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The nomenclature of symbiotic dinoflagellates harboured by animal hosts is reviewed with regard to its history and employment. Zooxanthella, Philozoon, Zoorhabdella, and Endodiniummay be regarded as synonyms of Amphidiniumwhich has priority. Gymnodiniumis considered to be incorrectly employed instead of Symbiodiniumwhen applied to S. microadriaticum. Chrysidellais illegitimate. It is proposed to reject Zooxanthellaas a confusing name widely applied to taxa not including its type.

Prochloronsp. isolated from Diplosoma virensand incubated in the light in NaH14CO3demonstrated a high photosynthetic capacity (up to 3.7 p. µgC· (µg Chlorophyll a)-1·hr-1). In vitrothese cyanobacteria release a maximum of 7% of the 14C they fix in the light. Dark fixation was found to be maximally 3% of light fixation and release in the dark averaged 26% of the total 14C fixed in the dark. These data imply that the organic carbon released by these cyanobacteria may not be quantitatively important to the host.The labeled compound released by Prochloronin the light is glycolic acid. The major compounds produced by light and dark carbon fixation in Prochloronare identified, and similarities to other photosynthetic cyanobacteria are noted.

Spawning and development of the clam T. squamosawas investigated in Belau, Western Caroline Islands in February and March 1980. Five of the six species of tridacnid clams spawned in response to various stimuli, but only T. squamosareleased mature eggs. Factors influencing gonad development and spawning are discussed.Development of T. squamosawas followed from post-fertilization to post-metamorphosis, with emphasis on the acquisition of the zooxanthella Symbiodinium (=Gymnodinium) microadriaticumFreudenthal. The symbiotic algae were not seen in either the fertilized eggs or trochophore stages. We found that all strains of S. microadriaticumintroduced to veliger clams were taken into the stomach via the mouth. Veligers ingested motile zooxanthellae more readily than non-motile ones. Within 2-9 days aftermetamorphosis, zooxanthellae moved by an unknown mechanism into the developing siphonal tissues. Most of these zooxanthellae appeared to be in spaces, probably the developing haemal sinuses. However, in some cases it was difficult to tell if the zooxanthellae were intra- or extracellular. Survival and growth of veligers and juveniles with zooxanthellae was greater than those without zooxanthellae. Juveniles with zooxanthellae can survive and grow in Millipore- filtered seawater with light as the sole energy source for over 10 months, illustrating the phototrophic aspect of the association.Our observations may have practical application pertinent to spawning, development, and growth of tridacnid clams in the context of commercial mariculture.

The ingestion and fate of four types of particles by endodermal cells of the scyphistomae of Cassiopeia xamachana were investigated by scanning and transmission electron microscopy. Ferritin was endocytosed pinocytotically by invagination of the plasmalemma. These small pinocytotic vesicles fuse with other similar vesicles to form larger ferritin-containing vacuoles, which eventually fuse with lysosomes. Such secondary lysosomes exhibit acid phosphatase activity. The cooccurrence of acid phosphatase activity and ferritin in secondary lysosomes achieved maximum frequency within 2 h of uptake of ferritin and was evident for at least 4 h following uptake. Artemia particles, live freshly isolated symbiotic algae (Symbiodinium microadriaticum), and heat-killed S. microadriaticum are phagocytosed by endodermal cells. Ferritin-labelled lysosomes fused with food vacuoles containing particles of Artemia. Vacuoles containing heat-killed S. microadriaticum also showed evidence of phago—lysosome fusion. S. microadriaticum in situ (i.e. in host cells) after 3 days exposure to the photosynthetic inhibitor, 3-(3-4-dichlorophenyl)-l, 1 -dimethylurea, appeared degenerate, and were found in loose-fitting host vacuoles, many in mid and apical portions of the host cell. More than 70% of these vacuoles with moribund algae contained the ferritin label, indicating that lysosome fusion had occurred. In contrast, live S. microadriaticum in control animals were almost always found at the base of the host cell in individual tight-fitting vacuoles with no evidence of lysosome fusion. Live S. microadriaticum apparently escape host digestion by prohibiting the fusion of lysosomes with the vacuole in which they reside. Vacuoles containing defunct algal symbionts, in contrast, were subject to lysosomal attack.

The effects of irradiance level and size on the rate of O2evolution and consumption was examined in Tridacna gigasusing an oxygen electrode. Seven photosynthesis-irradiance (P-I) curves were generated for intact clams ranging from 1 to 23 cm in shell length. Both alpha and Pmaxdecreased with increasing size of the clam. Oxygen evolution at 1000 µE·m–2·s–1and consumption in the dark were measured for an additional 9 clams ranging up to 38 cm in shell length. Oxygen evolved per gram clam tissue in the light, dark respiration, and the number of zooxanthellae per gram all decreased with increasing clam size. The average amount of shading experienced by the zooxanthellae in the clam tissues was estimated by comparing the P-I curves of different-sized clams to the P-I curves of zooxanthellae freshly isolated from these clams. Estimates of shading increased from negligible levels in small clams to 80% in the largest clams investigated. Use of these results to chose optimum light intensities for the mariculture of T. gigasis discussed.

This reports the first sequence for a small subunit (185) ribosomal RNA gene (SSU rDNA) fromTetraselmis convolutae.Tetraselmis (=Platymonas) species are important feed stocks for many organisms important in mariculture. This sequence is an essential molecular marker to distinguish the DNAs ofTetraselmis from the DNAs of other organisms in the culture. In addition thisTetraselmis SSU rDNA sequence provides an important entry for the gradually expanding database of symbiotic microalgae.