Coelenterate Hosts Research Articles

Additions to the genus Phycomenes Bruce, 2008 (Crustacea: Decapoda: Pontoniinae)

The genus Phycomenes was recently described by Bruce (2008)) for a small sea-grass inhabiting shrimp, Phycomenes zostericola Bruce, 2008, from south-east Queensland, Australia. The close similarity of this species to Periclimenes indicus (Kemp 1915) was noted. Subsequently specimens of Kemp’s species from the type locality, Chilka Lake, Orissa, India, were examined and the most characteristic features of the genus Phycomenes were found to be present, i.e., a transverse triangular median process on the fourth thoracic sternite and the greatly reduced size of the second pereiopods in comparison with other Periclimenes species, with a very well developed ocular ocellus. Periclimenes indicus is therefore transferred to the genus Phycomenes Bruce. Periclimenes cobourgi Bruce & Coombes, 1995 has also been noted as closely similar to Periclimenes indicus, showing the same major features and should also be considered as congeneric with Phycomenes zostericola. Similarly, examination of specimens of Periclimenes sulcatus Ďuriš, Horká, & Marin, 2008, and P. siankaanensis Martínez-Mayén, & Román-Contreras, 2006, kindly donated by Dr Zdenek Ďuriš and Dr Mario Martinez-Mayén to the Queensland Museum, Brisbane, show the same features and should be similarly placed in the genus Phycomenes. Martínez-Mayén and Román-Contreras (2006) considered P. siankaanensis to be a member of the “iridescens” species complex, including also P. iridescens Lebour, 1949, P. platalea Holthuis, 1951, P. antipathophilus Holthuis & Eibl-Eibesfeldt, 1964, P. patae Heard & Spotte, 1991, and P. mclellandi Heard & Spotte, 1997. Periclimenes platalea has recently been removed from this complex and placed in the genus Rapipontonia Marin by Marin (2007). No examples of these species have been examined but it seems likely that some may possibly be better placed in Phycomenes. Some of these taxa have been reported as associates of coelenterate hosts rather than from sea-grass habitat, but such a coelenterate association has also been reported in the case of the holotype specimen of P. cobourgi found on a gorgonian host. The specimens of P. indicus were kindly donated by the Zoological Survey of India, Calcutta (ZSI). The specimens examined are deposited in the collections of the Northern Territory Museum, Darwin (NTM) and Queensland Museum, Brisbane (QM).

Effects of symbiotic status, flow speed, and prey type on prey capture by the facultatively symbiotic temperate coral Oculina arbuscula

Symbiotic temperate corals can supplement prey capture by the coelenterate host with autotrophic carbon production by endosymbiotic zooxanthellae. To test the relationship between heterotrophic consumption and photosynthetic energy, prey capture by symbiotic and aposymbiotic specimens of the temperate scleractinian coral Oculina arbuscula (Verrill) was measured in January–April 2001. Corals were tested in a laboratory flume at five flow speeds, using Artemia franciscana cysts and nauplii as prey. Per-polyp capture rate and feeding efficiency were independent of symbiotic condition. Capture rate increased with flow speed, while capture efficiency declined. The location of capture shifted from the upstream to downstream side of the coral as flow speed increased. Differences in capture rate, location, and feeding efficiency for cysts and live brine shrimp nauplii were likely due to prey size rather than swimming ability.

High genetic diversity and relative specificity among Symbiodinium -like endosymbiotic dinoflagellates in soritid foraminiferans

Soritids are large calcareous foraminiferans abundant in Indo-Pacific coral reefs. Soritids are known to host endosymbionts morphologically and genetically similar to Symbiodinium-like dinoflagellates commonly found in corals and other marine invertebrates. In order to examine the phylogenetic relationships between symbionts present in foraminiferal and coelenterate hosts, we used DNA sequencing and PCR-based RFLP methods to analyse 157 foraminiferal and 110 coral DNA samples from 12 localities in Guam (Micronesia) collected in July 1999 and December 1999. Ribosomal DNA sequences were obtained for 14 foraminiferal and 12 coral samples. Sequence analyses allowed identification of six different Symbiodinium phylotypes among soritids and two phylotypes among examined coelenterates. A single phylotype, previously described as lineage C, was common in foraminiferans and corals. The PCR-based RFLP analysis of 157 foraminiferal and 110 coral samples shows that lineage C dominates coral symbiont communities, accounting for 78% in both sampling periods. On the other hand, our data show that lineages C and Fr6 dominated foraminiferal symbiont communities in July 1999 versus a clear predominance of lineages C and Fr3 in November 1999. The other three phylotypes present in soritids (Fr1, Fr4, Fr5) were uncommon and seem to occur seasonally. The phylogenetic analysis of the present data indicates relative specificity of soritid symbionts compared to other Symbiodinium-like dinoflagellates, but the causes of this specificity are not yet understood.

Mitotic indices of zooxanthellae: a comparison of techniques based on nuclear and cell division frequencies

Mitotic indices of zooxanthellae: a comparison of techniques based on nuclear and cell division frequencies

Photographic observations of the life style of a deep-sea ophiuroid Asteronyx loveni (Echinodermata)

The life style of a deep-sea ophiuroid, Asteronyx loveni was studied from underwater photographs (7 stations) and trawled samples (11 stations) between about 800 and 1700 m along the Pacific coast of Japan and in the Flores Sea, Indonesia. This ophiuroid typically clings to gorgonians ( Radicipes spp.) and pennatulids ( Funiculina quadrangularis and Anthoptilum sp.). The stomach contents of A. loveni included fragments of crustaceans, polychaete setae, sediment particles and flocculent material, but no tissues of the host coelenterates. Bottom photographs show the ophiuroids extending several arms into the water column presumably for suspension feeding. There was rarely more than one ophiuroid per coelenterate host, perhaps due to intraspecific competition for perch sites. Stereoscopic analysis of photographs revealed that most of the ophiuroids perched 20–35 cm above the sea floor. This may be the most effective height for feeding on particulate material resuspended from the sea floor by bottom currents.

Glycerol translocation in Condylactis gigantea

Sodium cyanide (NaCN) was used to partially uncouple respiration and photosynthesis in the symbiotic sea anemone Condylactis gigantea. NaCN significantly increased the ratio of gross photosynthesis to respiration in both intact tentacles and isolated zooxanthellae (Symbiodinium microadriaticum), increased carbon translocation from 17.7±3.5% of total fixed in controls to 43.5±5.8%, and doubled the amount of photosynthetically fixed carbon accumulating in the coelenterate host over that in controls. Only 2% of the non-particulate radioactivity recovered in the host tissue was 14C-glycerol when uninhibited symbiotic tentacles were incubated in 14C-bicarbonate for 1 h. At 10-5M NaCN, approximately 25% of the host nonparticulate radioactivity was recovered as 14C-glycerol, the absolute concentration of glycerol in the host tissue was three times higher than in controls, and 14C-glycerol was found in the medium. While glycerol has been proposed to play a major role in the translocation of photosynthetically fixed carbon from zooxanthellae to their coelenterate hosts, its concentration has never been measured in the animal and algal components of the symbiosis. The isolated zooxanthellae contained 3.62±0.33 mM glycerol, 26x the 0.141±0.02 mM found in the anemone. Aposymbiotic anemone tissue contained 0.169±0.06 mM glycerol. The rate of glycerol mineralization was not saturated even when exogenous glycerol levels were 70x internal concentrations. These data show that respiration and photosynthesis in symbiotic associations may be partially uncoupled by NaCN, and that this uncoupling allows the verification of the translocation and rapid catabolism of glycerol within the host.

A reevaluation of the role of glycerol in carbon translocation in zooxanthellae-coelenterate symbiosis

Glycerol has been traditionally viewed as the main form of carbon translocated from zooxanthellae to the coelenterate host. Most of this glycerol was postulated to be used by the coelenterate host for lipid synthesis. Recent work suggests that large amounts of photosynthetically fixed carbon is synthesized into lipid in the algae, and then translocated as lipid droplets to the host. These two hypotheses of carbon translocation are not mutually exclusive, but to reconcile them the role of glycerol must be reevaluated. In this study the short term metabolic fate of uniformly labelled 14C-glycerol, 14C-bicarbonate, and 14C-acetate was examined in zooxanthellae and coelenterate host tissue isolated from Condylactis gigantea tentacles. When host and algal triglycerides, synthesized during 90-min light and dark incubations in 14C-bicarbonate and 14C-acetate, were deacylated, more than 80% of the activity was found in the fatty acid moiety. In contrast, triglycerides isolated from zooxanthellae and coelenterate host tissue incubated in 14C-glycerol in the dark for 90 min were found to have more than 95% of their radioactivity in the glycerol moiety. During the 90-min 14C-glycerol incubations in the light, the percentage of radioactivity in the fatty acid moiety of zooxanthellae triglycerides increased to 37%. The percentage of radioactivity in the host tissue triglycerides fatty acid moiety stayed below 5% during the 90-min 14C-glycerol incubations in the light. These results show that neither the zooxanthellae nor the host can rapidly convert glycerol to fatty acid. Radioactivity from 14C-glycerol, which does eventually appear in host lipid, may have been respired to 14CO2, then photosynthetically fixed by the zooxanthellae and synthesized into lipid fatty acid.

A method of isolating clean and viable zooxanthellae by density gradient centrifugation

Attempts to prepare viable suspensions of zooxanthellae isolated from coelenterate hosts have been hampered by the large amounts of mucus secreted by the host tissues. A method is described which overcomes this by density gradient ultracentrifugation of the isolate, using the silica sol Percoll which forms its own density gradient during ultracentrifugation. Between 106 and 107 zooxanthellae can be isolated per gradient. Contamination is reduced to the occasional nematocyst or piece of animal cell debris. The zooxanthellae thus isolated are viable and appear to show normal respiration and photosynthesis.

The physiology and biochemistry of zooxanthellae symbiotic with marine coelenterates I. The assimilation of photosynthetic products of zooxanthellae by two marine coelenterates

The movement of organic compounds between endosymbiotic zooxanthellae and their marine coelenterate hosts was studied in the sea anemone,Anthopleura elegantissima(Brandt) (Anthozoa, Actiniaria) and the zoanthid,Palythoa townsleyi(Walsh and Bowers) (Anthozoa, Zoanthidea). In both animals,14C photosynthetically fixed by the algae moved into the animal tissues. InAnthopleura, this represents 45 to 50% of the total photosynthetic fixation in 24 h and, inPalythoa, 20 to 25%. The fixed14C accumulated by the animal tissues becomes incorporated principally into animal lipid and protein. The significance of translocation to the animal hosts is discussed.

Formation of polysaccharides by hydra from substrates produced by their endosymbiotic algae.

THE exact ways in which endosymbiotic algae serve their host tissues have been the subject of much research in the past 10 years. The view that the algae contribute to the nutrition of the host has gained much support from studies using radioactive tracers. Algae were shown to contribute material labelled with carbon-14 when the co-elenterate host (anemone1, coral2 or hydra3) was exposed to 14CO2 in the light. Muscatine has shown that algae isolated from hydra4 and from other freshwater invertebrates5 leak 14C-maltose into the media. The questions remain whether the algae release glucose or maltose in vivo, and in what way do the hydra utilize these compounds. We describe here experiments which show that the animal tissue of Chlorohydra viridissima incorporates a large proportion of the small molecules produced by their endosymbiotic algae during photosynthesis, and that most of these small molecules are converted by hydra into polysaccharide.