Mawlamyine University

The upper middle Eocene Pondaung Formation of central Myanmar has yielded some of the earliest stem anthropoids outside Afro-Arabia. In contrast, strepsirrhine primates are rare and previously known only from the small-bodied sivaladapids Kyitchaungia takaii and Paukkaungia parva. Here we report a new large-bodied sivaladapid based on an isolated M3 from Pondaung, described as Guangxilemur rarissimus sp. nov. The tooth exhibits diagnostic features of Guangxilemur, including a subrectangular outline, a deep trigon basin, an incipient mesostyle, a well-developed buccal cingulum, and pronounced enamel wrinkling. Its dimensions indicate a body mass of approximately 4.1-4.8 kg, substantially larger than previously known Pondaung strepsirrhines and closely matching estimates for the controversial partial postcranial skeleton NMMP 20, previously attributed to the amphipithecine Pondaungia. Because NMMP 20 displays clear strepsirrhine affinities and corresponds in size to G. rarissimus, we reassign this specimen to the new taxon. This resolves the long-standing debate over the phylogenetic identity of NMMP 20 and eliminates a major source of conflict between craniodental and postcranial data, hampering previous interpretations of early anthropoid evolution in Asia. Additional material of Paukkaungia supports the recognition of greater ecological diversity among sivaladapids within the Pondaung primate community.

The Eocene record of elasmobranchs in the eastern Neotethys (Indo-Pacific area) remains notably sparse, especially when compared to that of its western counterpart, which borders North America, Europe, and North Africa. This study provides the second comprehensive account of Middle–Late Eocene elasmobranch assemblages from Myanmar and documents the presence of seven Carcharhiniforms and Batoids, including a newly identified fossil species of carcharhinid. The faunal composition, dominated by euryhaline or freshwater-tolerant taxa such as Dasyatidae, Pristidae, and Odontorhytis pappenheimi, strongly indicates a depositional environment influenced by brackish water or substantial freshwater input, consistent with sedimentological evidence and observations from contemporary sites in North Africa. The occurrence of these taxa in Myanmar represents the easternmost record of several Late Eocene elasmobranchs, emphasizing ancient dispersal routes along the tropical Atlantic and Neotethys coasts. This modest assemblage highlights the potential for greater elasmobranch diversity in the dynamic Neotethys during the Palaeogene than is currently recognized and may signal early shifts of biodiversity hotspots towards the Indo-Pacific.

ABSTRACT Microplastic (MP) contamination was investigated in the gastrointestinal tract (GIT) and gills of 238 fish representing eight commercially important species collected from retail markets in Mawlamyine, Myanmar. MPs were detected in the GIT and/or gills of all examined fish, corresponding to a prevalence of 100%. Mean total abundance ranged from 5.44 ± 1.23 particles fish −1 in Rastrelliger sp. to 18.91 ± 2.74 particles fish −1 in Tenualosa ilisha , while mass‐normalized concentration ranged from 0.0464 to 0.2977 particles g − 1 . Paired gut–gill comparisons were evaluated using a Shapiro–Wilk‐dependent approach: Wilcoxon signed‐rank tests were applied to six species with non‐normal paired differences, and paired‐samples t ‐tests were applied to Polynemus paradiseus and T. ilisha , whose paired differences were compatible with normality. All eight tissue comparisons were significant at p < 0.001. Gut abundance exceeded gill abundance in six species, whereas Rastrelliger sp. and T. ilisha exhibited gill‐dominant burdens. Fibres were the dominant morphotype in six species, while paint‐like particles were prominent in Rastrelliger sp. and T. ilisha . Particles measuring 20–50 µm represented a substantial proportion of the recovered particles. ATR–FTIR analysis assigned 238 of 270 analysed particles (88.1%) to polyethylene terephthalate, polyethylene, polypropylene, polystyrene or polyamide/nylon. Under a hypothetical sole‐species consumption scenario based on a fish intake rate of 123 g person − 1 day − 1 , estimated daily intake ranged from 5.71 to 36.62 particles person − 1 day − 1 , and body‐weight‐normalized intake ranged from 0.0990 to 0.6347 particles kg − 1 day − 1 . The Exposure Risk Index ranged from 1.00 to 6.41 and was used only as a relative within‐study ranking; it is not a validated toxicological, regulatory or human‐health threshold.

The Nu-Salween River represents the second-longest riverand one of the last major free-flowing systems inSoutheast Asia, constituting a globally significant reservoirof freshwater biodiversity. However, basin-wide patterns offish diversity across taxonomic, phylogenetic, andfunctional dimensions, together with weighted endemism,remain poorly understood, and the environmentaldeterminants shaping these patterns are not well resolved.To address this limitation, a basin-scale analysis wasconducted using 26 998 georeferenced occurrence recordsencompassing 445 native freshwater fish speciesdistributed across 382 subdrainages. Species richness,phylogenetic diversity, functional diversity, and weightedendemicity exhibited unexpected bimodal distributionsalong the longitudinal gradient, revealing two distinct peaksfrom headwaters to downstream reaches. Climatic andgeographic gradients emerged as dominant drivers ofspatial structure. Mean annual air temperature, distance toriver mouth, elevation, and net primary productivity exertedstrong influences on both species richness andphylogenetic diversity. Functional diversity increasedprimarily with mean annual air temperature and annualtotal precipitation, whereas weighted endemicity declinedwith increasing subdrainage area. Although the conflictsbetween anthropogenic disturbances and fish diversity patterns were weak, protection coverage across priorityareas identified for different diversity facets remainedcritically low, ranging from 0.1% to 15.9%. Divergentspatial configurations among diversity dimensions,combined with inadequate representation within existingprotected-area networks, highlight an urgent need for moretargeted and context-specific conservation strategies.Effective management strategies must consider theatypical bimodal longitudinal structure of fish diversity andthe multidimensional relationships among diversity facetsto sustain ecosystem function and resilience underintensifying anthropogenic pressure.

Pyropia is a genus comprising red algae of the Bangiaceae family that is commonly found in intertidal zones worldwide. However, understanding of Pyropia species that are prone to tropical regions remains limited despite recent breakthroughs in genomic research. Within the realm of Pyropia s pecies thriving in tropical regions, P. vietnamensis stands out as a widely recognized species. In this study, we aimed to investigate Pyropia species in the southwest coast of Myanmar using physiological and molecular approaches, culture-based analyses, chloroplast rbcL and nuclear SSU gene sequencing, and whole chloroplast and mitochondrial genome sequencing. Physiological analysis showed that the Myanmar samples were more heat-tolerant than their Japanese counterparts, including those of subtropical origin. Additionally, molecular characterization revealed that the Myanmar samples were closely related to P. vietnamensis from India. This study is the first to sequence the chloroplast and mitochondrial genomes of Pyropia species from tropical regions. A unique deletion event was observed within a ribosomal RNA gene cluster in the chloroplast genome of the studied Pyropia species, which is a deviation from the usual characteristics of most Pyropia species. This study improves current understanding of the physiological and molecular characteristics of this comparatively understudied Pyropia species that grows in tropical regions.