INDIAN OCEAN NANOPLANKTON. I. RHABDOSPHAERACEAE (PRYMNESIOPHYCEAE) WITH A REVIEW OF EXTANT TAXA1

Family characteristics of the Rhabdosphaeraceae are revised to limit the genera to those having cyrtoliths; genera with placoliths are removed from the family. Rhabdoliths, cyrtoliths bearing a process in the central area, are present in all genera. Coccospheres having monomorphic coccoliths, all being rhabdoliths, form one group within the family, whereas genera with dimorphic coccoliths in the coccosphere comprise a second group. Cyrtoliths without processes in the latter group may be intermixed with rhabdoliths in some genera, whereas other genera have rhabdoliths located only in polar regions of the coccosphere. Two generic nomenclatural changes are proposed, Algirosphaera being the name applied to species previously placed in Anthosphaera, an invalid generic name, and Palusphaera is recognized as a valid monotypic genus, P. vandeli being the name applied to the species that has been named Rhabdosphaera longistylis in recent literature. A new combination is made, Rhabdosphaera xiphos (Deflandre et Fert) comb. nov., recognizing a species formerly known only in sediments as extant. Rhabdosphaera, Acanthoica and Algirosphaera are genera with dimorphic coccoliths in the coccospheres; Discosphaera, Palusphaera and Anacanthoica are genera having monomorphic coccoliths in the coccosphere.     

LIGHT AND ELECTRON MICROSCOPE OBSERVATIONS OF ALGIROSPHAERA ROBUSTA (PRYMNESIOPHYCEAE)1

The coccolithophore Algirosphaera robusta (Lohmann) R. E. Norris was isolated into laboratory culture for the first time. This species is of particular interest as the first deep photic coccolithophore to be cultured, the only member of the Rhabdosphaeraceae to have been successfully isolated, and the first coccolithophore with a coccolith structure including a complex disjunct central area to have been studied in detail. Observations on the culture strain supported the previous inference that the commonly recognized species A. robusta, A. oryza Schlauder, and A. quadricornu (J. Schiller) R. E. Norris are conspecific. However, A. meteora (Müller) R. E. Norris and A. cucullata (Lecal‐Schlauder) J. R. Young, Probert et Kleijne were recognized as discrete species. Coccolith rim formation in A. robusta follows the pattern of biomineralization documented in other heterococcoliths and was suggested to be universal. However, the prominent central hood had a unique ultrastructure and appeared to be formed by a distinctively different biomineralization mode. We suggest that this can provide a key to reinterpreting homology in coccolith structure and that this species is a promising target for comparative biochemical and genomic studies of biomineralization. In terms of cell ultrastructure, A. robusta exhibited marked similarities to Syracosphaera pulchra Lohmann, and a close evolutionary relationship between the families Rhabdosphaeraceae and Syracosphaeraceae is suggested.     

ULTRASTRUCTURE OF PRYMNESIUM NEMAMETHECUM SP. NOV. (PRYMNESIOPHYCEAE)1

Based on material collected from Cape Town, a new sand-dwelling, marine species of Prymnesium is described. Using light and electron microscopy, Prymnesium nemamethecum sp. nov. has been found to resemble other species of the genus in size, organelle arrangement, and swimming behavior. It differs from other described species in that it has three types of scales, one of which is confined to the region of appendage insertion and forms a sheath of simple plate scales over the haptonema. In addition, the scales constituting the proximal body scale layer(s) are unusual because they are not simple plate scales but are specifically ornamented.     

HETEROMORPHIC LIFE HISTORIES IN ARCTIC COCCOLITHOPHORIDS (PRYMNESIOPHYCEAE)1

During three visits to Disko Bay, West Greenland, we found four different types of prymnesiophyte flagellates with heterococcoliths from species of the genera Papposphaera Tangen and Pappomonas Manton and Oates in characteristic and consistent combinations with holococcoliths from species of the genera Turrisphaera Manton, Sutherland, and Oates and Trigonaspis Thomsen. We conclude that several taxa previously considered to be autonomous species are, in fact, part of life histories combining hetero- and holococcolithophorid forms in a manner somewhat similar to that known from studies of cultured strains of Coccolithus pelagicus (Wallich) Schiller and Crystallolithus hyalinus (Gaarder) Markali. Similarly, Calciarcus Manton, Sutherland and Oates and Wigwamma Manton, Sutherland and Oates also may be alternate phases of a coccolithophorid life history.     

ISOLATION AND CHARACTERIZATION OF A VIRUS INFECTING PHAEOCYSTIS POUCHETII (PRYMNESIOPHYCEAE)1

A virus infecting the haptophyte Phaeocystis pouchetii (Hariot) Lagerheim was isolated from Norwegian coastal waters in May 1995 at the end of a bloom of this phytoplankter. The virus was specific for P. pouchetii because it did not lyse 10 strains of P. globosa Scherffel, Phaeocystis sp., and P. antarctica Karsten. It was a double-stranded DNA virus, and the viral particle was a polyhedron with a diameter of 130–160 nm. The virus had a main polypeptide of about 59 kDa and at least five minor polypeptides between 30 and 50 kDa. The latent period of the virus when propagated in cultures of P. pouchetii was 12–18 h, and the time required for complete lysis of the cultures was about 48 h. The burst size was estimated to be 350–600 viral particles per lysed cell.     

THE FLAGELLAR APPARATUS OF CHRYSOCHROMULINA SP. (PRYMNESIOPHYCEAE)1

The flagellar apparatus of an undescribed species of Chrysochromulina Lackey that bears “eyelash” scales is reconstructed. The transitional region consists of two transitional plates each with an axosome, with no stellate pattern between them. Fine osmiophilic rings lie between the flagellar membrane and the outer doublets in the transitional region. The two jagella and the haptonema are inserted in a subapical depression that is lined ventrally by a spine-like projection formed by one of the parietal chloroplasts. The angles of insertion are similar to those of some other Chrysochromulina species in that both the haptonema and the right basal body lie at an extreme angle to the left basal body. The connectives of the apparatus consist of a striated distal band with a dorsal extension to the R1 and a ventral extension overlying the R2, a striated distal accessory band, an auxiliary connective from the right basal body to the adjacent ventral chloroplast, a well-developed intermediate band, two striated proximal bands, and a striated proximal accessory band. Of the microtubular roots in this Chrysochromulina species, three are associated with the left side of the cell (an R1 of 8+3; a small crystalline compound root, the R1C, associated with the R1; an R2 of three micro-tubules), and two are associated with the right basal body (an R3 of 2/2 microtubules with which the single-stranded R4 converges to form a 2/2+1 and then a 2/3 tiered arrangement). Comparisons are drawn with other species in the genus and related genera, particularly Prymne-sium.     

CELL AND GROWTH CHARACTERISTICS OF TYPES A AND B OF EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE) AS DETERMINED BY FLOW CYTOMETRY AND CHEMICAL ANALYSES1

Two morphotypes of Emiliania huxleyi (Lohmann 1902) Hay et al. 1967, types A and B, known to be unequally distributed in the oceans, were grown in dilution cultures at a range of photon flux densities (PFDs) (1.5–155 μmol photons·m^?2·s^?1) and two temperatures (10° and 15° C). Calcite carbon and organic carbon content of the cells as well as instantaneous growth rate, cell size, chlorophyll fluorescence, and light-scatter properties clearly depended on growth conditions and differed considerably for the two morphotypes. The ratio between calcite carbon and organic carbon production showed an optimum of 0.65 in E. huxleyi type A cells at PFD = 17.5. The ratio increased slightly with a temperature increase from 10° to 15°C but remained < 1.0 at both temperatures in light-limited cells. In contrast, calcite carbon production exceeded organic carbon production (ratio: 1.4–2.2) in phosphate-deprived cultures. Emiliania huxleyi type B generally showed a higher calcite carbon/organic carbon ratio than E. huxleyi type A, but the relation with PFD was similar. The content of calcite carbon and organic carbon as well as the instantaneous growth rate, cell size, chlorophyll fluorescence, and light-scatter properties showed large diel variations that were closely related to the division cycle. Our results show the importance of mapping the structure of any sampled cell population with respect to the phase in the cell division cycle, as this largely determines the outcome of not only “per cell” measurements but also short time (less than 24 h) flux measurements. For instance, dark production of calcite by E. huxleyi was negatively affected by cell division. Slowly growing (phosphate-stressed) cultures produced calcite in the light and in the dark. In contrast, rapidly growing cultures at 10°C produced calcite only in the light, whereas in the dark there was a significant loss of calcite due to dissolution.     

ISOLATION AND CHARACTERIZATION OF GOLGI FROM COCCOLITHUS PELAGICUS (PRYMNESIOPHYCEAE)1

Cells of the marine alga Coccolithus pelagicus (Wal-lich)J. Schiller grown in axenic cultures were homogenized and fractionated. The distribution of organelle markers was assessed enzymatically after centrifugation through zonal, density, and flotation gradients made with sucrose, sorbitol, or Percoll. Mitochondria (1.19 g·cm^-3) and chloroplasts (1.15 g·cm^-3) were recovered in sucrose gradients at densities similar to those observed for higher plants and most algae. The position of endoplasmic reticulum and plasma membrane in the gradients was monitored by NADPH cytochrome c reductase and vanadate-sensitive Mg²⁺-ATPase, respectively. Higher plant Golgi markers, latent undine diphosphatase (UDPase) and glucan synthase I, were colocalized at a density range including two peaks of activity at 1.13–1.15 g·cm^-3. Bound calcium was associated with high density (1.15 g·cm^-3) membranes. Ca²⁺-stimulated ATPase was found at high levels on membranes that did not coisolate with the latent UDPase-containing membranes. The Ca²⁺-stimulated ATPase, a possible participant during calcification, was associated with a chloroplast-enriched fraction in all the organelle separation systems. However, about 30% of the total activity was separated from both the chloroplasts and Golgi on 0–70% Percoll gradients containing 0.4 M sucrose. The possible relationship of the Golgi and the high-density organelle exhibiting Ca²⁺-stimulated ATPase to coccolithogenesis and the process of calcification and crystal formation is discussed.     

LOCALIZATION OF CA2+-STIMULATED ATPASE IN THE COCCOLITH-PRODUCING COMPARTMENT OF CELLS OF PLEUROCHRYSIS SP. (PRYMNESIOPHYCEAE)1

Cell homogenates of Pleurochrysis sp. (CCMP299) were fractionated by means of sucrose gradients. Ca²⁺-stimulated ATPase (EC 3.6.1.3., ATP phosphohydrolase) was associated primarily with the plasma membrane, Golgi, and high density (1.21 g·cm^?3) membranous structures. Ca²⁺-stimulated ATPase was highly enriched in the latter. Based on treatments with Triton X-100 and NBD ceramide, we conclude that the high-density structures were membrane-delimited organelles. These vesicle-like organelles contained complex polysaccharides, a high concentration of calcium, and, upon microscopic examination, structures resembling coccoliths. These findings are consistent with observations on the known composition of coccoliths and the presumed mineralizing function of the sub-cellular coccolith-producing compartment. The high-density vesicles were linked to the Golgi by means of colchicine-sensitive materials, presumably microtubules. These data and prior ultrastructural observations by other investigators indicating vectorial assembly and secretion suggest that the subcellular movement of the newly formed coccoliths may be directed and/or powered by colchicine-sensitive cytoskeletal elements. We interpret the data to mean that the high-density vesicles represent the coccolith-producing compartment previously observed by others in electron micrographs.     

DISTRIBUTION OF TWO TYPES OF EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE) IN THE NORTHEAST ATLANTIC REGION AS DETERMINED BY IMMUNOFLUORESCENCE AND COCCOLITH MORPHOLOGY1

Culture strains of Emiliania huxleyi (Lohmann 1902) Hay et al. 1967 were placed into two groups designated E. huxleyi type A and type B on the basis of coccolith morphology and immunological properties of the coccolith polysaccharide. We studied the distribution of these types in the North Atlantic region using an indirect immunofluorescence assay with antisera directed against the coccolith polysaccharide of E. huxleyi type A and type B and epifluorescence microscopy. In field samples taken in the Northeast Atlantic Ocean, E. huxleyi type A was found exclusively. In contrast, type B was dominant in the North Sea. Scanning electron microscopy of the samples revealed the same unequal distribution of the two types as found with the immunofluorescent-labelling assay.     

CARBONIC ANHYDRASE IN THE CHLOROPLAST OF A COCCOLITHOPHORID (PRYMNESIOPHYCEAE)1

The activity and subcellular distribution of carbonic anhydrase in a coccolithophorid alga, CCMP 299, was examined. The enzyme could not be detected in crude cell homogenates but was present at high specific activity (27.5 unit·mg^?1 protein) in chloroplasts (density, 1.14 g·cm^?3) isolated in a sucrose gradient. The carbonic anhydrase activity was sensitive to known inhibitors. Inhibition at 50% (I₅₀) was obtained with concentrations of 4.60 mM and 2.65 mM for acetazolamide and NaN₃, respectively. These levels are more consistent with patterns of inhibition previously observed for chloroplastic (as compared to periplasmic) carbonic anhydrase. In this organism, carbonic anhydrase was localized in the chloroplast stroma. These findings are discussed in terms of the relationship among dissolved inorganic carbon interconversions, photosynthesis, and calcification.     

COMPARISON OF GROWTH AND SINKING RATES OF NON-COCCOLITH- AND COCCOLITH-FORMING STRAINS OF EMILIANIA HUXLEYI(PRYMNESIOPHYCEAE) GROWN UNDER DIFFERENT IRRADIANCES AND NITROGEN SOURCES1

We examined the effect of the presence or absence of coccoliths on the growth and sinking rates of an oceanic isolate of the coccolithophore Emiliania huxleyi (Lohmann) Hay et Mohler isolated from the northeastern subarctic Pacific. Coccolith-forming and non-coccolith-forming (i.e. naked, nonmotile) strains were obtained from the same isolate and grown under both saturating and limiting irradiance levels with either nitrate or ammonium as the primary nitrogen source. Sinking rate, growth rate, and cell volume (excluding coccoliths) were measured for each culture. Under saturating irradiance, coccolith-forming cells grew significantly slower than naked cells, had significantly higher sinking rates, and had larger cell volumes than naked cells. Under limiting irradiance levels, growth rates of the two strains were identical, sinking rates were higher for coccolith-forming cells in stationary-phase cultures only, and cell volumes remained greater for coccolith-forming cells. The sinking rates achieved for this ubiquitous coccolithophore ranged from <0.1 to 0.5 m · d^?1. Sinking rates were not statistically different between coccolith-forming and naked strains of E. huxleyi under limiting irradiance conditions for log-phase cultures, but sinking rates were greater for coccolith-forming cells under some of the other conditions tested. However, the average sinking rate was never more than twice as great as for coccolith-forming cells, with the exception of nitrate-grown, senescent cells under limiting irradiance (3.4 times greater). Cell volumes (excluding coccoliths) were consistently ca. 1.5 times greater for coccolith-forming cells than for naked cells. Nitrogen source had an effect on growth rate and cell volume, with ammonium-grown cultures growing faster and having larger cell volumes than nitrate-grown cultures of both strains. However, despite the difference in growth rate and cell volume, nitrogen source had little if any effect on sinking rate.     

FIRST EVIDENCE OF PALYTOXIN ANALOGUES FROM AN OSTREOPSIS MASCARENENSIS (DINOPHYCEAE) BENTHIC BLOOM IN SOUTHWESTERN INDIAN OCEAN1

Benthic dinoflagellates of the genus Ostreopsis Schmidt are common in tropical and subtropical water, and some species produce toxins potentially involved in human intoxication events. A benthic bloom of Ostreopsis mascarenensis Quod was observed near Rodrigues Island during a survey of benthic dinoflagellates in the southwestern Indian Ocean. The morphology of O. mascarenensis was studied by LM and SEM. Preliminary screening of a crude extract of an O. mascarenensis bloom revealed neurotoxicity in mice similar to that induced by palytoxin. After partition of the crude extract, the highest toxicity was retained in the butanol‐soluble fraction, which retained hemolytic activity suggestive of palytoxin analogues. Two new toxins, mascarenotoxin‐A and ‐B, were resolved from this fraction by HPLC coupled to a diode array detector. The closed mass spectrum profile and fragmentation pattern obtained by advanced nano–electrospray ionization quadrupole time‐of‐flight mass spectrometry between purified toxins and a reference palytoxin confirmed the mascarenotoxins as palytoxin analogues. These results were confirmed by tandem mass spectrometry with the identification of specific fragment ion m/z 327. An on‐line liquid chromatography protocol coupled to tandem mass spectrometry was developed for detection of these palytoxin analogues. The present study describes the first purification, chemical, and toxicological characterization of new palytoxin analogues isolated from a benthic bloom of O. mascarenensis. These results suggest that O. mascarenensis, which is largely distributed in the southwestern Indian Ocean, could be a source of palytoxin poisoning in this tropical area.     

MORPHOLOGICAL AND GENETIC CHARACTERIZATION OF PHAEOCYSTIS CORDATA AND P. JAHNII (PRYMNESIOPHYCEAE), TWO NEW SPECIES FROM THE MEDITERRANEAN SEA

Two new Phaeocystis species recently discovered in the Mediterranean Sea are described using light and electron microscopy, and their systematic position is discussed on the basis of an analysis of their nuclear-encoded small-subunit ribosomal RNA gene (SSU rRNA) sequences. Phaeocystis cordata Zingone et Chrétiennot-Dinet was observed only as flagellated unicells. Cells are heart shaped, with two flagella of slightly unequal length and a short haptonema. The cell body is covered with two layers of thin scales. The outermost layer scales are oval, with a faint radiating pattern, a raised rim, and a modest central knob. The inner-layer scales are smaller and have a faint radiate pattern and an inflexed rim. Cells swim with their flagella close together, obscuring the haptonema, pushing the cell, and causing it to rotate about its longitudinal axis while moving forward. Phaeocystis jahnii Zingone was isolated as a nonmotile colony. It forms loose aggregates of cells embedded in a mucilaginous, presumably polysaccharide matrix without a definite shape or visible external envelope. The flagellated stage has the features typical of other Phaeocystis species. Cells are rounded in shape and slightly larger than P. cordata. The cell body is covered with extremely thin scales of two different sizes with a very faint radiating pattern toward their margin. Swimming behavior is similar to that of P. cordata, with the flagella in a posterior position as the cells swim. The SSU rRNA sequence analysis indicated that both species are distinct from other cultivated Phaeocystis species sequenced to date. Regions previously identified as specific for the genus Phaeocystis are not found in P. jahnii, and new genus-specific regions have been identified. P. cordata is more closely related to the colonial species P. globosa, P. antarctica, and P. pouchetii and has branched prior to the divergence of the warm-water P. globosa species complex from the cold-water species P. antarctica and P. pouchetii. These results are discussed within a framework ofthe available data on the evolution of the world’s oceans.     

INDUCED DIMORPHIC LIFE CYCLE OF A COCCOLITHOPHORID,CALYPTROSPHAERA SPHAEROIDEA (PRYMNESIOPHYCEAE,HAPTOPHYTA)1

The holococcolith Calyptrosphaera sphaeroidea Schiller was collected at Miyake‐jima Island, Japan and unialgal cultures established. Alternation of the holococcolith and heterococcolith phases was induced using new culture media (MNK, TR, and LO). Cells synchronized in the holococcolith phase were transferred into TR medium to induce a life cycle change. The heterococcolith phase, which has never been reported before, appeared after more than 40 days. The heterococcoliths were very small elliptical discs, about 0.5 μm wide and 1 μm long. Typical diploid‐type organic scales on the cell surface were observed. This phase was very stable in culture and was tolerant of unfavorable conditions. To reverse the life phase, cells in the heterococcolith phase were transferred into cold LO medium and exposed to low temperature (4°C) and low light (2 μmol photons·m^?2·s^?1) for 30 min before culturing at normal conditions (22.5°C and 20 μmol photons· m^?2·s^?1). The swimming behavior of the holococcolith cells seemed to be an indicator of the life cycle phase transition. This article reports for the first time a set of conditions that could control the transition of a coccolithophorid from one life phase to the other. Selected vitamins and trace metals induced the heterococcolith phase, whereas a slightly higher concentration of components in the basic medium along with concomitant stresses of light and temperature induced the holococcolith phase. Based on the results, we propose a hypothesis that the alternation of coccolithophorid life phases is regulated by changes between pelagic and coastal environments coupled with changes in seasonal conditions.     

TAXONOMIC STUDY OF TWO NEW GENERA OF FUSIFORM GREEN FLAGELLATES,TABRIS GEN. NOV. AND HAMAKKO GEN. NOV. (VOLVOCALES,CHLOROPHYCEAE)1

On the basis of LM, we isolated strains of two species of fusiform green flagellates that could be assigned to former Chlorogonium (Cg.) Ehrenb. One species, “Cg.”heimii Bourr., lacked a pyrenoid in its vegetative cells and required organic compounds for growth. The other was similar to Cg. elongatum (P. A. Dang.) Francé and “Cg.”acus Nayal, but with slightly smaller vegetative cells. Their molecular phylogeny was also studied based on combined 18S rRNA, RUBISCO LSU (rbcL), and P700 chl a‐apoprotein A2 (psaB) gene sequences. Both species were separated from Chlorogonium emend., Gungnir Nakada and Rusalka Nakada, which were formerly assigned to Chlorogonium. They were accordingly assigned to new genera, Tabris Nakada gen. nov. and Hamakko (Hk.) Nakada gen. nov. as T. heimii (Bourr.) Nakada comb. nov. and Hk. caudatus Nakada sp. nov., respectively. Tabris is differentiated from other genera of fusiform green flagellates by its vegetative cells, which only have two apical contractile vacuoles and lack a pyrenoid in the chloroplast. Hamakko, on the other hand, is distinguishable by the fact that its pyrenoids in vegetative cells are penetrated by flattened thylakoid lamellae.     

MANTONIELLA IN ANTARCTIC WATERS INCLUDING THE DESCRIPTION OF M. ANTARCTICA SP. NOV. (PRASINOPHYCEAE)1

We report the finding of two species of Mantoniella from the Weddell Sen and Prydz Bay, Antarctica. As well as M. squamata, a cosmopolitan species, we describe M. antarctica sp. nov., the second species in this genus. M. antarctica is covered with two distinctive types of discoid scales. The flagella bear only the smaller of the scale types whereas the cell body has both types, the larger overlying the smaller.     

STRUCTURE AND PHYSIOLOGY OF THE HAPTONEMA IN CHRYSOCHROMULINA (PRYMNESIOPHYCEAE). II. MECHANISMS OF HAPTONEMATAL COILING AND THE REGENERATION PROCESS1

The axoneme in the free part of the haptonema in Chrysochromulina acantha Leadbeater & Manton and C. simplex Estep et al. consists of seven single microtubules, except in the extreme distal swelling where, in C. simplex, there are only three microtubules. In the extended haptonema, the microtubules are arranged in a ring though they are not evenly spaced, the gap between two of the microtubules being larger than that between any other neighboring pairs. In the coiled haptonema, rearrangement of the microtubules occurs so that the ring becomes distorted and the microtubules form two superposed arcs. A sliding microtubule mechanism is considered as a means by which haptonematal movement might be affected, and this is discussed in relation to the fine structure of both embedded material and negatively stained demembranated cells. We show that haptonematal coiling is dependent on the presence of calcium ions and that an external concentration of between 10^?6 and 10^?7 M Ca²⁺ is the threshold below which the frequency of coiling on cell death is reduced. The results of experiments using ethylene bis-(oxyethylenenitrilo)-tetracetic acid (EGTA) and lanthanum ions to control extracellular and intracellular Ca²⁺ concentrations are discussed in terms of both external free calcium and intracellular pools. We also show that haptonematal regeneration following excision begins with a short lag phase. This is followed by a period of rapid growth, decreasing after approximately 4 h. Full haptonematal regrowth is not achieved until after 12–15 h. The rate of haptonematal regeneration is strongly affected when the flagella are regenerating simultaneously. These observations are interpreted in terms of competition for intracellular precursors.     

OCCURRENCE OF PHYIWATED CHLOROPHYLL c IN ISOCHRYSIS GALBANA AND ISOCHRYSIS SP. (CLONE T-ISO) (PRYMNESIOPHYCEAE)1

The pigment composition of two clones of Isochrysis galbana Parke (CCMP 1323 and CCAP 927/1), and Isochrysis sp. (clone T-ISO) was analyzed by high-performance liquid chromatography using a polymeric octadecylsilica column. Fluorescent peaks with retention times higher than chlorophyll a were detected for all three clones. The corresponding pigments were isolated and characterized in terms of their visible absorbance and fluorescence spectra. The pigments were similar to phytol-substituted chlorophyll c, previously isolated from Emiliania huxleyi (Lohm.) Hay and Mohler and other species containing chlmophyll c₃. The presence of phytol-substituted chlorophyll c in I. galbana which lacked chlorophyll c₃, increases the diversity of chlorophyll patterns for the Haptophyta, which can be grouped, at present, into six different pigment types. This is the jrst observation of a haptophyte containing the apolar phytylated chlorophyll c-like pigment but lacking chlorophyll c₃.     

THE ONCHIDIACEA (GASTROPODA, PULMONATA) OF HONG KONG WITH A WORLDWIDE REVIEW OF THE GENERA

The Onchidiacea are a superfamily of mainly marine intertidal,slug-like pulmonates. Twelve genera are recognizable, and theseare redefined. Four of these genera are represented in HongKong, each by a single species, and these are recorded herein.Two of these are new; a third has not been seen since it wasoriginally figured in 1850. ^*Present address: Palmers Sixth-Form College, Grays, Essex. (Received 18 August 1983;