A new species of deep-sea Booralana Bruce, 1986 (Crustacea: Isopoda: Cirolanidae) from The Bahamas, Western North Atlantic.

Booralana nickorum sp. nov. is described from the deep-water slope of the Exuma Sound, The Bahamas, from depths of 540 to 560 metres. It is the fourth species to be assigned to the genus and the second species described from the Western North Atlantic. The species can be distinguished from Booralana tricarinata Camp and Heard, 1988 and the other species by the sub-triangular pleotelson and the uropodal exopod of mature males being far longer than endopod, with both rami extending well beyond the posterior margin of the pleotelson. Additionally, pleopods 3 and 4 lack a prominent angle at midpoint of ramus.

New insights into risk variables associated with gas embolism in loggerhead sea turtles (Caretta caretta) caught in trawls and gillnets.

Tissue and blood gas embolism (GE) associated with fisheries bycatch are likely a widespread, yet underestimated, cause of sea turtle mortality. Here, we evaluated risk factors associated with tissue and blood GE in loggerhead turtles caught incidentally by trawl and gillnet fisheries on the Valencian coastline of Spain. Of 413 turtles (303 caught by trawl, 110 by gillnet fisheries), 54% (n = 222) exhibited GE. For sea turtles caught in trawls, the probability and severity of GE increased with trawl depth and turtle body mass. In addition, trawl depth and the GE score together explained the probability of mortality (P[mortality]) following recompression therapy. Specifically, a turtle with a GE score of 3 caught in a trawl deployed at 110 m had a P[mortality] of ~50%. For turtles caught in gillnets, no risk variables were significantly correlated with either the P[GE] or GE score. However, gillnet depth or GE score, separately, explained P[mortality], and a turtle caught at 45 m or with a GE score between 3 and 4 had a P[mortality] of 50%. Differences in the fishery characteristics precluded direct comparison of GE risk and mortality between these gear types. Although P[mortality] is expected to be significantly higher in untreated turtles released at sea, our findings can improve estimates of sea turtle mortality associated with trawls and gillnets, and help guide associate conservation efforts.

Established and Emerging Research Trends in Norway Lobster, Nephrops norvegicus.

The burrowing crustacean decapod Nephrops norvegicus is a significant species in European Atlantic and Mediterranean fisheries. Research over the decades has mainly focused on behavioral and physiological aspects related to the burrowing lifestyle, since animals can only be captured by trawls when engaged in emergence on the seabed. Here, we performed a global bibliographic survey of all the scientific literature retrieved in SCOPUS since 1965, and terminology maps were produced with the VOSviewer software to reveal established and emerging research areas. We produced three term-map plots: term clustering, term citation, and term year. The term clustering network showed three clusters: fishery performance, assessment, and management; biological cycles in growth, reproduction, and behavior; and finally, physiology and ecotoxicology, including food products. The term citation map showed that intense research is developed on ecotoxicology and fishery management. Finally, the term year map showed that the species was first studied in its morphological and physiological aspects and more recently in relation to fishery and as a food resource. Taken together, the results indicate scarce knowledge on how burrowing behavior and its environmental control can alter stock assessment, because of the poor use of current and advanced monitoring technologies.

Effect of water temperature on the duration of the internesting interval across sea turtle species.

Sea turtles generally lay several clutches of eggs in a single nesting season. While a negative correlation between water temperatures and the time required between constitutive nesting events (termed the internesting interval) has been previously reported in loggerhead Caretta caretta and green turtles Chelonia mydas, it is not understood whether this relationship remains constant across other sea turtle species. Here, we expanded upon these previous studies on loggerhead and green turtles by using larger sample sizes and including data from species with a wider range of body-sizes; specifically: hawksbill Eretmochelys imbricata, leatherback Dermochelys coriacea, and olive ridley turtles Lepidochelys olivacea. In total, we compiled temperature data from biologgers deployed over internesting intervals on 23 loggerhead, 22 green, 7 hawksbill, 26 leatherback and 11 olive ridley turtles from nesting sites in 8 different countries. The relationship between the duration of the internesting interval and water temperatures in green and loggerhead turtles were statistically similar yet it differed between all other turtle species. Specifically, hawksbill turtles had much longer internesting intervals than green or loggerhead turtles even after controlling for temperature. In addition, both olive ridley and leatherback turtles exhibited thermal independence of internesting intervals presumably due to the large body-size of leatherback turtles and the unique capacity of ridley turtles to delay oviposition. The observed interspecific differences in the relationship between the length of the internesting interval and water temperatures indicate the complex and variable responses that each sea turtle species may exhibit due to environmental fluctuations and climate change.

Design and fabrication of a stereo-video camera equipped unoccupied aerial vehicle for measuring sea turtles, sharks, and other marine fauna.

The recent commercialization of unoccupied aerial vehicles (UAVs) has facilitated their incorporation into a variety of ecological studies. While UAVs are able to provide accurate visual data of marine species from an aerial perspective, these devices have some limitations that make measuring marine animals below the surface challenging. Many marine organisms are often visible from the air, but are deeper in the water column, and current methods cannot measure animals below the surface. Here, we developed and tested a stereo-video camera (SVC) system that was mounted onto a commercially-available UAV. We used the SVC-UAV to conduct remote body-size measurements for two marine species: the green sea turtle (Chelonia mydas) and the nurse shark (Ginglymostoma cirratum). When comparing SVC measurements to those taken by hand, the SVC-UAV had a mean absolute error (MAE) of 4.44 cm (n = 6; mean percent error (MPE) = 10.6%) for green sea turtles and 7.16 cm absolute error (n = 1; PE = 3.6%) for the nurse shark. Using a linear model, we estimated the slope of the SVC versus hand measurements for green sea turtles to be 1.085 (±0.099 SE), and accounting for the standard error, a measurement bias was not apparent. Using model selection, based on a global model predicting MAE from animal distance to the SVC and body size, the top ranked model was the intercept-only model. This indicates that neither animal distance nor body size strongly influenced measurement error. Incorporating SVC systems into UAVs can allow for relatively accurate measurements of near surface-dwelling marine species. To our knowledge, there is no other stand-alone SVC for UAVs available that offers similar accuracy and utility.

Cultivating epizoic diatoms provides insights into the evolution and ecology of both epibionts and hosts.

Our understanding of the importance of microbiomes on large aquatic animals-such as whales, sea turtles and manatees-has advanced considerably in recent years. The latest observations indicate that epibiotic diatom communities constitute diverse, polyphyletic, and compositionally stable assemblages that include both putatively obligate epizoic and generalist species. Here, we outline a successful approach to culture putatively obligate epizoic diatoms without their hosts. That some taxa can be cultured independently from their epizoic habitat raises several questions about the nature of the interaction between these animals and their epibionts. This insight allows us to propose further applications and research avenues in this growing area of study. Analyzing the DNA sequences of these cultured strains, we found that several unique diatom taxa have evolved independently to occupy epibiotic habitats. We created a library of reference sequence data for use in metabarcoding surveys of sea turtle and manatee microbiomes that will further facilitate the use of environmental DNA for studying host specificity in epizoic diatoms and the utility of diatoms as indicators of host ecology and health. We encourage the interdisciplinary community working with marine megafauna to consider including diatom sampling and diatom analysis into their routine practices.

Five hundred million years to mobility: directed locomotion and its ecological function in a turtle barnacle.

Movement is a fundamental characteristic of life, yet some invertebrate taxa, such as barnacles, permanently affix to a substratum as adults. Adult barnacles became 'sessile' over 500 Ma; however, we confirm that the epizoic sea turtle barnacle, Chelonibia testudinaria, has evolved the capacity for self-directed locomotion as adults. We also assess how these movements are affected by water currents and the distance between conspecifics. Finally, we microscopically examine the barnacle cement. Chelonibia testudinaria moved distances up to 78.6 mm yr-1 on loggerhead and green sea turtle hosts. Movements on live hosts and on acrylic panels occasionally involved abrupt course alterations of up to 90°. Our findings showed that barnacles tended to move directly against water flow and independent of nearby conspecifics. This suggests that these movements are not passively driven by external forces and instead are behaviourally directed. In addition, it indicates that these movements function primarily to facilitate feeding, not reproduction. While the mechanism enabling movement remained elusive, we observed that trails of cement bore signs of multi-layered, episodic secretion. We speculate that proximal causes of movement involve one or a combination of rapid shell growth, cement secretion coordinated with basal membrane lifting, and directed contraction of basal perimeter muscles.

A Baseline Model For Estimating the Risk of Gas Embolism in Sea Turtles During Routine Dives.

Sea turtles, like other air-breathing diving vertebrates, commonly experience significant gas embolism (GE) when incidentally caught at depth in fishing gear and brought to the surface. To better understand why sea turtles develop GE, we built a mathematical model to estimate partial pressures of N2 (PN2), O2 (PO2), and CO2 (PCO2) in the major body-compartments of diving loggerheads (Caretta caretta), leatherbacks (Dermochelys coriacea), and green turtles (Chelonia mydas). This model was adapted from a published model for estimating gas dynamics in marine mammals and penguins. To parameterize the sea turtle model, we used values gleaned from previously published literature and 22 necropsies. Next, we applied this model to data collected from free-roaming individuals of the three study species. Finally, we varied body-condition and cardiac output within the model to see how these factors affected the risk of GE. Our model suggests that cardiac output likely plays a significant role in the modulation of GE, especially in the deeper diving leatherback turtles. This baseline model also indicates that even during routine diving behavior, sea turtles are at high risk of GE. This likely means that turtles have additional behavioral, anatomical, and/or physiologic adaptions that serve to reduce the probability of GE but were not incorporated in this model. Identifying these adaptations and incorporating them into future iterations of this model will further reveal the factors driving GE in sea turtles.

Validating the use of stereo-video cameras to conduct remote measurements of sea turtles.

Point 1: Stereo-video camera systems (SVCSs) are a promising tool to remotely measure body size of wild animals without the need for animal handling. Here, we assessed the accuracy of SVCSs for measuring straight carapace length (SCL) of sea turtles. Point 2: To achieve this, we hand captured and measured 63 juvenile, subadult, and adult sea turtles across three species: greens, Chelonia mydas (n = 52); loggerheads, Caretta caretta (n = 8); and Kemp's ridley, Lepidochelys kempii (n = 3) in the waters off Eleuthera, The Bahamas and Crystal River, Florida, USA, between May and November 2019. Upon release, we filmed these individuals with the SVCS. We performed photogrammetric analysis to extract stereo SCL measurements (eSCL), which were then compared to the (manual) capture measurements (mSCL). Point 3: mSCL ranged from 25.9 to 89.2 cm, while eSCL ranged from 24.7 to 91.4 cm. Mean percent bias of eSCL ranged from -0.61% (±0.11 SE) to -4.46% (±0.31 SE) across all species and locations. We statistically analyzed potential drivers of measurement error, including distance of the turtle to the SVCS, turtle angle, image quality, turtle size, capture location, and species. Point 4: Using a linear mixed effects model, we found that the distance between the turtle and the SVCS was the primary factor influencing measurement error. Our research suggests that stereo-video technology enables high-quality measurements of sea turtle body size collected in situ without the need for hand-capturing individuals. This study contributes to the growing knowledge base that SVCS are accurate for body size measurements independent of taxonomic clade.

Spatial distribution of epibionts on olive ridley sea turtles at Playa Ostional, Costa Rica.

There is a wealth of published information on the epibiont communities of sea turtles, yet many of these studies have exclusively sampled epibionts found only on the carapace. Considering that epibionts may be found on almost all body-surfaces and that it is highly plausible to expect different regions of the body to host distinct epibiont taxa, there is a need for quantitative information on the spatial variation of epibiont communities on turtles. To achieve this, we measured how total epibiont abundance and biomass on olive ridley turtles Lepidochelys olivacea varies among four body-areas of the hosts (n = 30). We showed that epibiont loads on olive ridleys are higher, both in terms of number and biomass, on the skin than they are on the carapace or plastron. This contrasts with previous findings for other hard-shelled sea turtles, where epibionts are usually more abundant on the carapace or plastron. Moreover, the arguably most ubiquitous epibiont taxon for other hard-shelled sea turtles, the barnacle Chelonibia spp., only occurred in relatively low numbers on olive ridleys and the barnacles Stomatolepas elegans and Platylepas hexastylos are far more abundant. We postulate that these differences between the epibiont communities of different sea turtle taxa could indicate that the carapaces of olive ridley turtles provide a more challenging substratum for epibionts than do the hard shells of other sea turtles. In addition, we conclude that it is important to conduct full body surveys when attempting to produce a holistic qualitative or quantitative characterization of the epibiont communities of sea turtles.

Synchronised nesting aggregations are associated with enhanced capacity for extended embryonic arrest in olive ridley sea turtles.

Sea turtle species in the genus Lepidochelys exhibit an unusual behavioural polymorphism, nesting in both aggregations and solitarily. Aggregated nesting events, termed 'arribadas', involve hundreds of thousands of females congregating at a single nesting beach over a few days to oviposit their eggs. Aggregate and solitary nesting behaviours are associated with distinct inter-nesting intervals, three and four weeks for non-arribada and arribada nesters respectively. Consequently, embryos are maintained in pre-ovipositional embryonic arrest in the hypoxic oviduct for different lengths of time depending on the mother's reproductive behaviour. However, sea turtle embryos are limited in their capacity to remain in arrest and will subsequently die if held in hypoxia too long. Here, we tested whether embryos oviposited during arribada or non-arribada nesting differ in their capacity to be maintained in pre-ovipositional arrest. Olive ridley turtle (Lepidochelys olivacea) eggs from eight clutches (four from each nesting tactic) were divided among seven treatments after oviposition; normoxia (control; 21% O2), or hypoxia (1% O2) for 3, 3.5, 4, 8, 15 or 30 days, before being returned to normoxia. Arribada eggs were capable of extending pre-ovipositional arrest for longer, with some eggs from the 8- and 15-day hypoxia treatment still hatching while no non-arribada eggs hatched after more than four days in hypoxia. This difference in embryonic capacity to survive extended periods of arrest may be an important mechanism facilitating arribada behaviour by allowing longer inter-nesting intervals. Our finding provides an intriguing insight into the physiological mechanisms that are integral to this unique mass-nesting behaviour.

Complexity of the prey spectrum of Agaronia propatula (Caenogastropoda: Olividae), a dominant predator in sandy beach ecosystems of Pacific Central America.

Olivid gastropods of the genus Agaronia are dominant predators within invertebrate communities on sandy beaches throughout Pacific Central America. At Playa Grande, on the Pacific Coast of Costa Rica, we observed 327 natural predation events by Agaronia propatula. For each predation event, we documented prey taxa and body size of both predator and prey. The relationship between predator and prey size differed for each of the four main prey taxa: bivalves, crustaceans, heterospecific gastropods, and conspecific gastropods (representing cannibalism). For bivalve prey, there was increased variance in prey size with increasing predator size. Crustaceans were likely subdued only if injured or otherwise incapacitated. Heterospecific gastropods (mostly Olivella semistriata) constituted half of all prey items, but were only captured by small and intermediately sized A. propatula. Large O. semistriata appeared capable of avoiding predation by A. propatula. Cannibalism was more prevalent among large A. propatula than previously estimated. Our findings suggested ontogenetic niche shifts in A. propatula and a significant role of cannibalism in its population dynamics. Also indicated were size-dependent defensive behavior in some prey taxa and a dynamic, fine-scale zonation of the beach. The unexpected complexity of the trophic relations of A. propatula was only revealed though analysis of individual predation events. This highlights the need for detailed investigations into the trophic ecology of marine invertebrates to understand the factors driving ecosystem structuring in sandy beaches.

Coastal leatherback turtles reveal conservation hotspot.

Previous studies have shown that the world's largest reptile - the leatherback turtle Dermochelys coriacea - conducts flexible foraging migrations that can cover thousands of kilometres between nesting sites and distant foraging areas. The vast distances that may be travelled by migrating leatherback turtles have greatly complicated conservation efforts for this species worldwide. However, we demonstrate, using a combination of satellite telemetry and stable isotope analysis, that approximately half of the nesting leatherbacks from an important rookery in South Africa do not migrate to distant foraging areas, but rather, forage in the coastal waters of the nearby Mozambique Channel. Moreover, this coastal cohort appears to remain resident year-round in shallow waters (<50 m depth) in a relatively fixed area. Stable isotope analyses further indicate that the Mozambique Channel also hosts large numbers of loggerhead turtles Caretta caretta. The rare presence of a resident coastal aggregation of leatherback turtles not only presents a unique opportunity for conservation, but alongside the presence of loggerhead turtles and other endangered marine megafauna in the Mozambique Channel, highlights the importance of this area as a marine biodiversity hotspot.

Epibiotic Diatoms Are Universally Present on All Sea Turtle Species.

The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtle species hosting at least two diatom taxa. We recommend that future research is undertaken to confirm whether diatom communities vary between sea turtle species and whether these diatom taxa are facultative or obligate commensals.

Global analysis of the effect of local climate on the hatchling output of leatherback turtles.

The most recent climate change projections show a global increase in temperatures along with precipitation changes throughout the 21(st) century. However, regional projections do not always match global projections and species with global distributions may exhibit varying regional susceptibility to climate change. Here we show the effect of local climatic conditions on the hatchling output of leatherback turtles (Dermochelys coriacea) at four nesting sites encompassing the Pacific, Atlantic and Indian Oceans. We found a heterogeneous effect of climate. Hatchling output increased with long-term precipitation in areas with dry climatic conditions (Playa Grande, Pacific Ocean and Sandy Point, Caribbean Sea), but the effect varied in areas where precipitation was high (Pacuare, Caribbean Sea) and was not detected at the temperate site (Maputaland, Indian Ocean). High air temperature reduced hatchling output only at the area experiencing seasonal droughts (Playa Grande). Climatic projections showed a drastic increase in air temperature and a mild decrease in precipitation at all sites by 2100. The most unfavorable conditions were projected for Sandy Point where hatching success has already declined over time along with precipitation levels. The heterogeneous effect of climate may lead to local extinctions of leatherback turtles in some areas but survival in others by 2100.