In tropical regions, different species of fiddler crabs coexist on the mangrove floor, which sometimes makes it difficult to define species-specific habitat by visual inspection. The aim of this study is to find key environmental parameters which affect the distribution of fiddler crabs and to determine the habitats in which each species was most abundant. Crabs were collected from 19 sites within the mudflats of Sepang-Lukut mangrove forest. Temperature, porewater salinity, organic matter, water content, carbon and nitrogen content, porosity, chlorophyll content, pH, redox potential, sediment texture and heavy metals were determined in each 1 m2 quadrate. Pearson correlation indicated that all sediment properties except pH and redox potential were correlated with sediment grain size. Canonical correspondence analysis (CCA) indicated that Uca paradussumieri was negatively correlated with salinity and redox potential. Sand dwelling species, Uca perplexa and Uca annulipes, were highly dependent on the abundance of 250 μm and 150 μm grain size particles in the sediment. Canonical Discriminative Analysis (CDA) indicated that variation in sediment grain size best explained where each crab species was most abundant. Moreover, U. paradussumieri commonly occupies muddy substrates of low shore, while U. forcipata lives under the shade of mangrove trees. U. annulipes and U. perplexa with the high number of spoon tipped setae on their second maxiliped are specialized to feed on the sandy sediments. U. rosea and U. triangularis are more common on muddy sediment with high sediment density. In conclusion, sediment grain size that influences most sediment properties acts as a main factor responsible for sediment heterogeneity. In this paper, the correlation between fiddler crab species and environmental parameters, as well as the interaction between sediment characteristics, was explained in order to define the important environmental factors in fiddler crab distributions.
Strombus canarium Linnaeus, 1758 is an important gastropod species within the study area and was traditionally collected for food by the locals. The objective of the present study is to assess the incidence of imposex and its severity in this species. Adult conchs were sampled during their main reproductive period, from October 2005 to January 2006, at Sungai Pulai estuary, Johor Straits, Malaysia. A total of 32.81% of adult females showed imposex characteristics, with varying degrees of severity though. The relative penis size (RPS) index ranged from 1.74 to 33.29 (mean = 13.40 ± 2.27, n = 21), while the relative penis length (RPL) index ranged from 6.28 to 55.19 (mean = 25.83 ± 3.33, n = 21). The use of vas deferens sequence (VDS) index was however cannot be applied as the presence of egg groove obscured any vas deferens development in affected females. Sequence of imposex (male penis) development in female conch, from merely a small stump to an advance male penis homologous was therefore carefully analyzed and described, and an alternative imposex classification scheme was proposed. S. canarium can be a good indicator for monitoring of organotin pollution within the study area. However, more studies are needed in order to further develop and test its validity and application, such as its correlation with levels of pollutant within the tissues and the environment, as well as its application on other Strombus species.
The tropical conch, Laevistrombus canarium (Linnaeus, 1758) and Canarium urceus (Linneaus, 1758) are ecologically and economically important shellfish species in Malaysia and neighboring region. Their populations, however are currently declining and this histopathological study investigates the aspect of parasitism and diseases that may affect their well-being. Conch samples were randomly collected from their natural habitat and histological sections (4-5 µm) of various organs and tissues were examined under light microscope. This was followed by ultrastructure analysis on infected tissues using transmission electron microscope (TEM). Based on the histological analysis, large numbers of gamonts, sporocysts and trophozoites of Apicomplexa-like parasites were observed in the vacuolated cells and pyramidal crypt cells of the digestive tubules, and in the digestive ducts. Furthermore, coccidian and oocysts-like Pseudoklossia sp. stages were also observed in the cells of the kidney. Apart from that, spores with cyst-like structure were observed in the digestive gland and kidney. Although the parasites were present in most of the organs analyzed, there was no obvious symptom, inflammatory response or mortality incurred on both species, which implies the possibility of a non-virulent relationship like commensalisms or mutualism. However, more investigations, including molecular studies, are needed to confirm the parasite identification and dynamics, and to further evaluate the nature of relationship between Apicomplexa parasites and their host.
This study was conducted to analyze variation in Strombus canarium larvae development, growth and survivals when cultured during wet (main reproductive period) and dry seasons. Larvae were reared at 200 larvae L(-1) in filtered seawater (0.22 microm) and fed with Isochrysis galbana at 1000 cells mL(-1) ad libitum. The culture environment was maintained at 29 +/- 1 degrees C, salinity of 30 +/- 1 PSU and photoperiod of 12:12 light dark cycle. Growth of the larvae was described on a length-at-age basis using the modified Gompertz regression. There was high correlation in shell length-at-age relationship for both wet season (R2 = 0.99) and dry season (R2 = 0.98) culture experiments. The maximal growth rate (M) and survival rate (S) were higher for larvae cultured during wet season (M = 62.44 microm day(-1), S = 14.36-2.31%), compared with dry season (M = 43.05 microm day(-1), S = 5 +/- 1.15%). The maximal attainable larval size (a) was however lower during wet season (950.19 +/- 66.93 microm shell length) compared with dry season (1343.05 +/- 586.51 microm shell length), which might be due to significantly low larvae density in the latter. Further studies are needed to investigate variation in bio-chemical composition of the egg mass, which was suggested as the main reason for the differences.
Catfish are a highly diverse group of fish that are found in various regions across the globe. The significance of catfish culture extends to various aspects, including food security, economic advancement, preservation of cultural legacy, and ecological stewardship. The catfish industry is presently encountering unprecedented challenges as a consequence of the variability in water temperature caused by climate change. Temperature is a significant abiotic component that regulates and restricts fish physiology throughout their life cycle. The impact of severe temperatures on various species of catfish is dependent upon the magnitude of the stressor and additional influencing factors. This paper presents an analysis of the effects of temperature fluctuations on various aspects of catfish species, including growth and survival, blood parameters, enzymatic and hormone response, oxygen consumption rates, sound generation and hearing skills, nutritional requirements, and other phenotypic attributes. While this review is certainly not exhaustive, it offers a broad synopsis of the ideal temperature ranges that are most favorable for several catfish species. In-depth research to investigate the interacting impacts of severe temperature occurrences in conjunction with other associated environmental stresses on a wider variety of catfish species is crucial in order to further our understanding of how catfish species will respond to the anticipated climate change in the future.
Brachionus plicatilis is used to feed fish and crustacean larvae in the aquaculture industry. It is well established that the type of microalgae may influence rotifer production. This experiment was conducted to determine the effect of five different locally available microalgae species at Fisheries Research Institute (FRI), Kampung Pulau Sayak, Kedah, Malaysia on the instantaneous growth rate (μ) of rotifer. Nannochloris sp., Tetraselmis sp., Isochrysis sp., Chlorella sp., and Nannochloropsis sp. were used as feed at different algae densities (0.1, 0.3, 0.7 and 1.5 × 106 cells/ml) and culture volumes (20, 70 and 210 ml). At algae densities ranging from 0.3 to 1.5 × 106 cells/ml, an average μ value of more than 0.90 per day were recorded for all algae species. However, at density of 0.1 × 106 cells/ml, only Tetraselmis sp. resulted in the significantly highest μ value compared with others (p < 0.05). In terms of volume, smaller culture volume of Tetraselmis sp. (20 ml) showed significantly higher μ compared with higher volume (70 and 210 ml cultures).
This study explores the gastrointestinal evacuation time (GET) and gastrointestinal evacuation rate (GER) of the popular Sabah grouper (Epinephelus fuscoguttatus × E. lanceolatus) adults using two established methods (X-radiography and serial slaughter) and square root modeling using different temperatures: 28 °C, 30 °C, 32 °C, and 34 °C and different diets: pellet (ash: 11.4 ± 0.08; moisture: 29.0 ± 0.01; protein 37.5 ± 0.80; lipid 15.0 ± 0.13) and trash fish: Sardinella sp. (ash: 2.3 ± 0.15; moisture: 78.5 ± 0.33; protein 55.4 ± 0.62; lipid 7.3 ± 0.25) and the impact on growth indices. The results indicate that the GET shortened as temperature increased from 28 °C to 30 °C; however, it was prolonged when it surged to 32 °C and 34 °C. The groupers fed with trash fish at a temperature of 30 °C had the shortest GER (0.41 ± 0.10 g hr-1) whereas groupers fed with pellet at 34 °C had the longest GER (0.95 ± 0.02 g hr-1). Likewise, the highest SGR (16.25 ± 2.11% day-1) was observed at 30 °C for groupers fed with a trash fish diet. The condition (K) value was lowest at 34 °C for groupers fed with a pellet diet (1.01 ± 0.04) and highest at 30 °C for groupers fed with trash fish (1.45 ± 0.04). Our results suggest that temperature and diet influence growth indices and GE of adult Sabah groupers. Incorporation of this information will allow better management of this commercially important grouper species when reared in a controlled aquaculture environment.