Seasonal occurrence of freshwater medusa Limnocnida indica annandale (Cnidaria: Limnomedusae) in a lake associated with the river Yamuna, India

A freshwater medusa, Limnocnida indica Annandale, 1912 was observed in the month of April and May of two consecutive years 1994, 1995 in a lake having free connection with the river Yamuna in Delhi. Medusae in the lake were abundant in those areas where the vegetation of Hydrilla sp. was moderately dense, whereas it was absent in areas with Potamogeton sp. The composition of planktonic community in the lake was different before and during the occurrence of medusae and after their disappearance. Moina sp. and Keratella sp. were totally absent and Mesocyclops sp. and nauplii were reduced in number during the occurrence of medusae which were either present or more in number before the occurrence of the latter. Dinophyceae was maximum in number during this period. These zooplankters reappeared after the disappearance of medusae. It is likely that ecological conditions which prevailed during April and May favour the seasonal occurrence of freshwater medusae.     

EVOLUTION OF LIFE CYCLE,COLONY MORPHOLOGY,AND HOST SPECIFICITY IN THE FAMILY HYDRACTINIIDAE (HYDROZOA,CNIDARIA)

Biased transitions are common throughout the tree of life. The class hydrozoa is no exception, having lost the feeding medusa stage at least 70 times. The family hydractiniidae includes one lineage with pelagic medusae (Podocoryna) and several without (e.g., Hydractinia). The benthic colony stage also varies widely in host specificity and in colony form. The five‐gene phylogeny presented here requires multiple transitions between character states for medusae, host specificity, and colony phenotype. Significant phylogenetic correlations exist between medusoid form, colony morphology, and host specificity. Species with nonfeeding medusae are usually specialized on a single host type, and reticulate colonies are correlated with nonmotile hosts. The history of feeding medusae is less certain. Podocoryna is nested within five lineages lacking medusae. This requires either repeated losses of medusae, or the remarkable re‐evolution of a feeding medusa after at least 150 million years. Traditional ancestral reconstruction favors medusa regain, but a likelihood framework testing biased transitions cannot distinguish between multiple losses versus regain. A hypothesis of multiple losses of feeding medusae requires transient selection pressure favoring such a loss. Populations of species with feeding medusae are always locally rare and lack of feeding medusae does not result in restricted species distribution around the world.     

Coral reproduction in the world��s warmest reefs: southern Persian Gulf (Dubai, United Arab Emirates)

Despite extensive research on coral reproduction from numerous geographic locations, there remains limited knowledge within the Persian Gulf. Given that corals in the Persian Gulf exist in one of the most stressful environments for reef corals, with annual variations in sea surface temperature (SST) of 12°C and maximum summer mean SSTs of 36°C, understanding coral reproductive biology in the Gulf may provide clues as to how corals may cope with global warming. In this study, we examined six locally common coral species on two shallow reef sites in Dubai, United Arab Emirates (UAE), in 2008 and 2009 to investigate the patterns of reproduction, in particular the timing and synchrony of spawning. In total, 71% colonies in April 2008 and 63% colonies in April 2009 contained mature oocytes. However, the presence of mature gametes in May indicated that spawning was potentially split between April and May in all species. These results demonstrate that coral reproduction patterns within this region are highly seasonal and that multi-species spawning synchrony is highly probable. Acropora downingi, Cyphastrea microphthalma and Platygyra daedalea were all hermaphroditic broadcast spawners with a single annual gametogenic cycle. Furthermore, fecundity and mature oocyte sizes were comparable to those in other regions. We conclude that the reproductive biology of corals in the southern Persian Gulf is similar to other regions, indicating that these species have adapted to the extreme environmental conditions in the southern Persian Gulf.     

Molecular characterization of aspartylglucosaminidase,a lysosomal hydrolase upregulated during strobilation in the moon jellyfish,Aurelia aurita

The life cycle of the moon jellyfish, Aurelia aurita, alternates between a benthic asexual polyp stage and a planktonic sexual medusa (jellyfish) stage. Transition from polyp to medusa is called strobilation. To investigate the molecular mechanisms of strobilation, we screened for genes that are upregulated during strobilation using the differential display method and we identified aspartylglucosaminidase (AGA), which encodes a lysosomal hydrolase. Similar to AGAs from other species, Aurelia AGA possessed an N-terminal signal peptide and potential N-glycosylation sites. The genomic region of Aurelia AGA was approximately 9.8 kb in length and contained 12 exons and 11 introns. Quantitative RT-PCR analysis revealed that AGA expression increased during strobilation, and was then decreased in medusae. To inhibit AGA function, we administered the lysosomal acidification inhibitors, chloroquine or bafilomycin A1, to animals during strobilation. Both inhibitors disturbed medusa morphogenesis at the oral end, suggesting involvement of lysosomal hydrolases in strobilation.     

Reproduction of the colonial hydroid Obelia geniculata (L., 1758) (Cnidaria,Hydrozoa) in the White Sea

Populations of the colonial hydroid Obelia geniculata in the White Sea reproduce asexually by frustule formation. Young medusae appear in the plankton during July and August. The number of medusae rarely exceeds 36 per m³, and the average number varies every year from 0.4 to 10 per m³. The size of medusae is smaller than reported from other regions. The umbrella of the largest recorded medusa was only 0.57 mm in diameter and the specimen had just 35 tentacles. Only a few mature medusae were found during the study. The colonies in the White Sea are epiphytic and grow only on laminarian thalli. At the beginning of July there are no colonies on thalli from the upper subtidal zone. By the end of August, colonies of O.␣geniculata had increased in density to 30 per m². Hydroid recruitment was attributed to active frustule production by colonies living below that zone. The frustules detach from the stems of the hydroids and are found in plankton. Production of frustules on branches occurs continuously during colony growth until water temperatures climb above 0 °C. We found that water temperature in this Arctic environment is generally too low for medusa maturation and planula development in the species. Propagation by frustule formation is the principal means of reproduction in Obelia geniculata within the White Sea, and this phenomenon accounts for the species being a dominant epiphyte on laminarian thalli there.     

Stranding events provide indirect insights into the seasonality and persistence of jellyfish medusae (Cnidaria: Scyphozoa)

It is becoming increasingly evident that jellyfish (Cnidaria: Scyphozoa) play an important role within marine ecosystems, yet our knowledge of their seasonality and reproductive strategies is far from complete. Here, we explore a number of life history hypotheses for three common, yet poorly understood scyphozoan jellyfish (Rhizostoma octopus; Chrysaora hysoscella; Cyanea capillata) found throughout the Irish and Celtic Seas. Specifically, we tested whether (1) the bell diameter/wet weight of stranded medusae increased over time in a manner that suggested a single synchronised reproductive cohort; or (2) whether the range of sizes/weights remained broad throughout the stranding period suggesting the protracted release of ephyrae over many months. Stranding data were collected at five sites between 2003 and 2006 (n = 431 surveys; n = 2401 jellyfish). The relationship between bell diameter and wet weight was determined for each species (using fresh specimens collected at sea) so that estimates of wet weight could also be made for stranded individuals. For each species, the broad size and weight ranges of stranded jellyfish implied that the release of ephyrae may be protracted (albeit to different extents) in each species, with individuals of all sizes present in the water column during the summer months. For R. octopus, there was a general increase in both mean bell diameter and wet weight from January through to June which was driven by an increase in the variance and overall range of both variables during the summer. Lastly, we provide further evidence that rhizostome jellyfish may over-wintering as pelagic medusa which we hypothesise may enable them to capitalise on prey available earlier in the year. Handling editor: K. Martens     

Planulation,larval biology,and early growth of the deep‐sea soft corals Gersemia fruticosa and Duva florida (Octocorallia: Alcyonacea)

Abstract. Although the reproductive biology and early life‐history stages of deep‐sea corals are poorly understood, such data are crucial for their conservation and management. Here, we describe the timing of larval release, planula behavior, metamorphosis, settlement, and early juvenile growth of two species of deep‐sea soft corals from the northwest Atlantic. Live colonies of Gersemia fruticosa maintained under flow‐through laboratory conditions released 79 planulae (1.5–2.5 mm long) between April and early June 2007. Peak planulation in G. fruticosa coincided with peaks in the chlorophyll concentration and deposition rates of planktic matter. Metamorphosis and settlement occurred 3–70 d post‐release. The eight primary mesenteries typically appeared within 24 h, and primary polyps grew to a height of ～6–10 mm and a stalk diameter of ～1 mm within 2–3 months. Planulae of Duva florida (1.5–2.5 mm long) were extracted surgically from several colonies and were successfully reared in culture. Primary polyps reached a height of ～3–4 mm within 2–3 months. No budding of primary polyps was observed in either species over 11–13 months of monitoring, suggesting a very slow growth rate.     

Phenotypic plasticity in hydrozoans: morph reversibility.

The life cycle of Hydrozoans typically comprises two phases: the polyp, either solitary or colonial, with generally a benthic habitat, and the medusa which lives in the plankton. In its typical metagenetic cycle, the medusa is budded from the polyp, which is the product of sexual reproduction of medusae. However, several alternative reproduction patterns have also been described. In particular some species are able to perform a regressive transformation of the medusae that transform themselves into polyps bypassing sexual reproduction. In a species with alternative morphs switched by the environment, the more labile is the correlation between environmental factors acting on the genetic switch and the factors to which the resulting form is adapted, the more hazardous will be the development of either body form. However, we can explain the evolutionary advantage offered by reversion between morphs of these plastic species living in shallow water unpredictable environments: should produced medusae be released in the "wrong" environment, they would still have a chance of survival under another form.     

Fire Season Effects on Flowering Characteristics and Germination of Longleaf Pine (Pinus palustris) Savanna Grasses

Pinus palustris (longleaf pine) savannas depend on contiguous grass cover to facilitate frequent surface fires. Enhanced flowering, seed production, and germination may be linked to season of fires. We assessed the effect of month of prescribed fire (February, April, May, and July) on percentage of plants with flowering culms (FCs%), FC/area, FC/plant, seed production, and germination for five warm seasons, fall‐flowering grasses. Multivariate analysis indicated the response of flowering and fruiting to burn month varied among the grass species. The dominant species, Sporobolus junceus and Schizachyrium scoparium var. stoloniferum, had greater numbers of most flowering characteristics when burnt during April, May, and July. Aristida purpurascens had increased FC/plant after May and July burns. In contrast, Ar. mohrii had the fewest FC/plant and seeds/FC when burnt in July. Germination was greatest (26–60%) for Ar. purpurascens. Seeds collected following July burns for Ar. purpurascens and Ar. ternarius and after May burns for S. junceus were within the highest germination values recorded. Germination of Sc. scoparium var. stoloniferum was very low after February and July burns (≤5%). With Ar. mohrii, only seed collected following February (2%) and April burns (3%) germinated. April, May, and July fires increased seed production of dominant matrix grasses, thus facilitating the potential for recruitment of these species and facilitating seed collection from potential donor sites for ground‐layer restoration projects. Varying prescribed fire burn month captured variation in flowering characteristics among these grasses.     

The freshwater medusae of the world – a taxonomic and systematic literature study with some remarks on other inland water jellyfish

Several medusa species have been described from inland waters in Australia, Eurasia, Africa and America. The chief objective of this study is to summarize all species described from freshwater and from saline lakes, because the knowledge about this group is sparse and scattered in the literature. I summarize all accessible literature to deduct how many species of freshwater medusae exist and to show their distribution, relation and their phylogenetic origin.All medusae described from freshwater except Halmomises are Olindiidae (Limnomedusae). More than 20 Olindiidae species (in 6 genera) have been recorded from freshwater. However, about half of them may not be valid species or have been described insufficiently or improperly. Within the genera Craspedacusta only 3 (or 5) species are certain (C. sowerbii, C. iseanum, C. sinensis (and maybe C. sichuanensis and C. ziguiensis)). The genera Limnocnida may consist of 6 species, three from Africa (L. tanganjicae, L. victoriae, L. congoensis) and 3 from India (L. indica, L. biharensis, L. nepalensis). The status of Astrohydra (from Japan), Mansariella and Keralika (both from India) is uncertain. Additionally, the present study suggests that Craspedacusta and at least one type of Calpasoma hydrants are identical and Astrohydra may be closely related to Craspedacusta and/or Calpasoma.A comparison of the freshwater medusae with species described from saline lakes and brackish sites (Australomedusae from Australia and Moerisia from Egypt, Black Sea, Caspian Sea and Ganges Estuary) shows that these two groups are not closely related.     

Synchronous reproduction of corals in the Red Sea

Multi-species synchronous spawning was first described on reefs off the east and west coast of Australia. In contrast, locally abundant species in the northern Red Sea and the central Pacific have little overlap in the time of reproduction. Consequently, the idea developed that high levels of spawning synchrony both within and among species was largely confined to Australian reefs. Here, we show that gamete maturity in colonies of the genus Acropora was highly synchronous in the Red Sea. In early April 2008, at two locations separated by 300 km, 13 of 24 species sampled had mature colonies, and a further 9 species had immature colonies. In late April–early May 2008, all colonies sampled had no oocytes, indicating colonies had spawned a few days after the full moon of 20 April 2008. Similarly, in 2009, 99% of colonies from 17 species at Hurghada were mature in late April, and all were empty in early May. Spawn slicks suggested many of these colonies had released gametes three night prior to the full moon on 8 May 2009. This level of synchrony in gamete maturity is among the highest ever recorded and similar to that typically recorded in Acropora assemblages on Australian reefs. While further work is required to document the night of gamete release, these data strongly suggest that high levels of spawning synchrony are a regular feature of these Red Sea coral assemblages and that multi-species spawning occurs on or around the full moon in April and/or May.     

Field Release and Establishment of the Decapitating Fly Pseudacteon curvatus on Red Imported Fire Ants in Florida

Decapitating phorid flies in the genus Pseudacteon are being studied as classical biological control agents of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae). Pseudacteon curvatus Borgmeier (Diptera: Phoridae) is a small decapitating fly that attacks small fire ant workers. We released a biotype of P. curvatus from Formosa, Argentina, at three sites near Gainesville, FL. Field releases were conducted in the spring and summer of 2003 and monitored monthly. Flies were discovered within 5 weeks at the spring site and then monthly thereafter. By late spring 2004, flies released at this site had expanded 1.6 km both north and south and about 0.8 km westward. Initially, we found no flies from the two summer 2003 releases but we were successful at finding them 8 months after release during spring 2004. This paper documents the first successful release(s) of P. curvatus on red imported fire ants in the United States.     

Large medusae in surface waters of the Northern California Current: variability in relation to environmental conditions

Blooms of jellyfish around the world have been correlated with climatic variables related to environmental causes. Sizeable populations of large medusae, primarily Chrysaora fuscescens and Aequorea sp., appear annually in shelf waters of the Northeast Pacific Ocean. Previous research has shown that C. fuscescens is abundant seasonally in the inner shelf and exhibits high feeding rates on zooplankton. We examined medusae caught in surface trawls over an 8-year period (2000–2007) using (1) mesoscale surveys sampling 8–10 transects in May, June, and September, and (2) biweekly surveys along two transects from April to August, relating abundance to environmental parameters. C. fuscescens abundances generally peaked in late summer, whereas Aequorea sp. peaked in May or June. General additive models of the mesoscale data indicated that station catches for both species correlated with latitude, temperature, salinity, and distance from shore (and chlorophyll a for Aequorea sp.). Analysis of interannual variability revealed that highest catches of medusae correlated with cool spring–summer conditions, or negative anomalies of the Pacific Decadal Oscillation, and low winter–summer runoff from the Columbia River. Results confirmed our hypothesis of connections between jellyfish populations and regional climate conditions in a region known for strong physical forcing of ecosystem processes.     

Cell adhesion to extracellular matrix is different in marine hydrozoans compared with vertebrates

Extracellular matrices (ECMs) of phylogenetically very distant organisms were tested for their ability to support cell adhesion, spreading and DNA replication in reciprocal xenograft adhesion tests. Mechanically dissociated cells of the medusa Podocoryne carnea (Cnidaria, Hydrozoa) were seeded on ECMs of polyps and medusa, and on several ECM glycoproteins or entire ECMs from vertebrates. In reciprocal experiments, cells from different vertebrate cell-lines were seeded on ECMs of polyps, medusae and also on electrophoresed and blotted extracts of both types of ECMs. The results demonstrate that medusa cells adhere and spread on polyp and medusa ECMs but do not recognize vertebrate ECMs or purified ECM glycoproteins. Vertebrate cells in contrast adhere, spread and proliferate on ECMs of polyps and medusae. The number of attached cells depends on the cell type, the type of ECM and, in certain cases, on the stage of the cell cycle. Cell adhesion experiments with pretreated ECMs of polyps and medusae, e.g. oxidation of carbohydrate residues with sodium-metaperiodate, or blocking of certain carbohydrate moieties with the lectin wheat germ agglutinin or a carbohydrate-specific monoclonal antibody, demonstrate that ECM carbohydrates are more important for cell-ECM interactions of medusa cells than for vertebrate cells. Furthermore, the experiments indicate that polyp and medusa ECMs contain different components which strongly modulate adhesion, spreading and DNA replication of vertebrate cells.     

Evolutionary meaning of non-synchronous medusa release and spawning in the most advanced bivalve-inhabiting hydrozoan, Eugymnanthea japonica

Circadial spawning times of medusa of the bivalve-inhabiting hydrozoans Eugymnanthea japonica Kubota and Eutima japonica Uchida are confirmed to be morning (possibly sunrise) for the former species and night for the latter. Eugymnanthea, with small, short-lived, univoltine medusae, seems to have evolved from a form similar to Eutima japonica, with larger, longer-lived, multivoltine medusae; the morning spawning of medusae in Eugymnanthea may therefore be a newly evolved trait. Medusa release from polyps and spawning of medusae are not synchronous in Eugymnanthea japonica. This non-synchrony may represent an evolutionarily transitional state leading to the most advanced state, synchrony of these two reproductive events, as in certain other ephemeral hydrozoan medusae.     

Response of <Emphasis Type="Italic">Chrysaora quinquecirrha</Emphasis> medusae to low temperature

Because of their high abundance in Chesapeake Bay, Chrysaora quinquecirrha medusae may be an important reservoir of organic matter. The timing and location of the decomposition of biomass from medusae may have implications for carbon cycling in the bay. Our objective was to identify the cause of C. quinquecirrha medusa disappearance to better understand when and where decomposition occurs. A time series of visual surface counts and vertical net hauls in the Choptank River, a tributary of Chesapeake Bay, showed that as temperatures approached 15°C, C. quinquecirrha medusae disappeared from the surface, but persisted in net hauls until temperatures reached 10°C. In order to test whether medusae sink upon cooling, we exposed C. quinquecirrha medusae to low temperatures in large static tanks and measured their depth and pulsation rates twice daily for at least 6 days. This procedure was repeated three times through the 2008 jellyfish season. On average, individuals exposed to temperatures below 15°C were found deeper and pulsed slower than those in the warmer control tank. This suggests that low temperatures cause the medusae to sink before cooling to the limit of their physiological tolerance and may have implications for the deposition of organic matter associated with the seasonal disappearance of medusae from Chesapeake Bay.     

Larval necrophilia: the odd life cycle of a pandeid hydrozoan in the Weddell Sea shelf

Colonies of an athecate hydroid were found at six stations in the high Antarctic (Weddell Sea) growing on dead specimens of Flabelligera mundata (Annelida, Polychaeta). All living specimens of F. mundata at the same stations were free of epibionts. Transplantation experiments showed that hydropolyps did not produce stolons on substrates other than the epidermal jelly coat and chetae of dead F. mundata specimens. The largest colonies (>1,000 polyps) producing medusa buds were cultured until medusa liberation: growth of medusae was then surveyed for the next 5 weeks, but development of adult features was extremely slow. Young medusae were ascribed to the suborder Pandeida by the presence of two main characters, namely (1) hollow marginal tentacles, and (2) a mouth with four simple lips. Considering polyp and young medusa features, this species is acknowledged as newly recorded for the Southern Ocean, and assigned to the genus Neoturris (Hydroidomedusae, Pandeidae).     

Effects of low salinity on settlement and strobilation of scyphozoa (Cnidaria): Is the lion’s mane <Emphasis Type="Italic">Cyanea capillata</Emphasis> (L.) able to reproduce in the brackish Baltic Sea?

Several species of scyphozoan medusae occur in river estuaries and other brackish waters but it is often unknown if the planulae settle and the scyphopolyps reproduce in those low-salinity waters. In the present study, scyphozoan species from the German Bight (North Sea) were tested in laboratory experiments to investigate their tolerance of low salinity. Planula larvae released from medusae in salinity 32 were still active after the salinity was reduced to 10 (Cyanea capillata, Cyanea lamarckii) and to 7 (Chrysaora hysoscella) in laboratory treatments. Planulae did not settle on the undersides of floating substrates when salinity was reduced to <20. By contrast, planulae released from C. capillata medusae in Kiel Bight (western Baltic Sea) in salinity 15 developed into polyps in laboratory cultures. Polyps reared from planulae in salinity 36 survived a reduction to 12 (C. capillata, C. lamarckii) and to 8 (Aurelia aurita). Polyps of all tested species strobilated and released young medusae (ephyrae) in salinity 12. These results show a high tolerance of planulae and polyps to low salinity, indicating their possible occurrence in estuaries and brackish waters. In addition to laboratory observations, young C. capillata ephyrae were collected in the western Baltic Sea (Kiel Bight) in salinity 15, which indicates that they were probably released by a local polyp population. We suggest that the polyps of the painfully stinging lion’s mane, C. capillata, may be more widespread in the Baltic Sea than previously assumed and that the occurrence of the medusae may not only depend on inflow of water masses from the North Sea.     

Gonad development and somatic growth patterns of Olindias sambaquiensis (Limnomedusae,Olindiidae)

The stinging hydromedusa Olindias sambaquiensis (Limnomedusae, Olindiidae) was examined monthly over a 24-month period in Blanca Bay (Buenos Aires, Argentina) in order to determine the relationship between gonad development and overall growth patterns of medusae. Olindias sambaquiensis occurred seasonally from November (spring) to late April (fall). Medusae grew until February (mean bell diameter: 76.2 mm ± 2.8), and began to decrease in diameter up to late April (mean bell diameter: 58.6 mm ± 4.2). From November to December, the gonads of medusae were either undifferentiated or not present (gonad index (GI) 4.9%). Sexually mature individuals were observed from January to late February, where GI increased up to 31.4%, reaching, in some cases, values higher than 70%. From late February to April, O.sambaquiensis spawn and GI decreased to 25%. Highest growth rates were observed during December (immature phase), and then decreased until February (maturation phase). Growth rates were negative throughout March and April (spent phase). Growth patterns of gonads were different from those of the rest of the medusa: (1) their growth rates (and shrinking rates) were higher than those of the rest of the body, and (2) the percent of ‘total organics’ (AFDW: ash-free dry weight) in gonads remained constant, while it decreased in the rest of the body. Medusa length-weight relationships were also affected by gonad weight: a positive allometry was observed only when gonad weight was included into the total weight (i.e., whole individual).     

In situ release of mucus and DOC-lipid from the corals Acropora variabilis and Stylophora pistillata in different light regimes

Rates of mucus and DOC-lipid release were determined for colonies of Acropora variabilis and Stylophora pistillata at 5 m depth and for a colony of A. variabilis at 23 m depth. In addition, colonies at 5 m were shaded to simulate ambient irradiance at 6 m, 10 m and 16 m depth to evaluate the effect of light on the rates of release. A. variabilis released more mucus and DOC-lipid at 5 m than at 23 m depth. For both corals, the night rates were about 30% those of the day. A reduction in total integrated irradiance decreased mucus output from the corals. Similarly, DOC-lipid release showed a diurnal pattern and diminished with reduction in daily irradiance. For both coral species, DOC-lipid release rates were greater in the afternoon than in the morning. The night rates were less than 55% those of the day. The DOC-lipid comprised wax esters and a phospholipid fraction. The diurnal variation was due to changes in yield of wax esters which contributed >90% of the carbon released as DOC-lipid. In situ release of mucus and DOC-lipid was infuenced by light effects on phototrophic carbon metabolism. A daily budget for carbon released as mucus and DOC-lipid was estimated for each coral species at 5 m depth.