgie", the Golden Greek Tortoise (Testudo graece terrestris)

"Georgie", formerly known as "George", presented to my place of work at a veterinary practice after laying an egg. This tortoise went by the name of "George" for 10 years up until recently after having laid an egg which led to the discovery that she was in fact a female.

 The owners were concerned that she may have been "egg-bound" because this breed of tortoise generally lays 3 eggs. To determine if she was harboring any more eggs, we took radiographs of her which revealed she had 2 eggs yet inside! After consulting with an exotic vet specialist, she was deemed healthy and the owners were made aware that it may take up to 3 months for "Georgie" to lay the remaining eggs. Unfortunately, "Georgie" is an only-tortoise-child, so her eggs are unfertilized and have no embryo.

The Golden Greek Tortoise, Testudo graeca terrestris, belongs to the Family Testudinidae. Testudinidae is a terrestrial family usually with distinguishable high, domed shells, and un-webbed feet. The un-webbed feet and stumpy legs aid in body support and movement on land. The high-domed shells are also known to provide protection from predators. Testudo graece is found in the Mediterranean basin, ranging east to Iran with some populations in North Africa, southern Europe, and east Asia. This species also has temperature-dependent sex determination. T. graece is distinguishable by its smaller and paler appearance than other Testudo species, has a high-domed shell, and has a yellow spot on either side of the head.

Works Cited

van Dijk, P.P., Corti, C., Mellado, V.P. & Cheylan, M. 2004.  Testudo graeca. The IUCN Red List of Threatened Species 2004: e.T21646A9305080. Downloaded on 30 March 2018

Gibson, Richard, and Durrel Wildlife Protection Trust. “A Guide to the Identification of Tortoises in the Genus Testudo.” British Chelonia Group, 1 Jan. 2018, www.britishcheloniagroup.org.uk/caresheets/identity.

Pough, F. Harvey. Herpetology. Sinauer Associates, Inc., Publishers, 2016.

Article Review: Hydric environmental effects on turtle development and sex ratio

A new article published in February 2018 to the journal Zoology by Itzel Sifuentes-Romero and colleagues found that moisture conditions, and not only environmental temperature, have an effect on sex-determination in turtles.

            There is much research and it is well understood that temperature is a major sex-determinant in turtles, but this article explained how and why moisture also plays a role in the developing embryos. The researchers incubated eggs from the species Trachemys scripta elegans and used four treatments with differing temperatures and moisture levels to determine the effect of moisture on sex ratios. They found that moisture has an effect on the incubation temperature of the eggs, which is different than air temperature, and therefore is a factor in sex-determination as well as size of the developing embryos. The results showed that at temperatures of 31°C, which would normally result in a high percentage of females, actually resulted in 100% male ratio at higher moisture temperatures and almost 50% at medium moisture levels. It was therefore that determined that wetter environments results in a much higher male sex ratio.

            This research greatly adds to our knowledge of sex-determination in turtles that we’ve learned in class. We can now understand how temperature and moisture interact to determine sex in turtles. This research is extremely valuable because in endangered species, many more females are being born than males because of the rising climate. Understanding how other factors effect this sex-determination can have an impact on conservation efforts for these organisms.

https://www.sciencedirect.com/science/article/pii/S0944200617302015?via%3Dihub

Sifuentes-Romero, I., Tezak, B. M., Milton, S. L., & Wyneken, J. (2018). Hydric environmental  effects on turtle development and sex ratio. Zoology, 126, 89-97. doi: 10.1016/j.zool.2017.11.009

Article Review: Breeding sex ratio and population size of loggerhead turtles from Southwestern Florida

A recent article pertaining to the sex ratio of loggerhead sea turtles was published in January of 2018 in PLOS One by Jacob A. Lasala, Colin R. Hughes, and Jeanette Wyneken.

Male turtles are difficult to account for in the loggerhead population because they do not come ashore as nesting females do. In order to study the sex ratio of adult loggerheads, researchers used breeding sex ratios throughout three seasons of nesting to see how many males and females are involved in breeding and adding diversity to the population that nests in Florida. They were able to genotype 64 of the females that came ashore to nest, and 989 loggerhead hatchlings from nests in the area. From their data, they determined that there were 126 different paternal males and found that there was more than one paternal male in 70 percent of the nesting sites that were evaluated. This high number of individual adult males could be a result of females storing sperm over the course of time between nesting seasons as they travel, accounting for the larger gene-pool. The article also suggests that the breeding sex ratio could be affected by the frequency that each gender mates throughout the year.

This study adds to our understanding of reptile reproduction pertaining to temperature-dependent sex determination, as discussed in lecture. Higher incubation temperatures in most turtles correlates to the undifferentiated gonads becoming ovaries, leading to higher numbers of female hatchlings.

These findings are valuable because global warming is a growing issue, which is a huge concern for the threatened loggerhead sea turtle species due to their temperature-dependent sex determination, where warmer temperatures have the potential to alter the sex ratio. This research exhibits the large number of paternal males contributing to nests along the coast of Florida, giving insight to the adult males that females are able to encounter in the population during their travels. Although the number of female hatchlings is observed to be much higher than male hatchlings, this study can offer a basis for comparison in the years to come to investigate the impact of global warming on the population of loggerhead turtles.

           This research interests me, as I am concerned for the status of the loggerhead sea turtle species and whether or not the temperature affects of climate change are contributing to a detrimental decrease in their population as a whole. I find it very interesting that these researchers used genetics as an alternative in order to investigate the current adult male population.

Citation: Lasala JA, Hughes CR, Wyneken J (2018) Breeding sex ratio and population size of loggerhead turtles from Southwestern Florida. PLoS ONE 13(1): e0191615. <http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0191615&type=printable>

 

Article Review: Egg Mass Polymorphism in Ambystoma maculatum

This article interested me because it brought together ideas from my Ecology class as well as information from our class in regards to a local salamander species. The article discussed an egg mass polymorphism that is found in Ambystoma maculatum. The ecologists were mainly interested in studying selection for alternative phenotypes via polymorphisms as they can lead to new adaptations that can help species better survive and occupy multiple niches. As we have learned in class, the spotted salamander produces jelly-layered eggs that allow for the entry of conspecific sperm and mediate interactions with the surrounding environment while keeping the larvae moist. A. maculatum produces either clear or white eggs (the polymorphism at the focus of the study). These morphs differ in consistency and protein make-up (presence or absence of a specific protein). The questions that the study aimed to answer were: Does hatchling size and time to hatching vary between egg mass morphs in high and low nutrient environments? If so, do differences in larval size persist throughout the larval period? Does the proportion of white egg masses in ponds correlate to pond conductivity, which can be an indicator of dissolved nutrient levels? How do performance differences between morphs influence population dynamics under different pond conditions? The researchers hypothesized that the egg mass polymorphism was adaptive with regard to varying dissolved nutrient levels in ponds. 
The researchers conducted mesocosm experiments (a bridge between a controlled lab experiment and a field experiment), collected field data, and created a population projection model to test their questions. In the embryonic development experimental setup, they deposited the egg masses in fishless ponds at the University of Mississippi Field Station. They collected 12 clear egg masses and 11 white ones after one night of breeding and placed them in individual cages in separate pools (either a high nutrient pool, or low nutrient pool). For the larval development experiment, they established wading pools of different nutrient levels. The measured/counted temperature, pH, DO, conductivity, and egg mass morphs. Then, the ecologists analyzed mean hatching date with clutch size, mean hatchling total length per clutch, and pool condition. 
They found that larvae took longer to hatch in white egg masses and high nutrient pools. They also found that hatchlings from white egg masses were larger than those from clear masses in low nutrient pools. Additionally, high nutrient pools had higher conductivity. They found that larval survival was higher in those hatched from white egg masses, but larvae were smaller in pools with more surviving offspring. Body size was greater in high nutrient pools- larvae from white masses where large in low nutrient pools, but larvae from clear masses were larger in high nutrient pools. 
Overall, the conclusions can be summed up as the following- the polymorphism in  A. maculatum is advantageous in different nutrient levels at breeding sites. The researchers highlight the importance of the role of environmental heterogeneity in the maintenance of this egg mass polymorphism. They also suggest that the polymorphism is adaptive to nutrient levels and affected by predation (species interactions). The polymorphism is not strong enough to lead to speciation, but it does have an effect on fitness. 
Why is this article important? For starters, I was completely unaware of the fact that a local species we have studied all semester even had this egg mass polymorphism that has a distinct effect on fitness. Secondly, it is important to see that amphibians can be the focus of ecological studies as it pertains to their relevance and role in our ecosystems. The study shows that specific environmental conditions can lead to major differentiations, making the study of herps even more interesting and complex. 

Pintar, M. R. and Resetarits, W. J. (2017), Persistence of an egg mass polymorphism in Ambystoma maculatum: differential performance under high and low nutrients. Ecology, 98: 1349–1360. doi:10.1002/ecy.1789

http://onlinelibrary.wiley.com/doi/10.1002/ecy.1789/full

Eastern Narrow-Mouthed frog (Gastrophryne carolinensis)

While trekking through the marshy area of the Francis Marion National Forest we came across this little guy! He is the only species of narrow-mouthed frogs in South Carolina. These frogs are secretive and solitary, so I'm glad we were able to catch one! It was easily identified by it's small, plump round body, short limbs, non-webbed toes, and pointed head that has a single skin fold across the back. G. carolinensis's body shape and the horn-like lumps on the hind feet are perfect for burrowing. They spend much of their life in terrestrial habitats underground. Since it is a fossorial species, its eyes are smaller than some other species of frogs. This individual was dark brownish/ gray when he was caught, but G. carolinensis can change it's coloration depending on the day or mood of the individual. But I found his belly to be very cute with the almost blue mottling. The skin-gland secretions of G. carolinensis are distasteful to predators, can be an irritant to humans and toxic to other amphibians. Their gland secretions also help prevent attacks from their main food source, which are ants and termites. G. carolinensis lay their eggs in temporary pools of water, so the tadpoles need to metamorphose fairly rapidly before their pool dries out.

Source:
http://www.arkive.org/eastern-narrowmouth-toad/gastrophryne-carolinensis/

The Yellow Bellied Slider (Trachemys scripta) at Dixie Plantation

On our trip to the Dixie Plantation in Hollywood, SC we encountered various types of testudines. The most significant organism that I personally handled was Trachemys scripta scripta, or the yellow bellied slider. There were multiple individuals of the same species captured in mesh traps that were baited with a sardine can. These traps were placed along the shoreline and secured to the bank with rope. The specific trap that captured T. s. scripta had multiple individuals of the same species in it as well as another common freshwater species, the Eastern Snapping Turtle, Chelydra serpentina. The specific turtle that I handled was approximately a foot long and was determined to be a female. This assumption was made based off of the individual's size due to the fact that T. s. scripta exhibits sexual dimorphism. The females are typically larger than the males so they could have a larger clutch size or produce larger eggs as a whole. This was also made as a size comparison to the four other T. s. scripta that were found in the trap as well. The size difference is one of the easiest ways to identify the sex of the species. All testudines utilize direct development and the individual that was collected was an adult. The habitat that these turtles were found in seemed to be an old retainment pond. The water was relatively slow moving and there was a lot of weed cover on top of the pond, which included things like duckweed. The traps were placed near heavy debris. The turtles were acting skittish in the traps and this is likely due to the large amount of people as well as the other larger C. serpentina that were occupying the trap with them. Once they were held, the T. s. scripta calmed down and tucked their heads back into their shells. They would occasionally claw with their long claws in a swimming motion. T. s. scripta was a significant herp to found due to its size and being one of the two testudines species to be found. It was a charismatic species that interacted well with the group. It was slow to move back into the pond. This was also one of the first testudines that I have encountered in the wild. 

Pertinent References: 
http://www.virginiaherpetologicalsociety.com/reptiles/turtles/yellow-bellied-slider/yellow-bellied_slider.php
Powell, R., Conant, R., & Collins, J.T. Perterson Field Guide to Reptiles and Amphibians of Eastern and Central North America, 4th edition, pg. 218-219. 2016: Houghton Millfin Harcourt Publishing Company.