More Like this

1. Immunogenetic diversity and transcriptomic response to fibropapillomatosis in Hawaiian green sea turtles

   https://doi.org/10.3354/esr01403  

   Adkins, JL; Martin, KR; Lynch, J; Banerjee, S; Allen, CD; Savage, AE; Chea, V; Rice, M; Jones, TT; Komoroske, LM (May 2025, Endangered Species Research)

   Sea turtles are one taxon of high conservation concern that encounter many pathogens, but their disease ecology is understudied, hindering our ability to predict impacts of disease on population viability. Fibropapillomatosis (FP) is a neoplastic tumor-forming disease that has been documented in all sea turtle species, with an especially high prevalence in green turtlesChelonia mydas.Here, we use Hawaiian green turtles (honu) as a study system to examine the roles of immunogenetic diversity and transcriptional modulation in sea turtle disease responses. Specifically, we quantified gene expression profiles associated with FP and characterized host diversity of major histocompatibility complex class I (MHCI) immune loci. We found 65 genes differentially expressed in blood between clinically healthy (n = 5) and FP-afflicted turtles (n = 5) with enriched biological processes of the innate immune system, aligned with expectations of reptilian immune systems and active disease resistance. Our results also suggest a role for disease tolerance in response to FP, as evidenced by enriched biological processes related to regulation of immune and metabolic homeostasis, increase in cellular detoxification, and increased tissue repair mechanisms. Honu (n = 89) had 23 unique MHCI alleles belonging to 3 distinct functional supertypes, but none were significantly associated with FP; this could be a result of intrinsic demographic properties of the population or reflect a lesser/differing role of the reptilian adaptive immune system. Our study advances the understanding of reptilian disease response and evolutionary mechanisms underlying immunogenetic diversity, both of which are important for promoting the adaptive potential of species vulnerable to extinction. 

   more » « less
2. Divergent sensory and immune gene evolution in sea turtles with contrasting demographic and life histories

   https://doi.org/10.1073/pnas.2201076120  

   Bentley, Blair P.; Carrasco-Valenzuela, Tomás; Ramos, Elisa K.; Pawar, Harvinder; Souza Arantes, Larissa; Alexander, Alana; Banerjee, Shreya M.; Masterson, Patrick; Kuhlwilm, Martin; Pippel, Martin; et al (February 2023, Proceedings of the National Academy of Sciences)

   Sea turtles represent an ancient lineage of marine vertebrates that evolved from terrestrial ancestors over 100 Mya. The genomic basis of the unique physiological and ecological traits enabling these species to thrive in diverse marine habitats remains largely unknown. Additionally, many populations have drastically declined due to anthropogenic activities over the past two centuries, and their recovery is a high global conservation priority. We generated and analyzed high-quality reference genomes for the leatherback ( Dermochelys coriacea ) and green ( Chelonia mydas ) turtles, representing the two extant sea turtle families. These genomes are highly syntenic and homologous, but localized regions of noncollinearity were associated with higher copy numbers of immune, zinc-finger, and olfactory receptor (OR) genes in green turtles, with ORs related to waterborne odorants greatly expanded in green turtles. Our findings suggest that divergent evolution of these key gene families may underlie immunological and sensory adaptations assisting navigation, occupancy of neritic versus pelagic environments, and diet specialization. Reduced collinearity was especially prevalent in microchromosomes, with greater gene content, heterozygosity, and genetic distances between species, supporting their critical role in vertebrate evolutionary adaptation. Finally, diversity and demographic histories starkly contrasted between species, indicating that leatherback turtles have had a low yet stable effective population size, exhibit extremely low diversity compared with other reptiles, and harbor a higher genetic load compared with green turtles, reinforcing concern over their persistence under future climate scenarios. These genomes provide invaluable resources for advancing our understanding of evolution and conservation best practices in an imperiled vertebrate lineage. 

   more » « less
3. Revealing Sea Turtle Behavior in Relation to Fishing Gear Using Color-Coded Spatiotemporal Motion Patterns With Deep Neural Networks

   https://doi.org/10.3389/fmars.2021.785357  

   Reavis, Janie L.; Demir, H. Seckin; Witherington, Blair E.; Bresette, Michael J.; Blain Christen, Jennifer; Senko, Jesse F.; Ozev, Sule (November 2021, Frontiers in Marine Science)

   Incidental capture, or bycatch, of marine species is a global conservation concern. Interactions with fishing gear can cause mortality in air-breathing marine megafauna, including sea turtles. Despite this, interactions between sea turtles and fishing gear—from a behavior standpoint—are not sufficiently documented or described in the literature. Understanding sea turtle behavior in relation to fishing gear is key to discovering how they become entangled or entrapped in gear. This information can also be used to reduce fisheries interactions. However, recording and analyzing these behaviors is difficult and time intensive. In this study, we present a machine learning-based sea turtle behavior recognition scheme. The proposed method utilizes visual object tracking and orientation estimation tasks to extract important features that are used for recognizing behaviors of interest with green turtles ( Chelonia mydas ) as the study subject. Then, these features are combined in a color-coded feature image that represents the turtle behaviors occurring in a limited time frame. These spatiotemporal feature images are used along a deep convolutional neural network model to recognize the desired behaviors, specifically evasive behaviors which we have labeled “reversal” and “U-turn.” Experimental results show that the proposed method achieves an average F1 score of 85% in recognizing the target behavior patterns. This method is intended to be a tool for discovering why sea turtles become entangled in gillnet fishing gear. 

   more » « less
4. Fecal and cloacal microbiomes of cold-stunned loggerhead Caretta caretta, Kemp’s ridley Lepidochelys kempii, and green sea turtles Chelonia mydas

   https://doi.org/10.3354/esr01220  

   Forbes, ZR; Scro, AK; Patel, SH; Dourdeville, KM; Prescott, RL; Smolowitz, RM (February 2023, Endangered Species Research)

   Investigating animal gut microbiomes can lead to a better understanding of their foraging preferences and their overall health. In this study, the fecal and cloacal microbiomes of 4 cold-stunned, frozen loggerhead Caretta caretta, 9 Kemp’s ridley Lepidochelys kempi , and 5 green sea turtles Chelonia mydas that stranded on beaches in Massachusetts, USA, were surveyed. Cloacal swabs and in situ fecal samples were collected from each turtle. From the extracted DNA, the hypervariable V1-V3 regions of the 16S rRNA gene were amplified with PCR, then sequenced using next generation Illumina MiSeq technology. Fecal and cloacal microbiomes were primarily composed of the phyla Proteobacteria , Bacteroidetes , and Firmicutes . Microbial communities varied significantly based on location of the gut sampled. Cloacal samples were largely dominated by Proteobacteria , while fecal samples appeared to have a greater distribution of taxa and higher alpha diversity. Green turtles had a higher abundance of Firmicutes and Bacteroidetes than Kemp’s ridley and loggerhead turtles, but a lower abundance of Proteobacteria . The information gained from this study contributes to knowledge of cold-stunned sea turtle gut microbiomes and may eventually be applied to rehabilitation efforts. 

   more » « less
5. Environmental drivers of diving behavior and space-use of juvenile endangered Caribbean hawksbill sea turtles identified using acoustic telemetry

   https://doi.org/10.3354/meps13466  

   Matley, JK; Jossart, J; Johansen, L; Jobsis, PD (October 2020, Marine Ecology Progress Series)

   null (Ed.)

   Space-use by aquatic ectotherms is closely linked to environmental factors such as temperature due to thermal-mediated metabolism and energy requirements. These factors are important, as they may alter an animal’s exposure to food/predators, hinder physiological function, increase competitive interactions, or even prompt population or biodiversity loss. Using general linear mixed-effects models, we investigated the influence of medium-term (months-years) environmental (diel period, water temperature, season, wind speed, air pressure, habitat type) and biological (turtle size) variation on space-use metrics for the Critically Endangered hawksbill sea turtle Eretmochelys imbricata , including dive duration, activity space, and rate of movement. We tracked 17 resident juveniles between August 2015 and May 2018 with a compact acoustic telemetry array (35-41 receivers in ~1 km 2 ) in Brewers Bay, US Virgin Islands. Diel differences in space-use were significant and highlighted periods of relative inactivity (e.g. resting) during the night and activity (e.g. foraging) during the day. Water temperature was also an important covariate influencing behavior leading to shorter dive durations and higher rates of movement in warmer temperatures. High contribution of random effects (individual and year) to model variation was also apparent, suggesting that juvenile hawksbills can operate outside the relatively narrow environmental range experienced within the study area. Nevertheless, ongoing climate trends (e.g. warmer temperatures and more extreme weather events) pose a significant concern for hawksbill populations, as juveniles spend their developmental period in shallow nearshore areas where environmental impacts will likely be greatest. 

   more » « less