Journal of Coastal Development ISSN: 1410-5217 Volume 5, Number 3, June 2002 : 101-110 Accredited: 69/Dikti/Kep/2000 Review CALCULATING THE CONTRIBUTION OF ZOOXANTHELLAE TO GIANT CLAMS RESPIRATION ENERGY REQUIREMENTS Ambariyanto*) Marine Science Department, Faculty of Fisheries and Marine Sciences, Diponegoro University, Semarang Indonesia. Email: [email protected] Received: April 24, 2002 ; Accepted: May 27, 2002 ABSTRACT Giant clams (Tridacnidae) are known to live in association with photosynthetic single cell dinoflagellate algae commonly called zooxanthellae. These algae which can be found in the mantle of the clams are capable of transferring part of their photosynthates which become an important source of energy to the host ( apart from filter feeding activity). In order to understand the basic biological processes of the giant clams , the contribution of zooxanthellae to the clam’s energy requirement need to be determined. This review describes how to calculate the contribution of zooxanthellae to the giant clam’s energy requirement for the respiration process. Key words: Giant clams, tridacnidae, zooxanthellae CZAR *) Correspondence: Tel. 024-7474698, Fax. 024-7474698, Email: [email protected] INTRODUCTION One of the important aspects of the biology of giant clams is the existence Giant clams (Family: Tridacnidae) are of zooxanthellae which occupy the mantle large bivalves that are commonly found in of the clams as endosymbiotic coral reef habitats especially in the Indo- dinoflagellate algae (Lucas, 1988). These Pacific region. This family consists of two zooxanthellae have a significant role, genera (Tridacna and Hippopus) and eight especially in the energy requirements of species: Tridacna gigas, T. derasa, T. giant clams, since they are capable of squamosa, T. maxima, T. crocea, T. translocating part of their photosynthetic tevoroa, Hippopus hippopus, and H. products to their host. This is why as a porcellanus (Braley, 1992). As well as member of bivalves giant clams do not being prominent members of healthy coral only supply their energy demand from reef ecosystems they are important to the filter feeding process, but also from the people of South East Asia and the Pacific energy translocation from zooxanthellae region as a source of food (meat) and (Klumpps et al., 1992). building material (shells). These clams This review aims to describe how have recently become an important export to calculate the contribution of commodity in several countries in this zooxanthellae to the daily respiration region (Tacconi and Tisdell, 1992; Tisdell energy requirements of giant clams. et al., 1994). 101 Journal of Coastal Development ISSN: 1410-5217 Volume 5, Number 3, June 2002 : 101-110 Accredited: 69/Dikti/Kep/2000 predominates in symbiosis, whilst in Zooxanthellae-Giant Clams Association culture there is alternation between the motile and non-motile (coccoid) stage Zooxanthellae are 'yellow-brown' dino- (Muscatine, 1980; Domotor and D'Elia, flagellate algae (Pyrrophyta) which live as 1986). Motile stages are reported to be endosymbionts in many marine phototactic and occur only for a short invertebrate species (Brandt, 1881). Taylor period of approximately 0.5 hour (Taylor, (1974) listed four different species of 1969a; Domotor and D'Elia, 1986). Fitt et zooxanthellae: (1) Gymnodinium (Symbio- al. (1981) demonstrated different motility dinium) microadriaticum (Freudenthal, patterns of zooxanthellae collected from 1962) which lives in protozoans, jellyfish (C. xamachana, C. frondosa), sea coelenterates, molluscs; (2) Amphidinium anemones (Aiptasia tagetes, A. pallida) chattonii in some coelenterates; and (3) A. and a giant clam (T. gigas) cultured in klebsii in platyhelminthes and (4) identical conditions. Amphidinium sp. in some protozoans. Schoenberg and Trench (1980a,b) Symbiodinium microadriaticum reported differences in isoenzyme patterns, was originally isolated from the jellyfish soluble protein, size, and the structure of Cassiopeia sp (Freudenthal, 1962). Later the cell wall of zooxanthellae collected Taylor (1971) proposed that zooxanthellae from different hosts. Using be placed in the genus Gymnodinium electrophoresis, Schoenberg and Trench because the free-living stage had great (1980a) investigated 40 cultures from 17 affinities to this genus. Loeblich and host species representing 12 strains and Sherley (1979) later suggested the use of found a unique combination of four Zooxanthella microadriatica when they isoenzyme patterns in each strain. Later found that the zooxanthellae isolated from Chang et al. (1983) found differences in Cassiopea xamachana differed slightly the photoadaptive mechanisms of three from Zooxanthella nutricula from the strains of zooxanthellae collected from a order Zooxanthellales (Brandt, 1881). clam (T. maxima), an anemone (A. Schoenberg and Trench (1980b), however, pulchella) and a coral (Montipora argued that the latter name was verrucosa). Similarly, Blank and Trench inappropriate, because the pyrenoids of the (1985a,b) showed several differences in algae described by Brandt (1881) are the number of chromosomes, chloroplasts, traversed by chloroplast thylakoids pyrenoid stalks, mitochondria, (Hollande and Carre, 1974), which is not chromosome volumes, nuclear volumes the case in S. microadriaticum from and thylakoid arrangements of Cassiopeia sp. zooxanthellae isolated from jellyfish Further work revealed that (Cassiopeia xamachana and C. frondosa), Symbiodinium microadriaticum are not anemone (Heteractis lucida) and coral (M. monospecific. Morphological, physio- verrucosa). These zooxanthellae were logical, biochemical and genetic reported to maintain their differences differences among S. microadriaticum when cultured in similar conditions. collected from different hosts are now The existence of these variations more the norm than the converse among zooxanthellae collected from (Schoenberg and Trench, 1980a,b; Blank different hosts suggests that zooxanthellae and Trench, 1985 a,b). There are represent dozens, perhaps even hundreds differences in the life cycle of of species. By investigating the zooxanthellae in symbiosis and in culture biochemical, physiological, conditions. The coccoid, non-motile stage morphological, and behavioural 102 Journal of Coastal Development ISSN: 1410-5217 Volume 5, Number 3, June 2002 : 101-110 Accredited: 69/Dikti/Kep/2000 differences, Trench and Blank (1987) existence of a tubular system associated introduced three new species into the with zooxanthellae within giant clams, genus Symbiodinium. These are S. goreauii previously reported by Mansour (1946). , S. kawagutii and S. pilosum isolated Norton et al. (1992) concluded that from the Caribbean sea anemone Ragactis zooxanthellae in clams are located in a lucida, stony coral Montipora verrucosa branched tubular structure, with a single and the Caribbean zoanthid Zoanthus layer of thin cells separating zooxanthellae sociatus respectively. Rowan and Powers and haemolymph (Rees et al., 1993). (1991, 1992) found 6 distinct differences There are two mechanisms by in small subunit RNA (ssRNA) genes of which zooxanthellae appear in the next zooxanthellae collected from 16 cnidarians generation of their symbiotic host. using the polymerase chain reaction (PCR) Zooxanthellae can be acquired by direct method. They could not distinguish any parental transmission via their egg, or by differences in the symbionts from direct acquisition from the environment. In individual corals of the same species, but giant clams, however, zooxanthellae are they found that different species of corals not being passed to the larvae (LaBarbera, have algae with unique sRNA sequences. 1975; Jameson, 1976; Fitt et al., 1984; However, multiple populations of 1986). This is proved by the fact that zooxanthellae have been reported from zooxanthellae are not found in the individual coral, Montrastea annularis, M. trochophore stage (Fitt and Trench, 1981). faveolata, and M. Franksi (Rowan and Giant clams larvae acquire zooxanthellae Knowlton 1995). de novo from the environment, soon after In more recent papers Baker and metamorphosis (Jameson, 1976; Fitt et al., Rowan (1997) reported genetic differences 1984). In the hatchery, zooxanthellae among zooxanthellae isolated from various isolated from adult clams are introduced to corals species collected from the veliger stages in order to promote a rapid Caribbean and Eastern Pacific. They found transition to the new stage (Gwyther and three different clades among those Munro, 1981; Fitt et al., 1984; Trinidad- zooxanthellae which were then termed as Roa, 1988). clade A, B, and C. All strains of Symbiodinium sp. are ingested by clams. Only a specific Zooxanthellae-Giant Clam Relationship strain, however, will eventually dominate a particular host (Fitt and Trench, 1981; Fitt, Giant clams are known to live in 1985b; Fitt et al., 1986). Strain selection association with symbiotic zooxanthellae by the clams entirely depends on how a (the term symbiosis being used throughout particular strain can grow, survive and this paper is to describe the mutualistic compete with other strains within the host interaction between zooxanthellae and the tissue (Fitt et al., 1986). host). In giant clams these zooxanthellae are extracellular, unlike hermatypic corals Contribution of Zooxan-Thellae to where zooxanthellae are located Giant Clams Respiration intracellularly. Initially it was agreed that zooxanthellae in giant clams are located Zooxanthellae have been found in the freely in the