Noraznawati Ismail

The Population Size and Movement of Coastal Horseshoe Crab, Tachypleus gigas (Müller) on the East Coast of Peninsular Malaysia

Horseshoe crabs have recently gained popularity as new exotic delicacies in Malaysia, especially in Johor. It has been reported and claimed by some fishermen that horseshoe crabs, particularly females, are being transported in bulk to Thailand. This claim has sparked interest to identify population size and study the behaviour of horseshoe crabs along the east coast of Peninsular Malaysia in an attempt to determine the effect of this demand on the existing population. A study was carried out from December 2011 to March 2012 to determine the coastal horseshoe crab Tachypleus gigas population size in Chendor and Cherating, Pahang, about 10 km apart on the east coast of Peninsular Malaysia, using a Capture-Mark-Recapture method. The sampling was carried out three times at both sites. The population size was calculated using Bailey’s Triple Catch formula with the assumption of an open population. The horseshoe crabs’ ‘traveling distance’ was also determined by attaching numbered, white button tags, each bearing the researcher’s phone number, to a total of 99 horseshoe crab individuals (61 in Chendor, 38 in Cherating). The total estimated populations were 7,140 in Chendor and 9,900 in Cherating. The two populations were found to be interchangeable as the tagged animals from Chendor were recaptured in Cherating and vice versa, thus confirming emigration and immigration. About 25 % of tagged animals were recaptured in various places (at Chendor, Cherating and also outside both locations) as reported by fishermen. Animals tagged in Cherating were caught in a few locations in Pahang, including Tanjung Lumpur which is more than 50 km to the south. Most recaptures (40 %) were from different locations remote from the site where the horseshoe crabs were tagged and released. This study is on-going and notifications are still expected regarding the future location of the tagged animals.

Trailing the Spawning Horseshoe Crab Tachypleus Gigas (Müller, 1785)at Designated Natal Beaches on the East Coast of Peninsular Malaysia

Due to limited availability of literature on the spawning activity of Malaysian horseshoe crab, Tachypleus gigas (Muller, 1785), the reproduction behaviour and biology of this arthropod remains poorly understood. Hence, an investigation was carried out from April-July to trail spawning horseshoe crab amplexus at Balok and Cherating, the only known T. gigas spawning grounds on the east coast of Peninsular Malaysia. Through visual tracking during daytime full moon spring tides, the release of air bubbles indicate nest digging by female crabs. While air bubble formation aggravated, flagged aluminium poles were carefully driven into the sediment to mark the nest. Out of the 13 spawning T. gigas amplexus tracked, only one pair was able to dig up to 12 nests and release up to 2,575 eggs within the 2.5 hour spawning period. The female crabs dug nests at the intertidal regions, ranging 1.3-43.2 m from the highest tide marking on the beach. Interestingly after spawning, the horseshoe crabs returned to high seas during the residing tides as amplexus because the male crabs remained clinging onto the female crab’s opisthosoma. The incidence of recapturing a tagged female crab with different attached male crab at Cherating indicates this spawning ground as natal beach. In addition, the presence of 8 horseshoe crab amplexus at Balok compared to only 5 amplexus at Cherating highlight preferable beach settings for spawning and/or the presence of larger spawning crab assemblages at the former beach. Since only 13 spawning horseshoe crab pairs were witnessed at Balok and Cherating, identification of factors that alter beach sediment composition and water chemistry as well as gender-specific poaching and excessive boating activities should be regulated to restore wild T. gigas populations.

Genome sequence of Serratia marcescens subsp. sakuensis strain K27, a marine bacterium isolated from sponge (Haliclona amboinensis)

ABSTRACT Serratia marcescens subsp. sakuensis strain K27 was isolated from sponge (Haliclona amboinensis). The genome of this strain consists of 5,325,727 bp, with 5,140 open reading frames (ORFs), 3 rRNAs, and 67 tRNAs. It contains genes for the production of amylases, lipases, and proteases. Gene clusters for the biosynthesis of nonribosomal peptides and thiopeptide were also identified.

Understanding the properties of chitosan aryl substituted thioureas in their role and potential as antibacterial agents

In this study, the effort was to design and synthesize a series of thiourea-chitosan derivatives featuring five aryl substituted members namely N-chitosan-N’-(4-nitrobenzoyl) thiourea (1), N-chitosan-N’-(4-chlorobenzoyl) thiourea (2), N-chitosan-N’-(4-methylbenzoyl) thiourea (3), N-chitosan-N’-(2-iodobenzoyl) thiourea (4), and N-chitosan-N’-(2-methylbenzoyl) thiourea (5) via SN2 reaction pathway having different donating and withdrawing groups. Their molecular structures were then characterised by FT-IR, UV-Vis, and thermogravimetric analysis (TGA). The antimicrobial activities of these derivatives against four species bacteria Bacillus cereus, Staphylococcus aureus, Salmonella typhi, and Escherichia coli of both Gram-positive and Gram-negative type bacteria at minimum concentration 6mg/ml were carried out to investigate their potential as antibacterial agents. Compound 1 exhibited specific activity as it can only inhibit Gram-positive bacteria while other compounds 2-5 showed broad range spectrum activit...

Marine Bacteria Associated with Horseshoe Crabs, Tachypleus gigas and Carcinoscorpius rotundicauda

Bacteria associated with marine organisms have received major attention worldwide due to their potential in pharmaceutical industries. A total of 32 bacterial strains were isolated and identified, 22 from Tachypleus gigas and 10 from Carcinoscorpius rotundicauda from Balok Beach, Malaysia. Overall, Gram-negative bacteria showed dominancy on both species. A combination of biochemical tests, macro morphology, and micro morphology was used to roughly determine genus of bacterial isolates; where results from 16S rDNA sequencing were taken as the end results due to its high reliability. Results from the molecular approach showed only Pseudoalteromonas sp. (38.46 %), Vibrio sp. (46.15 %), and Photobacterium sp. (15.38 %) might exhibit mutualism with horseshoe crabs, T. gigas and C. rotundicauda. Study on the diversity of bacteria associated with horseshoe crabs can enhance the understanding of these animals and the potential sustainability of producing useful compounds for defense mechanisms.