Lingulid shell (Brachiopoda: Lingulata) is a marine invertebrate that still exists. The mangrove profile on the north coast of East Java shows the potential to become a habitat for lingulid shell. Despite the significant potential, the lack of similar previous data on substrate profiles, population, and species distribution in East Java shows that the presence of lingulid shells has received less attention, suggesting the need for conservative efforts to conserve and sustainable uses of marine resource. Therefore, this study aimed to describe the habitat ecology of lingulid shell on the north coast of East Java based on regency or city, population structure, internal distribution pattern, and substrate profile, as well as identify species distribution. In addition, confirm the lingulid shell species by molecular identification based on cytochrome oxidase subunit I (COI) gene. Sampling was carried out using the purposive sampling method by digging the substrate in the plot area to a depth of 5-10 cm on the north coast of East Java to obtain lingulid frame substrate which was tested based on the fraction (size). The results showed that lingulid shell could be found in Surabaya City as well as other regencies including Pasuruan, Probolinggo, Situbondo, Bangkalan, Pamekasan, and Sumenep. The discovery results identified the Lingula anatina species based on morphological and molecular characteristics. The population density of lingulid shell in East Java was found to be 52.6 individuals.m-2, while the internal distribution had no continuity. Furthermore, the presence and distribution of Lingula anatina had a preference for silt substrates.

Estuaries are diverse coastal ecosystems that act as transitional zones between freshwater and seawater. The Don Hoi Lot tidal flat, located in the upper Gulf of Thailand, is one of Thailand's most important estuarine ecosystems. Nonetheless, the Don Hoi Lot area faces increasing environmental pressures due to human activities and natural changes. One of the most prominent species well-known in this area is the razor clam Solen regularis. This study investigated the effects of salinity fluctuations on the osmotic properties and antioxidant enzyme activities of the five tissues: foot, mantle, adductor muscle, gill, and digestive gland from the razor clam S. regularis collected from the Don Hoi Lot tidal flat. Razor clams were exposed to a range of salinity levels (0-35 PSU) for 7 days. The results indicated that the hemolymph osmolality of S. regularis increased with increasing salinity, demonstrating an osmoconforming pattern. Salinity changes significantly affected the activities of antioxidant enzymes (SOD, CAT, and GPX) in various tissues. In most tissues, SOD and CAT activities increased at higher salinities (30-35 PSU), while GPX activity generally increased across all tissues with increasing salinity. GST activity was not significantly affected by salinity changes. These findings suggest that S. regularis can activate antioxidant defense systems to reduce oxidative stress caused by salinity fluctuations. This study provides valuable insights into the physiological responses of S. regularis to environmental salinity changes, which can inform conservation efforts for this ecologically important species in estuarine ecosystems.

This study examined the osmoregulatory responses to hypo-osmotic shock in the commercially and ecologically important crab Episesarma mederi (H. Milne Edwards, 1853). After the acclimation for one week at a salinity of 25 PSU, Adult males E. mederi were immediately exposed to salinities of 5 PSU and 25 PSU (the control group). The time course of changes in haemolymph osmolality, gill Na+/K+ ATPase (NKA) activity, oxygen uptake rates, and mRNA expression levels of ion-transport related genes, including the NKA-α subunit, V-type H+ATPase (VT) and Na+/K+/2Cl-(NKCC), were determined. The results showed that E. mederi was a strong hyperosmoregulator after exposure to 5 PSU, achieved by modulations of NKA activity in their posterior gills rather than the anterior gills. The crabs acclimated to 5 PSU increased oxygen uptake, especially during the initial exposure, reflecting increased energetic costs for osmotic stress responses. In the posterior gills, the NKA activities of the crabs acclimated to 5 PSU at 3, 72 and 168 h were significantly higher than those in the control group. Elevated NKA-α subunit expression levels were detected at 6 h and 12 h. Increased expression levels of VT and NKCC were identified at 6 h and 12 h, respectively. Our results indicate that elevated gill NKA activity at 3 h could result from enzyme activity and kinetic alterations. On the other hand, the gill NKA activity at 72 and 168 h was sustained by elevated NKA-α subunit expression. Hence, these adaptive responses in osmoregulation enable the crabs to withstand hypo-osmotic challenges and thrive in areas of fluctuating salinity in mangroves and estuaries.

The sesarmid crab Episesarma mederi (H. Milne Edwards, 1853) lives in mid to upper intertidal mangroves, while its physiological responses to salinity are still poorly known. Here, we examined the effects of salinity on osmoregulatory and antioxidant enzyme responses of E. mederi. The crabs were exposed to experimental salinities ranging from 5 to 40 PSU for 96 h under the laboratory conditions. After that, haemolymph osmolality, oxygen consumption rates (OCR), gill Na+/K+ ATPase (NKA) activity and selected antioxidant enzyme activities of the crabs were analysed. Our results showed that E. mederi was a euryhaline hyper-hypo-osmoregulator. Hyperosmoregulation at low salinities was achieved by elevated gill NKA activity. The crabs acclimated to 5 PSU exhibited a significant increase in their OCRs compared to those in the control group (25 PSU). Conversely, the gill NKA activities were unchanged at high salinities. The OCRs increased only at a salinity of 35 PSU under high salinity conditions. Salinity changes can cause modulations in gill catalase (CAT) activity, while the gill superoxide dismutase (SOD) activity was unaffected. This result indicates that the crab gills could experience some degrees of oxidative stress during salinity acclimation. Overall, these physiological abilities can enable E. mederi to thrive in salinity-fluctuating areas.

High suspended loading is one of the environmental stressors which could affect survival rates and feeding activities of marine bivalves especially the coastal species. Therefore, this study aimed to examine the effects of suspended particles (SP) on filtration rates of the green-lipped mussel Perna viridis, which is a commercial bivalve species in Thai coastal waters. The large and small mussels were subjected to 250 mg and 500 mg of SP/l, and a control treatment (0 mg of SP/l) in the experimental laboratory. Filtration rates of the mussels were measured at day 0, day 15, and day 20 after the exposure to SP. The results showed that filtration rates of two class-sizes of the mussels significantly decreased after the exposure to SP for 15 and 20 days. Before the exposure to SP (day 0), the large mussels had significantly greater filtration rates than the smaller individuals, indicating the size-dependent effects. Filtration rates of the mussels decreased with increasing concentrations of SP. Gill abnormalities, e.g., loss of cilia on the gill lamella, were detected in the selected mussels at 500 mg of SP/l. The small mussels exhibited less capability in maintaining filtration rates compared with the larger mussels under high SP concentration. Moreover, changes in filtration rates over the exposure time were also discussed based in our study. Overall, the results can reflect deleterious effects of high SP on the mussels, particularly in filter-feeding activities. These findings could raise environmental concerns over high SP that could damage cultured mussels and coastal ecosystems.

The kidney of fish contains numerous nephrons, each of which is divided into the renal corpuscle and renal tubules. This glomerular structure is the filtration unit of the nephron and is important for the kidney function, but it has been reported that the renal corpuscle was lost in at least four independent linages of fish (i.e., aglomerular kidney). In this study, the authors newly described renal structures for three species by histological and ultrastructural observations: two aglomerular kidneys from a seahorse Hippocampus barbouri and a toadfish Allenbatrachus grunniens and a glomerular kidney from a snake eel Pisodonophis boro. The renal development of H. barbouri was also described during 1-35 days after birth. In all species tested, the anterior kidney was comprised of haematopoietic tissues and a few renal tubules, whereas the posterior kidney contained more renal tubules. Although the glomerular structure was present in P. boro, light microscopic observations identified no glomeruli in the kidney of H. barbouri and A. grunniens. Ultrastructurally, abundant deep basal infoldings with mitochondria in the renal tubules were observed in A. grunniens compared to H. barbouri and P. boro, suggesting the possible role of basal infoldings in maintaining the osmotic balance. By integrating the results from the three species and comprehensive literature search, the authors further showed that 56 species have been reported to be aglomerular, and that the aglomerular kidney has evolved at least eight times in bony fishes.

Many marine organisms, especially molluscs, produce mucus, which can be used in several physiological processes, such as locomotion and defence. In addition to utilization for themselves, mollusc mucus may influence intertidal community dynamics. Therefore, the biochemical composition of Onchidium typhae Buchannan, 1800 mucus was investigated. The effects of mucus on the microphytobenthos growth rate, representing the ecological functions of the mucus, were also tested. The results showed that the mucus was mainly composed of water (82.5%), and a large proportion of the organic content in mucus consisted of proteins (40%), followed by carbohydrates (13.33%) and lipids (0.19%). The effects of mucus on microphytobenthos growth were conditional and genus-specific. Growth of Navicular sp. and Nitzschia sp. significantly responded to different concentrations and incubation times of the slug mucus. Fresh and concentrated mucus inhibited the growth of both species; low mucus concentration and longer incubation time showed a significant increase in the growth rates of both species. However, no effect of mucus on the Thalassiosira sp. growth rate was observed. These effects of mucus on diatom growth are discussed. Moreover, our findings suggested that the intertidal slug O. typhae may act as an intertidal ecosystem engineer, which can facilitate and influence benthic phytoplankton community dynamics.

The health status of the zebra-snout seahorse, Hippocampus barbouri in captivity has been required for approval for aquaculture. In this study, we investigated the histopathological appearance of three vital organs including gill, kidney and liver in captive H. barbouri during its juvenile and adult stages, by using histological techniques. In juveniles from stage 14-days (100% prevalence) towards stage 30-days adults (100% prevalence), the gills exhibited intraepithelial edema and necrosis while hepatic tissue showed evidence of intracytoplasmic vacuoles. In addition, histological alteration to renal tissues was observed the degeneration of renal tubules, the presence of melanomacrophage, and the infection of trematode parasites. The parasites were found in stage 30-days adult fish in the kidney (33.3 % prevalence). Taken together, this study highlights the issue of health in captive rearing of H. barbouri, in particular histopathological alterations in gill, liver and kidney tissues, suggesting that aquaculture of this seahorse species requires improved methods and protocols for maintenance and preventing infection.

The activity of the sensory organ in the eye structure of the teleost fish is essential as it plays an important role in regulating fish-feeding behaviours. Unfortunately, the above information of zebra-snout seahorse Hippocampus barbouri, an aquaculture species in Thailand, has not been described. In this study, the eye structure, together with the retinal structure of juvenile [5th and 20th day after birth (DAB)] and adult (35th DAB), H. barbouri reared in captivity was investigated. All DABs were carried out and histologically observed. Light microscopic level explored the external-lateral surface of eye structure of H. barbouri, which consisted of the external, middle, and inner layers, as similarly reported in other teleost species. A well-differentiated retinal and photoreceptor cell layer were observed at 35th DAB compared to that at other DABs. This feature might be adequate to support the base of the increased feeding activity of adult seahorse in captivity for further research.

The mud crab Scylla olivacea is a well-known commercially and ecologically important species that inhabits intertidal mangroves. These mud crabs spend juvenile and adult stages in mangroves where they can experience daily fluctuations in salinity. They are almost certainly adapted to deal with salinity challenges. Although S. olivacea has a wide salinity tolerance, there is a lack of studies on its osmoregulatory responses. Antioxidant enzymes play crucial roles to counteract oxidative stress in various tissues of aquatic animals. However, salinity changes affecting antioxidant responses are not well studied in tropical decapod crustaceans. Therefore, this study aims to characterize the osmoregulatory and antioxidant responses of the male S. olivacea when exposed to salinity changes. Haemolymph osmolality, Na+/K+ ATPase and antioxidant enzyme activities in gills were analysed after they were exposed to various salinities. The results showed that S. olivacea is a hyper-hypoosmoregulator. The salinity had greater effects on Na+/K+ ATPase and antioxidant enzyme activities in the posterior gills than the anterior gills. Notably, the modifications of gill SOD activity were detected only in the posterior gills, which function highly in active ion uptake. These findings may imply some associations between osmoregulatory and antioxidant responses during salinity challenges. The increase in gill SOD activities be a response for coping with elevated ROS levels due to high metabolic demands for osmoregulation under salinity stress. Moreover, the crabs exhibited some modified activities of gill CAT in several salinity levels. Overall, the results demonstrated that S. olivacea were well-adapted to the salinity changes based on their osmoregulatory and antioxidant responses. These physiological adaptations may allow these crabs to disperse in some areas of mangroves. The salinity range of 15-25 psu would likely be the recommended optimal range for adult S. olivacea, which may enhance growth and minimize oxidative stress in gills of crabs, especially in aquaculture conditions.

The Indo-Pacific seahorse, Hippocampus barbouri, is one of the most important marine fish and a potential target of aquaculture, but basic biological information on this fish is largely missing. In this study, we described the hepatocyte ultrastructure and the ontogeny of the liver in H. barbouri during the 1st and the 35th day after birth (DAB). The histological observation of the liver structure identified that hepatocytes have a centrally placed oblong to round nucleus surrounded by the basophilic cytoplasm. Extensive accumulation of lipid droplets and glycogen was observed in the cytoplasm of the hepatocytes. Transmission electron microscope observation confirmed that the hepatocytes contained cisternae of granular endoplasmic reticulum associated with mitochondria of various shapes. Secretory granules of uniform density were scatted in hepatocytes, which were considered as the glycogen storage granules. According to the liver ontogeny analysis, the basic liver structure such as a network of the hepatocyte and sinusoid capillary was present at the 1st DAB and a large amount of collagen accumulation was observed by the 14th DAB. These results increase the knowledge about the initial development of H. barbouri, which will be useful to assess nutritional status of this species during aquaculture development.

Microplastics (MPs) can be defined as small pieces of plastics that are less than five millimetres in diameter. MPs can be consumed and may be accumulated by filter-feeding organisms such as mussels. Therefore, this study aimed to determine the acute effects of different types, sizes and concentrations of artificially synthesized MPs on the mortality rate and MP accumulation of the green mussel Perna viridis. The samples were exposed to 66, 333, 666, and 1333 items/L of small MPs (<30 mu m), medium MPs (30-300 mu m), and large MPs (300-1000 mu m) polystyrene (PS), polypropylene (PP), and polybutylene succinate (PBS) for 96 h. MPs accumulation in the soft tissue of mussels and mortality effects from MPs ingestion were assessed. There was no mortality observed in the control group. Small PP particles can lead to more mortality than PS and PBS particles of the same size. However, medium-and large PS caused a higher mortality percentage than the same size particles of PP and PBS. Large PS, PP, and PBS showed higher mortality potential than other sizes. MPs largely accumulated in the soft tissues rather than in gill tissues following the 96-hour exposure period. Increased accumulation of the three types of MPs was accompanied by an increase in the percentage of mussel mortality. The study highlights how particle size and type are key factors in plastic particulate toxicity.