Rosalind Hinde

Isolation of Oscillatoria spongeliae, the filamentous cyanobacterial symbiont of the marine sponge Dysidea herbacea

The tropical marine sponge Dysidea herbacea (Keller) (Dictyoceratidae: Dysideidae) is always found associated with the filamentous cyanobacterium (blue-green alga) Oscillatoria spongeliae (Schulze) Hauck (Cyanophyceae: Oscillatoriaceae), which occurs abundantly throughout the sponge mesohyl. Intact, metabolically active, trichomes of O. spongeliae were isolated from the sponge by chopping the sponge tissue with a razor blade and squeezing the trichomes into a seawater-based medium containing polyvinylpyrrolidone, bovine serum albumin, dithiothreitol, glycerol, KCl and Na2CO3. The isolated cyanobacteria were concentrated by centrifugation and then washed several times in fresh medium. The isolated O. spongeliae have photosynthetic rates which are similar to the intact sponge-alga association for periods of at least 6 h after isolation. Addition of sponge homogenate to the isolated cyanobacteria causes rapid cell lysis.

Population dynamics of an association between a coral reef sponge and a red macroalga

Sponges are often as abundant as corals on tropical coral reefs and many species are symbiotic with algae. These associations may contribute significantly to reef primary productivity. This paper describes the first study ever made of the population biology of any of the known associations between sponges and macroalgae. Populations of the symbiotic association between the sponge, Haliclona cymiformis (Esper), and the red macroalga, Ceratodictyon spongiosum Zanardini, were studied in One Tree Lagoon, southern Great Barrier Reef. The association primarily occurs in areas where the substratum consists of dead coral rubble (rubble banks), at the edge of the lagoon, where it can reach a biomass of up to 270 g wet weight m−2. Fragmentation is the primary mode of reproduction of the Haliclona/Ceratodictyon association at One Tree Reef. Although algal sporangia were frequently encountered during the summer, sperm cysts were infrequently found in the sponge, and oocytes and larvae were never observed. The size-frequency distribution of the clumps at the rubble bank sites was strongly skewed toward small individuals (longest branch length generally ≤80 mm). Haliclona/Ceratodictyon was also abundant at one site in the centre of the lagoon; at this site, which was not affected by strong currents or wave energy, the size-frequency distribution of the association was normal. Populations of the association at the rubble bank sites are very mobile, with intact clumps moved more than 30 cm per day under calm conditions and up to 1 m per day during rough weather. Survivorship of fragments or mobile clumps of the association is very high. At one site, the biomass of the association was not affected by two cyclones and at least one severe storm. At another site, up to 50% of the biomass of the population was lost following each of these storms, but the recovery of the biomass was largely complete within 9 months. The Haliclona/Ceratodictyon association has a rapid growth rate, of 8 mg (g wet weight)−1 day−1, which exceeds that of many other coral reef sponges, but it is within the range of growth rates reported for other species of marine macroalgae.

Studies on a nudibranch that contains zooxanthellae. I. Photosynthesis, respiration and the translocation of newly fixed carbon by zooxanthellae in Pteraeolidia ianthina

Zooxanthellae of the genus Symbiodinium are present in the tissues of the aeolid nudibranch Pteraeolidia ianthina. Individuals with widely differing densities of zooxanthellae are found living off the mid-central coast of eastern Australia. Nudibranchs with low densities of zooxanthellae (0.02-0.5 x 106 cells mg-1 protein) are common in winter populations, whereas those with comparatively higher densities (1–3 x 106 cells mg-1 protein) are the most common form at other times of the year. Zooxanthellae at all densities in the host exhibit the capacity for photosynthesis, and they grow while resident in the host. The mitotic indices of the zooxanthellae were found to vary as a function of the population density of the algae in the host and were highest in those animals with the lowest densities of zooxanthellae. Oxygen flux was measured as a function of irradiance. Maximum photosynthetic capacity (Pmax), light utilization efficiency (α) and compensation irradiance (Ic) varied between animals, although most of the variation was attributable to differences in the density of zooxanthellae between animals. Pmax and α were positively correlated with density (r2 = 0.82 and 0.88 respectively); Ic exhibited an exponential decrease with the density of zooxanthellae in the host (r2 > 0.81). Icfor animals with 1–2 x 106 cells mg-1 protein had values of I c between 30 and 50 μE m-2 s-1 (1 μE = 6 x 1017 photons), similar to values of Ic measured for shade-adapted corals in other studies. Between 25 and 50% of the total photosynthetic products synthesized over 1 h were shown to move from the alga to the animal in that hour. The total respiratory rate of the association was positively correlated with the density of zooxanthellae (r2 = 0.94). This relation was used to estimate the respiratory rate of a zooxanthella in vivo. Estimates were, however, unreasonably high; this result suggests that zooxanthellae may directly influence the respiratory rate of the host, possibly by increasing the supply of respiratory substrates.

Structure and development of the mycetome in the cabbage aphid, Brevicoryne brassicae

Abstract The mycetome symbiotes of the cabbage aphid Brevicoryne brassicae , have been investigated by light and electron microscopy. Their staining properties and ultrastructure indicate that they are gram-negative, coccoid microorganisms, 2 μ in diameter, and belong to the family Rickettsiaceae. The mycetome is composed of separate mycetocytes, each with a single, large, somewhat lobed nucleus and distinct nucleolus. The cytoplasm of the mycetocytes is packed with symbiotes, and contains sparse endoplasmic reticulum and a few mitochondria, which are much smaller than the symbiotes. The number of mycetocytes increased during early nymphal stages, and then remained fairly steady until after the birth of most of the embryos. This indicates that degeneration of symbiote cells is probably not a source of protein nitrogen for developing embryos of the host.

Factors Produced by Symbiotic Marine Invertebrates which Affect Translocation between the Symbionts

The translocation of nutrients between the partners is known to be a vital feature of the association in most symbioses involving close contact between the cells of the partners, and is probably important in all such associations. There is abundant evidence that this is a well-controlled process. Work so far suggests that, at least in marine invertebrates with algal symbionts, translocation is controlled largely by the animal host. In spite of much work in this area, the processes and signals involved are not well understood. This paper will examine evidence that even in the well-studied symbioses between invertebrates and dinoflagellates (“zooxanthellae”) the control of translocation is not as simple as suggested by the literature, and will discuss some directions for future research and some potentially useful models.

Nutrition of the temperate Australian soft coral Capnella gaboensis

Capnella gaboensis Verseveldt, 1977 (Coelenterata: Octocorallia: Alcyonacea: Nephtheidae) is an abundant soft coral in the temperate waters of south-eastern Australia. From 1981 to 1984, using material collected from Sydney Harbour (33°50′S; 151°15′E), we investigated certain aspects of its apparently obligate association with its symbiotic zooxanthellae, Symbiodinium sp. Numbers of zooxanthellae and chlorophyll content were recorded throughout the first year, then net photosynthesis and respiratory rates of the coral as a function of photo-flux densities, temperature and season were measured in later years. The fractions into which photosynthetically fixed carbon was incorporated were also determined. The zooxanthellae contained a mean of 4.1 μg chlorophyll a 10-6 zooxanthellae. Neither the numbers of zooxanthellae in C. gaboensis nor the chlorophyll a content varied on a seasonal basis. Photon-flux densities in the field ranged from 5 to 120 μE m-2 s-1 over the year. The maximum net oxygen-exchange rate recorded for C. gaboensis was 9.4 μmol O2 mg-1 chlorophyll a h-1 at 871 μE m-2 s-1. The maximum carbon fixation rate obtained was 65.6 μmol C mg-1 chlorophyll a h-1 at 100 μE m-2 s-1. Photosynthesis of C. gaboensis was not light-saturated at 871 μE m-2 s-1; the light compensation point was in the range 50 to 90 μE m-2 s-1 and the optimum temperature was 25°C. Photosynthetic rates were highest in populations sampled in summer. Labelling with 14C showed that photosynthetically fixed carbon was initially incorporated into the aqueous-methanol (low molecular weight) fraction of the coral tissues. From 20 to 100 min after the introduction of the 14C label the rate of incorporation was fairly evenly divided between the aqueous methanol-soluble, the chloroform-soluble (lipid) and the insoluble fractions. In the light, little 14C was released as particulate and/or dissolved organic carbon. Translocation of products of photosynthesis represented up to approximately 10% of the total fixation.

Studies on a Nudibranch that Contains Zooxanthellae II. Contribution of Zooxanthellae to Animal Respiration (CZAR) in Pteraeolidia ianthina with High and Low Densities of Zooxanthellae

Daily budgets of photosynthetically fixed carbon were constructed for Pteraeolidia ianthina with high and low densities of zooxanthellae, for irradiances typical of latitude 34° S in winter, spring and summer. Whereas nudibranchs with high densities of zooxanthellae were potentially phototrophic with respect to carbon, animals with densities of zooxanthellae less than 0.5 x 106 cells mg-1 protein were not. The proportion of dividing zooxanthellae (mitotic index) in P. ianthina was followed over 48 hours. The diel pattern of mitotic index was asynchronous; the indices were higher in animals with low densities of zooxanthellae (20.1±6.2%) than in animals with high densities of zooxanthellae (4.7±1.8%). Specific growth rates of zooxanthellae, calculated from mitotic indices, ranged between 0.100 and 0.399 d-1, indicating that zooxanthellae in P.ianthina have the potential to grow at rates comparable to those found in free-living and other symbiotic dinoflagellates. Zooxanthellae in the host photosynthesized at similar rates, irrespective of their density in P. ianthina. Because of the greater amount of newly synthesized carbon dedicated to the population growth of zooxanthellae, low-density populations did not have excess organic carbon available for host respiration. High density populations, however, were able to supply 79% of the animal’s respiratory carbon demand in winter, 121% in spring and 173% in summer. These results demonstrate that the metabolic relationship of zooxanthellae and their invertebrate hosts may change during the establishment of a symbiotic association.

Heterotrophy on ultraplankton communities is an important source of nitrogen for a sponge-rhodophyte symbiosis.

SUMMARY Grazing on ultraplankton by the sponge partner of an invertebrate/algal symbiotic association can provide enough particulate organic nitrogen to support the nitrogen needs of both partners. The previously unknown natural diet of the sponge in the Haliclona–Ceratodictyon association consists of bacteria and protozoans, which are rich sources of nitrogen. Retention of ultraplankton varied with season and time of day. During the winter there was an order of magnitude more nitrogen taken up than in summer. Time of day during each season also affected the amount of ultraplankton retained. In summer retention was higher at night whereas the opposite was true during winter. Overall, the Haliclona–Ceratodictyon association is able to meet its metabolic nitrogen demands through grazing on the naturally occurring water column community.

Maintenance of aphid cells and the intracellular symbiotes of aphids in vitro

Abstract The behavior of both cells and intracellular symbiotes of the cabbage aphid, Brevicoryne brassicae, in primary culture in three arthropod tissue culture media is described. The insect cells usually survived for 2–3 wk, but in one culture cells survived for 16 wk. The symbiotes survived for approximately the same period as the cells, and probably multiplied slowly, at least in some of the cultures. A preliminary experiment with tissues from the green peach aphid, Myzus persicae, gave similar results.

The role of habitat in determining the distribution of a sponge-red alga symbiosis on a coral reef

At One Tree Reef, populations of the symbiotic association between the sponge, Haliclona cymiformis (Esper, 1794), and the red macroalga, Ceratodictyon spongiosum Zanardini (1878), occur predominantly on the rubble banks inside the northeastern side of the reef crest surrounding One Tree Lagoon, immediately behind the most exposed section of the reef crest. There is only one population in the centre of One Tree Lagoon, where the substratum is sand rather than coral rubble. When clumps of the association were transplanted from the edge to the sandy centre of the lagoon, to areas where it did not occur naturally, some clumps survived for at least 349 days and more than tripled their original biomass, while control clumps left at the rubble bank did not grow noticeably larger. Fusion experiments between individuals collected from different sites showed some histocompatibility, suggesting that all the existing populations of Haliclona/Ceratodictyon may have originated, via fragmentation, from the same parent population. These experiments suggest that the lack of Haliclona/Ceratodictyon in the centre of the lagoon may be due to an inability of fragments or propagules of the association to colonize these sites, because of a lack of solid substrata for attachment, rather than to differences in the physical environment.