Pleistocene climate oscillations, environmental factors, and gene flow have profoundly shaped the phylogeographic patterns of marine species. However, our understanding of phylogeographic patterns of broadcast-spawning marine molluscs studies remains limited. To elucidate the phylogeography pattern of the gold-mouth turban Turbo chrysostomus in the South China Sea (SCS), individuals from five populations of T. chrysostomus SCS, including two northern SCS populations and three southern SCS populations, were collected for mitochondrial cytochrome oxidase subunit I and double-digest restriction-site associated DNA sequencing analyses. Our results indicated a weak geographic pattern in T. chrysostomus, with shallow genetic differentiation between the northern and southern populations. Demographic history analyses showed that T. chrysostomus in the SCS colonized and expanded during the Last Interglacial (130–75 ka), facilitated by elevated sea levels and increasing temperatures, with ancestral clusters that can be traced to glacial refugia. In addition, phylogeographic analyses revealed a north-to-south expansion pattern, contrasting with the tropical-to-temperate expansion observed in many marine taxa. This pattern suggests that ancestral lineages of T. chrysostomus originating from western Pacific refugia dispersed into the SCS via the Luzon Strait during periods of rising sea levels and increasing temperatures. Results of our redundancy analysis and BayeScan revealed that ocean temperature may be a factor maintaining the north-south genetic differentiation. Our study provides important insights into the genetic structure and demographic history of T. chrysostomus across the SCS, highlighting the impacts of Pleistocene climatic oscillations and environmental gradients on phylogeographic patterns.
Understanding how shorebirds respond to changes in prey dynamics is essential for interpreting their ecological adaptability in coastal systems. In this study, we investigated temporal variation in foraging behaviour, diet composition, and prey-specific consumption of the Kentish Plover on sandy beach along the west coast of India. Foraging observations were conducted using high-definition video recordings from 2020 to 2024, and successful prey captures were analysed in relation to superficial and deep foraging modes. Diet composition was assessed using NMDS and PERMANOVA, while prey-specific trends were examined using generalized linear mixed-effects models. Results showed a significant decline in successful superficial captures and a corresponding increase in successful deep captures over time. Despite these behavioural shifts, overall diet composition remained stable, with sand crabs consistently dominating the diet across all years. However, prey-specific analysis revealed a significant increase in sand crab consumption, alongside declines in aquatic insects, bivalves and small crabs. Deep foraging was more strongly associated with sand crab capture, whereas superficial foraging was linked to small crabs and aquatic insects. These findings indicate that Kentish Plover responds to changes in prey dynamics primarily through behavioural adjustments rather than dietary shifts. The study highlights that stable diet composition can mask important prey-specific changes and emphasizes the role of behavioural flexibility in maintaining feeding efficiency in dynamic sandy beach environments.
Analyzing the behavior and body patterns of octopuses in nature is challenging due to their camouflage capabilities, changes in skin texture and color, body deformations, and frequent occlusions. Underwater lighting and turbidity further complicate these challenges. Addressing the lack of large-scale annotated datasets, we introduce HideAndSeg, a minimally supervised, AI-based tool for segmenting octopus videos. HideAndSeg integrates SAM2 with a custom-trained YOLOv11 object detector. First, the user provides point coordinates to generate the initial segmentation masks with SAM2. These masks serve as training data for the YOLO model. Our approach automates the pipeline by providing a bounding-box prompt to SAM2, eliminating manual intervention. We introduce two unsupervised metrics – temporal consistency and new component count – to quantitatively evaluate segmentation quality and guide mask refinement in the absence of real-world information used to train, validate, and test AI models. HideAndSeg reduces segmentation noise compared to the manually prompted approach. Our method can re-identify and segment the octopus even after complete occlusion, a scenario in which the manually prompted model fails. By reducing manual analysis in real-world scenarios, this work provides a practical tool that enables more efficient behavioral studies of wild octopuses.
Dinoflagellate algae from the family Symbiodiniaceae are essential endosymbionts of reef-building corals. However, environmental changes such as shifts in temperature, light, or turbidity can disrupt this association and alter Symbiodiniaceae community structure. In the Eastern Tropical Pacific (ETP), Pocillopora corals exhibit regional differences in their symbiont assemblages. This study examined how the structure of Symbiodiniaceae communities associated with Pocillopora mtORF type 1 lineage varies spatially along a coastal-oceanic gradient. We analyzed 181 coral colonies collected across three depths (1–5 m, 5–10 m, and > 10 m) at four localities in the Colombian Pacific. Symbionts were identified using next-generation sequencing of the ITS2 region and analyzed with the SymPortal platform. We detected Durusdinium glynnii, as well as Cladocopium C3, C. latusorum, and C. goreauii. Symbiont community composition varied with both coastal proximity and depth, suggesting that environmental gradients influence current patterns of Symbiodiniaceae structure. However, despite a significant contribution of Chlorophyll-a, Sea Surface Salinity, Colored Dissolved Organic Matter, and Sea Surface Temperature, these factors explained a limited portion (16.9
In coastal ecosystems, interactions among grazers, microorganisms, and plants play a crucial role in shaping plant health and ecosystem dynamics. Recent work shows that snail grazing on live seagrass creates wounds that can facilitate fungal infection, a potential pathway of invertebrate top-down control. Whether density-dependent snail grazing measurably affects fungal infection and seagrass health in the field remains untested. We combined field surveys with a manipulative experiment to examine how fungal infection and health of Thalassia testudinum vary with different densities of the herbivorous smooth tegula, Tegula fasciata snail in Bocas del Toro, Panama. Surveys showed that smooth tegula density was positively associated with scarring prevalence and increased brown tissue (indicative of fungal infection). In a four-week experiment manipulating smooth tegula density (0, 1, 2, 4, and 6 snails per 0.25 m2), we detected no significant effects on seagrass metrics including biomass, productivity, shoot density, or degree of fungal colonization, despite visible emergence of radulation scars on blades. The only significant effect was on shoot number, with one-snail treatments producing more shoots than six-snail treatments. Although snail presence increased scarring on new growth blades relative to snail-free controls, tissue damage did not translate into detectable effects on plant performance or fungal biomass. These results suggest that T. testudinum compensates effectively for snail grazing over short timescales, as it does for larger grazers such as turtles, and that the grazer-pathogen facilitation pathway documented in other marine plant systems may not operate over short experimental timescales in turtlegrass. Together, these findings suggest a degree of ecological co-tolerance between T. testudinum and invertebrate grazers, though whether this tolerance holds under sustained grazing pressure or compounding environmental stressors warrants further investigation.
