Heat shock proteins in Aurelia (Cnidaria, Scyphozoa)

Heat shock proteins (hsp) in Aurelia identified by one-dimensional SDS-PAGE are of sizes 93,83,70,68,45, and 39 kD, the most rapidly labeled being hsp 70 in all developmental stages. Labeled hsp in the polyp are found mostly in the epidermis; gastrodermal nuclei are also labeled. The minimum temperature for induction of the proteins is about the same (27 degrees to 28 degrees C), regardless of whether polyps have been cultured at 15 degrees or 24 degrees C. Adults and planulae taken from natural water at 28 degrees C do not show accumulation of hsp 70. Induction of strobilation by raising polyps from 15 degrees to 25 degrees C is not associated with appreciable labeling of hsp. Polyps transferred to higher or lower salinity have decreased protein synthesis but do not synthesize stress proteins.     

Life Cycle Reversal in Aurelia sp.1 (Cnidaria,Scyphozoa)

The genus Aurelia is one of the major contributors to jellyfish blooms in coastal waters, possibly due in part to hydroclimatic and anthropogenic causes, as well as their highly adaptive reproductive traits. Despite the wide plasticity of cnidarian life cycles, especially those recognized in certain Hydroza species, the known modifications of Aurelia life history were mostly restricted to its polyp stage. In this study, we document the formation of polyps directly from the ectoderm of degenerating juvenile medusae, cell masses from medusa tissue fragments, and subumbrella of living medusae. This is the first evidence for back-transformation of sexually mature medusae into polyps in Aurelia sp.1. The resulting reconstruction of the schematic life cycle of Aurelia reveals the underestimated potential of life cycle reversal in scyphozoan medusae, with possible implications for biological and ecological studies.     

On some features of embryonic development and metamorphosis of Aurelia aurita (Cnidaria, Scyphozoa)

Aurelia aurita is a cosmopolite species of scyphomedusae. Its anatomy and life cycle are well investigated. This work provides a detailed study on development and structure of A. aurita planula before and during its metamorphosis. Intravital observations and histology study during the settlement and metamorphosis of the planulae demonstrated that the inner manubrium lining of primary polyp (gastroderm) develops from the ectoderm of the planula posterior end. The spatial and temporal dynamics of serotonergic cells from the early embryonic stages until the formation of the primary polyp were studied for the first time. In addition, the distribution of tyrosinated tubulin and neuropeptide RF-amide at different stages of A. aurita development was traced.     

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     

Early development, pattern, and reorganization of the planula nervous system in Aurelia (Cnidaria, Scyphozoa)

We examined the development of the nervous system in Aurelia (Cnidaria, Scyphozoa) from the early planula to the polyp stage using confocal and transmission electron microscopy. Fluorescently labeled anti-FMRFamide, antitaurine, and antityrosinated tubulin antibodies were used to visualize the nervous system. The first detectable FMRFamide-like immunoreactivity occurs in a narrow circumferential belt toward the anterior/aboral end of the ectoderm in the early planula. As the planula matures, the FMRFamide-immunoreactive cells send horizontal processes (i.e., neurites) basally along the longitudinal axis. Neurites extend both anteriorly/aborally and posteriorly/orally, but the preference is for anterior neurite extension, and neurites converge to form a plexus at the aboral/anterior end at the base of the ectoderm. In the mature planula, a subset of cells in the apical organ at the anterior/aboral pole begins to show FMRFamide-like and taurine-like immunoreactivity, suggesting a sensory function of the apical organ. During metamorphosis, FMRFamide-like immunoreactivity diminishes in the ectoderm but begins to occur in the degenerating primary endoderm, indicating that degenerating FMRFamide-immunoreactive neurons are taken up by the primary endoderm. FMRFamide-like expression reappears in the ectoderm of the oral disc and the tentacle anlagen of the growing polyp, indicating metamorphosis-associated restructuring of the nervous system. These observations are discussed in the context of metazoan nervous system evolution.     

Predation potential of the jellyfish Drymonema larsoni Bayha & Dawson (Scyphozoa: Drymonematidae) on the moon jellyfish Aurelia sp. in the northern Gulf of Mexico

The jellyfish Drymonema larsoni bloomed in the northern Gulf of Mexico in the Fall of 2000 and fed voraciously on the moon jellyfish Aurelia sp., especially where they were concentrated in frontal convergence. We evaluated the predation potential of D. larsoni on Aurelia sp. medusa using laboratory and field data. Our data set represents the most complete study to date on the new scyphozoan family Drymonematidae and indicates that D. larsoni may be one of the most effective predators on other jellyfish recorded to date. On average, each D. larsoni medusa contained 2.7 Aurelia sp. prey, but as many as 34. In addition, 94% of moon jellyfish unassociated with D. larsoni showed scarring from previous contact with D. larsoni tentacles. Digestion times for D. larsoni feeding on individual Aurelia sp. ranged from 2 to 3 h and averaged 2.7 h. Potential clearance rates for predation on Aurelia sp. were extremely high (320–1043.5 m³ d⁻¹) and indicate that D. larsoni is potentially an important predator on Aurelia sp. blooms where the species co-occur. When the two species co-occur in numbers, predation by D. larsoni medusae could reduce moon jellyfish blooms, possibly alleviating predation pressure on lower trophic levels utilized by Aurelia sp., such as copepods and the early life history stages of ecologically and economically important fish and invertebrate species.     

Induction of segmentation in polyps of Aurelia aurita (Scyphozoa, Cnidaria) into medusae and formation of mirror-image medusa anlagen

Polyps of Aurelia aurita can transform into several medusae (jellyfish) in a process of sequential subdivision. During this transformation, two processes take place which are well known to play a key role in the formation of various higher metazoa: segmentation and metamorphosis. In order to compare these processes in bilaterians and cnidarians we studied the control and the kinetics of these processes in Aurelia aurita. Segmentation and metamorphosis visibly start at the polyp's head and proceed down the body column but do not reach the basal disc. The small piece of polyp which remains will develop into a new polyp. The commitment to the medusa stage moves down the body column and precedes the visible onset of segmentation by about one day. Segmentation and metamorphosis can start at the cut surface of transversely cut body columns, leading to a mirror-image pattern of sequentially developing medusae.     

Physiological and chemical analysis of neurotransmitter candidates at a fast excitatory synapse in the jellyfish Cyanea capillata (Cnidaria, Scyphozoa)

Motor nerve net (MNN) neurons in the jellyfish Cyanea capillata communicate with one another by way of fast, bidirectional excitatory chemical synapses. As is the case with almost all identified chemical synapses in cnidarians, the identity of the neurotransmitter at these synapses is unclear. MNN neurons are large enough for stable intracellular recordings. This, together with the fact that they can be exposed, providing unlimited access to them and to their synapses, prompted a study of the action of a variety of neurotransmitter candidates, including those typically associated with fast synapses in higher animals. Only the amino acids taurine and β-alanine produced physiological responses consistent with those of the normal EPSP in these cells. Moreover, chemical analysis revealed that both taurine and β-alanine are present in the neurons and released by depolarization. These various findings strongly suggest that either or both of these amino acids, or a closely related compound is the neurotransmitter at the fast chemical synapses between MNN neurons.     

Dissociation and reaggregation of cells of Chrysaora quinquecirrha (Cnidaria, Scyphozoa)

Cells of scyphistomae, strobilae, and ephyrae were dissociated with trypsin and reaggregated. Clumping was inhibited in low Ca++ and by puromycin, but not by collagenase or sugars. Reaggregates from the oral end of the polyp developed tentacles and mouths first and basal structures later, whereas the opposite sequence occurred with cells from the lower gastric region. Nile-blue-stained cells from hypostome or peduncle did not form specific structures in the reconstructed polyp, but were distributed throughout the animal. Ephyra cell aggregates showed little morphogenesis, whereas cells from presumptive ephyra tissue gave rise to structures with tentacles and multiple oral openings. Mixed reaggregates containing equal proportions of polyp and ephyra cells formed irregular structures with transparent outer layer and opaque inner cell mass, suggesting stage-specific sorting.     

On natural metamorphosis inducers of the cnidarians Hydractinia echinata (Hydrozoa) and Aurelia aurita (Scyphozoa)

 Hydractinia echinata and Aurelia aurita produce motile larvae which undergo metamorphosis to sessile polyps when induced by external cues. The polyps are found at restricted sites, A. aurita predominantly on rocks close to the shore, H. echinata on shells inhabited by hermit crabs. It has been argued that the differential distribution of the polyps in their natural environment largely reflects the distribution of the natural metamorphosis-inducing cues. In the case of H. echinata, bacteria of the genus Alteromonas were argued to meet these conditions. We found that almost all substrates collected in the littoral to induce metamorphosis in H. echinata, and several bacterial strains isolated from the sea, including the common E. coli, induce metamorphosis efficiently. In A. aurita metamorphosis may be induced by the water–air interface, whereby metamorphosis precedes (final) settlement. Received: 7 December 1998 / Accepted: 8 July 1999     

Systematics and biogeography of the Andean genusEriocnemis (Aves: Trochilidae)

Summary With 11 currently recognised species, the genusEriocnemis (Reichenbach, 1849) is one of the most diversified Andean trochilid groups occupying mainly open montane habitats such as the edges of cloud forest or páramos. On the basis of distributional and morphological patterns, this study highlights the geographical variation and biogeography of the taxon. Characteristics common to all these species are the greenish dorsal plumage, the conspicuous and mostly whitish tibial tufts, and a fairly pronounced tail bifurcation. With the help of plumage synapomorphies for a cladistic analysis (PAUP*), several species groups or superspecies can be distinguished: theE. vestitus group (incl.E. vestitus, E. godini, E. nigrivestis), theE. luciani group (incl.E. luciani, E. cupreoventris, E. sapphiropygia), and theE. alinae group (incl.E. alinae, E. mirabilis).E. glaucopoides, E. mosquera, andE. derbyi differ quite widely in morphology and ecological requirements from the other species. Three new subspecies are described,E. vestitus arcosi from southern Ecuador and northern Peru, andE. luciani baptistae from central and southern Ecuador. A previously overlooked specimen ofE. luciani from the Andes of Mérida represents the first species record for Venezuela, about 1100 km northeast of the main population range, and should be recognised taxonomically asE. luciani meridae, subsp. nov., on the basis of its unique plumage morphology and geographical separation. Additionally, the unique type ofE. ventralis (Salvin, 1891) is probably of hybrid origin (E. vestitus × cupreoventris). The genus may have evolved in the northern Andes, subsequently spreading southward and invading the central Andes. Its recent range and phylogenetic patterns indicate vicariance events as the major speciation factor inEriocnemis.In memoriam Dr. Luis F. Baptista (1941–2000)     

A newly discovered oxidant defence system and its involvement in the development of Aurelia aurita (Scyphozoa, Cnidaria): reactive oxygen species and elemental iodine control medusa formation

In Aurelia aurita, applied iodine induces medusa formation (strobilation). This process also occurs when the temperature is lowered. This was found to increase oxidative stress resulting in an increased production of iodine from iodide. One polyp produces several medusae (initially termed ephyrae) starting at the polyp's oral end. The spreading of strobilation down the body column is controlled by a feedback loop: ephyra anlagen decrease the tyrosine content in adjacent polyp tissue by producing melanin from tyrosine. Endogenous tyrosine is able to remove iodine by forming iodiferous tyrosine compounds. The reduced level of tyrosine causes the ephyra-polyp-border to move towards the basal end of the former polyp. We argue that an oxidant defence system may exist which makes use of iodide and tyrosine. Like other marine invertebrates, polyps of Aurelia contain iodide ions. Inevitably produced peroxides oxidise iodide into iodine. The danger to be harmed by iodine is strongly decreased by endogenous tyrosine which reacts with iodine to form iodiferous tyrosine compounds including thyroxin. Both substances together, iodide and tyrosine, form an efficient oxidant defence system which shields the tissue against damage by reactive oxygen species. In the course of evolution (from a species at the basis of the animal kingdom like Aurelia to a highly evolved species like man) the waste product thyroxin (indicating a high metabolic rate) has developed into a hormone which controls the metabolic rate.     

Bacterially induced stolon settlement in the scyphopolyp ofAurelia aurita (Cnidaria,Scyphozoa)

Unsettled stoloniferous scyphopolyps ofAurelia aurita Lamarck were offered different substrates for settlement under defined conditions. On addition of different biogenic and abiotic substrates, a pure strain of bacteria, a species of Micrococcaceae, was observed to trigger the settlement of the stolon. The settlement reaction only takes place following direct contact with the bacteria; sterile filtrated culture medium of the same bacterial strain was not able to induce settlement. The bacteria were found to be effective on stolon settlement during the logarithmic growth phase, but not during the stationary phase.     

Differential gene expression in the jellyfish Aurelia aurita

The body of Aurelia aurita, as well as other diploblasts, consists of two epithelial layers: ectodermal and gastral epithelium. These two tissues are separated by mesoglea, or extracellular matrix. In most coelenterates mesoglea is acellular. In A. aurita mesogleal cells are scattered in mesoglea. Differential display PCR was used to compare mRNA pools from ectodermal epithelium, gastral epithelium and mesoglea. 4 novel gene fragments were cloned and sequenced. According to RTPCR results, one of these fragments is differentially expressed in the ectodermal epithelium.     

Systematics and cladistics of Megalostomis Chevrolat,and the biogeography of Clytrini (Coleoptera: Cryptocephalinae)

We present a cladistic analysis of the subtribe Megalostomina, a Neotropical group of ‘case‐bearer’ leaf beetles. A comparative study of the external and internal adult morphology of Clytrini was undertaken. New characters are described for the subtribe Megalostomina, from the internal sac of aedeagus, which provide a useful phylogenetic signal. More than 180 photographs illustrating the most important characters (74 characters and their respective states) used in the cladistic analysis are provided. The cladistic analysis of 57 terminal taxa and 95 characters was undertaken, under equal weights, and also using implied weights as a means to down‐weight homoplasious characters. We test the monophyly and explore intergeneric relationships of the subtribe Megalostomina, and reconstruct the relationships among the species of Megalostomis Chevrolat. The 42 species recognized can be assigned either to a group mostly containing species of North and Central America, or to a larger one of mostly South American species. Support is low, and the formal naming of groups is deferred pending a revision of all Megalostomina. We confirm the subgenera of Megalostomis of previous classifications are unnatural, and the following changes in the generic classification of the subtribe Megalostomina are proposed: Coleorozena Moldenke syn.n. of Coscinoptera Lacordaire; Coleothorpa Moldenke syn.n. of Coscinoptera Lacordaire; and Euryscopa (Coleoguerina) Moldenke syn.n. of Coscinoptera Lacordaire. Furthermore, six formerly recognized subgenera of Megalostomis are considered junior synonyms of Megalostomis Chevrolat: Megalostomis (Minturnia) Lacordaire syn.n. ; Megalostomis (Heterostomis) Lacordaire syn.n. ; Megalostomis (Scaphigenia) Lacordaire syn.n. ; Megalostomis (Snellingia) Moldenke syn.n. ; Megalostomis (Coleobyersa) Moldenke syn.n. ; and Megalostomis (Pygidiocarina) Moldenke syn.n. Thus, no subgenera are recognized within Megalostomis. Previous hypotheses on Clytrini biogeography were revisited in the light of new biogeographic and phylogenetic knowledge. We hypothesize an origin of Clytrini in tropical/subtropical Gondwana, when South America, Africa, Madagascar and India were connected. Changes in the configuration of the tectonic plates in the Cenozoic allowed the dispersal of Clytrina to the Palaearctic and Nearctic regions, and dispersion of Babiina and Megalostomina through the Nearctic region.     

Systematics, cladistics and biogeography of the American genus Farrodes (Ephemeroptera: Leptophlebiidae: Atalophlebiinae)

Cladistic and biogeographic analyses of the genus Farrodes are presented. Two species groups are delineated within Farrodes: F. caribbianus and F. bimaculatus. Three species formerly placed in other genera– Thraulus caribbianus Traver, Thraulus roundsi Traver and Homothraulus maculatus (Needham & Murphy)–are transferred to Farrodes. The species of the F. caribbianus species group are revised. Three new species are described: F. savagei from Venezuela, F. maya and F. mexicanus from Mexico. Keys to separate the two species groups of Farrodes and the species of the F caribbianus species group are provided. Successive cladistic analyses were carried out on both adult and nymphal characters using Hennig86 and CLADOS. The matrix was composed of all available data (nymphal characters were missing for some species), from nymphal and adult stages separately and on taxa represented by both adult and nymphal characters. Species of the genera Simothraulopsis and Homothraulus (components of the Farrodes lineage) were included in the analyses, and Ecuaphkbia was used as the outgroup. Results of the four analyses are compatible. The historical biogeography of Farrodes , with a distribution from nordiern Argentina to southern Texas, is analysed using the program COMPONENT. Areas of endemism are established, and some of their relationships compared with those of other groups available in the literature.