Platysternon Research Articles

The Effects of Water Depth and Substrate Conditions on Changes in Body Weight and Health Status of Captive Big-headed Turtles (Platysternon megacephalum) during Hibernation

The Effects of Water Depth and Substrate Conditions on Changes in Body Weight and Health Status of Captive Big-headed Turtles (Platysternon megacephalum) during Hibernation

Husbandry and propagation of the Chinese big-headed turtle (Platysternon megacephalum) at the Wildlife Conservation Society's Prospect Park Zoo

Turtles worldwide are facing increasing pressures on their wild populations and many are listed as endangered or critically endangered. Chinese big-headed turtles (Platysternon megacephalum) are currently listed on IUCN's Red List as endangered and on Cites Appendix II. As part of the Wildlife Conservation Society's initiative on turtle and tortoise conservation, this species became a focus for propagation at Prospect Park Zoo (PPZ) in 2008. PPZ successfully bred and obtained eggs, with successful hatchings in 2013 and 2014. The staff fluctuated water and ambient temperatures along with photoperiod in order to simulate seasonal changes. Each May, the female was placed in the male's enclosure daily for at least 15 min for breeding. Once two confirmed copulations were observed, breeding introductions were discontinued. The female laid her eggs in July and August, and clutch sizes ranged from 5 to 6 eggs. Eggs were successfully incubated in a RCOM Juragon reptile incubator at 23.3°C with 90-95% humidity. The eggs hatched after an average incubation period of 102 days (98-105 days, n = 9). Hatchlings had a mean body mass of 8.84 g (8.11-10 g) and average carapace length × width of 36.17 × 32.20 mm. This article aims to share the team's experiences working with this species as well as build upon previous publications and successes. Our hope is that with continued efforts to increase our knowledgebase a future viable, sustainable North American captive population will become a reality for this species.

Spatial ecology of endangered big‐headed turtles (Platysternon megacephalum): Implications of its vulnerability to illegal trapping

ABSTRACTMost populations of big‐headed turtles (Platysternon megacephalum), a species distributed in 6 countries in Southeast Asia, have been heavily depleted because of severe hunting pressure for the food and pet trade. As with many other Southeast Asian turtles, low densities of individuals and few remaining populations have limited our ability to study, and thus understand, the ecology of this stream‐dwelling species. We conducted a radiotelemetry study on 31 adult big‐headed turtles to investigate their home range, movements, and habitat use. The home ranges of big‐headed turtles were small, with a mean 100% home‐range length of 97 m and 100% minimum convex polygon size of 996 m2. Movements by male and female big‐headed turtles did not differ and both sexes moved longer distances in wet seasons than in dry seasons. Both males and females showed non‐random habitat use, preferring to stay in pools rather than in other in‐stream or terrestrial habitats. Stream width and depth, and substrate type affected microhabitat use. Big‐headed turtles were highly aquatic and movements in terrestrial habitats were rare. Thus, turtle populations are concentrated in streams where they may be easily targeted by illegal trappers. We recommend increasing patrol efforts along streams to remove any traps or fish hooks. Innovative methods, such as installation of infrared‐triggered cameras equipped with remote viewing near or along streams, may be needed to tackle illegal turtle trapping effectively. © 2015 The Wildlife Society.

Haemogregarines of freshwater turtles from Southeast Asia with a description of Haemogregarina sacaliae sp. n. and a redescription of Haemogregarina pellegrini Laveran and Pettit, 1910.

The uniform morphology of the developmental stages of Haemogregarina species and the insufficient information supplied by the simplistic descriptions of previous authors complicates their differential diagnosis and proper species identification. In this study, we detected Haemogregarina spp. in 6 out of 22 (27.2%) examined turtles originating from Southeast Asia, Malayemys subtrijuga (n = 4), Sacalia quadriocellata (n = 1) and Platysternon megacephalum (n = 1), and compared them with the available literature data. Microscopic analysis of our isolates distinguished 2 morphological species, Haemogregarina pellegrini and one new species, being described in this paper as Haemogregarina sacaliae sp. n. Phylogenetic analyses based on 1210 bp long fragment of 18S rDNA sequences placed both haemogregarines firmly within the monophyletic Haemogregarina clade. Isolates of H. pellegrini from 2 distantly related turtle hosts, M. subtrijuga and P. megacephalum, were genetically identical. Despite the fact that numerous Haemogregarina species of turtles have been described, the incompleteness of the morphological data and relatively low host specificity provides the space for large synonymy within this taxon. Therefore, a complex approach combining microscopic analyses together with molecular-genetic methods should represent the basic standard for all taxonomic studies.

Growth Rate and an Evaluation of Age Estimation for the Endangered Big-Headed Turtle (Platysternon megacephalum) in China

Understanding growth patterns is critical for determining age and size at sexual maturity and longevity in species that are severely threatened by over-collection and habitat loss, particularly in poorly understood species in tropical East Asia. Using data collected during a 9-year mark–recapture study, we fit the von Bertalanffy and logistic growth models to examine growth patterns of the endangered Big-headed Turtle (Platysternon megacephalum). Growth rate of P. megacephalum was best described by the von Bertalanffy model. Mean age at maturation for female and male P. megacephalum was 8 and 13 years. At maturity for female and male P. megacephalum, mean carapace length was 100 mm and 130 mm, respectively. We determined that counting growth rings on the carapace and plastron was not a reliable method for estimating ages. The long time to maturation in P. megacephalum may be costly in harvested populations, with individuals potentially being removed from populations prior to first reproduction. The growth patterns we have documented, and associated information on body size and age at sexual maturity, yield metrics that may be used to assess the effects of harvesting in populations and may contribute to conservation efforts for this endangered species.

Reproduction of endangered Big-headed Turtle, Platysternon megacephalum (Reptilia: Testudines: Platysternidae)

The big-headed turtle ( Platysternon megacephalum ) is heavily harvested to support tremendous demands from food and pet markets, and thus its ecology remains poorly understood. The presence of self-sustaining populations in Hong Kong (22°09’-22°37’N, 113°50’-114°30’E) provides important opportunities to advance our understanding of this species. We employed mark-recapture surveying, radio-tracking of two gravid females, and directed streamside searches to document the reproductive ecology of the species between September 2009 and June 2011 in Hong Kong. We found seven gravid females between 20-27 June 2010 and 2011, and which subsequently oviposited on average three eggs (range 2-8), with mean length and width of 36 mm and 21 mm, in early July. There was positive correlation between the size of females and clutch sizes. We found one clutch in leaf litter 1.6 m away from the stream, which hatched between 14 to 18 October. The incubation period was estimated to be between 103 and 110 days. The results of this study provide important information to formulate conservation plan for this endangered species.

Isolation and Characterization of 14 Polymorphic Microsatellite Loci in the Big-Headed Turtle (Platysternon megacephalum)

The big-headed turtle (Platysternon megacephalum) is critically endangered because of overharvesting, illegal trade, and habitat destruction. Assessment of genetic variability in existing populations becomes very important to the taxonomy and conservation of this species. Here we describe 14 microsatellite loci isolated from an enriched genomic library of the big-headed turtle, and the polymorphisms of these loci were assessed in 28 individuals from Huizhou, Heyuan, Zhaoqing, and Shaoguan of Guangdong, China. The range of polymorphism information content is 0.305-0.738, and no evidence of significant linkage disequilibrium was found among any pairs of loci. These 14 new polymorphic microsatellite loci can be used in population genetics, taxonomy, phylogeography, behavior ecology, and conservation efforts of Platysternon megacephalum.

Recombination and evolution of duplicate control regions in the mitochondrial genome of the Asian big-headed turtle, Platysternon megacephalum.

Complete mitochondrial (mt) genome sequences with duplicate control regions (CRs) have been detected in various animal species. In Testudines, duplicate mtCRs have been reported in the mtDNA of the Asian big-headed turtle, Platysternon megacephalum, which has three living subspecies. However, the evolutionary pattern of these CRs remains unclear. In this study, we report the completed sequences of duplicate CRs from 20 individuals belonging to three subspecies of this turtle and discuss the micro-evolutionary analysis of the evolution of duplicate CRs. Genetic distances calculated with MEGA 4.1 using the complete duplicate CR sequences revealed that within turtle subspecies, genetic distances between orthologous copies from different individuals were 0.63% for CR1 and 1.2% for CR2app:addword:respectively, and the average distance between paralogous copies of CR1 and CR2 was 4.8%. Phylogenetic relationships were reconstructed from the CR sequences, excluding the variable number of tandem repeats (VNTRs) at the 3′ end using three methods: neighbor-joining, maximum likelihood algorithm, and Bayesian inference. These data show that any two CRs within individuals were more genetically distant from orthologous genes in different individuals within the same subspecies. This suggests independent evolution of the two mtCRs within each P. megacephalum subspecies. Reconstruction of separate phylogenetic trees using different CR components (TAS, CD, CSB, and VNTRs) suggested the role of recombination in the evolution of duplicate CRs. Consequently, recombination events were detected using RDP software with break points at ≈290 bp and ≈1,080 bp. Based on these results, we hypothesize that duplicate CRs in P. megacephalum originated from heterological ancestral recombination of mtDNA. Subsequent recombination could have resulted in homogenization during independent evolutionary events, thus maintaining the functions of duplicate CRs in the mtDNA of P. megacephalum.

Field body temperature and thermal preference of the big-headed turtle Platysternon megacephalum

Abstract The big-headed turtle Platysternon megacephalum is a stream-dwelling species whose ecology is poorly known. We carried out field and laboratory investigations to determine field body temperatures and thermal preference of this species. In the field, the body temperatures of the turtles conformed to the water temperature, with little diel variation in either summer or autumn. Over the diel cycle, the mean body temperatures ranged from 20.8°C to 22.2°C in summer and from 19.3°C to 21.2°C in autumn; the highest body temperatures ranged from 22.1°C to 25.0°C in summer and from 20.6°C to 23.8°C in autumn. In the laboratory, the preferred body temperature (Tp) was 25.3°C. Food intake was maximized at 24.0°C, whereas locomotor performance peaked at 30.0°C. Consequently, Tp was closer to the thermal optimum for food intake than for locomotion. Therefore, this freshwater turtle has relative low field body temperatures corresponding to its thermal environment. In addition, the turtle prefers low temperatures and has a low optimal temperature for food intake.

Demographic Evidence of Illegal Harvesting of an Endangered Asian Turtle

Harvesting pressure on Asian freshwater turtles is severe, and dramatic population declines of these turtles are being driven by unsustainable collection for food markets, pet trade, and traditional Chinese medicine. Populations of big-headed turtle (Platysternon megacephalum) have declined substantially across its distribution, particularly in China, because of overcollection. To understand the effects of chronic harvesting pressure on big-headed turtle populations, we examined the effects of illegal harvesting on the demography of populations in Hong Kong, where some populations still exist. We used mark-recapture methods to compare demographic characteristics between sites with harvesting histories and one site in a fully protected area. Sites with a history of illegal turtle harvesting were characterized by the absence of large adults and skewed ratios of juveniles to adults, which may have negative implications for the long-term viability of populations. These sites also had lower densities of adults and smaller adult body sizes than the protected site. Given that populations throughout most of the species' range are heavily harvested and individuals are increasingly difficult to find in mainland China, the illegal collection of turtles from populations in Hong Kong may increase over time. Long-term monitoring of populations is essential to track effects of illegal collection, and increased patrolling is needed to help control illegal harvesting of populations, particularly in national parks. Because few, if any, other completely protected populations remain in the region, our data on an unharvested population of big-headed turtles serve as an important reference for assessing the negative consequences of harvesting on populations of stream turtles. Evidencia Demográfica de la Captura Ilegal de una Tortuga Asiática en Peligro.

New Species of Falcaustra (Nematoda: Kathlaniidae) In Platysternon megacephalum (Testudines: Platysternidae) from China

Falcaustra taimoshanensis n. sp. (Ascaridida, Kathlaniidae) from the feces of Platysternon megacephalum (Testudines; Platysternidae) is described and illustrated. Falcaustra taimoshanensis n. sp. represents the 32nd Oriental species assigned to the genus and is distinguished from other species by the distribution pattern of the caudal papillae (6 precloacal, 2 adcloacal, 12 postcloacal, and 1 median), length of spicules (765-791 µm), and presence of 1 pseudosucker.

Genetic divergence and phylogeny of turtles inferred from mitochondrial DNA 16SrRNA sequence

In order to investigate the genetic divergence and phylogeny of turtles,mitochondrial DNA 16SrRNA gene segment sequences of 13 turtle individuals were obtained by PCR amplification and sequencing.16SrRNA sequences of other 47 turtles from NCB were downloaded and its phylogenetic characters were analyzed together with their own 13 sequences.The results were as follows:480 bp consensus sequences of 16SrRNA were obtained from these 60 sequences after aligned.Twenty hundreds and twenty nine variable sites were detected in all turtle individuals,accounting for 47.7% of total variable sites,with 186 parsim-informative and 80 indels.The average contents of A,T,G,and C were 33.6%,24.3%,18.5%,and 23.7%,respectively.The Ts:Tv ratio was 1.95.The K-2-P distances between the seven hinged turtles were 0.004-0.063,with average value 0.03;between 17 genus within Geoemydidae 0.053-0.120,with average 0.091;and between 8 families within Cryptodira(excluding Platysternon megacephalum) 0.071-0.259,with average 0.169.The results indicate that family Emydidae is the sister taxon to Geoemydidae plus Testudinidae,and Geoemydidae is closer to Testudinidae compared to Emydidae;the taxonomica status of Chinemys should be revised,and classified into Genus Mauremys,and that Pyxidea should be classified into Cuora;the results do not support the idea that the genus Cuora should be divided into two genera as Cuora and Cistoclemmys.

Development of 19 Dinucleotide Microsatellite Markers from the Enriched Library of Platysternon megacephalum

Development of 19 Dinucleotide Microsatellite Markers from the Enriched Library of Platysternon megacephalum

Movements and Microhabitat Use of Translocated Big-Headed Turtles (Platysternon megacephalum) in Southern China

Asian turtles have declined substantially in recent decades because of the large-scale collection of wild individuals for the food, pet, and medicine trades. This has hampered studies into the ecology and natural history of turtles in their natural habitats because many species have become so rare that they are simply unavailable for study. One way to re-establish or supplement these turtle populations is through translocation (either of wild-caught individuals or those raised in farms). However, successful translocation is partly dependent upon released individuals maintaining site fidelity. We translocated 16 big-headed turtles, Platysternon megacephalum, in southern China to study their movements and microhabitat use in the wild and use this information to evaluate the feasibility of translocation as a conservation technique for this species. Translocated turtles generally moved short distances (daily range: 0–89.6 m), with males moving further than females and both sexes moving further at night than during the day. Additionally, big-headed turtles rarely used terrestrial habitats (the maximum distance an individual was located from the stream was 5.8 m) and remained hidden in refugia most of the time. Some sex differences in microhabitat use were also apparent; females were visible less often, spent more time on land (which coincided with the nesting season), remained closer to the stream bank, used shallower water, and used different types of refugia than males. The very short distances that big-headed turtles moved, combined with their consistent fidelity to the stream and cryptic behavior, all suggest that this species would be a good candidate for larger-scale translocation experiments. To our knowledge, this is the first published study of movement patterns and habitat use of translocated semiaquatic or aquatic turtles outside of Europe and the first published radiotelemetry study of turtles from mainland China.

The anatomy of the respiratory system in Platysternon megacephalum Gray, 1831 (Testudines: Cryptodira) and related species, and its phylogenetic implications

We discuss the morphology of the respiratory system regarding the phylogenetic relation among selected Testudines (Tetrapoda: Amniota). Lung structure and the associated coelomic organization are compared in Platysternon megacephalum and in representatives of the most-likely closely related taxa Chelydridae and Testudinoidea (Emydidae + Testudinidae). P. megacephalum shows horizontal intrapulmonary septation in the medial chambers, dividing them into dorsal and ventral lobes. This structure is found only in Platysternon and in the Emydidae, and is interpreted as a possible synapomorphy for these two taxa. In addition to further suggested synapomorphies for Platysternon and the Testudinoidea, we found – in contrast to previous reports – a small post-pulmonary septum (PPS) and incomplete coelomic compartmentalization in the Chelydridae. Thus, all major taxa of Testudines possess a PPS. Since this structure is also present in mammals, archosaurs and some lepidosaurs, the plesiomorphy of a coelomic compartmentalization by the PPS in amniotes in general should be considered. These preliminary results indicate that further comparative study of the respiratory apparatus might help resolve the phylogenetic relationships among the Testudines, as well as to shed light on its evolution among the Amniota.

New microsatellite resources in Chinese big-headed turtle (Platysternon megacephalum)

The Chinese big-headed turtle (Platysternon megacephalum) is listed as an endangered species in CITES II and IUCN list EN. Understanding the genetic structure of the wild population is an important part of future conservation and management. In this paper, we report 14 novel polymorphic microsatellite loci in P. megacephalum. And all the loci were evaluated with a population of twenty-one individuals collected from Guangdong provincial wildlife rescue center in Guangzhou. All loci were polymorphic with three to eleven alleles. After Bonferroni correction, five loci significantly deviated from Hardy–Weinberg equilibrium and one pair of loci showed significant linkage disequilibrium. These microsatellite loci will be useful in population genetics and conservation of the wild Chinese big-headed turtle population.

Arsenic, Cadmium, Chromium, Lead, Mercury, and Selenium Levels in Blood of Four Species of Turtles from the Amazon in Brazil

Using blood as a method of assessing metal levels in turtles may be useful for populations that are threatened or endangered or are decreasing. In this study the levels of arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and selenium (Se) in blood of four species of turtles from the tributaries of the Rio Negro in the Amazon of Brazil were examined. The turtles included the six-tubercled Amazon (river) turtle (Podocnemis sextuberculata), red-headed Amazon (river) turtle (Podocnemis erythrocephala), big-headed Amazon (river) turtle (Peltocephalus dumerilianus), and matamata turtle (Chelus fimbriatus). Blood samples were taken from the vein in the left hind leg of each turtle. There were significant interspecific differences in the sizes of the turtles from the Rio Negro, and in concentrations of Pb, Hg, and Se; the smallest species (red-headed turtles) had the highest levels of Pb in their blood, while Se levels were highest in big-headed turtles and lowest in red-headed turtles. Hg in blood was highest in matamata, intermediate in big-headed, and lowest in the other two turtles. Even though females were significantly larger than males, there were no significant differences in metal levels as a function of gender, and the only relationship of metals to size was for Cd. Variations in metal levels among species suggest that blood may be a useful bioindicator. Metal levels were not high enough to pose a health risk to the turtles or to consumers, such as humans.

Fourteen nuclear genes provide phylogenetic resolution for difficult nodes in the turtle tree of life

Advances in molecular biology have expanded our understanding of patterns of evolution and our ability to infer phylogenetic relationships. Despite many applications of molecular methods in attempts at resolving the evolutionary relationships among the major clades of turtles, some nodes in the tree have proved to be extremely problematic and have remained unresolved. In this study, we use 14 nuclear loci to provide an in depth look at several of these troublesome nodes and infer the systematic relationships among 11 of the 14 turtle families. We find strong support for two of the most problematic nodes in the deep phylogeny of turtles that have traditionally defied resolution. In particular, we recover strong support for a sister relationship between the Emydidae and the monotypic bigheaded-turtle, Platysternon megacephalum. We also find strong support for a clade consisting of sea turtles, mud and musk turtles, and snapping turtles. Within this clade, snapping turtles (Chelydridae) and mud/musk turtles (Kinosternidae) are sister taxa, again with strong support. Our results emphasize the utility of multi-locus datasets in phylogenetic analyses of difficult problems.

Low optimal temperatures for food conversion and growth in the big-headed turtle, Platysternon megacephalum

We held juvenile big-headed turtles, Platysternon megacephalum, from eastern China, at temperatures from 20 to 29.4 °C to determine effects on feeding, growth and food conversion. Food intake increased significantly from 20 to 22.4 °C, remained high until 27.1 °C, and then decreased dramatically at 29.4 °C. Digestive efficiency for energy decreased as temperature increased, whereas the digestive efficiency of protein increased from 20 to 25 °C, and decreased at higher temperatures. The relationships between specific growth rate (SGR), food conversion coefficient (Cc) and temperature (T) were curvilinear, and could be described by quadratic equations: SGR=−0.01 T2+0.47 T − 5.24 and Cc=−0.37 T2+17.20 T − 181.85. Maximum growth was estimated to occur at 23.9 °C, with 90% of the maximum being achieved within the range of 21.9–25.8 °C; maximal food conversion occurred at 23.2 °C, with a 90% range from 21.0 to 25.4 °C. The temperature range (22–25 °C) found to promote best growth and food conversion in juvenile P. megacephalum is lower than for many other freshwater turtles. Temperatures of 22–25 °C are recommended for use in culture of this species to maximize growth and food conversion.

Phylogenetic Relationships of Mesozoic Turtles

Presented herein is the first morphological analysis of turtle relationships to examine the monophyly of many turtle groups by using only single species as terminals and by integrating a large number of primitive fossil taxa. The data matrix consists of 136 osteological parsimony informative characters with 169 derived character states for 45 fossil and 22 living species of the clade Testudinata. The results corroborate the monophyly of a large number of previously hypothesized clades, but refute the accepted hypothesis regarding the basal split of living turtles. In particular, the primitive turtles Proterochersis robusta, Kayentachelys aprix, Mongolochelys efremovi, Meiolania platyceps, and Kallokibotion bajazidi are removed from their current position as crown turtles and placed along the phylogenetic stem of this clade. The age of the turtle crown is thereby adjusted from the Late Triassic to the Late Jurassic, which is relevant to testing molecular clock hypotheses. This revised topology has important implications for the evolution of several character complexes, because it implies that the common ancestor of all living turtles must have had a partially braced brain case and a primitive trochlear mechanism. Other noteworthy conclusions include the tentative exclusion of protostegids from Chelonioidea, the placement of Platysternon megacephalum outside of Chelydridae, and the tentative interpretation of Sandownia harrisi as a basal eucryptodire.