Abstract: Five species of sergestid shrimps viz., Acetes indicus, Acetes japonicus, Acetes intermedius, Acetes vulgaris and Acetes serrulatus were identified from the different coastal region of Peninsular Malaysia and East Malaysia. Acetes indicus was recorded from the coastal waters of Klebang Besar in the state of Malacca and also in Kuala Gula Perak. The widely distributed shrimp A. japonicus was identified from the coastal waters of Klebang Besar (Malacca), Kuala Gula (Perak), Bagan Ajam (Pulau Pinang), Kuala Sala (Kedah) and Sungai Berembang (Perlis). Acetes intermedius was collected from the coastal waters of Klebang Besar (Malacca), Seberang Takir (Terengganu) and Bintulu (Sarawak). Acetes vulgaris and A. serrulatus were restricted to the coastal waters of Pontian and Kukup in southwestern Johor.
INTRODUCTION
The shrimp of the genus Acetes from family Sergestidae is a minor planktonic crustacean group represented by a small number of species but formed one of the economically important organisms in Asia and East African waters (Omori, 1975). The family Sergestidae is divided into two subfamilies, Sergestinae and Luciferinae. The genus Acetes was established by Milne-Edwards, 1830) following a collection from the mouth of the River Ganges, India and was recommended to be placed on the official list of generic names in zoology by Holthuis (1962). After that Acetes spp. are included in the FAO species catalogue of shrimps and prawns by Holthuis (1980). Six species of Acetes are reported very briefly from the Malay Peninsula and Singapore: A. erythraeus Nobili, A. indicus Milne-Edwards, A. japonicus Kishinouye, A. sibogae Hansen, A. serrulatus Hansen and A. vulgaris Hansen (Pathansali, 1966). The last two species, A. serrulatus and A. vulgaris, were recorded from Singapore waters and other four species of the genus Acetes were recorded only from the Malay Peninsula. The present aim was to update on the taxonomy of the genus Acetes (H. Milne-Edwards), occurring in the different geographical location throughout the coastal waters of Peninsular Malaysia and certain places in Bintulu East Malaysia.
| Fig. 1: | Geographical location of the sampling sites in the Peninsular Malaysia. a: Klebang Besar, Malacca; b: Kuala Gula, Perak; c: Bagan Ajam, Pulau Pinang; d: Kuala Sala, Kedah; e: Sungai Berembang, Perlis; f: Sebarang Takir, Terengganu |
MATERIALS AND METHODS
Collection of samples: Samples of Acetes spp. were collected from Klebang Besar between February 2005 and March 2007 (Fig. 1) by using the push net. The Acetes samples from Perlis, Kedah, Pulau Pinang, Perak, Terengganu, Johor and Bintulu (Fig. 1, 2) were obtained from the fishermen Acetes trawl net as well as push net. Fresh Acetes samples were preserved in 10% formalin immediately after collection and they were transported back to the laboratory for further taxonomic analyses.
Sample identification: The specimens were identified in the laboratory using a Nikon dissecting microscope (Nikon-122764, Japan). Sex was determined by the presence or absence of petasma on the first pleopods and clasping spine on the lower antennular flagellum (Omori, 1975). The work of Omori (1975) and Zafar (2000) were followed for the identification of Acetes spp.
RESULTS
Taxonomic account:
| Order | : | Decapoda |
| Family | : | Sergestidae |
| Subfamily | : | Sergestinae |
| Genus | : | Acetes H. Milne Edwards |
| Fig. 2: | Geographical location of the sampling site in the coast of Bintulu, Sarawak |
A total of five different species of the genus Acetes (A. indicus, A. japonicus, A. intermedius, A. vulgaris and A. serrulatus) were identified from the different sampling locations of the Malaysian coastal waters. Descriptions and comments of Acetes spp. found in the coastal waters of Malaysia are given below:
Acetes indicus Milne-Edwards, 1830 (Fig. 3 and
Fig. 4)
Sample locality: Acetes indicus was identified from the coastal
waters of Klebang Besar in Malacca and also from Kuala Gula in Perak. Both places
located in the Straits of Malacca. In Malaysia, this species is landed by the
push net while the stock in Kuala Gula Perak is intensively harvested using
the Acetes trawl net. This species is important in the postharvest industry
of making shrimp paste and other fermented products.
Descriptive remarks: Procurved tooth present between bases of first pair of pleopods both male and female (Fig. 4a). In the males the lower antennular flagellum with one clasping spine (Fig. 4b) and 11-12 segmented. The petasma without pars astringens and distal part of the capitulum is expanded and bears numerous small hooks along the outer margin and the end (Fig. 4c). In females the apex of telson is almost triangular (Fig. 4d). Third thoracic sternite of female is deeply channelled longitudinally (Fig. 4e). Inner margin of basis of third pereiopod without sharply pointed projection. The endopods of uropod has 2-4 red spots.
Acetes japonicus Kishinouye, 1905 (Fig. 5 and Fig. 6): Acetes japonicus was recorded from the coastal waters of Klebang Besar in Malacca, Kuala Gula (Perak), Bagan Ajam in Penang, Kuala Sala (Kedah) and Sungai Berembang in Perlis. The shrimp is known by different local names according to the localities. Regardless of the species composition, all Acetes shrimps landed by the fishermen is known as ‘geragau’ in Malacca, Johor and Perak. In the northern states of the Peninsular they are known as ‘udang siring’.
| Fig. 3(a-b): | Photograph of Acetes indicus. (a) male (x6) and (b) female (x6) |
| Fig. 4(a-e): | Acetes indicus. a, procurved tooth (x25); b, clasping spine (x40); c, petasma without pars astringens (x50); d, telson of female (x40); e, third thoracic sternite is deeply channelled (x30) |
For the people in the east coast of Peninsular Malaysia, it is known as ‘udang baring’ while the fisherman folks in Bintulu Sarawak called the shrimp as ‘udang bubok’.
Descriptive remarks: In male individual, lower antennular flagellum bears 2 clasping spines (Fig. 6a) with 10-12 segments. In the petasma, the distal part of the capitulum is expanded like a bulb and has numerous hooks (Fig. 6b). The appendix masculina has 2 hooks.
| Fig. 5(a-b): | Photograph of Acetes japonicus. (a) male (x20) and (b) female (x20) |
| Fig. 6(a-d): | Acetes japonicus. a, clasping spine (x150); b, capitulum of petasma (x130); c, third thoracic sternite (x25); d, Apex of female telson (x100) |
The third thoracic sternite is produced backwards or posteriorly in females (Fig. 6c). The endopods of the uropod has one red spot on the proximal part in both females and males. The tip of the female telson is broadly rounded (Fig. 6d).
| Fig. 7(a-b): | Photograph of Acetes intermedius. (a) male (x6) and (b) female (x6) |
| Fig. 8(a-d): | Acetes intermedius Omori (a) clasping spine (x 130), (b), petasma (x 100), (c) segments of antennular peduncle (x 130) (female) (1-1st segment, 2-2nd segment; 3rd-segment) and (d) apex of the telson triangular (x 30) (male) |
Acetes intermedius Omori, 1975 (Fig.
7 and Fig. 8)
Sample locality: Acetes intermedius was identified from the coastal
waters of Klebang Besar (Malacca), Seberang Takir (Terengganu) and Bintulu (Sarawak).
It is also known as ‘Udang geragau’ in the coastal region of Malacca
(West coast of Peninsular Malaysia), ‘Udang baring’ in Terengganu
(East coast of Peninsular Malaysia) and ‘Bubok’ in the Bintulu, Sarawak
(East Malaysia).
Descriptive remarks: In the males lower antenular flagellum is 13 or 14 segmented with 1 clasping spine (Fig. 8a). The petasma pars astringens and capitulum of petasma with 4 subsequently large hooks along outer margin (Fig. 8b). The coxa of the third pereiopod lacks a tooth on the distal inner margin. Appendix masculine hold 3 hooks. In females, first segment of antennular peduncle at most as long as second and third segments combined (Fig. 8c). The lower antennular flagellum is 12-15 segmented. There is a small procurved tooth between the bases of the first period in both females and males. The apex of telson in male is sharply pointed and triangular (Fig. 8d).
Acetes vulgaris Hansen (Fig. 9 and Fig.
10)
Sample locality: Acetes vulgaris was only identified from the
coastal waters of Pontian (Johor), Peninsular Malaysia. It is locally known
as udang geragau in the area.
Descriptive remarks: The antennule consisted of three basal segments, the peduncle and a pair of multi-jointed flagella. In females the lower antennular flagellum is 20-24 segmented. While in males the lower antennular flagellum is 17-21 segmented and there was only one clasping spine on the lower antennular flagellum (Fig. 10a). The first segment of the main branch is with small swelling which bears 4-6 basal spinules with the segment opposite the tip of the clasping spine bears 4-5 spinules. The petasma was with pars astrigen (Fig. 10b). The capitulum of the petasma is thick, twice as long as broad and bared 3 large falcate hooks on the outer margin (Fig. 10c). The distal part of the capitulum is broadly obtuse with 7-8 small hooks. The main external characteristics of A. vulgaris included the triangular shape of the apex of telson in male (Fig. 10d). The genital area of the females is having a pair or large round protuberances on the anterior part of the third thoracic sternite. Behind the protuberances a deep procurved furrow runs transversally across the body. In males, the anterior margin of the genital coxa was pointed (Fig. 10e). However, the apex of telson was rounded in females (Fig. 10f).
| Fig. 9(a-b): | Photograph of Acetes vulgaris (a) male and (b) female |
| Fig. 10(a-f): | Acetes vulgaris (a) clasping spine (x 40); (b) petasma (x40); (c) capitulum of petasma (x40); (d) apex of the telson triangular (male, x40); (e) genital coxa (x40) and (f) apex of the telson triangular (female, x40) |
| Fig. 11(a-b): | Photograph of Acetes serrulatus. (a) male and (b) female |
Acetes serrulatus Kroyer (Fig. 11 and Fig.
12)
Sample locality: Acetes serrulatus was recorded from samples
taken in the coastal waters of Pontian (Johor Bahru), Peninsular Malaysia. It
is also familiar as udang geragau in the shallow coastal area of Johor, south
western part of Peninsular Malaysia.
| Fig. 12(a-d): | Acetes serrulatus (a) clasping spine, (b) capitulum of petasma (c) appendisc masculine and (d) tip of telson |
Descriptive remarks: In the males, the lower antennular flagellum with two clasping spines (Fig. 12a) and 11 segmented. The petasma without pars and processus ventralis; the capitulum borne 5-7 hooks on the convex outer margin and there is one large hook at the end (Fig. 12b). The antennular flagellum is 10-12 segmented in females. The appendix masculina bears one hook (Fig. 12c). Apex of telson of in both males and females are truncated (Fig. 12d).
DISCUSSION
Seven species of sergestid shrimps (A. erythraeus, A. indicus, A. japonicus, A. serrulatus, A. johni, A. sibogae and A. vulgaris) are reported by Pathansali (1966) from the Indo-Malaysian region. Ten species are distributed in the Indo-West Pacific and the Indo-Malaysian region according to Omori (1975). Six species were recorded by Zafar (2000) from Bangladesh waters. In the present study five species of the sergestid shrimps were found from the different coastal waters of Malaysia; their identifying characters were very closely similar with the descriptions given by Omori (1975) and Zafar (2000).
The specimen A. indicus are easily identified and agreed well with the description by Omori (1975). The appendix masculina in all cases bears two hooks instead of three as described by Omori (1975). The shape of the petasma descried by Omori (1975) also coincides with the present investigation. The species A. japonicus is most abundant species in the coastal waters of Malacca, Perak, Pulau Pinang and Kedah. It agrees well with the diagnosis and illustrations by Omori (1975). The structure of the genital area in female is slightly different. The third thoracic sternite is produced backwards as a large plate. These variations may be due to size and maturity. The tip of the female telson is rounded which is similar with Omori (1975) but dissimilar with the result of Tirmizi and Ghani (1982).
The species A. intermedius is previously reported from Bangladesh (Zafar, 2000); Taiwan, Philippines and south coast of Java, Indonesia (Omori, 1975) and now in the coastal waters of Malacca. It is one of the most important commercial shrimp resources and is also an important component of the marine ecosystem in the coastal waters of south-west Taiwan (Chiou et al., 2000). The present specimens afford the first subsequent record of the species A. intermedius and extend considerably the range of distribution, being the first to be known from the cost of Malacca, Terrengganu and Bintulu, Malaysia.
The species A. vulgaris and A. serrulatus is reported only from the coastal waters of Pontian Johor, Peninsular Malaysia. The occurrence of A. vulgaris is also reported for the first time in the coastal waters of Pontian, Johor. The petasma of A. vulgaris with 3 large hooks on the outer margin and the distal part of the capitulum is broadly obtuse with 7-8 small hooks which are almost similar to those described by Omori (1975) and Zafar (2000).
CONCLUSIONS
Five sergestid shrimps; A. indicus, A. japonicus, A. intermedius, A. vulgaris and A. serrulatus were identified from different coastal waters of Malaysia. Among them A. intermedius from Malacca and A. serrulatus from south-western Johor were recorded for the first time. These two species are new record to the coastal waters of Malaysia. Our study still requires further updates, as there are other locations that are not yet included in the sample acquisition.