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Introduction Regeneration has been well documented in many animal phyla and plays an essential role in tissue maintenance and wound healing and thus in overall organismal survivability. It is evident [...], Cubozoans have the most intricate visual apparatus within Cnidaria. It comprises four identical sensory structures, the rhopalia, each of which holds six eyes of four morphological types. Two of these eyes are camera-type eyes that are, in many ways, similar to the vertebrate eye. The visual input is used to control complex behaviors, such as navigation and obstacle avoidance, and is processed by an elaborate rhopalial nervous system. Several studies have examined the rhopalial nervous system, which, despite a radial symmetric body plan, is bilaterally symmetrical, connecting the two sides of the rhopalium through commissures in an extensive neuropil. The four rhopalia are interconnected by a nerve ring situated in the oral margin of the bell, and together these structures constitute the cubozoan central nervous system. Cnidarians have excellent regenerative capabilities, enabling most species to regenerate large body areas or body parts, and some species can regenerate completely from just a few hundred cells. Here we test whether cubozoans are capable of regenerating the rhopalia, despite the complexity of the visual system and the rhopalial nervous system. The results show that the rhopalia are readily regrown after amputation and have developed most, if not all, neural elements within two weeks. Using electrophysiology, we investigated the functionality of the regrown rhopalia and found that they generated pacemaker signals and that the lens eyes showed a normal response to light. Our findings substantiate the amazing regenerative ability in Cnidaria by showing here the complex sensory system of Cubozoa, a model system proving to be highly applicable in studies of neurogenesis.

Introduction The cubomedusan nervous system includes a centralized system of four rhopalia interconnected by a nerve ring, and peripheral nerve nets in several parts of the medusa that serve motor, [...], Acute responses to mechanical, electrical, and photic stimuli were used to describe neural conducting systems in the cubomedusan jellyfish Carybdea marsupialis underlying three behaviors: contractile responses of single tentacles, protective crumple responses, and alterations of swimming activity by the visual system. Responses of single tentacles consisted of tentacular shortening and inward pedalial bending, and were accompanied by bursts of extracellularly recorded spike activity that were restricted to the stimulated tentacle. With nociceptive stimuli delivered to the subumbrella or margin, all four tentacles produced similar responses in a crumple response. The spike bursts in all four tentacles showed coordinated firing as long as the nerve ring was intact. Crumples were still produced following cuts through the nerve ring, but the activity in individual tentacles was no longer coordinated. Responses to light-on stimulation of a rhopalium, as recorded from the pacemaker region, were weak and inconsistent, but when present, resulted in a stimulation of swimming activity. In comparison, light-off responses were robust and resulted in temporary inhibition of swimming activity. Light-off responses were conducted in the nerve ring to unstimulated rhopalia. In conclusion, three conducting systems have been described as components of the rhopalia-nerve ring centralized system in Carybdea: the swim motor system, the crumple coordination system, and the light-off response system.

Introduction The subumbrellar swim musculature of scyphozoan jellyfish presents an interesting problem for neuronal control due to several unique features. First, the ectodermal muscle, composed of striated muscle cells, is [...], Antibodies to α- or β-tubulin and to the bioactive peptide FMRFamide were used to investigate the organization of the ectodermal nervous structures in five species of scyphomedusae. Within the swim system, morphological evidence, including a developmental sequence, suggests that the tubulin-immunoreactive nerve net in the subumbrella is the Giant Fiber Nerve Net (Motor Nerve Net) that directly activates the swim musculature, and the FMR-Famide-immunoreactive nerve net is the Diffuse Nerve Net that serves a sensory function and also enhances swim muscle activity. Similar dual labeling was found in other structures, including those involved in feeding and protective reactions (pedalia and tentacles, radial strips of smooth muscle), and in the exumbrella, where the networks were associated with batteries of nematocysts. In addition, FMRFamide immuno-staining in the rhopalia and rhopalial niches suggests that sensory components of these networks may aid in the gravitational sense of scyphomedusae.

In order to quantify the trophic impact of gelatinous predators, digestion time estimates are commonly applied to counts of prey in the guts. Three primary approaches are used, the Manual-feeding, Natural-feeding and Steady-state methods; these differ in methodology and their underlying assumptions. The criteria used to define the end-point of digestion, and the resolution at which digestion progress is observed, also vary across studies. To understand the impact of such differences, we estimate digestion times of the scyphomedusa Aurelia aurita fed adult females of the copepod Acartia tonsa using these various approaches. We find ~ fourfold differences which can be attributed to bias towards the slowest rates of digestion by some end-point criteria, and overestimation from low observation resolution. Artificial manipulation and the degree to which swimming and feeding behaviour are natural may also influence estimates. We provide recommendations for those quantifying digestion times of Aurelia aurita medusae and gelatinous predators., Introduction Aurelia spp. is a ubiquitous scyphomedusa, commonly found worldwide in estuarine and coastal waters (Mayer 1910; Dawson and Jacobs 2001; Dawson and Martin 2001). It is the most studied [...]

Jellyfish blooms or invasions could be detected in an early phase of development if the youngest medusa stages (ephyrae) and their early growth stages (post-ephyrae) were identifiable in plankton samples but a useful identification key for ephyrae in early growth stages is lacking for most species. In the present study, the identification characteristics of adult North Sea scyphomedusae (Aurelia aurita, Cyanea capillata, Cyanea lamarckii, Chrysaora hysoscella, Rhizostoma octopus) collected around the island of Helgoland (German Bight) in July-August 2003 and 2004 are described. Planula larvae were measured and reared to polyps in the laboratory. The process of ephyrae development asexually produced by the polyps (strobilation) was photo-documented. Photographs of the ephyrae growth stages were combined with drawings of features useful for the species identification. The provided identification key allows discrimination among post-ephyrae from plankton samples, probably leading to conclusions on the development of jellyfish blooms and their causes., Introduction The scientific interest in jellyfish has increased in recent decades because of increasing problems with jellyfish mass occurrences ('blooms'). Fisheries, aquaculture, coastal industries, and tourism are negatively affected when [...]

Introduction The giant jellyfish Nemopilema nomurai Kishinouye 1922 is one of the biggest scyphozoan jelly fishes in the world, attaining a bell diameter of 2 m and a wet weight [...], Production of podocysts is the exclusive form of asexual reproduction by polyps of the giant jellyfish Nemopilema nomurai, which has been recurrently blooming in the East Asian seas in the last decade. Podocycts consist of a dome-shaped chitinous capsule with laminated structure that encapsulates a mass of cyst cells filled with granules containing nutrient reserves such as proteins, carbohydrates, and lipids. Mitochondria, rough endoplasmic reticulum, and Golgi complexes are scarce in the cytoplasm of these cells, and the staining reaction for RNA is weak, indicating very low metabolic activity. Podocysts are capable of dormancy for at least 5 years without significant change of internal structure or nutrient reserves. Integrated information about spontaneous and artificially induced metamorphosis suggests that the following processes occur during excystment: (1) nematocyst formation in the internal cell mass, (2) stratification of the cell mass into endoderm and ectoderm, (3) extrusion of the cell mass through a gradual opening of the capsule, (4) formation of primordial polyp mouth and tentacles, and (5) metamorphosis to a polyp. We morphologically confirmed that N. nomurai podocysts have the capacity for long-term dormancy, an ability that should contribute to the periodic nature of the massive blooms of medusae of this species.

A stable phylogenetic hypothesis for families within jellyfish class Scyphozoa has been elusive. Reasons for the lack of resolution of scyphozoan familial relationships include a dearth of morphological characters that reliably distinguish taxa and incomplete taxonomic sampling in molecular studies. Here, we address the latter issue by using maximum likelihood and Bayesian methods to reconstruct the phylogenetic relationships among all 19 currently valid scyphozoan families, using sequence data from two nuclear genes: 18S and 28S rDNA. Consistent with prior morphological hypotheses, we find strong evidence for monophyly of subclass Discomedusae, order Coronatae, rhizostome suborder Kolpophorae and superfamilies Actinomyariae, Kampylomyariae, Krikomyariae, and Scapulatae. Eleven of the 19 currently recognized scyphozoan families are robustly monophyletic, and we suggest recognition of two new families pending further analyses. In contrast to long-standing morphological hypotheses, the phylogeny shows coronate family Nausithoidae, semaeostome family Cyaneidae, and rhizostome suborder Daktyliophorae to be nonmonophyletic. Our analyses neither strongly support nor strongly refute monophyly of order Rhizostomeae, superfamily Inscapulatae, and families Ulmaridae, Catostylidae, Lychnorhizidae, and Rhizostomatidae. These taxa, as well as familial relationships within Coronatae and within rhizostome superfamily Inscapulatae, remain unclear and may be resolved by additional genomic and taxonomic sampling. In addition to clarifying some historically difficult taxonomic questions and highlighting nodes in particular need of further attention, the molecular phylogeny presented here will facilitate more robust study of phenotypic evolution in the Scyphozoa, including the evolution characters associated with mass occurrences of jellyfish. doi: 10.1093/icb/icq074

Pax transcription factors are involved in a variety of developmental processes in bilaterians, including eye development, a role typically assigned to Pax-6. Although no true Pax-6 gene has been found in nonbilateral animals, some jellyfish have eyes with complex structures. In the cubozoan jellyfish Tripedalia, Pax-B, an ortholog of vertebrate Pax-2/5/8, had been proposed as a regulator of eye development. Here we have isolated three Pax genes (Pax-A, Pax-B, and Pax-E) from Cladonema radiatum, a hydrozoan jellyfish with elaborate eyes. Cladonema Pax-A is strongly expressed in the retina, whereas Pax-B and Pax-E are highly expressed in the manubrium, the feeding and reproductive organ. Misexpression of Cladonema Pax-A induces ectopic eyes in Drosophila imaginal discs, whereas Pax-B and Pax-E do not. Furthermore, Cladonema Pax-A paired domain protein directly binds to the 5' upstream region of eye-specific Cladonema opsin genes, whereas Pax-B does not. Our data suggest that Pax-A, but not Pax-B or Pax-E, is involved in eye development and/or maintenance in Cladonema. Phylogenetic analysis indicates that Pax-6, Pax-B, and Pax-A belong to different Pax subfamilies, which diverged at the latest before the Cnidaria--Bilateria separation. We argue that our data, showing the involvement of Pax genes in hydrozoan eye development as in bilaterians, supports the monophyletic evolutionary origin of all animal eyes. We then propose that during the early evolution of animals, distinct classes of Pax genes, which may have played redundant roles at that time, were flexibly deployed for eye development in different animal lineages. biodiversity | Cladonema radiatum | Cnidaria | evo-devo | gene duplication doi/ 10.1073/pnas.1008389107

Mycoplasma mobile, a parasitic bacterium lacking a peptidoglycan layer, glides on solid surfaces in the direction of a membrane protrusion at a cell pole by a unique mechanism. Recently, we proposed a working model in which cells are propelled by leg proteins clustering at the protrusion's base. The legs repeatedly catch and release sialic acids on the solid surface, a motion that is driven by the force generated by ATP hydrolysis. Here, to clarify the subcellular structure supporting the gliding force and the cell shape, we stripped the membrane by Triton X-100 and identified a unique structure, designated the 'jellyfish' structure. In this structure, an oval solid 'bell' [approximately equal to] 235 wide and 155 nm long is filled with a 12-nm hexagonal lattice and connected to this structure are dozens of flexible 'tentacles' that are covered with particles of 20-nm diameter at intervals of [approximately equal to] 30 nm. The particles appear to have 180[degrees] rotational symmetry and a dimple at the center. The relation of this structure to the gliding mechanism was suggested by its cellular localization and by analyses of mutants lacking proteins essential for gliding. We identified 10 proteins as the components by mass spectrometry and found that these do not show sequence similarities with other proteins of bacterial cytoskeletons or the gliding proteins previously identified. Immunofluorescence and immunoelectron microscopy revealed that two components are localized at the bell and another that has the structure similar to the [F.sub.1]-ATPase [beta] subunit is localized at the tentacles. bacteria | electron microscopy | gliding motility | immunofluorescence | protein identification

Scyphomedusae are ubiquitous in marine and estuarine systems, where they frequently play an important role in trophodynamics. Many scyphomedusae are cruising predators, and feeding rates depend, in part, on swimming behavior. Yet, no model of medusa swimming exists. An individual-based correlated random walk (CRW) model of medusa swimming behavior in three dimensions was developed. The model was validated using a previously published dataset of the swimming of 19 Chrysaora quinquecirrha (Desor, 1848) medusae that were observed in the presence or absence of zooplankton prey in laboratory mesocosms in August-October 1998 (Matanoski et al. in Mar Biol 139:191-200, 2001). In the presence of prey, medusae swam at a constant moderate rate in looping trajectories. In the absence of prey, medusae alternated periods of slow and fast swimming in more linear trajectories. In the model, looping trajectories were reproduced only when changes in movement by a medusa were oriented to its current position and orientation; more linear trajectories were reproduced by movement oriented to a fixed framework. This suggests that medusae change from swimming behavior oriented to local stimuli (e.g., contact with prey) to long-range stimuli (e.g., gravity) depending on the availability of prey. The model reproduced cyclical changes in swimming speeds by medusae in the absence of prey by simulating switching in the behavior controlling the strength of swimming bell pulsations using a probabilistic function. Model results also demonstrated that medusae tend to swim toward the surface, avoid contact with the bottom, increase time spent in prey patches if they alter swimming patterns in the presence of prey, and exhibit significant periodicities in swimming patterns that are the result of deterministic behavior. The model will permit the simulation of the complex behavior of medusae., Introduction Movement is an integral part of most processes necessary for an organisms survival. Although some motions are due to external forcing (e.g., wind or currents), many are an active [...]

Two types of metamorphosis occur in the life cycle of Carybdea marsupialis Linnaeus 1758 (Cubozoa, Carybdeidae). In addition to the metamorphosis described several times over, during which the entire polyp transforms into one medusa, we investigated a second type of metamorphosis which leaves a regenerative remnant. This mode of medusa formation seems to be derived from the strobilation known from Scyphozoa. Both types are described and the implications these results have on the idea about the origin of the class Cubozoa, are discussed., Introduction Although cubomedusae are well known from the literature due to their potential to cause life threatening envenomations in humans (for review see Burnett 1996), little is known about their [...]

The annual cycle of abundance and distribution of the scyphozoan medusae Aurelia aurita and Cyanea capillata was studied in the Bornholm Basin (central Baltic Sea) in 2002. Seasonal changes in prey composition and predatory impact were investigated by analyzing stomach contents. A. aurita occurred from July to November, with a maximum mean abundance of 2.3 ind. per 100 [m.sup.3] in August, whereas C. capillata was caught in much smaller numbers from July to September. No ephyrae of either species were found; therefore, advection of medusae from the western Baltic Sea is assumed. From July to October, ~80% of A. aurita medusae was distributed in the upper 20 m above the thermocline, whereas C. capillata occurred only in the halocline below 45 m. A. aurita did not migrate vertically and fed mainly on the most abundant cladoceran species Bosmina coregoni maritima. Further prey organisms were the cladocerans Evadne nordmanni and Podon spp., mollusk larvae and copepods. Copepod nauplii and copepodite stages I-III were not eaten by the medusae, neither were fish eggs and larvae used as prey. Based on mean medusa and zooplankton abundance from the upper 20 m, the predatory impact was very low. In August, when mean abundance of A. aurita was highest, only 0.1% of the copepod and 0.5% of the cladoceran standing stock were eaten per day. However, in regions with higher medusa or lower zooplankton abundance, up to 7.9% of the cladoceran standing stock was consumed per day. Hence, A. aurita did not regulate the zooplankton community in the Bornholm Basin, and fish larvae did not suffer from competition with and predation by the medusae.

The copepod Paramacrochiron maximum was found in high numbers (up to 5,675 copepods/medusa) on the oral arms of the scyphozoan Catostylus mosaicus. This association was considered to be commensalism for the following reasons: P. maximum (Lichomolgidae) was abundant on the medusae (approximately 805 copepods/kg of medusae) and very rare in the water column (approximately 5.99 x 10-4 copepods/kg of water); copepodites and adults of the symbiont were present on the host; the copepods were on the medusae both day and night, at different times (nine occasions between March 1999 and May 2000) and diffferent locations (Botany Bay and Lake Illawarra, NSW, Australia). Over 40 taxa of plankton were found on the oral arms of C. mosaicus (including protists, cnidarians, polychaetes, molluscs, a wide range of holoplanktonic and meroplanktonic crustaceans, chaetognaths and fish eggs). These taxa were abundant in the water column and we concluded that they were prey. Symbiotic amphipods and carangid fishes were found with medusae. We conclude that there is a symbiotic association between P. maximum and C. mosaicus and care should be taken not to confound these copepods with the prey of C. mosaicus. Poecilostomid copepods are well known for consuming mucus and feeding is likely to be a major reason for the association., Introduction The nature of interactions between scyphozoans and invertebrates can vary greatly (Kingsford et al. 2000). There are examples of parasitism (Phillips et al. 1969), commensalism (Bruce 1988) and predator-prey [...]

We have clarified, for the first time, the spatiotemporal patterns of intracellular [Ca.sup.2+] increases at fertilization and the [Ca.sup.2+]-mobilizing mechanisms in eggs of hydrozoan jellyfish, which belong to the evolutionarily old diploblastic phylum, Cnidaria. An initial [Ca.sup.2+] increase just after fertilization took the form of a [Ca.sup.2+] wave starting from one cortical region of the egg and propagating to its antipode in all of four hydrozoan species tested: Cytaeis uchidae, Cladonema pacificum, Clytia sp., and Gonionema vertens. The initiation site of the [Ca.sup.2+] wave was restricted to the animal pole, which is known to be the only area of sperm-egg fusion in hydrozoan eggs, and the wave propagating velocity was estimated to be 4.2-5.9 [micro]m/s. After a [Ca.sup.2+] peak had been attained by the initial [Ca.sup.2+] wave, the elevated [Ca.sup.2+] gradually declined and returned nearly to the resting value at 7-10 min following fertilization. Injection of inositol 1,4,5-trisphosphate (I[P.sub.3]), an agonist of I[P.sub.3] receptors (I[P.sub.3]R), was highly effective in inducing a [Ca.sup.2+] increase in unfertilized eggs; I[P.sub.3] at a final intracellular concentration of 12-60 nM produced a fully propagating [Ca.sup.2+] wave equivalent to that observed at fertilization. In contrast, a higher concentration of cyclic ADP-ribose (cADPR), an agonist of ryanodine receptors (RyR), only generated a localized [Ca.sup.2+] increase that did not propagate in the egg. In addition, caffeine, another stimulator of RyR, was completely without effect. Sperm-induced [Ca.sup.2+] increases in Gonionema eggs were severely affected by preinjection of heparin, an inhibitor of [Ca.sup.2+] release from I[P.sub.3]R. These results strongly suggest that there is a well-developed I[P.sub.3]R-, but not RyR-mediated [Ca.sup.2+] release mechanism in hydrozoan eggs and that the former system primarily functions at fertilization. Our present data also demonstrate that the spatial characteristics and mechanisms of [Ca.sup.2+] increases at fertilization in hydrozoan eggs resemble those reported in higher triploblastic animals. Keywords: Fertilization; Hydrozoan egg; Calcium; I[P.sub.3]; cADPR; Caffeine; Cytaeis; Cladonema; Clytia; Gonionema

Morphological variation in qualitative and quantitative features is compared among species of Aurelia defined a priori using molecular criteria. Macro-morphological features were more numerous than previously implied (28 cf. 17), most were variable (26 of 28), and all species were morphologically distinguishable using univariate, multivariate and phylogenetic statistics. However, due to discrepant morphological descriptions, Aurelia spp. 3, 4, and 6 could not be assigned reliably to any previously described species, and there are still insufficient macro-morphological characters and variation to reconstruct a statistically robust phylogeny for even the 12 known species of Aurelia. Yet it is shown that Aurelia aurita is most likely endemic to the boreal Atlantic Ocean and northern European seas, Aurelia labiata is neither as morphologically diverse nor widespread as recently described, and the circumglobal Aurelia sp. 1 is probably introduced across much of its range. Electronic Supplementary Material is available for this article if you access the article at http://dx.doi.org/ 10.1007/s00227-003-1070-3. A link in the flame on the left on that page takes you directly to the supplementary material.

The globally distributed coronate scyphomedusa Periphylla periphylla (Peron and Lesueur, 1809) occurs in permanent and extremely high abundance in some Norwegian fjords. Studies on the species in Lurefjorden, 40 km north of Bergen, have revealed a holopelagic life cycle with direct development. We distinguished 14 successive developmental stages, characterised by size and morphology. Eggs and early stages are non-mobile, neutrally buoyant, and found mainly at intermediate depths. Rearing studies indicated a development time of 2-3 months from fertilisation to stage 9, when the medusa starts feeding and becomes motile. The fjord population usually shows a strong diel vertical migration, with aggregations at shallower depths during the night. The development includes a gradual increase in pigmentation (porphyrins), starting with the stomach, and thereafter extending to tentacles and the whole exumbrella. This pigment is photodegraded by natural light. Rearing experiments in the laboratory have shown a lethal effect of light. Here, development stops at stage 5. Pigments become visible in stage 7. Older medusae are severely damaged and killed within a few days by exposure to daylight. All stages of P. periphylla are bioluminescent, with this capacity increasing with growth, probably in connection with the development of the nervous net. The light reaction starts at the point of stimulation and spreads at two different speeds corresponding to the two nerve nets of the medusae. The coronal furrow has a central function in transmission of the reaction. It is hypothesised that the bioluminescence is used mainly as a warning to some potential predators, signalling that the porphyrin-containing medusa is unpalatable. P. periphylla has the same two categories of nematocysts as other coronates, with a total of six different types. Nematocyst abundance, distribution and morphology indicate their function. The giant euryteles (capsule up to 100 [micro]m and tubule up to 1160 [micro]m) are the largest ones known among Scyphozoa, and are unique in that this size increases during medusa development.

Osamu Shimomura (1)(*) Per R. Flood (2) Satoshi Inouye (3) Bruce Bryan (4) Akemi Shimomura (1) Abstract. Bioluminescence of the medusa Periphylla is based on the oxidation of coelenterazine catalyzed [...]

Research has been conducted on the jellyfish Aurelia aurita. The fatty acid composition of the aquarium-reared and natural common jellyfish has been examined and the results indicate that fatty acid composition reflects that of the jellyfish diets.

It appears that wild-type green fluorescent protein of the bioluminescent jellyfish Aequorea and its mutants clearly shows multiexponential fluorescence decays at all excitation wavelengths. The photochromicity effect does not change the fluorescence lifetimes, but only the pre-exponential factors.

A Fourier transform infrared (FTIR) spectroscopy was conducted to examine the chemiluminescent function of the green fluorescent protein in the jelly fish Aequorea victoria. The presence of a high quantum yield of fluorescence emitted upon ultraviolet illumination demonstrated that the aromatic amino acids formed a connected system from which resonance energy is transferred to the chromophore. The findings may aid in the discovery of yet another photoactive protein which can perform photoconversion more readily than GFP.

The present paper describes the total chemical synthesis of the precursor molecule of the Aequorea green fluorescent protein (GFP). The molecule is made up of 238 amino acid residues in a single polypeptide chain and is nonfluorescent. To carry out the synthesis, a procedure, first described in 1981 for the synthesis of complex peptides, was used. The procedure is based on performing segment condensation reactions in solution while providing maximum protection to the segment. The effectiveness of the procedure has been demonstrated by the synthesis of various biologically active peptides and small proteins, such as human angiogenin, a 123-residue protein analogue of ribonuclease A, human midkine, a 121-residue protein, and pleiotrophin, a 136-residue protein analogue of midkine. The GFP precursor molecule was synthesized from 26 fully protected segments in solution, and the final 238-residue peptide was treated with anhydrous hydrogen fluoride to obtain the precursor molecule of GFP containing two Cys(acetamidomethyl) residues. After removal of the acetamidomethyl groups, the product was dissolved in 0.1 M Tris[center dot]HCl buffer (pH 8.0) in the presence of DTT. After several hours at room temperature, the solution began to emit a green fluorescence ([[Lambda].sub.max] = 509 nm) under near-UV light. Both fluorescence excitation and fluorescence emission spectra were measured and were found to have the same shape and maxima as those reported for native GFP. The present results demonstrate the utility of the segment condensation procedure in synthesizing large protein molecules such as GFP. The result also provides evidence that the formation of the chromophore in GFP is not dependent on any external cofactor.

An experiment is conducted to determine the crystal structure of a blue emission variant of the jellyfish 'Aequorea victoria' green fluorescent protein using molecular replacement. X-ray diffraction data and samples of blue fluorescent protein are used for the study. Results show that the chromophore in the intact protein is electrically neutral. In addition, fluorescence transmission is not identified with excited-state photon transfer.

Introduction Cnidarians are the earliest extant animals to have a nervous system and, as such, they may provide useful information about the evolution of the nervous system and its components. [...], Two antisera against the sulfonated amino acid taurine were applied to subumbrella tissue of the jellyfish Cyanea capillata. Taurine-immunoreactive nerve nets were found in both the ectoderm and endoderm. The ectoderm had two morphologically and immunocytochemically distinct populations of neurons, the motor nerve net (MNN), which was immunoreactive to the taurine-like molecule, and the diffuse nerve net (DNN), which was immunoreactive to the neuropeptide Phe-Met-Arg-Phe-N[H.sub.2] (FMRFamide). In the endoderm, immunoreactivity was found in the endodermal DNN. This localization was confirmed by double-labeling experiments, which also revealed that the endodermal DNN neurons may contain both taurine and FMRFamide-related peptide. The presence of a taurine immunoreactivity in the MNN supports the hypothesis that taurine or some chemically related compound is the neurotransmitter at synapses within the MNN of Cyanea.

Analysis of the migration pattern of Aurelia aurita in a British Columbian fjord reveals that it performs sun-compass migration during daytime. A. aurita undergoes random orientation and passive dispersion due to tidal currents during overcast nights. This causes swarms of medusae that regroup in the southeastern part of the fjord. A. aurita spawning in such swarms proves that inter-fjord reproduction and population maintenance are sustained by sun-compass migration and group behavior.

The characterization of the green-fluorescent protein chromophore of Aequorea victoria was described. The papain-derived chromophore-containing hexapeptide is formed upon cyclization of the residues Ser-dehydroTyr-Gly within the polypeptide. Amino acid analysis and enzymatic cleavage of the peptide demonstrated that a phenylalanine is present at the amino terminus and that the carboxyl-terminal sequence is Val-Glx.

Since the earliest behavioral investigations of scyphomedusan and cubomedusan swimming, swim contractions were found to be controlled by multiple pacemaker/sensory centers that were spread around the margin of the jellyfish. Coordination of swim pacemakers was presumed to be due to a simple dominance hierarchy, in which a discharge in one pacemaker would reset all of the other pacemakers. The resultant pacemaker redundancy was examined in three previous modeling studies in which contractile activity in a piece of jellyfish containing a single rhopalium was used to construct models of multiple-pacemaker networks. In all three studies, pacemakers were connected to one another with re-setting linkages similar to those described in earlier works. We conducted a similar study on the cubomedusa Carybdea marsupialis, but our initial results are not consistent with a model in which pacemakers interact via simple resetting linkages, thus challenging the decades-old notion of how pacemakers interact in cubozoan and scyphozoan jellyfish. In our study, real electrophysiological data were compared to resetting and independent computer model networks of pacemakers. The real data fell between that of the two models suggesting that pacemakers show a degree of independence. Our models also suggest that this type of semi-independent network may allow a greater sensitivity to asymmetrical stimuli, and thus allow significant directional responses to these stimuli.

Radially symmetrical and composed of acellular mesoglea, two cell layers, and a primitive nervous system, jellyfish are an elegantly simple launching point to investigate how material properties of the musculoskeletal system shape the dynamics of locomotion. Mesoglea, composed of mucopolysaccharides, collagen, and water, has a characteristic nonlinear response to an applied strain. This study asks how such nonlinearities determine the dynamical response of a jellyfish's simple geometry subject to periodic forcing. We compare the strain-dependent stiffness of mesoglea between three species of jellyfish, Mitrocoma cellularia, Polyorchis penicillatus, and Aequorea victoria, each with a distinctive overall shape. Because of the nonlinear and time-dependent behavior of mesoglea, we measure the complex modulus by recording its stress in response to sinusoidal strains at a variety of frequencies and mean lengths. Using a simple power law to fit the resultant relationships between complex modulus and mean length, we describe the strength of nonlinearity in mesoglea by the size of the exponent. Aequorea victoria, a jellyfish with unevenly distributed mesoglea and unusual swimming kinematics, has the highest mesoglea exponent, making it the most strongly nonlinear, while Mitrocoma cellularia, a jellyfish with a relatively simple geometry and typical swimming kinematics, has the lowest. The exponent describing the mesoglea of Polyorchis penicillatus falls in between, although it more closely resembles Aequorea. Armed with these estimates, we use a simple dynamical model to show that very subtle changes in the strength of the nonlinearity are manifest as significant changes in the spectral responses of the musculoskeletal system to periodic forcing.

Small wounds (1.2 mm in diameter) made in the sheet of myoepithelial cells forming the 'swimming' muscle of the jellyfish, Polyorchis penicillatus, were closed within 10 h by epithelial cells migrating centripetally to the wound center. Some 24 to 48 h later these cells redifferentiated into fully contractile muscle cells. Labeling with bromodeoxyuridine failed to reveal any cell proliferation during this process. Phenotype switching (within 1 h) from contractile muscle cells to igratory cells did not require synthesis of new protein as shown by treatment with 40 [micro]M cycloheximide. Excitation-contraction coupling in undamaged muscle depended on entry of [Ca.sup.2+] through voltage-gated ion channels, as shown by a block of contractility by 40 [micro]M nitrendipine and also on calcium released from intracellular stores since caffeine (10 [micro]M) caused a 25% reduction in contractile force. In contrast, migratory cells did not require a source of extracellular calcium since migration was unimpeded by low (1 [micro]M) free [Ca.sup.2+] or nitrendipine. Instead, modulatory calcium was derived from intracellular stores since caffeine (10 mM) and thapsigargin (10 [micro]M) slowed migration. This lack of dependence on calcium influx in migratory cells was further confirmed by a dramatic down-regulation in voltage-gated inward current as shown by whole-cell patch recordings. Key Words: wound healing; striated muscles; cell motility; calcium; jellyfish.

Monitoring calcium fluxes in real time could help to understand the development, the plasticity, and the functioning of the central nervous system. In jellyfish, the chemiluminescent calcium binding aequorin protein is associated with the green fluorescent protein and a green bioluminescent signal is emitted upon [Ca.sup.2+] stimulation. We decided to use this chemiluminescence resonance energy transfer between the two molecules. Calcium-sensitive bioluminescent reporter genes have been constructed by fusing green fluorescent protein and aequorin, resulting in much more light being emitted. Chemiluminescent and fluorescent activities of these fusion proteins have been assessed in mammalian cells. Cytosolic [Ca.sup.2+] increases were imaged at the single-cell level with a cooled intensified charge-coupled device camera. This bifunctional reporter gene should allow the investigation of calcium activities in neuronal networks and in specific subcellular compartments in transgenic animals.

The cubozoan jellyfish, Carybdea marsupialis, has four rhopalia, one on each quadrant of the bell. Each rhopalium contains one large eye; one small eye, and four ocelli. Both the large and small eyes have a cornea, lens, and retina of cilitated photoreceptors. Each photoreceptor contains a basally-located nucleus, medially-located pigment granules, and a ciliated apex filled with stacks of membrane. The base of each photoreceptor projects into a neural plexus while the apical end extends into a small space beneath the lens. Antisera that detect rhodopsin, and the green, red, blue, or ultraviolet opsin proteins in zebrafish were applied to the jellyfish eyes. Both the large and small eyes exhibited positive staining for rhodopsin, blue opsin, green opsin, and ultraviolet opsin. Rhodopsin, blue opsin, and green opsin staining were observed in the apical stacks of photoreceptor membranes, whereas UV opsin staining was observed in the mid to basal regions of some of the photoreceptors. Jellyfish eyes exposed to antibodies that recognize all photoreceptors, larval and adult, of Drosophila showed no staining.

The work of some researchers into the box jellyfish, the sting of which is capable of killing a human within minutes, is examined. Heather Walling, a research officer at the Cooperative Research Centre's Reef Research Centre at James Cook University in north Queensland, Australia, and Lisa-ann Gershwin, a doctoral student at the Australian Institute of Marine Science, are both doing research into the box jellyfish in order to find an antidote for its sting.