Light intensity influences the production and translocation of fatty acids by zooxanthellae in the jellyfish Cassiopea sp.

The influence of light intensity on the fatty acid profiles of the scyphozoan jellyfish Cassiopea sp. and its endosymbiotic zooxanthellae was investigated using a manipulative experiment. The aims of the study were to: 1) identify changes related to light intensity in the fatty acid profiles of the host jellyfish and zooxanthellae; 2) determine if jellyfish exposed to low light intensities compensated for reduced rates of photosynthesis by increasing heterotrophic feeding; and 3) determine if concentrations of zooxanthellae and chlorophyll a (chl a) increased in jellyfish exposed to reduced light intensity. Jellyfish were collected from an artificial urban tidal lake in southeast Queensland, Australia. Two were frozen for immediate analysis and 15 were randomly allocated to each of nine mesocosms. Three replicate mesocosms were then randomly allocated to each of three light treatments: 100%, 25%, and 10% PAR. The mesocosms were supplied with unfiltered, continuous flowing seawater and jellyfish fed on natural zooplankton, supplemented with frozen Mysis shrimp. Three jellyfish were sampled, with replacement, from each mesocosm 3, 15, 22, 39 and 69 days after the experiment commenced. Fatty acids as methyl esters in the host tissue (mesoglea) and zooxanthellae were determined separately using gas chromatography and verified by mass spectrometry. The fatty acid profiles of the host jellyfish and zooxanthellae remained unchanged in the 100% PAR treatment throughout the experiment but varied in the lower light treatments. A decrease in light intensity caused a reduction in the concentrations of some polyunsaturated fatty acids such as 18:1ω9 and 18:4ω3 in the zooxanthellae, the latter being abundant in dinoflagellates. Concomitantly, the concentrations of these fatty acids increased in the host tissues, suggesting a possible transfer of zooxanthellate fatty acids to the jellyfish. Jellyfish in the 10% PAR treatment shrank during the experiment and their fatty acid profiles did not reflect any shift towards increased heterotrophy. On days 22 and 69 concentrations of chl a, zooxanthellae and [chl a] zooxanthella^− 1 were determined. [chl a] and [chl a] zooxanthella^− 1, initially increased in the lower light treatments but decreased by the end of the experiment indicating that jellyfish may adapt to reduced light intensity in the short-term but that long-term exposure to reduced light results in compromised performance.     

Loss of Symbiodinium from bleached soft corals Sarcophyton ehrenbergi, Sinularia sp. and Xenia sp.

The deleterious effects of temperature-induced coral bleaching, a process by which corals lose their endosymbiotic algae (zooxanthellae; genus Symbiodinium) primarily at temperatures above mean yearly maximums, has not been well described for alcyonacean soft corals (Coelenterata, Octocorallia). The study of Symbiodinium cells lost from Sarcophyton ehrenbergi, Sinularia sp., and Xenia sp., which have not been compared in bleaching studies, indicate that the soft coral S. ehrenbergi released the greatest number of symbiont cells, however, it was less susceptible to heat stress surviving temperatures of 34 °C for >39 h. Sinularia sp. showed intermediate levels of bleaching tolerance to elevated temperatures, surviving prolonged exposures at 32 °C, but dying within 24 h at 34 °C. Xenia sp., however, was the most vulnerable to high heat stress maximally releasing Symbiodinium at temperatures ≤30 °C. This evidence indicates that Xenia sp. is even more susceptible to elevated temperatures than Acropora spp., previously reported to be the most vulnerable coral species to elevated temperature-induced bleaching.

Molecular analysis showed that the more resistant soft coral species (S. ehrenbergi) had the same type of Symbiodinium (clade C) as less resistant soft corals (Xenia sp.). In comparison to scleractinian corals collected from the same region that show similar bleaching resistance to high temperatures (e.g. Porities solida—more robust; Favites complanata—moderate resistance; Acropora hyacinthus—less robust), all scleractinian corals were symbiotic with Symbiodinium from clade C. A. hyacinthus, however, was found to possess multiple symbionts (clades B and C), and this represents a first report of Clade B in any Acropora species.     

Morphological differences between,and reproductive isolation of,two populations of the jellyfish Cyanea in Long Island Sound,USA

Two populations of Cyanea, one in the Niantic River estuary and the other in the adjacent Niantic Bay portion of Long Island Sound, were studied for more than a decade. The estuary and the bay are connected by a narrow channel: this and hydrographic features constrain transport between them. Specimens from each site exhibit morphological and seasonal differences comparable to those which distinguish C. capillata from C. lamarckii in European waters. Reproducing River medusae never cooccurred with reproducing Bay medusae. Estuarine jellyfish are sometimes found in the Bay, but reproducing individuals have not been seen there. Reproductively mature Bay jellyfish occasionally appear in the River, but benthic samples show that they do not deposit planulae at this site and thus do not contribute to the next generation of medusae in the River. Such differences suggest an absence of gene flow between these two populations, indicating that the River medusae and Bay medusae might be separate species.     

Behavioural responses of zooplankton to the presence of predatory jellyfish

The major objective of this study was to investigate the behavioural responses of several zooplankton species to the presence of the scyphozoan jellyfish, Catostylus mosaicus. Specific aims included: identifying taxa that were not captured by C. mosaicus; investigating whether some of these taxa were able to detect and avoid water that had been exposed to C. mosaicus; and determining if positive phototaxis of crab megalopae was suppressed in the presence of C. mosaicus. Zooplankton not caught by C. mosaicus were identified by comparing the zooplankton present in the water column to those on the oral arms of the jellyfish. C. mosaicus mainly caught mollusc veligers and copepods, but did not catch crab megalopae, small prawns or post-flexion fish larvae. The hypothesis that these taxa were able to avoid swimming in water exposed to C. mosaicus was tested using water-choice experiments in a flume tank. A significant proportion (18-25%) of larval barramundi (Lates calcarifer) avoided swimming in the plume of water that had been exposed to C. mosaicus but mud crab (Scylla serrata) megalopae and juvenile prawns showed no response. The effect of C. mosaicus on the positive phototaxis of S. serrata megalopae was tested using 1 m tall glass towers. Megalopae were exposed to one of four treatments: filtered seawater (a control), an oral arm of C. mosaicus, an oral arm that had been sealed in plastic, and mucus from C. mosaicus. Megalopae migrated higher into the water column in the control than in treatments containing cues from the jellyfish. These findings suggest that blooms of jellyfish may induce behavioural changes in some zooplankton.     

UeberPipilo virescens n. sp.

Ohne Zusammenfassung     

UeberMyiozetetes icterophrys n. sp.

Ohne Zusammenfassung     

Purification and properties of the xylanases from the termite Macrotermes bellicosus and its symbiotic fungus Termitomyces sp.

Four xylanases were purified, two from the termite Macrotermes bellicosus workers (X1T and X2T) and two from its symbiotic fungus Termitomyces sp. (X1Mc and X2Mc). The analysis of the step required for the purification of X1T and X1Mc and the comparison of their different properties suggested that xylanases X1T and X1Mc were the same enzyme, X1. The determination of the reducing sugars by TLC revealed that X1 was an endoxylanase (EC 3.2.1.8) and X2T and X2Mc were exoxylanases (EC 3.2.1.37). The apparent molecular weights of the three xylanases, determined by SDS-polyacrylamide gel electrophoresis, were 36 kDa for X1, 56 kDa for X2T and 22.5 kDa for X2Mc. The optimal pH of the three xylanases was 5.5, and K_m values determined with birchwood xylan as substrate were 0.2% for X1, 0.1% for X2T and 0.3% for X2Mc, showing a high affinity for this substrate. The three enzymes differed also by their thermal stability.     

Purification and properties of a chitinase from Penicillium sp. LYG 0704

The chitinase producing Penicillium sp. LYG 0704 was procured from soil of the Chonnam National University crop field. The chitinase activity was detected after the first day which increased gradually and reached its maximum after 3 days of cultivation. The chitinase was purified from a culture medium by precipitation with isopropanol and column chromatography with Mono Q and Butyl-Sepharose. The molecular mass of chitinase was estimated to be 47 kDa by SDS–PAGE. Optimal pH and temperature were 5.0 and 40 °C, respectively. The N-terminal amino acid sequence of the enzyme was determined to be ¹AGSYRSVAYFVDWAI¹⁵. The fully cloned gene, 1287 bp in size, encoded a single peptide of 429 amino acids. BLAST search of the chitinase gene sequence showed similarity with chitinase of Aspergillus fumigatus Af293 chitinase gene (58%) and A. fumigatus class V chitinase ChiB1 gene (56%).     

A review and synthesis on the systematics and evolution of jellyfish blooms: advantageous aggregations and adaptive assemblages

Pelagic gelatinous invertebrates in many diverse phyla aggregate, bloom, or swarm. Although typically portrayed as annoying to humans, such accumulations probably are evolutionary adaptations to the environments of pelagic gelatinous zooplankton. We explore this proposition by systematic analysis completed in three steps. First, using the current morphological taxonomic framework for Scyphozoa, we summarize relevant information on species that aggregate, bloom, and swarm and on those species that do not. Second, we establish a molecular phylogenetic framework for assessing evolutionary relationships among classes and many orders of Medusozoa and among most families of Scyphozoa (particularly Discomedusae). Third, we interpret the phylogenetic distribution of taxa and of characteristics of jellyfish that aggregate, bloom, or swarm, in terms of species diversity—a proxy for evolutionary success. We found that: (1) Medusae that occur en masse are not randomly distributed within the Phylum Cnidaria but instead they are found primarily within the Scyphozoa which have a metagenic life history. (2) Midwater and deep-sea medusae rarely bloom or swarm. (3) Epibenthic medusae do not swarm. (4) Large carnivores that feed on large prey do not bloom strongly. (5) Large medusae that feed exclusively on small prey both bloom and swarm. (6) Pelagia, the only holoplanktonic, epipelagic scyphomedusan, both blooms and swarms, demonstrating that a metagenic life cycle is not required for blooming or swarming at sea. (7) Environmental change (overfishing, species introductions, and eutrophication) may induce or inhibit blooms. (8) Taxa that bloom or swarm are often more diverse than taxa that do not. (9) Speciation in scyphozoans can occur rapidly. (10) Morphological stasis in holozooplankton masks genetic variability. (11) Selection for convergent evolution in the sea is strong because mass occurrence has evolved multiple times in independent evolutionary lineages under similar circumstances. Thus, attributes possessed by many taxa that occur en masse appear to be evolutionarily advantageous, i.e., adaptations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: K. A. Pitt & J. E. Purcell Jellyfish Blooms: Causes, Consequences, and Recent Advances     

In vitro recruitment of Ulva sp. and Enteromorpha sp. on gametophytic and tetrasporophytic thalli of four populations of Chondracanthuschamissoi from Chile

Chondracanthus chamissoi is a red alga which is acquiring an increasing economic importance in Chile and becoming a target species for cultivation. Because epiphytism is a major problem in the mariculture of seaweeds, the recruitment of Ulva sp. and Enteromorpha sp. on gametophytic (cystocarpic) and tetrasporophytic thalli of C. chamissoi was tested in vitro on four populations from different locations in Chile. For Ulva sp., the density, cover and length of the recruits varied between the reproductive phases of the host and among the studied populations of C. chamissoi. In most experiments, a larger number of epiphytic thalli was observed on gametophytic plants of C. chamissoi; populations from Calderilla and Lechagua had a higher resistance to epiphytism. For Enteromorpha sp., its ability to grow epiphytically on both phases of the host showed a greater variability, but was inferior to that of Ulva sp. The differential resistance to epiphytism in both reproductive phases and in plant origin indicates the possibility of obtaining selected strains of C. chamissoi with lower susceptibility to epiphytism that could be utilized in planning maricultural programs.     

UeberTetrao falcipennis, nov. sp.

Ohne Zusammenfassung