ABE Yoshihisa

HISADA Michio

紀要類（bulletin）departmental bulletin pape

ABE, Yoshihisa

HISADA, Michio

Tohoku University Repository (TOUR) / 東北大学機関リポジトリ

ON A NEW REARING METHOD OF COMMON JELLYFISH,AURELIA AURITA著者 ABE Yoshihisa, HISADA Michiojournal orpublication titleThe bulletin of the Marine Biological Stationof Asamushi, Tohoku Universityvolume 13number 3page range 205-209year 1969-03-25URL http://hdl.handle.net/10097/00131336BULLETIN OF THE l\IARINE BIOLOGICAL STATION OF ASAl\IUSID, VOL. XIIT, NO. 3. 1969 ON A NEW REARING METHOD OF COMMON JELLYFISH, AURELIA AURITA By Y OSHIHISA ABE and iVliCHIO HISADA * • • • A m • ~ The U eno Zoo Aquarium, Tokyo, Japan In the Ueno Zoo Aquarium the life-cycle of the common jelly-fish, Aw·elia aurita has been exhibited from August 1967. The ephyras, strobilas and polyps kept alive in Petri-dishes, are exhibited by the three shadow projectors with magnifica-tion from 10 to 20 times. The adult medusae, reared from the ephyras, are pnt in a large table tanlr with bottom-sand filtration for exhibition. The rearing of AuTeliC! C!UTitC! in the laboratory to determine its life-cycle had been accomplished by many authors in Japan and abroad (Hirai, 1958, and others). Recently, Kakinuma (1961, 1962) studied on the factors of the initia-tion of strobilation in the same species as mentioned above, and concluded that the treatment of the polyps under a temperature of 15°0 with lighting is effective for the initiation, even in midsummer when strobilation is never observed at roon1 temperature. As Hisada and Abe (1968) reported, we tried to rear the common jelly-fish mainly by these laboratory methods since the end of 1965 and succeeded to obtain some 70 adult medusae in the tank. We have developed some improvements on the rearing method and now can obtain more adnlt medusae more efficiently. The present paper is a report on the method of rearing the common jelly fish in our Aquarium. The polyps were usually kept in several table tanks with bottom-sand filtra-tion and feel on sufficient larvae of brine shrimp. From autumn to spring the strobilations spontaneously occurred at room temperature and consequently the ephyras were produced. From late N ovcmber to December and in April the strobilations were observed frequently. The active strobilations of these periods apparently corresponded to the water temperature 15°0. In the other seasons the strobilations were initiated by Kakinuma's method. At these times the strobilations were effectively initiated on the polyp population over 200 individuals in a Petri-dish of 12 em in diameter. I) Contributions from the Marine Biological Station of Asarnushi, Aomori Ken, No. 367 205 206 Y. ABE AND M. HISADA The ephyras produced by these treatments were transferred to Petri-dishes of 12 em in diameter and 9 em in depth. Ten individuals of the ephyras were kept in every Petri-dish containing 500 m1 of sea water and fed on 1,000 to 2,000 larvae of the brine shrimp. The water was renewed once a day. After 30 days some of the ephyras grew to young medusae of which the umbrella measured about 10 n1m in diameter. During this period numerous deformed medusae were developed and died, and about 20 per cent or less ephyras were usually grown to normal young medusae (Fig. 1). Owing to being able to make better growth, we made some observations on the rearing condition, dissolved oxygen and the water movement. The dissolved oxygen is consumed by the living and decompos-ing organisms which consist of the ephyras, the live and dead larvae of the brine shrimp and their excrement. Some analytical experiments showed that the amount of oxygen consumption of the decomposing organisms exceeded that of the living ones, but it was proved that ephyras as well as young medusae never suffered from the decrease of the dissolved oxygen. Another factor which seemecl to affect the gro\ving ephyras in the Petri-dishes, was the motion of the water. In standing water, ephyras swam actively near the surface of the water in their early stage, but in the meantime they sank to the bottom. The ephyras had to pulsate their umbrella to keep afloat and when the pulsations stopped they began to sink. Browne (1897) reported on the necessity of the water current to keep the medusae alive in good condition. We thought that if the water current is produced by air-lift or some other type of pump might be favourably applied to the rearing of ephyras, and that the filtering apparatus may be usecl by these pumps. But the ephyras were unable to resist even a weak current and consequently no kind of filter could be applied directly to the containers of them. Therefore we tried to keep the ephyras by using a comparatively large quantity of water supplied with a convective current by air bubbles, and unexpectedly succeeded in rearing them efficiently. At the same rate as in the Petri-dish rearing, 1,000 individuals of ephyras were kept in a vessel containing 50 I of water ancl fed on 100,000 to 200,000 of larvae of the brine shrimp once a clay. The water was aerated and unchanged during the rearing period (Fig. 2). After 30 days more than 60 per cent of the ephyras grew to nonnal young 1nedusae. They were measured to be about 10 mm in diameter of the umbrella (Fig. 3). No water change for the 30 days with aeration seemed to be sufficient to the ephyras and young medusae. By the convective current of the water the ephyras or the young medusae were kept afloat and could be continually and equally fed on the food suspended in the water current. These young medusae were transferred to and reared in another container dipped in a table tank with bottom-sand filtration (Fig. 4). The container is a A REARh'fG METHOD OF AURBLIA AURI1'A 201 plastic tank with many small pores each of about 3 mm in diameter on the sides and bottom. The water was altered very slowly with the outside water. The young medusae during this period could not be kept directly in the tank with bottom-sand filtration because of their weak activity. In the following 30 days they grew to about 50 to 60 mm in diameter of the umbrella and then were transferred to the exhibition tank. They were fed on larvae of the brine shrimp or chopped meat of the clam and shrimp. Finally, we wish to express our hearty thanl<S to Drs. Eturo. Hirai and Yoshiko Kakinuma of the Marine Biological Station of Asamushi for their valuable sugges-tions on the methods of the rearing. Ll'fERA'fUR CITED BROWNE, E.T., 1897. On keeping medusae alive in an aquarium. ,Jour. Mar. Biol. Assoc., s, 176-180. HIRAI, E., 1958. On the developmental cycles of Aurelia aurita and Dactylometra pacifica. Bull. Mar. Biol. Stat. Asamushi, 9: 81 HrsADA, 1\L and Y. Abe, 1968 On the rearing and exhibition of common jellyfish at the Ueno Zoo Aquarium. Oral report at the General Meeting of the Japa.nese Association of Zoos and Aquariums, Sapporo, May. lCAKINUMA, Y., 1961. Hydrozoa and Scyphozoa, found on Asamushi and adjacent wate1's. Aomori Pref. Bioi. Soc., 4. (1.2): 10-17.(In Japanese) --- 1962. On some factors for the differentiations of Oladonema uchidai and of Aurelia aurifa. Bull. Mar. Biol. Stat. Asamushi, 1.1: 81-85 208 Y. ABE AND l\L HISADA A REARING METHOD OF AURELlA AURI'l'A 209 Fig. l. The deforn:ecl young medusae Fig. 3. The yonng medusae af ter 30 days rearing in t he vessel Fig. 2. The rea ring vessel (50 I) F ig. 4. The conta iner for the young med usae 

ON A NEW REARING METHOD OF COMMON JELLYFISH, AURELIA AURITA

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ON A NEW REARING METHOD OF COMMON JELLYFISH, AURELIA AURITA

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