CRABS AND SHRIMPS

Research on decapod crustaceans of Sarawak dates back to the Brooke era and continued during the Japanese occupation of the State. Nonetheless, the fauna of Bako has not received as much attention as the Santubong region and Sarawak River. The reasons may be due to the relatively isolated location of the Bako Peninsula, being further from Rajah Brooke’s administrative centre (present day Kuching City), the more complex logistical requirements for a cruise along the seasonally rough seas off the rocky coastline, and the risk of pirate attack

Crabs

The decapod brachyurans are species rich (6,793 species in 1,271 genera and 93 families) of the world’s decapod brachyurans (Ng et al., 2008), and many species are of commercial value. There have been relatively few documentations of the group in the coastal waters of Sarawak, compared to their freshwater cousins (see Grinang, 2016). The earliest collection of marine brachyurans was made by Michael Wilmer Forbes Tweedie (then the Director of Raffles Museum in Singapore) in December 1948, from mangrove and nipah habitats around what is today Jalan Satok, Kuching. He recorded 13 species and described a new genus and three new species from this small collection (Tweedie, 1950). Voucher specimens including the holotypes were deposited in the Raffles Museum (presently Lee Kong Chian Natural History Museum, Singapore). Over half a century later, Elizabeth C. Ashton conducted a community ecological study at the Sematan mangroves, focusing on invertebrates, among which were 31 species of crabs (Ashton et al., 2003). Voucher specimens from the collection are presently housed in the Sarawak Biodiversity Centre. Another collection was made at the Sematan mangroves in 2015 by Lou Wei Cheong, for feeding experiments, of which 13 genera were recorded (Lou, 2016). The last significant collection was that of Ikhwanuddin (2011), who studied the biology of two mangrove species (Scylla olivacea and S. tranquebarica) from the Sematan mangroves

A review of the freshwater crabs (Decapoda: Brachyura) of Borneo

An update on the freshwater crab fauna of Borneo (Potamidae, Gecarcinucidae and Sesarmidae) is presented here based on literature and current data. A total of 106 species in 17 genera and three families of freshwater crabs in Borneo are known. Most species are endemic to the island, with some species restricted to unique habitats such as limestone caves and mountainous terrains. This current list does not reflect Borneo's true crab diversity because many remote areas have not been explored. Compared to Sarawak, the crab fauna in other regions of Borneo is relatively less studied. While there has been some progress in the taxonomic studies of Bornean freshwater crabs, there is a lack of studies on their ecology and biology. This data is crucial for prioritizing habitat protection and conservation efforts of the Bornean freshwater crabs

Parosphromenus barbarae, a new species of Licorice Gourami from Sarawak, Borneo (Teleostei: Osphronemidae)

In Sarawak, there are two main populations of Parosphromenus known, the eastern population linked to the Rejang River basin being P.allani, and the western population linked to the Batang Kayan basin, is herein described as P. barbarae, new species. Parosphromenus barbarae differs from its most similar species, P. allani, in having a distinct black ocellus on caudal-fin base, indistinct dark brown ocellus on posterior base of dorsal-fin; presence of clearly demarcated subdistal hyaline band on anal fin (vs. faint); dorsal-fin rays XI–XIV, 4–5 (total count 15–18, mode 17); anal-fin rays XI–XIII, 6–10 (total count 19–21, mode 21); lateral scales 29–31½ (mode 29)

Typhlachirus lipophthalmus, a rare eye-less sole from Borneo (Teleostei: Soleidae)

An example of the eye-less sole, Typhlachirus lipophthalmus, was collected from a tidal section of the Sadong River in Sarawak, Malaysian Borneo, in January 2018. It is apparently the second known record of this species since its description in 1882. A description based on selected meristic and morphometric data gathered from the speci-men, supported by radiographs and photographs of it, as well as notes on its capture and habitat, are presented

Ecological characteristics of the freshwater crab, Isolapotamon bauense in one of Wallace’s collecting sites

Effective conservation of biodiversity requires good ecological information on species, populations and communities. This is particularly true for the Malaysia state of Sarawak in Borneo, whose rich biological diversity remains poorly documented, with many wetland species facing serious threats resulting from habitat alteration, pollution and overexploitation. This study aims to quantify the ecological characteristics of an endemic potamid freshwater crab, Isolapotamon bauense Ng 1987, a species listed as ‘Vulnerable’ in the IUCN Red List of Threatened Species. A capture-mark-recapture exercise was conducted at two sites along a stream at Gunung Serambu in the Bau region to better understand the ecology of this species. Our results reveal a sex ratio of 1:1, whereas analysis of carapace width-weight relationship document a negative allometric growth pattern and a relatively low condition factor for intermediate sized specimens. Males and females do not differ significantly in body mass and there is no obvious sexual size dimorphism. Over the month long study, the size frequency of carapace classes indicates the population was dominated by smaller size-classes. A linear regression shows a trend in the number of crabs captured with lower air temperatures and higher relative humidity. It also suggests a strong positive correlation with the depth of associated streams, used as a proxy for soil water saturation. We use the MARK program to estimate the overall population size at 90 m2 sampling area, utilizing Akaike’s Information Criterion for model selection. The best model incorporated individual heterogeneity and the effect of rain during the survey on capture probability. The population estimate is 133 individuals with 95 % confidence interval of 106–187. Other ecological aspects of the species, such as local distribution and, habitat and food preferences, will need to be studied in order to develop a concise conservation plan for the species

A new species of highland vampire crab (Crustacea: Brachyura: Sesarmidae: Geosesarma) from Serian, Sarawak

Ng, Peter K. L., Grinang, Jongkar (2018): A new species of highland vampire crab (Crustacea: Brachyura: Sesarmidae: Geosesarma) from Serian, Sarawak. Zootaxa 4508 (4): 569-575, DOI: https://doi.org/10.11646/zootaxa.4508.4.

Geometric morphometric analysis in female freshwater crabs of Sarawak (Borneo) permits addressing taxonomy-related problems

The taxonomy of freshwater crabs requires a paradigm change in methodological approaches, particularly in investigations that use morphological techniques. The traditional morphometric approach (two-dimensional measurements) tends to be inappropriate for the identification of freshwater crabs due to their variable external morphology and lack of gonopods (conventionally used for the identification of male crabs) in females. In this study, we explore the potential use of the geometric morphometric technique for identification of female freshwater crabs, and identify taxonomic key characteristics of species. The shape of the carapace could be a good characteristic for the identification of female crabs, especially when the geometric morphometric technique is used. It was observed that the shape of the carapace has an advantage over the shape of the pleon and chela because its relatively flat orientation allows more consistent and easier data preparation for geometric morphometric analysis. The geometric morphometric technique is inexpensive, relatively less time consuming to employ, and accurate. This technique is convenient when dissection to examine the gonopods is not possible, which can damage the specimen in the case of endangered or rare species. Since the technique was used herein for only two species, more compelling and extensive evidence is needed before the reliability of the method can be proven

The identity of the semiterrestrial crab Terrathelphusa kuchingensis (Nobili, 1901) (Crustacea: Decapoda: Brachyura: Gecarcinucidae), with descriptions of four new species from southwestern Sarawak, Borneo, Malaysia

Four new species of semiterrestrial gecarcinucid crabs are described from limestone and sandstone habitats in southwestern Sarawak, Malaysia: Terrathelphusa aglaia n. sp., T. cerina n. sp., T. kundong n. sp., and T. mas n. sp. The taxonomy of T. kuchingensis (Nobili, 1901) is discussed, its precise identity ascertained from fresh material, and its actual distribution determined. This increases the number of Terrathelphusa species in Borneo to eight