Inneke F. M. Rumengan

Karyotypes of S and L type rotifers Brachionus plicatilis O. F. Müller

Abstract A comparative study on the karyotypes of S and L types of the rotifer Brachionus plicatilis O.F. Muller was carried out to clarify their cytological differences. Embryos, stained with alcoholic hydrochloric acid-carmine, were made into squash chromosome preparations. Mitotic chromosomes of S type prometaphase cells and L type metaphase cells were studied. The two karyotypes differed in chromosome number and morphology. The female diploid embryo of the S type had 25 chromosomes (2 n = 25), whereas that of L type had 22 chromosomes (2 n = 22). The chromosome numbers of male haploid embryos of S and L types were n = 12 and 11, respectively. Differences in karyotypes suggest that S and L types are so differentiated they should be considered different species. The possible evolutionary steps of chromosomes changes leading to the two types are discussed.

The fecundity patterns of S and L type rotifers of Brachionus plicatilis

Fecundity patterns of S and L type rotifers Brachionus plicatilis, which were previously found to have distinct growth ability, were analyzed using data of age-specific fecundity. The data were obtained by individual cultures of S and L type strains at 17, 24 and 34 °C. The pattern was analyzed by using normal probability functions. When the age was transformed into logarithmic value, the S and L types had an identical pattern of fecundity at every temperature. This fact indicates that the difference of the growth response to the temperature between S and L type strains stemmed only from the differences in net reproduction rate, not from the pattern.

Chromosomes and isozymes of hypotriploid strains of the rotifer Brachionus plicatilis

Some S type strains of the rotifer Brachionus plicatilis were found to have particular band patterns of certain enzymes, which suggested that the strains were triploids or trisomics for some chromosomes. Chromosomes of the strains were then observed by a conventional squash method of preparation. Analysis of chromosomes was made in comparison with the karyotype of amictic female S type rotifer. The strains were found to be hypotriploids. A strain which was derived from one of the hypotriploid strains was also studied, and was found to be diploid. The relationship between the chromosomes, the isozyme patterns, the origin of the hypotriploid strain and the derived diploid strain were discussed.

MEKANISASI SISTEM PANEN PADA KULTUR MASSAL ROTIFER, Brachionus rotundiformis

Rotifer adalah salah satu jenis zooplankton yang populer dimanfaatkan sebagai pakan alami untuk pemeliharaan larva fauna air. Beberapa kajian dewasa ini juga mempromosikan rotifer sebagai sumber senyawa bioaktif seperti khitin. Salah satu permasalahan utama dalam upaya pemanfaatan rotifer untuk akuakultur maupun untuk memproduksi senyawa bioaktif, adalah ketidakberlanjutan dan rendahnya produksi rotifer. Berdasarkan eksperimen di laboratorium menyangkut biologi dan ekologi rotifer, kultur massal yang intensif telah berhasil dilakukan pada kolam beton berukuran panjang 5 m, lebar 1 m, dan dalam 1 m. Teknik panen dan hal lain yang terkait, dipandang sebagai faktor penting yang mempengaruhi keberhasilan sistem kultur massal tersebut. Mengacu pada beberapa aspek teknik yang sedang dijalankan, studi ini dilakukan untuk memperbaiki mekanisasi teknik pemanenan yang diharapkan akan meningkatkan efektivitas produksi biomassa rotifer yang bermutu baik. Beberapa uji penerapan dari hasil mekanisasi teknik pemanenan, menampilkan kapasitasnya dalam memperbaiki mutu produksi rotifer, mereduksi waktu panen dan tenaga kerja, serta mempertahankan kontinuitas siklus produksi.