Study on reproduction of razor clam, Solen regularis Dunker, 1862 (Bivalvia : Solenidae in the western part of Sarawak, Malaysia
Razor clam or ‘ambal’ is a highly priced marine bivalve collected using traditional methods from several intertidal sandy beaches and mudflats by local people of Sarawak. ‘Ambal’ of Sarawak belongs to Family Solenidae with three different species namely i) Solen regularis Dunker, 1862, ii) S. lam...
محفوظ في:
| المؤلف الرئيسي: | |
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| التنسيق: | أطروحة |
| اللغة: | English |
| منشور في: |
2012
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| الموضوعات: | |
| الوصول للمادة أونلاين: | http://ir.unimas.my/id/eprint/9346/1/AILEEN%20MAY%20ANAK%20RIDIS%20RINYOD%20ft.pdf |
| الوسوم: |
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| الملخص: | Razor clam or ‘ambal’ is a highly priced marine bivalve collected using
traditional methods from several intertidal sandy beaches and mudflats by local
people of Sarawak. ‘Ambal’ of Sarawak belongs to Family Solenidae with three
different species namely i) Solen regularis Dunker, 1862, ii) S. lamarckii Chenu,
1843 and iii) S. sarawakensis von Cosel, 2002. In this study, the reproduction of
S. regularis was monitored for a duration of two years (March 2007 until
February 2009) at Asajaya Laut and Buntal, located in the western part of
Sarawak. Samples were taken at a two-week interval or monthly with in-situ
physico-chemical parameters of sea water (temperature, dissolved oxygen, pH
and salinity) measurement and analysis of chlorophyll-a concentration in the
water. This study has two main parts which were gonadal condition index
(GCI) study and histological study on the gonad. The objectives of this study
were to determine the reproductive cycle of S. regularis, to observe the possible
effect of environmental factors on the clam’s reproduction and to elucidate the
stages of gonadal development through drawing up a gametogenic scale using
histological methods.
GCI study was monitored for 24 months (March 2007 to February 2009)
as an initial approach to sexual development through monitoring the
reproductive cycle of the razor clam and to observe the effect of environmental
factors towards the cycle. A maximum of 30 specimens were dissected from each
sampling for sex identification and GCI. The male gonad appeared beige in
colour while female gonad is whitish. Throughout the study, the mean GCI
ranged from 0.000 to 0.247 (± 0.077) at Asajaya Laut and 0.000 to 0.253 (± 0.079) at Buntal. Based on the mean GCI pattern, the reproductive cycle for both
study sites showed similar pattern with five stages as follows; i) gonadal
development (during the increment of GCI value) ii) maturation (during the
maxima GCI value), iii) spawning (indicated by the decreasing GCI value after
the maxima), iv) spent (occurred after the last spawning which indicate the end
of active phase of reproduction) and v) resting period (during the minima GCI
value). Spawning period was observed from end of March-April to September
and followed by a resting period from end of October to January in the following
year. Throughout the study, there were slight differences in the timing of the
reproductive cycle stages occurred at each site whereas only at Buntal that
chlorophyll-a showed moderate correlation with the mean GCI (r = 0.513, p =
0.001).
The gametogenic cycle was determined using histological methods
together with GCI data. In Asajaya Laut, study was carried out starting from
February 2008 until February 2009 while the study in Buntal started one month
later. Results showed that the histological structures of males and females S.
regularis gametes can be characterized into seven gametogenic cycle stages as
follows; i) sexual rest (Stage 0), ii) start of gametogenesis (Stage I), iii) advance
gametogenesis (Stage II), iv) ripe (Stage IIIA), v) spawning (Stage IIIB), vi)
restoration (Stage IIIC) and vii) spent (Stage IV). The result of histological
study validates the GCI findings. It was noted that during the maxima GCI
value, majority of the individuals were in Stage III while during the minima
GCI value, they were in their sexual rest (Stage 0). At both locations, S.
regularis populations were in their Stage 0 from November to December and
gametogenesis (Stage I) began in January. S. regularis showed prolonged spawning activity indicated by their active phase of reproduction (Stage IIIA,
IIIB and IIIC) from February to September and January to October for Asajaya
Laut and Buntal, respectively. High percentage of razor clam individuals
entered their spent stage in October for both sites which complete the whole
gametogenic cycle. However, towards the end of spawning period and early part
of the gametogenesis, individuals collected within the same month did not show
a uniform gametogenic cycle stage.
Infestation of endoparasites in the gonadal cavity was also observed in S.
regularis involving two types of endoparasites (nematodes and trematode).
However, detail investigation was not carried. Therefore, study on the
infections of those endoparasites is crucial in order to investigate the effect of
the endoparasites infection to the razor clam reproduction and food safety status
for human consumption.
The outcomes of this study had provided valuable information on the
reproduction of S. regularis. Findings from this can be used for the conservation
purpose, establishment of sustainable razor clam fishery management and for
future aquaculture in Sarawak.
Keywords: Solen regularis, Gonadal Condition Index (GCI), histological,
reproductive and gametogenic cycle, Asajaya Laut, Buntal. |
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