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.
