Effects of Different Microalgae on the Survivorship of Giant Clams Larvae (Tridacna squamosa)

Abstract

Salah satu kendala yang dihadapi dalam usaha memproduksi Kima (giant clams, Bivalvia: Tridacnidae) adalah tingkat kelangsungan hidup larva yang rendah. Terdapat dua sumber energi utama bagi kima yang mempengaruhi kelangsunganhidup dan pertumbuhannya, yakni translokasi hasil fotosintesa dari zooxanthellae dan melalui proses fiIter feeding. Dalam penelitian ini larva kima diproduksi melalui teknik induce spawning dengan mengkombinasikan metoda kenaikan suhu dan penyuntikan serotonin pada gonad induk. Selanjutnya larva kima yang berumur 2 hari dan 9 hari diberi pakan beberapa jenis mikroalgae. Pengamatan terhadap jumlah larva dilakukan selama masing-masing 5 hari. Hasil penelitian menunjukkan tidak terdapat perbedaan yang nyata dari mikroalgae yang berbeda terhadap kelangsunganhidup larva kima. Namun terdapat kecenderungan bahwa larva yang diberi pakan mikroalgae dari genus Chaetaceros mempunyai laju kelangsunganhidup yang lebih tinggi dibandingkan dengan larva yang diberi pakan mikrolagae jenis lain maupun kontrol. Disamping itu, tidak seperti yang dilaporkan oleh peneliti lain, ternyata larva kima mampu mencapai metamorfosis walaupun tanpa pemberian pakan alami. Diduga hal ini disebabkan larva tersebut mampu memanfaatkan sumber energi lain dari lingkungan air laut disekitarnya .

Kata kunci: kima, pakan alami, mikroalgae, kelangsunganhidup

One of the major problems in giant clams (Bivalvia: Tridacnidae) production is low level of survival rate, especially within larvae development. There are two different important sources of energy required. which influence the survivorship of the clams, i.e. through zooxanthellae translocation and filter feeding processes. The best microalgae that can be fed to clams larvae, however has not known yet. The present study aimed to investigate the influence of various microalgae on the survival rate of giant clams larvae. The larvae produced by inducing adult giant clams using the combination of temperature increment and serotonin injection. Two different stages of larvae were used in this study i.e. 2 and 9 days old larvae. The number of larvae were monitored daily for 5 days. Statistical analysis showed that there was no significant effects of different microalgae on the survivorship of the larvae. However. larvae which were fed by Chaetoceros had higher survival rate than other treatments and control. Furthermore, unlike other reports, this study shows that larvae which were not fed by microalgae have reached metamorphoses. It is believed that these larvae are capable of utilizing other energy sources from their sorrounding environment.

Keywords: giant clams larvae, natural feed, microalgae, survival rate