Evidence for Host Selectivity and Specialization by Epizoic Chelonibia Barnacles Between Hawksbill and Green Sea Turtles

Epibionts are organisms that utilize the exterior of other organisms as a living substratum. Many affiliate opportunistically with hosts of different species, but others specialize on particular hosts as obligate associates. We investigated a case of apparent host specificity between two barnacles that are epizoites of sea turtles and illuminate some ecological considerations that may shape their host relationships. The barnacles Chelonibia testudinaria and Chelonibia caretta, though roughly similar in appearance, are separable by distinctions in morphology, genotype, and lifestyle. However, though each is known to colonize both green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) sea turtles, C. testudinaria is >5 times more common on greens, while C. caretta is >300 times more common on hawksbills. Two competing explanations for this asymmetry in barnacle incidence are either that the species’ larvae are spatially segregated in mutually exclusive host-encounter zones or their distributions overlap and the larvae behaviorally select their hosts from a common pool. We indirectly tested the latter by documenting the occurrence of adults of both barnacle species in two locations (SE Florida and Nose Be, Madagascar) where both turtle species co-mingle. For green and hawksbill turtles in both locations (Florida: n = 32 and n = 275, respectively; Madagascar: n = 32 and n = 125, respectively), we found that C. testudinaria occurred on green turtles only (percent occurrence – FL: 38.1%; MD: 6.3%), whereas the barnacle C. caretta was exclusively found on hawksbill turtles (FL: 82.2%; MD: 27.5%). These results support the hypothesis that the larvae of these barnacles differentially select host species from a shared supply. Physio-biochemical differences in host shell material, conspecific chemical cues, external microbial biofilms, and other surface signals may be salient factors in larval selectivity. Alternatively, barnacle presence may vary by host micro-environment. Dissimilarities in scute structure and shell growth between hawksbill and green turtles may promote critical differences in attachment modes observed between these barnacles. In understanding the co-evolution of barnacles and hosts it is key to consider the ecologies of both hosts and epibionts in interpreting associations of chance, choice, and dependence. Further studies are necessary to investigate the population status and settlement spectrum of barnacles inhabiting sea turtles.

Fishers' Ecological Knowledge and Stable Isotope Analysis Reveal Mangrove Estuaries as Key Developmental Habitats for Critically Endangered Sea Turtles

Successful conservation of endangered, migratory species requires an understanding of habitat use throughout life stages. When dedicated scientific studies are difficult to conduct, local expert knowledge can provide crucial baseline data to guide study design and aid data interpretation. In 2008, fishers in El Salvador demonstrated that eastern Pacific hawksbill sea turtles (Eretmochelys imbricata)—a population conservation biologists considered virtually extirpated—use mangrove estuaries as nesting habitat rather than open-coast beaches used by hawksbills in other regions. We confirmed and amplified this observation by using fishers' ecological knowledge to guide biological sampling for stable isotope analysis to assess if eastern Pacific hawskbills use mangrove-dominated estuaries as developmental habitats. We found that immature hawksbills experience a pelagic stage and then recruit to estuaries at ~37 cm curved carapace length, where they increase reliance on estuarine resources until they approach adult sizes. This life history strategy makes them especially vulnerable to in-water nearshore threats, and necessitates targeted expansion of conservation efforts throughout the eastern Pacific. Our analysis also provides a model for integrating traditional scientific approaches with local knowledge—a model that could yield crucial advances in other understudied regions.

Strandings of sea turtles on beaches around the oil capital in Brazil

The south-western region of the Atlantic Ocean has feeding and nesting areas for the five species of sea turtles registered in Brazil, which are in different degrees of extinction threat, mainly due to anthropogenic factors. Fishing and the ingestion of solid waste, were identified as causing stranding and the mortality of sea turtles. In this work, data from the monitoring of beaches in the Municipalities of Macaé and Rio das Ostras, important oil zone in Brazil, in the north-central region of the State of Rio de Janeiro, were used in order to analyse the effects of seasonality on the sea turtle stranding. The monitoring was carried out daily from September 2017 to June 2019, in a study area covering 23.8 km long beach. Stranding data were obtained from active (n = 126) and passive (n = 66) monitoring of beaches and included the records of Chelonia mydas (n = 151), Caretta caretta (n = 23), Lepidochelys olivacea (n = 14), Dermochelys coriacea (n = 2) and Eretmochelys imbricata (n = 1). The largest stranding record occurred in the summer (n = 61) and spring (n = 60), a period compatible with the reproductive season of the species. The results obtained in this study emphasise the importance of the analysis of strandings of sea turtles, which provide relevant data on the biology of the group, the intra and interspecific dynamics and the state of conservation of these animals.

Proteção e Conservação da Tartaruga-de-Pente (Eretmochelys imbricata)

A tartaruga-de-pente (Eretmochelys imbricata), também conhecida como tartaruga-legítima, é uma espécie de réptil da família Cheloniidae, que está criticamente ameaçada de extinção. O presente resumo teve como eixo temático a pesquisa realizada acerca da necessidade de preservação desse animal cujo objetivo foi a conscientização acerca da importância dessa espécie para a manutenção do ecossistema marinho. O nome dado à tartaruga-de-pente deve-se ao uso que era feito de seu casco, que se tratava da fabricação de pentes, armações de óculos, entre outros artefatos. Essa espécie de tartaruga marinha vive em recifes de corais, em águas rasas, sendo raramente encontrada em grandes profundidades, estando presente principalmente em águas tropicais e subtropicais; e sua alimentação abrange vários tipos de animais, entre eles, esponjas, moluscos e crustáceos, que habitam as fendas dos recifes de corais. A metodologia de pesquisa utilizada envolveu a análise dos principais riscos de extinção dessa espécie (sendo esses a caça predatória, a captura incidental durante pescas com rede e o desenvolvimento costeiro, pois acarreta a ocupação da orla e alto nível de emissão de poluentes) e o levantamento de referências teóricas já analisadas, como o Projeto Científico Avaliação do Estado de Conservação da Tartaruga Marinha, Eretmochelys imbricata (Linnaeus, 1766) no Brasil. Mediante a pesquisa apresentada, foi possível estruturar um banco de dados a respeito do comportamento do animal e seu local de desova, assim, descrevendo um levantamento da quantidade de ninhos e estabelecendo uma base acerca da população restante de tartarugas-de-pente no Brasil. Para tartarugas marinhas, o número de ninhos é usualmente adotado como índice de abundância, segundo Meylan et al. (1995). A desova da tartaruga-depente ocorre, normalmente, à noite e no litoral dos estados da Bahia, de Sergipe, do Rio Grande do Norte, da Paraíba, do Ceará, do Espírito Santo e de Pernambuco. Sua área de destaque é o litoral norte da Bahia, em que é possível observar até mil desovas em período reprodutivo. Em cada postura, essas tartarugas podem colocar até 135 ovos, e o sexo de seus filhotes é determinado de acordo com a temperatura do ninho: quanto mais elevada a temperatura, maior o número de fêmeas a nascer. Portanto, é possível concluir que, no litoral baiano, que é uma grande área de desova, nasce um número maior de fêmeas quando comparado ao número de machos. Vale destacar que o aumento da temperatura do planeta pode causar sérios riscos às tartarugas-de-pente devido ao papel que aquela desempenha na determinação do sexo dos embriões. Além disso, por se tratar de espécie de natureza altamente migratória, mudanças de recursos alimentares, circulação de correntes marinhas e ventos podem comprometer seu ciclo de vida longo e complexo. Este resumo teve como propósito conscientizar e mobilizar a sociedade quanto a uma causa ambiental: a preservação da tartaruga-de-pente, desse modo, propiciando à população mais conhecimento sobre essas tartarugas marinhas e a importância da conservação e manutenção das praias nas quais ocorre a desova para que esses seres possam sempre migrar para um novo círculo de reprodução e perpetuação da espécie. PALAVRAS-CHAVE: Conservação, Eretmochelys imbricata, Preservação, Tartaruga marinha

Hawksbill Nesting in Hawai‘i: 30-Year Dataset Reveals Recent Positive Trend for a Small, Yet Vital Population

Evaluating wildlife population trends is necessary for the development of effective management strategies, which are particularly relevant for highly threatened species. Hawksbill marine turtles (Eretmochelys imbricata) are considered endangered globally and are rare in Hawai‘i. Remnant hawksbill nesting beaches were identified in Hawai‘i in the late 1980s and the primary sites have been monitored since that time. In this study we summarize all available hawksbill nesting activity around the Hawaiian Islands between 1988 and 2018, highlighting relevant demographic and geographic data for the species. Because monitoring effort varied substantially across space and time, we implemented a predictive modeling approach that accounted for varying effort to explore potential trends in annual number of nesting females and nests over time. Field monitoring efforts documented an annual average of 14 ± 4.3 (range: 5–26) nesting females and 48 ± 19.0 (range: 12–93) nests, with a cumulative total of 178 individual nesting females and 1,280 nests recorded across all years. Nesting has been documented on four Hawaiian Islands, with the overwhelming majority of nesting females (78.4%) and nests (86.5%) recorded at four beaches along the southern coast of Hawai‘i Island. Recent monitoring (2018) at a beach on Moloka‘i Island revealed numbers similar to the most important beaches on Hawai‘i Island. Despite difficulty discerning obvious trends when looking solely at the raw tabulated numbers from field monitoring, our analysis suggests both the number of nesting females and nests have been positively trending since 2006, and this is supported by a higher percentage (57.1% of annual cohorts) of neophyte (vs. remigrant) nesters over the second half of the monitoring timeframe. The masking of obvious trends in the tabulated numbers is likely due to decreased overall monitoring effort as a result of reduced funding in recent years, coupled with a shift in focal monitoring effort from the historical primary nesting site of Kamehame, to the more recently established nesting site of Pōhue. Although the positive trend is encouraging, our findings highlight the precarious state of hawksbills in Hawai‘i and the need to enhance monitoring across all sites to support more robust population assessments and management decision making.

Plesiochorus cymbiformis (Rudolphi, 1819) Looss, 1901 (Digenea: Gorgoderidae) in Olive Ridley Sea turtles Lepidochelys olivacea (Eschscholtz, 1829) (Testudines: Chelonidae) from the Brazilian coast: New geographic occurrence and associated injuries

Summary The present study reports the first occurrence of Plesiochorus cymbiformis (Digenea: Gorgoderidae), in two Olive Ridley Sea turtles Lepidochelys olivacea (Testudines: Chelonidae), from the states of São Paulo and Sergipe in Brazilian coast. Concerning the Neotropical region, P. cymbiformis has been previously reported in green sea turtles (Chelonia mydas) from Panama and Brazil, in loggerhead sea turtles (Caretta caretta) from Brazil, in hawksbill sea turtles (Eretmochelys imbricata) from Puerto Rico, and in Olive Ridley Sea turtles only in Costa Rica. Lesions resulting from the presence of parasites in the hosts’ urinary bladders are also presented. This is the second report on endoparasites in Olive Ridley sea turtles from Brazil.

Conservación de la tortuga carey (Eretmochelys imbricata) en Rincón del Mar, Colombia

Se describen los procesos de conservación y ecología de anidación de la tortuga carey (Eretmochelys imbricata), producto del monitoreo sistemático entre 2018 y 2019 en el corregimiento de Rincón del Mar, San Onofre, Sucre. Se registraron seis nidadas de tortuga carey, todos fueron dejadas in situ y un nido fue saqueado por humanos. Las hembras desovaron un total de 761 huevos en cinco nidadas (promedio ± DE: 152,2 ± 15,5 huevos por nidada). El éxito de eclosión fue en promedio 78,2 ± 12,4 % y el éxito de emergencia fue en promedio 74,7 ± 14,1 % (n = 5). El periodo de incubación fue en promedio de 54 ± 7,8 días (n = 4). Fueron liberadas 591 crías al mar, de las cuales 22 (3,72 %), fueron rescatadas y liberadas con la comunidad. Además, se realizaron mediciones físicas de los nidos (ancho, profundidad, distancia a la playa), medidas morfométricas de los neonatos (ARC, LRC y peso) y se identificaron amenazas en el sector. Nuestros resultados contribuyen al conocimiento del estado actual de la tortuga carey, así como lo indispensable de la participación comunitaria para su conservación en Rincón del Mar.

Nesting preferences of the green sea turtle (Chelonia mydas L.) and the hawksbill sea turtle (Eretmochelys imbricata L.) in the SW of Mahe Island in the Seychelles

Data concerning 212 turtles emerging on the southwest beaches of Mahe Island in the Seychelles were collected in 2017 and 2018. These data were used to model the probability of eggs being laid in relation to several variables. The probability of successful laying after emergence was highest on certain beaches and in areas of short vegetation, between open sand and trees. We found successful laying was related to the physical properties of the soil, indicating that survivability of embryos and hatchlings is higher in certain areas. The turtles appeared to choose zones where soil had low salinity, good drainage but ability to retain water, and absence of spring tides and extreme temperatures.