Carapace Of Turtles Research Articles

Growing older, growing more diverse: Sea turtles and epibiotic cyanobacteria.

Cyanobacteria are known for forming associations with various animals, including sea turtles, yet our understanding of cyanobacteria associated with sea turtles remains limited. This study aims to address this knowledge gap by investigating the diversity of cyanobacteria in biofilm samples from loggerhead sea turtle carapaces, utilizing a 16S rRNA gene amplicon sequencing approach. The predominant cyanobacterial order identified was Nodosilineales, with the genus Rhodoploca having the highest relative abundance. Our results suggest that cyanobacterial communities become more diverse as sea turtles age, as we observed a positive correlation between community diversity and the length of a sea turtle's carapace. Since larger and older turtles predominantly utilize neritic habitats, the shift to a more diverse cyanobacterial community aligned with a change in loggerhead habitat. Our research provides detailed insights into the cyanobacterial communities associated with loggerhead sea turtles, establishing a foundation for future studies delving into this fascinating ecological relationship and its potential implications for sea turtle conservation.

A Novel Method for the Object Detection and Weight Prediction of Chinese Softshell Turtles Based on Computer Vision and Deep Learning.

With the rapid development of the turtle breeding industry in China, the demand for automated turtle sorting is increasing. The automatic sorting of Chinese softshell turtles mainly consists of three parts: visual recognition, weight prediction, and individual sorting. This paper focuses on two aspects, i.e., visual recognition and weight prediction, and a novel method for the object detection and weight prediction of Chinese softshell turtles is proposed. In the individual sorting process, computer vision technology is used to estimate the weight of Chinese softshell turtles and classify them by weight. For the visual recognition of the body parts of Chinese softshell turtles, a color space model is proposed in this paper to separate the turtles from the background effectively. By applying multiple linear regression analysis for modeling, the relationship between the weight and morphological parameters of Chinese softshell turtles is obtained, which can be used to estimate the weight of turtles well. An improved deep learning object detection network is used to extract the features of the plastron and carapace of the Chinese softshell turtles, achieving excellent detection results. The mAP of the improved network reached 96.23%, which can meet the requirements for the accurate identification of the body parts of Chinese softshell turtles.

Morphological variation of the cirri and penis in the hermaphroditic sea-turtle barnacle Chelonibia testudinaria (Linnaeus, 1758) (Cirripedia: Balanomorpha: Chelonibiidae)

Abstract Phenotypic plasticity of the penis and cirri of acorn barnacles is well documented for intertidal species. We investigated whether these phenomena also occur in the epizoic sea-turtle barnacle, Chelonibia testudinaria (Linnaeus, 1758). We compared the morphologies of the penis and cirri, and fertilization rates for adult, hermaphroditic barnacles on different regions of the carapace of sea turtles, and at different levels of crowding on the carapace. Barnacles were more abundant in the posterior position of loggerhead sea turtles, Caretta caretta (Linnaeus, 1758), followed by the central, central costal, and anterior positions. Barnacles in clustered groups were fertilized 68% more often than solitary individuals. Penis size increased with barnacle size and among individual sea turtles. Cirrus length and width also varied with barnacle size, among individual sea turtles, and among positions. Larger barnacles had longer and wider feeding cirri, and cirri were longer and wider in the central and posterior positions of the carapace than in the anterior and central costal positions. The phenotypic plasticity of the morphologies of the penis and cirrus is far less dramatic in Ch. testudinaria than in intertidal species. This may be explained by the epizoic barnacles not being permanently fixed and able to move to preferred positions on the host shell.

Plasticity and variation of cirral attributes in Chelonibia spp. barnacles

Prior studies suggest that many species of intertidal Balanomorph barnacles exhibit plastic responses to wave action and variable rates of water flow, with this environmental variability intrinsic to shaping the morphology of feeding cirri. However, this idea has not been quantitatively demonstrated in barnacles of the family Coronulidae, which exhibit obligatory epibiotic life-history patterns as adults. If the recent single-species classification of Chelonibia testudinaria continues to be upheld, the species represents a cosmopolitan and highly diverse life history with settlement on sea turtles, manatees, dugongs, and crustaceans. This species is therefore exposed to a wide variety of environmental conditions, including changes in ecosystems, water flow, pressure, and salinity. While spatial distribution of C. testudinaria on loggerhead turtle (Caretta caretta) carapaces—and therefore areas of variable flow—presents some evidence for potential plasticity in epibiotic cirri, interhost comparisons are lacking. To determine if morphology differs significantly by host, we conducted discriminant function analyses (DFAs) with twelve cirral measurements from barnacle specimens collected from both sea turtle and manatee hosts. Overall, we show greater than 94% discrimination in the classification of original grouped cases and cross-validated grouped cases in generalized and stepwise discriminant models. While plasticity remains evident within the Chelonibia genus, our data provide evidence contradictory to the currently accepted hypothesis that this plasticity is dependent upon, and strongly correlated with, host association. Therefore, we suggest that the single-species designation of the Chelonibia testudinaria complex be reevaluated.

Epibiotic bacteria on the carapace of hawksbill and green sea turtles

In this study, epibiotic bacteria on the carapace of sea turtles at three different sites in the Persian Gulf were studied. Bacterial density counted using a Scanning Electron Microscope showed that the highest (9.4 × 106 ± 0.8 × 106 cm−2) and lowest (5.3 × 106 ± 0.4 × 106 cm−2) average bacterial densities were found on the green and hawksbill sea turtles, respectively. Bacterial community analysis using Illumina 16S rRNA gene sequencing showed that Gamma- and Alpha-proteobacteria were the dominant classes on all substrates. Some genera, such as Anaerolinea, were site- and substrate-specific. In general, bacterial communities on sea turtles differed from those on the non-living substrate, stones, and exhibited lower species richness and diversity compared to the latter. Despite some similarities, the majority of bacterial communities on the two sea turtles were different. This study provides baseline information about the epibiotic bacteria of sea turtles of different species.

New insights into the association between epizoic diatoms and the sea turtle Chelonia mydas: new Mastogloia taxon (Bacillariophyceae) from Iran

ABSTRACT Two epizoic species of Mastogloia, one of them a new taxon, have been found for the first time growing on the carapace of sea turtle Chelonia mydas from the Strait of Hormuz (Iran). Before this work, taxa belonging to the genus Mastogloia had never been identified as epibionts of C. mydas. The cleaned material of diatoms, collected from turtle carapaces was studied by light (LM) and scanning electron microscopy (SEM). Mastogloia hormuzensis sp. nov. is elliptical to linear-elliptical in valve view with rounded to slightly rostrate apices. Partecta are of different size and shape, with the larger one at the centre, and there is a very short partectal flange. The new epizoic diatom is unique in its morphology, and can be compared with Mastogloia exigua and M. pusilla, which show a similar combination of characters (e.g. the shape of areolae, type of partectal ring). Mastogloia hormuzensis sp. nov. fits into Hustedt’s species group Inaequales, to which it adds the feature of having a very short partecta flange. A second species, Mastogloia paradoxa, was also found living as epizoic for the first time.

BONE MODIFICATION FEATURES RESULTING FROM BARNACLE ATTACHMENT ON THE BONES OF LOGGERHEAD SEA TURTLES (Caretta caretta), CUMBERLAND ISLAND, GEORGIA, USA: IMPLICATIONS FOR THE PALEOECOLOGICAL, AND TAPHONOMIC ANALYSES OF FOSSIL SEA TURTLES

Abstract Sea turtles are characterized by a wide variety of invertebrate ectoparasites. Few of these ectoparasites leave a permanent indication of their presence on the skeletal remains of their host taxa and thus represent ecological information doomed to be lost in the paleontological record. Some barnacle taxa provide an exception to this, in that they cause the formation of small, subcircular to circular divots, pits, and holes on the skull, mandible, carapace or plastron of sea turtles. Loggerhead Sea Turtle (Caretta caretta) skeletons from Cumberland Island, Georgia, USA were examined to assess the presence, frequency, and loci of occurrence of barnacle pits, and to establish which taxa are involved in pit development. Six types of divot and pit attributed to barnacles are identified in this study. Type I traces are shallow, oval/semi-circular in outline, with smooth, gently sloped bases. Type II traces are deep, hemispherical pits with smooth bases. Type III traces are deep, circular to subcircular pits with flat bases. Type IV traces are deep, circular to subcircular pits with multiple (4–6) small sub-pits on their bases. Type V traces are cylindrical, penetrative holes. Type VI traces comprise shallow ring-shaped grooves on the surface of the bone. Type I through III traces are identical to the ichnotaxon Karethraichnus lakkos. Type IV traces have not, as yet, been described in the rock record. Type V traces are identical to K. fiale. Type VI traces are identical to Thatchtelithichnus holmani. Barnacle taxa identified as emplacing non-penetrative divots and pits on C. caretta skulls, mandibles, and shell bones include Chelonibia caretta (Type I), Platylepas hexastylos (Types I–IV), Calyptolepas bjorndalae (Types I and II), and Stomatolepas elegans (Types I and II). Type V traces were most likely emplaced by either Stephanolepas muricata or Chelolepas cheloniae. Type VI traces reflect the former attachment of balanid or lepadid barnacles. Embedded barnacles were observed in epidermal material associated with Types I through IV traces but not for Type V and VI traces and thus the relationship is inferred for these latter traces. Barnacle-related pits, divots, and holes are believed to result from barnacle mediated chemical corrosion into the outer surface of sea turtle bone. The occurrence of these traces provides one of the few preservable lines of evidence of barnacle interactions with sea turtle hosts. Identification of definitive barnacle borings in fossil material will provide evidence of the evolution of platylepadid barnacles and the development of their commensal relationship with chelonid turtles.

THE OCCURRENCE OF BONE MODIFICATION FEATURES IN THE CARAPACE AND PLASTRON OF THE EXTANT RED-EARED SLIDER TRACHEMYS SCRIPTA ELEGANS (WIED-NEUWIED, 1839): IMPLICATIONS FOR PALEOECOLOGICAL ANALYSES OF FOSSIL TURTLE ASSEMBLAGES

Abstract The carapace and plastron bones of fossil turtles are often characterized by bone modification features such as pits, grooves, and holes. The significance, origin, and frequency of these features remains unclear because they have not been described from the bones of modern turtles. Taxon-specific description and analyses of defleshed turtle shell is essential for assessing the paleoecological significance of bone modification features. This study focuses on bone modification features on carapace and plastron bones of the emydid turtle Trachemys scripta elegans. Four subadult and 14 adult turtle shells were examined for non-ontogenetic features such as pits, grooves, holes, wounds, abrasions, and pathological growth structures. Bone modification features were lacking on subadult specimens but observed on each adult. Shallow, circular to subcircular pits (similar to the ichnotaxon Karethraichnus lakkos), and to a lesser extent pit clusters, are the most common feature noted on T. scripta elegans shells. Although they occur on both the plastron and the carapace, they proved far more common on the lower shell. Sparsely distributed ring-shaped grooves similar to the ichnotaxon Thatchtelithichnus holmani were present on approximately half of the turtle plastra studied. Amorphous surface etching was observed on several turtles, most commonly near the plastron midline (posterior portion of the hyoplastron/anterior portion of the hypoplastron). Pathological responses to these marks are lacking, but were noted on two turtles in response to sustained injuries. The occurrence of circular and subcircular pits, pit clusters, and ring traces on the external surface of every adult turtle analyzed in this study (regardless of sex or geographical occurrence), their discrete size and shape, and the lack of evidence of a systemic pathological response by the host suggests parasites, possibly leeches, as the etiological agent responsible for these features.

Temporal and Spatial Stability on the Population Structure of Consumed and Illegally Traded Big-Headed Amazon River Turtle in the Negro River Basin, Central Amazon, Brazil

Freshwater turtles are a valuable food resource for riverine human communities and have been historically overharvested throughout all major tropical large river basins, with consequent gradual population decreases. Even species considered to be abundant are declining, and in many cases were brought to a condition of near extinction. The collection of adult females during breeding season on nesting beaches is considered a major factor in population decline and subsequent loss of food sources for humans. There is growing consensus that adult females constitute the category which turtle populations can least afford to lose. In the Negro River Basin, the podocnemidid big-headed Amazon River turtle,Peltocephalus dumerilianus, is heavily exploited for consumption and poached for illegal trade among riverine communities and cities. Between 1997 and 2002 and in 2019, we measured live turtles and carapaces of big-headed turtles in the city of Barcelos and its surroundings, and among the riverine families living in the Jaú National Park. We compared body sizes and sex ratios between areas, periods, and between consumed and traded individuals. We found no differences between areas, even those close to Barcelos and the ones belonging to remote areas where pressure levels are lower. The individuals consumed in Jaú National Park are larger than those poached for illegal trade in both areas. There was an increase in average size between 1997 and 2002. Sex ratio was slightly skewed toward males, which were larger, and did not differ between areas and periods. Results indicate stability on size of harvested populations, which may be supporting current extraction levels. Data suggest this could be related to the absence of adult female capture during nesting for this species. We recommend protection strategies for other Amazon Podocnemidid species that focus on the protection of nesting beaches and surrounding areas where adults occupy, specifically in areas under communal protection.

First Assessment of Mercury (Hg) Concentrations in Skin and Carapace of Flatback Turtles (Natator depressus) (Garman) From Western Australia

Mercury pollution in the surface ocean has more than doubled over the past century. Within oceanic food webs, sea turtles have life history characteristics that make them especially vulnerable to mercury (Hg) accumulation. In this study we investigated Hg concentrations in the skin and carapace of nesting flatback turtles (Natator depressus) from two rookeries in Western Australia. A total of 50 skin samples and 52 carapace samples were collected from nesting turtles at Thevenard Island, and 23 skin and 28 carapace samples from nesting turtles at Eighty Mile Beach. We tested the influence of turtle size on Hg concentrations, hypothesising that larger and likely older adult turtles would exhibit higher concentrations due to more prolonged exposure to Hg. We compared the rookeries, hypothesising that the turtles from the southern rookery (Thevenard Island) were more likely to forage and reside in the Pilbara region closer to industrial mining activity and loading ports (potential exposure to higher environmental Hg concentrations) with turtles from the northern rookery (Eighty Mile Beach) more likely to reside and feed in the remote Kimberley. Turtles from the Eighty Mile Beach rookery had significantly higher skin Hg concentrations (x̄ = 19.4 ± 4.8 ng/g) than turtles from Thevenard Island (x̄ = 15.2 ± 5.8 ng/g). There was no significant difference in carapace Hg concentrations in turtles between Eighty Mile Beach (x̄ = 48.4 ± 21.8 ng/g) and Thevenard Island (x̄ = 41.3 ± 16.5 ng/g). Turtle size did not explain Hg concentrations in skin samples from Eighty Mile Beach and Thevenard Island, but turtle size explained 43.1% of Hg concentrations in the carapace of turtles from Eighty Mile Beach and 44.2% from Thevenard Island. Mercury concentrations in the flatback turtles sampled in this study are relatively low compared to other sea turtles worldwide, likely a result of the generally low concentrations of Hg in the Australian environment. Although we predicted that mining activities would influence flatback turtle Hg bioaccumulations, our data did not support this effect. This may be a result of foraging ground overlap between the two rookeries, or the predominant wind direction carrying atmospheric Hg inland rather than seaward. This is the first Hg study in skin and carapace of flatback turtles and represents a baseline to compare Hg contamination in Australia’s surrounding oceans.

The macroevolutionary and developmental evolution of the turtle carapacial scutes

The scutes of the carapace of extant turtles exhibit common elements in a narrow range of topographical arrangements. The typical arrangement has remained constant since its origin in the clade Mesochelydia (Early Jurassic), after a period of apparent greater diversity in the Triassic. This contribution is a review of the development and evolutionary history of the scute patterns of the carapace, seen through the lens of recent developmental models. This yields insights on pattern variations in the fossil record. We reinterpret the “supracaudal” scute and propose thatProganochelyshad five vertebral scutes. We discuss the relationship between supramarginal scutes and Turing processes, and we show how a simple change during embryogenesis could account for origin of the configuration of the caudal region of the carapace in mesochelydians. We also discuss the nature of the decrease in number of scutes over the course of evolution, and whether macroevolutionary trends can be discerned. We argue that turtles with complete loss of scutes (e.g., softshells) follow clade-specific macroevolutionary regimes, which are distinct from the majority of other turtles. Finally, we draw a parallel between the variation of scute patterns on the carapace of turtles and the scale patterns in the pileus region (roof of the head) of squamates. The size and numbers of scales in the pileus region can evolve over a wide range, but we recognized tentative evidence of convergence towards a typical configuration when the scales become larger and fewer. Thus, typical patterns could be a more general property of similar systems of integumentary appendages.

Reparative regeneration of histogenetically different bones

The bone plates that forming the turtle shell differ in histogenesis. Thus, the costal and neural plates of the carapace (dorsal shield) have mesenchymal origin and develop by indirect perichondral osteogenesis from vertebrae and ribs. The bone plates of the plastron - abdominal shield, are known to be formed from neuroectodermal cells of the neural crest and develop by intramembrane osteogenesis in the dermis of the skin. The aim of the study was to compare the reparative regeneration of histogenetically different bone tissue of the carapace and plastron of freshwater red-eared turtles Trachemys scripta. The experiment was performed on freshwater red-eared turtles Trachemys scripta aged 3 months. 2 defects of carapace and plastron bone plates with a diameter of 5 mm and a depth of up to "soft tissues” were formed with further histological examination. It was found that the regeneration of the bone plates of the plastron is characterized by the formation of bone tissue in a larger volume and at an earlier date. After 30 days a layer of continuous newly formed bone tissue is formed. By 90 days the proportion of bone tissue in the carapace regenerate was 40,5% of the defect area, while in the plastron the regenerate occupied 47,4%. Thus, intramembranous formed bone tissue of neuroectodermal histogenesis has a more pronounced regenerative potential compared to perichondral formed bone of mesenchymal origin.

Ectoparasite borings, mesoparasite borings, and scavenging traces in early Miocene turtle and tortoise shell: Moghra Formation, Wadi Moghra, Egypt

AbstractBorings and bite marks on fossil turtle carapaces and plastra from the Miocene Moghra Formation, northern Egypt, are herein described. All fossil turtle material from Moghra exhibits ichnofossils. The positions of invertebrate borings on external surfaces of tortoise and turtle shell material at Moghra are consistent with the activities of ectoparasites or mesoparasites.A single invertebrate ichnotaxon, Karethraichnus lakkos Zonneveld et al., 2016, occurs on Moghra tortoise fossils. This trace fossil was likely emplaced by ixodid arthropods (ticks). Bite marks assigned to Nihilichnus occur on a carapace peripheral and are interpreted to reflect postmortem scavenging. An abundant and moderately diverse assemblage of invertebrate borings characterizes Moghra aquatic turtle shells. Karethraichnus lakkos and Thatchtelithichnus holmani Zonneveld et al., 2016 traces on aquatic turtles are interpreted to reflect leech and/or trematode parasitism. Gunnellichnus moghraensis (new ichnogenus new ichnospecies) and G. akolouthiste (n. isp.) likely reflect bacterial and/or fungal infections on aquatic turtle shells that rarely dried out.UUID: http://zoobank.org/f0a3977d-deff-4954-b196-536adc405854

Specificity of diatom communities attached on the carapace of the European pond turtle (<em>Emys orbicularis</em>)

Periphytic diatoms growing on aquatic turtle carapaces provide an interesting example of biofouling on an animal substrate. This study dealt with the question of the specificity of epizoic diatom communities for the case of the European pond turtle (Emys orbicularis) and across five water bodies in South-Eastern France. 375 diatom taxa have been identified on the European pond turtle carapace. The results showed that the epizoic communities of the five sites were significantly different from each other. The epizoic diatom communities could be clearly distinguished from epilithic and epiphytic communities only in two out of five sites. The differences in composition at the two sites resulted from the greater abundance of some species and life forms. However, the characteristic pattern of diatom communities on the carapaces was not the same at the two sites. It therefore appeared that the European pond turtle’s carapace did not harbour specific diatom communities and can rather be considered a neutral substrate.

Predation of satellite-tagged juvenile loggerhead turtles Caretta caretta in the Northwest Atlantic Ocean

We present evidence of predator interactions with 8 juvenile loggerhead sea turtles Caretta caretta equipped with pop-up satellite archival transmitting tags (PSATs) following incidental capture in the Northwest Atlantic. Ingestion of PSATs occurred up to 5 mo after tagging and was identified by an abrupt change in depth distribution, a stabilization and/or increase in ambient temperature and a marked drop in light levels to near zero, with cessation of diel light level cycling. In some cases, following expulsion from the digestive tract of predators, positively buoyant PSATs descended to the sea floor or beyond the programmed release depth threshold (1800 m), indicating that they remained tethered to the indigestible carapaces of turtles and that the entire turtle was originally consumed. PSAT data, combined with the sudden termination of satellite uplinks from 2 loggerheads also equipped with platform transmitting terminals, provided additional evidence of whole-turtle predation. PSAT data indicated that both endothermic and ectothermic sharks ingested tags. Based on PSAT-logged temperature data, dive patterns and geographic distribution, the following shark species were considered as candidate predators: white, porbeagle, shortfin mako, tiger and blue. This study represents the first analysis of data collected by loggerhead turtle PSATs inside predators. The results expand the list of shark species known to prey on large juvenile loggerheads and point to the importance of acknowledging predation as an important source of mortality for loggerhead turtles in the Northwest Atlantic Ocean.

Thermal Ecology of Spotted Turtles (Clemmys guttata) in Two Southern Populations

The ecology of many ectotherms depends heavily on their ability to navigate the surrounding thermal environment in a manner that maintains body temperature (Tb) within or near some optimal temperature range at least some of the time. From April–December 2016, we measured shell temperatures (Ts) and water temperatures (Tw) in two Spotted Turtle (Clemmys guttata) populations in southeastern Georgia using iButton temperature loggers. We attached radio transmitters and iButtons to the carapace of adult Spotted Turtles (n = 18 and 11 in each population, respectively) in early spring. Temperature loggers recorded a Ts measurement every 90 minutes (accuracy = 0.5°C), and we restricted our analyses to temperatures recorded between sunrise and sunset. Monthly mean Ts ranged from 12.3±3.4 to 27.1±2.7°C (SD), and seasonal variation accounted for a majority of the observed variation in temperatures. We found a strong positive correlation between weekly mean Ts and weekly mean Tw at one site that remained flooded throughout the study (P < 0.0001, R2 = 0.99). Tw could not be measured at the other site because it dried completely early in the study. Spotted Turtles did occasionally (<5% of total temperature observations) bask to raise Ts above that of the surrounding Tw. Gravid females achieved significantly higher daily maximum temperatures (26.2°C) than males (24.5°C) during the four weeks surrounding egg development (P = 0.043). In general, Spotted Turtles at the southern end of their range appear to spend a majority of their time conforming to environmental temperatures that often fall within the preferred range for the species.

Phylogeographic Resolution of the Barnacle (Chelonibia testudinaria) from the North-Eastern Mediterranean Loggerhead Sea Turtles Epibiont Community

Barnacles are common epibionts on a wide range of marine organisms, including turtles. Chelonibia testudinaria is a successful epibiotic barnacle species, and mainly turtles are responsible for their wide range dispersal. In the present study, the mitochondrial Cytochrome Oxidase I (COI) gene haplotypes of C. testudinaria from Caretta caretta hosts were evaluated. The samples were collected from three dead C. caretta turtle carapaces in 2014 from the Middle East Technical University, Institute of Marine Sciences coastline. Results were also compared with those samples submitted to databases (NCBI and BOLD-system, 139 in total). By comparison, three clades were recorded like previous studies: the Atlantic-Mediterranean clade (Clade-α), the IndianPacific Ocean clade (Clade-β), and Magdalena Bay (Eastern Pacific- Clade-) clade; all samples collected from Turkish shores clustered in the Atlantic-Mediterranean group (Clade-α). The gene flow between the three clades was deficient and highly significant (0.02, 0.03, and 0.03, respectively). According to network age estimation, present study samples’ clade (Clade-α) diverged from the Clade-β approximately 200 kya (SDs=0.22, SDy=4402.90) and Clade- 130 kya (SDs=0.17, SDy=3494.55). In the present study, eight haplotypes were observed in total, two of which were specific to the region.

Majewskaea gen. nov. (Bacillariophyta), a new marine benthic diatom genus from the Adriatic Sea

During a survey of the diatom flora attached to carapaces of loggerhead sea turtles (Caretta caretta) from the Adriatic Sea, a large population of an unknown marine achnanthoid species was observed that could not be assigned to any of the currently described monoraphid diatom genera. Detailed morphological analysis based on scanning electron microscopy observations and comparison with a large number of monoraphid genera such as Madinithidium, Scalariella, Kolbesia and Karayevia, resulted in the description of the new benthic marine genus Majewskaea gen. nov. with the newly described Majewskaea istriaca sp. nov. as generitype. The new genus is characterized by a sternum valve showing a clear recurving ridge surrounding the entire valve margin, the presence of macroareolae closed internally by perforated hymenes, separated by a longitudinal hyaline area, a well-developed sternum and vestigial raphe slits. The raphe valve has a simple straight raphe with bent terminal fissures, a very fine striation pattern composed of macroareolae cut in two by a longitudinal hyaline zone, and a very shallow mantle. The new genus is illustrated using both LM and SEM observations and compared with other resembling marine and brackish Planothidium monoraphid species.

Biodiversity of carapace epibiont diatoms in loggerhead sea turtles (Caretta caretta Linnaeus 1758) in the Aegean Sea Turkish coast.

BackgroundThe Aegean Sea coast of Turkey hosts one of the most important nesting grounds for loggerhead sea turtles (Caretta caretta) in the Mediterranean Sea. Previous studies have revealed that the sea turtle carapace provides favourable conditions for various epibiontic organisms. Epibionts occurring on the carapace have been examined from different locations in the oceans.MethodsThis is the first time such a high number (39) of samples collected from nesting turtles during such a long time period (extending from 2011 to 2018) has been used for the study of the diatom component of the microbiome on the turtle carapaces. A total of 33 samples were investigated in terms of light microscopy (LM) and scanning electron microscopy (SEM). Six unprocessed biofilm fragments were subject to SEM observations.ResultsA total of 457 epizoic diatom taxa belonging to 86 genera were identified. Epizoic forms, e.g., Achnanthes spp., Chelonicola spp. or Tripterion spp. (also identified by SEM observations of the undisturbed pieces of the microbiome) dominated in terms of relative abundance, but the highest numbers of taxa were ubiquitously represented by Navicula (79), Nitzschia (45), Amphora (40), Cocconeis (32), Diploneis (25) and Mastogloia (23). Navicula perminuta and Delphineis australis were the most frequent taxa, present in 65% of the samples, both with an average relative abundance of 10%. The results of our study revealed that diatoms are an essential component of the loggerhead sea turtles’ microbiome, in terms of high biodiversity and abundance. Although strict epibionts provide a signature of the turtle microbiome, the carapace as a solid substrate attracts numerous benthic diatom species which are considered opportunistic forms and can be found in the surrounding benthic habitats of the vast ocean littoral space.

Diatoms on sea turtles and floating debris in the Persian Gulf (Western Asia)

ABSTRACT The current study investigated diatom communities on juvenile green turtles foraging in neritic habitats around five Iranian islands. The primary objectives were to (1) compare species composition, growth form structure, and abundance of diatom communities associated with sea turtles foraging within the restricted boundaries of local feeding pastures, and (2) assess the level of uniqueness of the epizoic diatom flora in comparison with biofilms growing on floating debris. All observations and diatom counts were performed using scanning electron microscopy. The effect of the sampling location was apparent among sea turtle samples and reflected in significantly different cell densities. Diatom abundances were significantly higher on sea turtles (758–1836 cells mm−2) than on floating debris samples (9–189 cells mm−2). Epizoic diatom communities were composed of 20 diatom taxa and dominated by erect forms belonging to the so-called ‘marine gomphonemoids’, Chelonicola and Poulinea, previously reported on sea turtles from other geographical regions. The diatom flora found on floating debris was composed of 21 taxa. Only four taxa, Amphora cf. bigibba, Cocconeis cf. neothumensis var. marina, Psammodictyon constrictum, and Tabularia affinis, were recorded from both sea turtles and floating debris samples, and none of these exceeded 4% of the average relative abundance on the sea turtle carapaces. The study reveals a clear substratum preference in sea turtle-associated diatoms, with no evidence for species turnover across the investigated region over different sampling seasons, thus confirming previous speculations that sea turtle diatom communities would show a high level of uniqueness and stability.