Communication range predicts dolphin alliance size in a cooperative mating system.

It is well known that communication range, often termed active space,1 varies with habitat structure, and this variation can influence individual vocal behavior across taxa.2,3 While theoretical predictions imply that communication distances can drive the evolution of mammalian alliance sizes,4 empirical tests of this hypothesis are currently lacking. In Shark Bay, Western Australia, unrelated male bottlenose dolphins form multilevel alliances, where males work together in pairs or trios to herd single estrus females.5,6,7,8 Here, we use empirical measures of male dolphin vocalizations, ambient noise levels, and high-resolution bathymetry data to estimate variation in active space across the study site. We combine this with long-term data on male alliance behavior to determine how active space influences alliance group size and mating success. We show that the active space of vocalizations used by allied males in a reproductive context predicts the number of preferred alliance partners with whom individuals cooperate over the longer term, ultimately contributing significantly to male access to mating opportunities. These results reveal that variation in sensory ecology driven by heterogeneous habitat influences optimal cooperative group size and mating success within a single population of wild animals.

Geographic genetic variation in the Coral Hawkfish, Cirrhitichthys oxycephalus (Cirrhitidae), in relation to biogeographic barriers across the Tropical Indo-Pacific.

The Tropical Indo-Pacific (TIP) includes about two thirds of the world's tropical oceans and harbors an enormous number of marine species. The distributions of those species within the region is affected by habitat discontinuities and oceanographic features. As well as many smaller ones, the TIP contains seven large recognized biogeographic barriers that separate the Red Sea and Indian Ocean, the Indian from the Pacific Ocean, the central and eastern Pacific, the Hawaiian archipelago, the Marquesas and Easter Islands. We examined the genetic structuring of populations of Cirrhitichthys oxycephalus, a small cryptic species of reef fish, across its geographic range, which spans the longitudinal limits of the TIP. We assessed geographic variation in the mitochondrial cytb gene and the nuclear RAG1 gene, using 166 samples collected in 46 localities from the western to eastern edges of the TIP. Sequences from cytb show three well-structured groups that are separated by large genetic distances (1.58-2.96%): two in the Tropical Eastern Pacific (TEP), one at Clipperton Atoll another occupying the rest of that region and the third that ranges across the remainder of the TIP, from the central Pacific to the Red Sea and South Africa. These results indicate that the ~4,000 km wide Eastern Pacific Barrier between the central and eastern Pacific is an efficient barrier separating the two main groups. Further, the ~950 km of open ocean that isolates Clipperton Atoll from the rest of the TEP is also an effective barrier. Contrary to many other cases, various major and minor barriers from the Central Indo-Pacific to the Red Sea are not effective against dispersal by C. oxycephalus, although this species has not colonized the Hawiian islands and Easter Island. The nuclear gene partially supports the genetic structure evident in cytb, although all haplotypes are geographically mixed.

Temporal patterns in coral disease prevalences at Thudufushi Island, Maldives, 2010-2022.

Coral reefs are lately suffering a fast decline in biodiversity due to the coupled effect of climate change and disease outbreaks, which in recent decades have been reported with higher frequency and shorter intervals. Limited studies have been conducted on coral diseases in the Maldives resulting in the impossibility of assessing the temporal trend in their dynamics. In this context, we evaluated the change in the distribution, prevalence, and host range of 4 diseases, namely black band disease (BBD), brown band disease (BrB), skeletal eroding band (SEB) and white syndrome (WS), in the reef system around Thudufushi Island after an interval of 12 yr since the last assessment. In this period, the overall disease prevalence increased, except for BrB, with SEB showing the most severe increase in 2022 in comparison to 2010. The overall average prevalence of coral diseases is approximately 2%, indicating an increase of about 0.7% since 2010. Diseased coral colonies were found in all the investigated sites, with the east site being the most affected and SEB emerging as the most prevalent disease across all the investigated sites. The affected colonies belong to 13 genera, with Psammocora genus showing the highest overall mean disease prevalence. This study depicted a basic temporal trend in disease prevalence that confirms an increase in coral diseases in the region and calls for a dedicated national monitoring protocol to better understand and predict future coral disease dynamics at regional scales.

Preliminary study of marine sponges (Porifera) in the littoral of Spermonde Archipelago, Indonesia.

Previous ecological studies show higher sponge diversity in the Spermonde Archipelago, SW Sulawesi, Indonesia, compared to the World Porifera Database. This study aims to provide an updated checklist of sponges of the Spermonde Archipelago, focusing particularly on the littoral area. Systematic sampling was executed through several observations, with roving techniques, e.g., snorkeling and SCUBA diving. In situ photographs of living sponges were taken using an underwater digital camera. Some specimens were collected and stored at the Naturalis Biodiversity Center, Leiden. Fragments of samples were analyzed using light and scanning electron microscopy. A total of 27 sponges (Calcarea and Demospongiae) were catalogued from the littoral area of the Spermonde Archipelago. Some of these are new records for the Sulawesi Sea/Makassar Strait marine ecoregion, including four potentially novel taxa. Preliminary morphological descriptions of all examined samples are presented. This study highlights the sponge assemblage flourishing in a shallow area characterized by a paucity of live corals and a predominant environment by macroalgae, rocks, and rubble.

Machine-learning based detection of marine mammal vocalizations in snapping-shrimp dominated ambient noise.

Passive acoustics is an effective method for monitoring marine mammals, facilitating both detection and population estimation. In warm tropical waters, this technique encounters challenges due to the high persistent level of ambient impulsive noise originating from the snapping shrimp present throughout this region. This study presents the development and application of a neural-network based detector for marine-mammal vocalizations in long term acoustic data recorded by us at ten locations in Singapore waters. The detector's performance is observed to be impeded by the high shrimp noise activity. To counteract this, we investigate several techniques to improve detection capabilities in shrimp noise including the use of simple nonlinear denoisers and a machine-learning based denoiser. These are shown to enhance the detection performance significantly. Finally, we discuss some of the vocalizations detected over three years of our acoustic recorder deployments using the robust detectors developed.

Neutral processes and taxonomic scale drive beta species-genetic diversity correlations in a submesophotic tropical reef fish.

If similar evolutionary forces maintain intra- and interspecific diversity, patterns of diversity at both levels of biological organization can be expected to covary across space. Although this prediction of a positive species-genetic diversity correlation (SGDC) has been tested for several taxa in natural landscapes, no study has yet evaluated the influence of the community delineation on these SGDCs. In this study, we focused on tropical fishes of the Indo-Pacific Ocean, using range-wide single nucleotide polymorphism data for a deep-sea fish (Etelis coruscans) and species presence data of 4878 Teleostei species. We investigated whether a diversity continuum occurred, for different community delineations (subfamily, family, order and class) and spatial extents, and which processes explained these diversity patterns. We found no association between genetic diversity and species richness (α-SGDC), regardless of the community and spatial extent. In contrast, we evidenced a positive relationship between genetic and species dissimilarities (ß-SGDC) when the community was defined at the subfamily or family level of the species of interest, and when the Western Indian Ocean was excluded. This relationship was related to the imprint of dispersal processes across levels of biological organization in Lutjanidae. However, this positive ß-SGDC was lost when considering higher taxonomic communities and at the scale of the entire Indo-Pacific, suggesting different responses of populations and communities to evolutionary processes at these scales. This study provides evidence that the taxonomic scale at which communities are defined and the spatial extent are pivotal to better understand the processes shaping diversity across levels of biological organization.

Remote sensing-based mangrove blue carbon assessment in the Asia-Pacific: A systematic review.

Accurate measuring, mapping, and monitoring of mangrove forests support the sustainable management of mangrove blue carbon in the Asia-Pacific. Remote sensing coupled with modeling can efficiently and accurately estimate mangrove blue carbon stocks at larger spatiotemporal extents. This study aimed to identify trends in remote sensing/modeling employed in estimating mangrove blue carbon, attributes/variations in mangrove carbon sequestration estimated using remote sensing, and to compile research gaps and opportunities, followed by providing recommendations for future research. Using a systematic literature review approach, we reviewed 105 remote sensing-based peer-reviewed articles (1990 - June 2023). Despite their high mangrove extent, there was a paucity of studies from Myanmar, Bangladesh, and Papua New Guinea. The most frequently used sensor was Sentinel-2 MSI, accounting for 14.5 % of overall usage, followed by Landsat 8 OLI (11.5 %), ALOS-2 PALSAR-2 (7.3 %), ALOS PALSAR (7.2 %), Landsat 7 ETM+ (6.1 %), Sentinel-1 (6.7 %), Landsat 5 TM (5.5 %), SRTM DEM (5.5 %), and UAV-LiDAR (4.8 %). Although parametric methods like linear regression remain the most widely used, machine learning regression models such as Random Forest (RF) and eXtreme Gradient Boost (XGB) have become popular in recent years and have shown good accuracy. Among a variety of attributes estimated, below-ground mangrove blue carbon and the valuation of carbon stock were less studied. The variation in carbon sequestration potential as a result of location, species, and forest type was widely studied. To improve the accuracy of blue carbon measurements, standardized/coordinated and innovative methodologies accompanied by credible information and actionable data should be carried out. Technical monitoring (every 2-5 years) enhanced by remote sensing can provide accurate and precise data for sustainable mangrove management while opening ventures for voluntary carbon markets to benefit the environment and local livelihood in developing countries in the Asia-Pacific region.

Endocrine-Disrupting Chemical Exposure Induces Adverse Effects on the Population Dynamics of the Indo-Pacific Humpback Dolphin.

Cetaceans play a pivotal role in maintaining the ecological equilibrium of ocean ecosystems. However, their populations are under global threat from environmental contaminants. Various high levels of endocrine-disrupting chemicals (EDCs) have been detected in cetaceans from the South China Sea, such as the Indo-Pacific humpback dolphins in the Pearl River Estuary (PRE), suggesting potential health risks, while the impacts of endocrine disruptors on the dolphin population remain unclear. This study aims to synthesize the population dynamics of the humpback dolphins in the PRE and their profiles of EDC contaminants from 2005 to 2019, investigating the potential role of EDCs in the population dynamics of humpback dolphins. Our comprehensive analysis indicates a sustained decline in the PRE humpback dolphin population, posing a significant risk of extinction. Variations in sex hormones induced by EDC exposure could potentially impact birth rates, further contributing to the population decline. Anthropogenic activities consistently emerge as the most significant stressor, ranking highest in importance. Conventional EDCs demonstrate more pronounced impacts on the population compared to emerging compounds. Among the conventional pollutants, DDTs take precedence, followed by zinc and chromium. The most impactful emerging EDCs are identified as alkylphenols. Notably, as the profile of EDCs changes, the significance of conventional pollutants may give way to emerging EDCs, presenting a continued challenge to the viability of the humpback dolphin population.

Melanella martarum sp. nov. (Gastropoda: Eulimidae): the first parasitic deep-sea snail reported for the Salas & Gomez Ridge.

Eulimidae is a highly diverse family of gastropods that are often parasites of echinoderms. They are cosmopolitan and live from the intertidal to great depths. Despite its wide geographic and bathymetric distribution, no species of Eulimidae have been reported for the Salas & Gómez Ridge to date. In this study, we describe Melanella martarum sp. nov., which was collected during the EPIC oceanographic cruise onboard RV Mirai (JAMSTEC, Japan) in 2019. Seven specimens were collected with a modified Agassiz trawl on the summit of seamount "Pearl" (Zhemchuznaya) in the Salas & Gómez Ridge (25.59°S, 89.13°W) at 545 m depth. The morphology of M. martarum sp. nov. was compared with other Melanella species reported for the area, including Chile and Rapa Nui. DNA was extracted and partial sequences of the mitochondrial genes Cytochrome Oxidase 1 (COI) and 16S rDNA, and the nuclear gene Histone 3 (H3) were sequenced. Melanella martarum sp. nov. has morphological characteristics that separate it from other species of Melanella, such as the thickness and color of the shell, and the shape of the protoconch. In addition, M. martarum sp. nov. was genetically differentiated from other Melanella spp. sequences (uncorrected p distances from 18,1-8.6% in mitochondrial COI and 16S rDNA to 3% in nuclear H3 sequences). Although there is not much molecular data available for Eulimidae, the phylogenetic analysis confirms the results obtained by morphology, placing the species found on the Salas & Gómez Ridge within the genus Melanella. The current study advances the understanding of the poorly known benthic fauna found on seamounts in the easternmost part of the Sala & Gómez ridge, a location distinguished by a high level of endemism.

Cenozoic Indo-Pacific warm pool controlled by both atmospheric CO2 and paleogeography.

The Indo-Pacific warm pool (IPWP) is crucial for regional and global climates. However, the development of the IPWP and its effect on the regional climate during the Cenozoic remain unclear. Here, using a compilation of sea surface temperature (SST) records (mainly since the middle Miocene) and multimodel paleoclimate simulations, our results indicated that the extent, intensity and warmest temperature position of the IPWP changed markedly during the Cenozoic. Specifically, its extent decreased, its intensity weakened, and its warmest temperature position shifted from the Indian to western Pacific Ocean over time. The atmospheric CO2 dominated its extent and intensity, while paleogeography, by restricting the distribution of the Indian Ocean and the width of the tropical seaways, controlled the shift in its warmest temperature position. In particular, the eastward shift to the western Pacific Ocean from the middle to late Miocene inferred from compiled SST records likely resulted from the constriction of tropical seaways. Furthermore, by changing the atmospheric thermal structure and atmospheric circulation, the reduced extent and intensity of the IPWP decreased the annual precipitation in the western Indian Ocean, eastern Asia and Australia, while the shift in the warmest temperature position from the Indian to western Pacific Ocean promoted aridification in Australia. Qualitative model-data agreements are obtained for both the IPWP SST and regional climate. From the perspective of past warm climates with high concentrations of atmospheric CO2, the expansion and strengthening of the IPWP will occur in a warmer future and favor excessive precipitation in eastern Asia and Australia.

Broad-scale impacts of coastal mega-infrastructure project on obligatory inshore delphinids: A cautionary tale from Hong Kong.

Inshore marine habitats experience considerable anthropogenic pressure, as this is where many adverse effects of human activities concentrate. In the rapidly-changing seascape of the Anthropocene, Hong Kong waters at the heart of world's fastest developing coastal region can serve as a preview-window into coastal seas of the future, with ever-growing anthropogenic footprint. Here, we quantify how large-scale coastal infrastructure projects can affect obligatory inshore cetaceans, bringing about population-level consequences that may compromise their long-term demographic viability. As a case in point, we look at the construction of world's longest sea crossing system and broad-scale demographic, social and spatial responses it has caused in a shallow-water delphinid, the Indo-Pacific humpback dolphin (Sousa chinensis). Soon after the infrastructure project began, dolphins markedly altered their home range near construction sites such that these waters no longer functioned as dolphin core areas despite the apparent presence of prey, indicating that anthropogenic impacts outweighed foraging benefits. The contraction of key habitats has in turn led individuals to interact over spatially more constricted area, reshaping their group dynamics and social network. Although there was no apparent decline in dolphin numbers that could be detected with mark-recapture estimates, adult survival rates decreased drastically from 0.960 to 0.904, the lowest estimate for these animals anywhere across the region to date, notably below the previously estimated demographic threshold of their long-term persistence (0.955). It is apparent that during an advanced stage of this coastal infrastructure project, dolphins were under a major anthropogenic pressure that, if sustained, could be detrimental to their long-term persistence as a viable demographic unit. As effective conservation of species and habitats depends on informed management decisions, this study offers a valuable lesson in environmental risk assessment, underscoring the implications of human-induced rapid environmental change on obligatory inshore delphinids-sentinels of coastal habitats that are increasingly degraded in fast-changing coastal seas.

The adaptive significance of large size at birth in marine snakes.

Evolutionary shifts from one habitat type to another can clarify selective forces that affect life-history attributes. Four lineages of snakes (acrochordids and three clades within the Elapidae) have invaded marine habitats, and all have larger offspring than do terrestrial snakes. Predation by fishes on small neonates offers a plausible selective mechanism for that shift, because ascending to breathe at the ocean surface exposes a marine snake to midwater predation whereas juvenile snakes in terrestrial habitats can remain hidden. Consistent with this hypothesis, snake-shaped models moving through a coral-reef habitat in New Caledonia attracted high rates of attack by predatory fishes, and small models (the size of neonatal terrestrial snakes) were attacked more frequently than were large models (the size of neonatal sea snakes). Vulnerability to predatory fishes may have imposed strong selection for increased offspring size in marine snakes.

Mass mortality event of the giant barrel sponge Xestospongia sp.: population dynamics and size distribution in Koh Phangan, Gulf of Thailand.

Marine sponges are prominent organisms of the benthic coral reef fauna, providing important ecosystem services. While there have been increasing reports that sponges are becoming one of the dominant benthic organisms in some locations and ecoregions (e.g. Caribbean), they can be impacted by changing environmental conditions. This study presents the first documentation of a mass mortality event of the barrel sponge Xestospongia sp. in the lower Gulf of Thailand and its consequences on population dynamics and size distribution. Two anthropogenic impacted reefs (Haad Khom and Mae Haad) of the island Koh Phangan and two anthropogenic non-impacted reefs of the islands Koh Yippon and Hin Yippon within the Mu Ko Ang Thong Marine National Park were surveyed in the years 2015 and 2016. The results showed a strong shift in population densities at Koh Phangan. Fatal "bleaching" ending up in mass mortality was observed for these reefs in 2015. Xestospongia sp. abundance decreased from 2015 to 2016 by 80.6% at Haad Khom and by 98.4% at Mae Haad. Sponges of all sizes were affected, and mortality occurred regardless of the survey depth (4 and 6 m). However, Xestospongia population densities in the Marine Park were at a constant level during the surveys. The abundances in 2015 were 65% higher at the Marine Park than at Koh Phangan and 92% higher in 2016. The most likely causes of the mass mortality event was a local harmful algal bloom event, pathogens, undetected local higher water temperatures, or a combination of these factors, whereas sea surface temperature analyses showed no marine heatwave during the observed mass mortality event in 2015. Considering the ecological importance of sponges such as Xestospongia sp., long-term monitoring of reefs and their environmental parameters should be implemented to prevent such mass die-offs.

National assessment and variability of blue carbon in seagrass ecosystems in Thailand.

Seagrass ecosystems are important organic carbon (Corg) sinks with great potential to contribute to climate change mitigation strategies. However, the high spatial and temporal variability is a barrier to the accurate assessment of national Corg stocks. This study provides a national assessment of Corg within seagrass meadows, including spatial and temporal variations. The highest Corg stocks were within mangrove-associated (44.3 ± 8.27 Mg ha-1), while near-surface sediments were highest in reef-associated meadows (10.20 ± 3.69 Mg ha-1). Regionally, the highest stocks were in the Upper Andaman coast in monospecific meadows (51.7 ± 7.14 Mg ha-1). Corg stocks in near-surface sediments were significantly different across historical trends (p < 0.001), with the highest stocks in stable meadows (9.28 ± 3.39 Mg ha-1). The national Corg stock within seagrass meadows sediment was 40.45 ± 11.59 Mg C ha-1. The results of this study highlighted the complexity of blue carbon in seagrass meadows and the associated impacts on national Corg assessments, carbon accounting, and conservation strategies.

Blue carbon assessments of seagrass and mangrove ecosystems in South and Southeast Asia: Current progress and knowledge gaps.

Coastal blue carbon ecosystems can be an important nature-based solution for mitigating climate change, when emphasis is given to their protection, management, and restoration. Globally, there has been a rapid increase in blue carbon research in the last few decades, with substantial investments on national scales by the European Union, the USA, Australia, Seychelles, and Belize. Blue carbon ecosystems in South and Southeast Asia are globally diverse, highly productive and could represent a global hotspot for carbon sequestration and storage. To guide future efforts, we conducted a systematic review of the available literature on two primary blue carbon ecosystems-seagrasses and mangroves-across 13 countries in South and Southeast Asia to assess existing national inventories, review current research trends and methodologies, and identify existing knowledge gaps. Information related to various aspects of seagrass and mangrove ecosystems was extracted from 432 research articles from 1967 to 2022. We find that: (1) blue carbon estimates in several countries have limited data, especially for seagrass meadows compared to mangrove ecosystems, although the highest reported carbon stocks were in Indonesia and the Philippines with 4,515 and 707 Tg within mangrove forest and 60.9 and 63.3 Tg within seagrass meadows, respectively; (2) there is a high difference in the quantity and quality of data between mangrove and seagrass ecosystems, and the methodologies used for blue carbon estimates are highly variable across countries; and (3) most studies on blue carbon stocks are spatially biased towards more familiar study areas of individual countries, than several lesser-known suspected blue carbon hotspots. In sum, our review demonstrates the paucity and variability in current research in the region, and highlights research frontiers that should be addressed by future research before the robust implementation of these ecosystems into national climate strategies.

Podarkeopsischinensis sp. nov. (Annelida, Hesionidae) from southeastern China.

Podarkeopsischinensissp. nov. (Annelida, Hesionidae) is described based on specimens collected from the coast of southeast China. It is the first Podarkeopsis species described from the Indo-Pacific, although there are already nine valid Podarkeopsis species known from other parts of the world. This new species can be distinguished from the other Podarkeopsis species in having a palpostyle as long as the palpophore and double aciculae in both notopodia and neuropodia, and in bearing bifid furcate chaetae which have a smooth base on the shorter tine. A phylogenetic analysis based on the concatenated sequences of five gene fragments (COI, 16S rRNA, 18S rRNA, 28S rRNA, and histone H3) from 18 specimens of P.chinensissp. nov. showed that they formed a monophyletic clade that is sister to P.levifuscina. K2P genetic distances indicated that the four gene fragments (COI, 16S rRNA, 18S rRNA, and 28S rRNA) of P.chinensissp. nov. diverged from the corresponding sequences of the closest related species of Podarkeopsis in GenBank and BOLD Systems by 21.1-27.5%, 20.3-23.1%, 0.1-0.2%, and 2.1-3.2%. An identification key is provided for species in the genus Podarkeopsis.

The Exploitation of Toxic Fish from the Terminal Pleistocene in Maritime Southeast Asia: A Case Study from the Mindoro Archaeological Sites, Philippines.

Representatives of the Diodontidae family (porcupinefish) are known to have been fished by prehistoric Indo-Pacific populations; however, the antiquity of the use of this family is thus far unknown. We report here on the presence of Diodontidae in the archaeological sites of Bubog I, II, and Bilat in Mindoro, Philippines, dating back to c. 13,000 BP (Before Present). This evidence demonstrates the early exploitation by islanders of poisonous fish. Every part of porcupinefish can be toxic, but the toxicity is mostly concentrated in some organs, while other parts are edible. The continuous presence of Diodontidae remains throughout the stratigraphic record of these Philippines shell middens suggests that porcupinefish were prepared by human inhabitants of the sites to render them safe for consumption, indicating an advanced cultural knowledge of the preparation needed to separate the toxic principle from the edible parts. This constitutes one of the rare examples of poison processing by humans, aside from the contentious wooden stick poison applicator from Border Cave (South Africa).

Entanglement in recreational fishing gear poses a threat to estuarine and coastal dolphins: Animal welfare and population level impacts should guide intervention decision making.

Derelict and active fishing gear poses a threat to marine wildlife. This study details Indo-Pacific bottlenose dolphin entanglements in recreational fishing gear in the Peel-Harvey Estuary, Western Australia between 2016 and 2022. Eight entanglements were recorded, three resulted in death. While concerning from an animal welfare perspective, the impact of entanglements on the viability of the local dolphin population was low. This is as majority of affected individuals were juvenile males. Should entanglements result in the loss of reproductive females, or impact their reproductive success, the population trajectory could quickly change. As such, management decision making should consider population level impacts as well as the welfare of entangled individuals. Government agencies, together with relevant stakeholders, should work together to maintain preparedness to respond to entanglements and take preventative action that lowers the risk of interactions with recreational fishing gear.

Hormonal biomarkers provide insights into the reproductive biology and pollutants-associated health hazards of endangered dolphins.

Contaminants are known to contribute to the reproductive health hazards of wildlife, but pollutants-associated detrimental impacts on the endangered Indo-Pacific humpback dolphins (Sousa chinensis, IPHD) are largely unknown due to a lack of reproductive parameters. Here we validated and applied blubber progesterone and testosterone as reproductive biomarkers to assess reproductive parameters of IPHD (n = 72). The gender-specific progesterone concentrations and progesterone/testosterone (P/T) supported progesterone and testosterone as valid biomarkers in identifying the genders of IPHD. Significant month-to-month variations of two hormones indicated a seasonal reproduction, in accordance with the observation of photo-identification approach, further supporting testosterone and progesterone as ideal reproductive biomarkers. Progesterone and testosterone concentrations showed significant differences between Lingding Bay and West-four region, possibly due to chronically geographic-specific pollutants differences. The significant relationships between sex hormones and multiple contaminants suggested that contaminants contribute to the disruption of testosterone and progesterone homeostasis. The best explanatory models between pollutants and hormones suggested that dichlorodiphenyltrichloroethanes (DDTs), lead (Pb) and selenium (Se) were the major risk factors jeopardizing the reproductive health of IPHD. This is the first study on the relationship between pollutant exposure and reproductive hormones in IPHD and represents a substantial advance in understanding the detrimental reproductive impacts of pollutants on endangered cetaceans.

Introduction to the Special Issue: Theory and Practice of Connectivity in the Indo-Pacific-Spheres, Logics, and Regional Dynamics.

This short introduction to the Special Issue entitled "Theory and Practice of Connectivity in the Indo-Pacific - Spheres, Logics, and Regional Dynamics" serves four objectives. It first briefly outlines the rationale for theoretical and empirical engagement with the concept of connectivity, which has become a ubiquitous term in the policy parlance of key global actors in recent years. The introduction then provides a short leader on the connectivity initiatives of key players, specifically China, the USA, Japan, the European Union, and Russia, with a particular focus on the Indo-Pacific space. Third, the seven articles that comprise the Special Issue are summarised. The contributions include a theoretically and conceptually oriented lead article, which introduces an analytical framework for the study of connectivity, and six more empirically motivated contributions that draw upon the said framework. Finally, key takeaways arising from the articles with respect to a broader research agenda on connectivity are discussed.