A study of the reproductive cycle of the hard clam, Meretrix lyrata, was documented based on histological observation and Gonad Index (GI). Samples were taken from estuarine waters of the Buntal River in Sarawak, Malaysia. The gonad of M. lyrata started to develop in September 2013. Gametogenesis continued to develop until the maturation and spawning stage from February to April 2014. The GI pattern for a one-year cycle showed a significant correlation with chlorophyll a. The corresponding GI with chlorophyll a suggested that the development of the reproductive cycle of M. lyrata required a high amount of food to increase gametogenesis.
The length-weight relationships (LWRs), condition factor (Kn), growth, mortality and exploitation status of three polynemid fishes, i.e., Filimanus xanthonema (Valenciennes, 1831), Polynemus melanochir (Valenciennes, 1831) and Polynemus paradiseus (Linnaeus, 1758) from Batang Lassa River estuary were estimated. Fish samples were caught during April 2019 to September 2020 using the ESBN (locally called Gnian) having 1.25 to 4.00 cm mesh size. The total length (TL) and body weight of each individual fish was measured to the nearest 0.1 cm and 0.01 g respectively. The growth coefficients (b) for F. xanthonema, P. melanochir and P. paradiseus, were 2.880, 2.717 and 2.724 with the R 2 values 0.956, 0.972 and 0.936 respectively. Estimated growth coefficients indicated a negative allometric growth pattern for all three threadfin fishes. To date, information regarding length-weight relationships for F. xanthonema and P. melanochir is insufficient whereas the information is available for P. paradiseus. About 40-48% of fishes exhibited flat or thin body shape (Kn < 1), 48-50% were rounded or fat (Kn > 1) and only 1-3% of fishes showed proportional body shape (Kn = 1). The growth parameters L∞ , K and ϕ' were estimated at 15.75 cm, 0.95 yr-1 and 2.37 for F. xanthonema; 27.61 cm 0.87 yr-1 and 2.82 for P. melanochir; and 27.30 cm, 0.58 yr-1 and 2.64 for P. paradiseus; respectively. The estimated natural mortality (M) included 2.10, 1.69 and 1.30 yr-1; the fishing mortality (F) 0.57, 0.67 and 0.60 yr-1; and exploitation ratio (E) 0.21, 0.28 and 0.31 for F. xanthonema, P. melanochir and P. paradiseus respectively. The study concluded that the stocks are still under exploitation (E < 0.5) condition. However, the studied Batang Lassa estuary could be a potential nursery ground considering the minimum lengths of 5.0, 3.8 and 4.0 cm for F. xanthonema, P. melanochir and P. paradiseus respectively. Therefore, management initiatives are needed to escape juvenile catches.
The morphology and 12 shell morphometric features proportionate to shell length were analysed between local hard clam; Meretrix lyrata, M. meretrix and M. lusoria from Sarawak, Malaysia. Meretrix spp. was observed to comprise a unique feature of a pallial sinus scar for each species. Analysis of variance revealed significant differences among Meretrix spp. using proportion ratios of SL for SW; LL; AL; LCT; AW; PW and PS (p<0.05). Cluster analysis among morphometric features of M. lyrata, M. meretrix and M. lusoria were discriminated at 98.5% similarities and supported by the principal component analysis. The present study suggests that pallial sinus scar shape, together with interior and exterior morphometric features, were suitable as identification keys for Meretrix spp. Hence, the present study emphasizes on the application of interior, rather than exterior morphology and morphometric features in hard clam identification before further investigation can be performed through genetic identification means.
Mud lobsters are crustaceans from the genus Thalassina which are lesser known and seldom seen but are nevertheless an important organism to the mangrove ecosystem. In Malaysia and Thailand, mud lobsters are eaten by locals as treatment for asthma. It is traditionally believed that they are effective in reducing the number of asthma attacks and severity of asthma symptoms. However, the therapeutic potential of mud lobster extract remains unclear and has not been fully elucidated or reported in any scientific study. The objectives of this study are to investigate the anti-inflammatory potential of mud lobster, Thalassina anomala extracts (hexane, chloroform and methanol) in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages, and to identify the potential bioactive compounds involved. An MTT assay was performed to determine the cytotoxicity of the T. anomala extracts on RAW 264.7 macrophages. Nitrite quantification assay and enzyme-linked immunosorbent assay (ELISA) were conducted to investigate the ability of the T. anomala extracts to suppress the secretion and expression of nitric oxide (NO), Prostaglandin E2 (PGE2) and proinflammatory cytokines (TNF-α, IL-6 and IL-1β) in LPS-stimulated macrophages. GC-MS analysis was done to identify putative metabolites. The hexane extract of T. anomala showed anti-inflammatory activity by significantly inhibiting the LPS-induced production of NO, PGE2, interleukin- (IL-) 6, IL-1β and tumour necrosis factor-alpha (TNF-α) in a concentration-dependent manner. Hexane extract treatment with 100 μg/mL has decreased the NO secretion into 37 μM. Meanwhile, hexane extract at concentration of 100 μg/mL able to significantly suppressed PGE2,TNF-α, IL-6 and IL-1β production into 2015 pg/mL, 2406 pg/mL, 460 pg/mL and 9.6 pg/mL, respectively. GC-MS analysis of the hexane extract revealed the presence of 19 putative compounds. The identified compounds were reported to have anti-inflammatory, antioxidant and antibacterial activities. These results suggest that the hexane extract of T. anomala potentially has anti-inflammatory properties and concentration dependently suppressed NO, PGE2 and proinflammatory cytokines' production in LPS-stimulated macrophages. The findings provide a rational basis of the traditional use of mud lobster for inflammation-associated ailments.
Samples of threadfin breams Nemipterus japonicus were collected from a village in Kuala Nyalau and a fish landing centre at Bintulu from April 2013 to March 2014. A total of 360 individuals of N. japonicus (214 male and 146 female) were used in this reproductive study.? The total length (TL) of individuals were measured to the nearest 0.1 cm and body weight (BW) was recorded to the nearest 0.1 g. Month-wise distribution of the sexes was significantly higher for males in September and March, while in the month of May the number of females was significantly higher (X(2) = 6.53; P < 0.05). Males showed a preponderance in the size-class of 19.0-20.9 cm (X(2) = 80.24; P < 0.001), 21.0 -22.9 cm (X(2) = 56.39; P < 0.001) and 23.0 -24.9 cm (X(2) = 17; P < 0.001). The gonadosomatic index (GSI) values of N. japonicus ranged from 0.07 to 0.19 for males and 0.34 to 4.99 for females. Females had higher GSI than males throughout the study period. For males, a higher GSI (0.11-0.19) was observed during January to February, while it was found to be higher (2.73-4.99) for females during January to March, indicating the spawning season. The present study revealed that ovarian maturity based on histological analysis of N. japonicus was classified into seven stages namely, immature (I), immature (II), maturing (III), mature (IV), ripe (V), spawning (VI) and spent (VII). The fecundity of N. japonicus was estimated to be within a range of 19221 to 85923 with higher GSI (3.08-6.78) from the coastal waters of Bintulu, Sarawak.