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.

This study describes the parasites and pathological condition of infected organ of the green mussel Perna viridis from Merambong Shoal, Western Johor Straits, Malaysia. Samples were collected randomly in November and December 2013. Histopathology techniques using Masson’s Trichrome staining protocol were performed and the thin sections were observed under light microscope. Result showed that gonad was the most infected organ followed by the digestive tubule, adductor muscle, intestine and mantle tissue. The parasites (apicomplexa) such as spore-like Nematopsis, macrogamont-like coccidian, mature oocyst-like coccidian, unidentified coccidian and protozoan were found in the adductor muscle, gonad and mantle. Meanwhile, the pathological conditions were found in all infected organs except the gill, such as particular melanin deposits in cytoplasm, Rickettsia-like or Chlamydiae organism and bacteria-like inclusions. Haemocytic infiltrations were found in the surrounding connective tissues of all infected organs. However, these light infections are not causing morbidity and mortalityof the green mussel P.viridis. This study provides baseline information on health profile of the green mussel P.viridis. Further investigations are needed particularly on parasite species identification and their ecology. Understanding of the morphology and pathology of parasites infecting mollusks are very important for management of the resources.

The ability of Ulva intestinalis as a biofilter in the intensive culture of rotifer Brachionus plicatilis was evaluated. 20 g wet weight of U. intestinalis was added into a 40 liters beaker containing 10 liters sea water of the cultured rotifer with quality index 0.36 ± 0.28 mg/L of NH3–N, 0.069 ± 0.025 mg/L of NO2––N, 0.90 ± 0.77 mg/L of NO3––N and 0.993 ± 0.0058 mg/L of PO43– and the alkalinity reading 114 ± 0.1 mg/L, pH 7.23 ± 0.08, temperature 26.3 ± 0.1OC and salinity was 30 ± 0.1 psu. The result of the following day of treatment with U. intestinalis, the water quality index changed to 0.001 mg/L of NH3–N, 0.090 ± 0.014 mg/L of NO2––N, 0.70 ± 0.60 mg/L of NO3––N and 0.89 ± 0.03 mg/L of PO43– while the alkalinity was 114 ± 0.1 mg/L, pH 7.45 ± 0.05, temperature 26.0 ± 0.10OC and the salinity was 30.0 ± 0.1 psu. The biofiltration capacity of U. intestinalis was confirmed by significantly reduced concentration of the NH3–N and 10% of PO43– compared to control only 2% over one day treatment. However from day two onwards the readings were conflicting from the first day readings. These findings were probably because U. intestinalis live in intertidal zone and flushing area therefore the use of U. intestinalis as a biofilter by continuous immersion in cultured water is unnatural. Therefore using U. intestinalis as a biofilter should be used not more than 24 hours.