Clostridium chrysemydis sp. nov., isolated from the faecal material of a painted turtle

A strict anaerobic, Gram-stain-positive rod-shaped bacterium, designated PTT, was isolated from the faecal material of a painted turtle (Chrysemys picta). Based on a comparative 16S rRNA gene sequence analysis, the isolate was assigned to Clostridium sensu stricto with the highest sequence similarities to Clostridium moniliforme (97.4 %), Clostridium sardiniense (97.2 %) and the misclassified organism Eubacterium multiforme (97.1 %). The predominant cellular fatty acids of strain PTT were C14 : 0, C16 : 0 and an unidentified product with an equivalent chain length of 14.969. The G+C content determined from the genome was 28.8 mol%. The fermentation end products from glucose were acetate and butyrate with no alcohols detected and trace amounts of CO2 and H2 also detected; no respiratory quinones were detected. Based on biochemical, phylogenetic, genotypic and chemotaxonomic criteria, the isolate represents a novel species of the genus Clostridium for which the name Clostridium chrysemydis sp. nov. is proposed. The type strain is strain PTT (=CCUG 74180T=ATCC TSD-219T).

Exposure to low temperature prepares the turtle brain to withstand anoxic environments during overwintering

In most vertebrates, anoxia drastically reduces the production of the essential adenosine triphosphate (ATP) to power its many necessary functions, and consequently, cell death occurs within minutes. However, some vertebrates, such as the painted turtle (Chrysemys picta bellii), have evolved the ability to survive months without oxygen by simultaneously decreasing ATP supply and demand, surviving the anoxic period without any apparent cellular damage. The impact of anoxia on the metabolic function of painted turtles has received a lot of attention. Still, the impact of low temperature has received less attention and the interactive effect of anoxia and temperature even less. In the present study, we investigated the interactive impacts of reduced temperature and severe hypoxia on the electrophysiological properties of pyramidal neurons in painted turtle cerebral cortex. Our results show that an acute reduction in temperature from 20 to 5°C decreases membrane potential, action potential width and amplitude, and whole-cell conductance. Importantly, acute exposure to 5°C considerably slows membrane repolarization by voltage-gated K+ channels. Exposing pyramidal cells to severe hypoxia in addition to an acute temperature change slightly depolarized membrane potential but did not alter action potential amplitude or width and whole-cell conductance. These results suggest that acclimation to low temperatures, preceding severe environmental hypoxia, induces cellular responses in pyramidal neurons that facilitate survival under low oxygen concentration. In particular, our results show that temperature acclimation invokes a change in voltage-gated K+ channel kinetics that overcomes the acute inhibition of the channel.

Skeletal Muscle Histidine Containing Dipeptide Contents are Increased in Freshwater Turtles (Chrysemys picta bellii) with Cold-Acclimation

Freshwater turtles found in higher latitudes can experience extreme challenges to acid-base homeostasis while overwintering, due to a combination of cold temperatures along with the potential for environmental hypoxia. Histidine containing dipeptides (HCDs; carnosine, anserine and balenine) may facilitate pH regulation in response to these challenges, through their role as pH buffers. We measured the HCDs content of three tissues (liver, cardiac muscle and skeletal muscle) from the anoxia-tolerant painted turtle (Chrysemys picta bellii) acclimated to either 3 or 20 C. HCDs were detected in all tissues, with the highest content shown in the skeletal muscle. Turtles acclimated to 3 C had more HCD in their skeletal muscle than those acclimated to 20 C (carnosine = 20.8 +/- 4.5 vs 12.5 +/- 5.9 mmol/kg DM; ES = 1.59 (95%CI: 0.16 - 3.00), P = 0.013). The higher HCD content observed in the skeletal muscle of the cold-acclimated turtles suggests a role in acid-base regulation in response to physiological challenges associated with living in the cold, with the increase possibly related to the temperature sensitivity of carnosine's dissociation constant and buffering power of the skeletal muscle during anoxic submergence.

Contribution to the special issue on reptile cognition: Context-specific cue use in the Eastern painted turtle (Chrysemys picta) and its effects on decision making

Many species consider both prior experiences and the context of current stimuli when making behavioural decisions. Herein, we explore the influence of prior experience and novel incoming stimuli on the decision-making in the Eastern painted turtle (Chrysemys picta). We used a free-choice Y-maze to assess the preferences of turtles wavelength and intensity of light. We then trained naïve turtles to associate one arm of a maze with a food reward, and then tested the relevance of light colour and intensity on the turtles’ decision-making regarding arm choice. Turtles avoided bright light, even when presented on the side of the maze with which they had learned to associate a food. When light intensities of both sides were the same — irrespective of intensity — turtles chose the side they had previously learned to associate with the food reward. C. picta in our study showed a weak attraction to blue light and a strong avoidance of yellow light, a response generally consistent with previous work in sea turtles. Future studies should examine the ecological and evolutionary relevance of these decisions in field-oriented tests.

Karyotypic Evolution of Sauropsid Vertebrates Illuminated by Optical and Physical Mapping of the Painted Turtle and Slider Turtle Genomes

Recent sequencing and software enhancements have advanced our understanding of the evolution of genomic structure and function, especially addressing novel evolutionary biology questions. Yet fragmentary turtle genome assemblies remain a challenge to fully decipher the genetic architecture of adaptive evolution. Here, we use optical mapping to improve the contiguity of the painted turtle (Chrysemys picta) genome assembly and use de novo fluorescent in situ hybridization (FISH) of bacterial artificial chromosome (BAC) clones, BAC-FISH, to physically map the genomes of the painted and slider turtles (Trachemys scripta elegans). Optical mapping increased C. picta’s N50 by ~242% compared to the previous assembly. Physical mapping permitted anchoring ~45% of the genome assembly, spanning 5544 genes (including 20 genes related to the sex determination network of turtles and vertebrates). BAC-FISH data revealed assembly errors in C. picta and T. s. elegans assemblies, highlighting the importance of molecular cytogenetic data to complement bioinformatic approaches. We also compared C. picta’s anchored scaffolds to the genomes of other chelonians, chicken, lizards, and snake. Results revealed a mostly one-to-one correspondence between chromosomes of painted and slider turtles, and high homology among large syntenic blocks shared with other turtles and sauropsids. Yet, numerous chromosomal rearrangements were also evident across chelonians, between turtles and squamates, and between avian and non-avian reptiles.

Passive transport of Eastern Elliptio (Elliptio complanata) by freshwater turtles in New England

Dispersal of freshwater mussels (order Unionida) is primarily as glochidia on the fins and gills of host fish. Adult mussels are more sessile, generally moving short distances (<2 m/week) along lake and river beds. Between 2007 and 2016, we observed seven instances of adult Eastern Elliptio (Elliptio complanata) and one instance of a fingernail clam (Sphaerium sp.) attached to the feet of freshwater turtles in streams and ponds of New England, United States. Observations included five instances of mussels attached to Wood Turtles (Glyptemys insculpta) in Maine and Massachusetts, one instance of a mussel attached to the fingernail of an Eastern Painted Turtle (Chrysemys picta) in Massachusetts, one instance of a mussel attached to a Snapping Turtle (Chelydra serpentina) in Massachusetts, and one instance of a fingernail clam attached to the fingernail of an Eastern Painted Turtle in Massachusetts. We suggest that Eastern Elliptio may be susceptible to transport by freshwater turtles foraging in mussel beds and that transport of adult mussels by freshwater turtles could result in otherwise atypical long-distance, upstream, or overland dispersal between waterbodies.