Eucheuma and Kappaphycus are important carrageeno phytes and account for over 80% of world's carrageenan production. These taxa are abundant in the Philippines, tropical Asia, East Africa, and the Western Pacific region. Of more than two dozen species known, only Kappaphycus alvarezii (Doty) Doty (formerly known as Eucheuma cottoni Weber van Bosse) and Eucheuma denticulatum (Burman) Collins et Hervey (formerly known as Eucheuma spinosum [Sonder] J. Agardh) are of major commercial importance. During the last 30 years, these species have been success fully introduced to more than 20 countries for commercial cultivation. The thalli of Eucheuma and Kappaphycus are cartilaginous, cylindrical to compressed, and branched. Some taxa may be prostrate or erect in habit. Gametophytic and sporophytic thalli have been reported for many species. Fertile female thalli develop distinct cystocarps, which appear as mammillate struc tures. The life cycle is triphasic (same as in Gracilaria) and consists of three stages: tetrasporophyte (2n), gameto phyte (n), and carposporophyte (2n). The gametophyte is dioecious. The male thallus produces ameboid
Figure 4 (a-d) Bottom stocking of Gracilaria using direct and plastic tube method. (a) Transplantation of rocky substrata with attached Gracilaria to new sites. (b) Gracilaria attached to rocks, with rubber bands for anchorage in soft sediments. (c) Insertion of Gracilaria into soft sediments using a fork. (d) Gracilaria attached to sand filled plastic tubes. (e-g) Attachment of Gracilaria to ropes. (a-d) Modified from Santelices B and Doty M (1989) A review of Gracilaria farming. Aquaculture 78: 98-133; Oliveira EC and Alveal K (1990) The mariculture of Gracilaria (Rhodophyta) for the production of agar. In: Akatsuka I (ed.) Introduction to Applied Phycology, pp. 553-564. The Hague, The Netherlands: SPB Academic Publishing; from Critchley AT and Ohno M (eds.) (1997) Cultivation and farming of marine plants. In: CD-ROM, Expert Centre for Taxonomic Identification (ETI), University of Amsterdam, Amsterdam, ISBN 3-540-14549-4. Newyork: Springer. (e-g) From Critchley AT and Ohno M (eds.) (1997) Cultivation and farming of marine plants. In: CD-ROM, Expert Centre for Taxonomic Identification (ETI), University of Amsterdam, Amsterdam, ISBN 3-540-14549-4. Newyork: Springer.
spermatia within spermatangia. The female thallus pro duces many few celled carpogonial branches in the cortex of the thallus, of which the tip acts as the carpogonium or receptor cell for the spermatia. Fertilization results in the carposporophyte within the tissue of the female gameto phyte. The carposporophyte produces carpospores (2n) mitotically that once released develop into the tetrasporophyte phase. Subsequently, the tetrasporophyte produces tetrasporangia, which undergo meiotic divisions producing tetraspores (n). Upon their release, the tetra spores develop into male and female gametophytes, thus completing the life cycle.
The steps in the farming of these genera include: (1) site selection, (2) selection of cultivation methodology, (3) farm maintenance, and (4) harvesting and drying.
Site selection is very important. The site should be far from sources of freshwater such as rivers, creeks, and estuarine areas, as well as other sources of nutrient or industrial wastes. The site should be protected from strong tidal or wind generated waves, which can destroy the farm. A fixed, off bottom monoline method is the most popular and convenient method used. Floating methods (raft or long lines) are used when space prohibits the use of the off bottom monoline method. Maintenance of the farm consists of weeding, repair to the support system, replace ment of lost seedlings, and removal of benthic grazers. Farm maintenance is a critical aspect of euchemoid (= Kappaphycus) cultivation. Usually, the plants are har vested after 6 weeks, when each seedling weighs up to 1 kg (Figure 5).
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