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Like that of most scyphozoans, the ontogeny of Cyanea capillata medusae involves substantive alterations in feeding structures and mechanics. We used video and optical microscopy approaches to quantify these ontogenetic changes in morphology, flow, and feeding of C. capillata medusae. We found that alterations in gross morphology and nematocyst distributions coincided with a shift from prey capture on the manubrium or lappets of ephyrae (bell diameter 0.2-0.4 cm) to capture primarily on the tentacles in adult medusae (diameter >1.0 cm). These changes occurred within a hydrodynamic framework that itself changed due to medusan growth. Viscous forces were important in flows around small ephyrae (maximum Re < 10¹), whereas viscosity was less influential in the inertially dominated flows around adult medusae (Re > 10²). The relative timing of these events indicates that ontogenetic processes are closely synchronized with alterations in the hydrodynamic environment within which C. capillata medusae develop. [ABSTRACT FROM AUTHOR]

Abstract: Fire corals (Millepora spp.) cause severe pain and inflammatory effects in humans upon contact, and the organs responsible for these effects are called nematocysts. Here, we isolated an active cytotoxin of ca. 18kDa (MCTx-1) from nematocysts of Millepora dichotoma var. tenera. MCTx-1 was potently cytotoxic (EC50 value 79ng/mL) towards L1210 mouse leukemia cells, hemagglutinated a 0.8% suspension of sheep erythrocytes (0.2μg protein/mL) and was lethal in crayfish (LD50, 106μg/kg). We deduced the primary structure of MCTx-1 from the corresponding cDNA sequence and found that MCTx-1 is a novel dermatopontin that is an extracellular matrix protein in mammals. This is the first characterization of a proteinaceous toxin from fire coral. [Copyright &y& Elsevier]

Abstract: Two of the most abundant proteins found in the nematocysts of the box jellyfish Chironex fleckeri have been identified as C. fleckeri toxin-1 (CfTX-1) and toxin-2 (CfTX-2). The molecular masses of CfTX-1 and CfTX-2, as determined by SDS-PAGE, are approximately 43 and 45kDa, respectively, and both proteins are strongly antigenic to commercially available box jellyfish antivenom and rabbit polyclonal antibodies raised against C. fleckeri nematocyst extracts. The amino acid sequences of mature CfTX-1 and CfTX-2 (436 and 445 residues, respectively) share significant homology with three known proteins: CqTX-A from Chiropsalmus quadrigatus, CrTXs from Carybdea rastoni and CaTX-A from Carybdea alata, all of which are lethal, haemolytic box jellyfish toxins. Multiple sequence alignment of the five jellyfish proteins has identified several short, but highly conserved regions of amino acids that coincide with a predicted transmembrane spanning region, referred to as TSR1, which may be involved in a pore-forming mechanism of action. Furthermore, remote protein homology predictions for CfTX-2 and CaTX-A suggest weak structural similarities to pore-forming insecticidal δ-endotoxins Cry1Aa, Cry3Bb and Cry3A. [Copyright &y& Elsevier]

Abstract: Two species of venomous pelagic cnidaria are compared according to their enzymatic, cytotoxic and haemolytic potency. The widely distributed jellyfish Cyanea capillata and Cyanea lamarckii were collected in the North Sea at the coasts of the Orkney Island and the Island of Helgoland. Purified cnidocyst extracts from fishing and mesenteric tentacles were prepared and tested for their bioactivity. The haemolysis induced by toxins of C. capillata was determined with respect to organism size and toxigenic organs. The haemolytic activity of the related species C. lamarckii was documented for the first time. Dose dependent haemolytic activities have been detected by means of protein equivalents at concentrations above 20μgprotein/mL. Extracts of fishing tentacle cnidocysts showed a less potent haemolytic activity compared to extracts of mesenteric tentacles. In vitro studies with permanent cells of a hepatoma cell line have shown a time and concentration dependent loss of cell vitality up to 90% at 33.3μgprotein/mL (10μgprotein/105 cells). Supplementing the cell based toxicity tests an enzyme assay was performed to measure a phospholipase A2 (PLA2) activity. A PLA2-like activity could be demonstrated in cnidocysts extracts prepared from mesenteric and fishing tentacles of both jellyfish species. [Copyright &y& Elsevier]

Abstract: Venom profiles of two age groups of the medically important Australian box jellyfish Carukia barnesi [Southcott, R.V., 1967. Revision of some Carybdeidae (Scyphozoa, Cubomedusae), including description of jellyfish responsible for the ‘Irukandji’ syndrome. Aust. J. Zool. 15, 651–657] were compared. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed differences in protein banding of tentacular venom between immature and mature animals. This correlates to a change in diet from invertebrate prey in immature C. barnesi medusae to vertebrate prey in mature medusae. Unlike other cubozoan studies, a change in venom did not equate to a change in nematocyst types or their relative frequencies. Additionally, comparison of tentacle structure and bell wart number showed developmental differences between the two age classes. Observations of prey capture in mature individuals and differences in bell warts between immature and mature medusae suggest different methods of prey capture are employed at different life stages of C. barnesi. [Copyright &y& Elsevier]

This study examines the mechanisms of aposematism (unprofitability of prey combined with a conspicuous signal) in the aeolidioidean Cratena peregrina (Gmelin, 1791). We investigated if marine fish avoid attacking aeolidioidean nudibranchs, which are an unprofitable group of prey for most predators. We analysed the interaction between aeolids and predatory fish in laboratory and field assays, with both live aeolids and artificial models. In the first experiment, we offered normal and blue-dyed C. peregrina to fish in the field. The number of attacks by fish was independent of the density of the prey, albeit the normal aeolids were attacked less frequently than the blue ones. The fact that all normal C. peregrina survived, whereas 12–20% of the blue aeolids died after fish attacks, suggests that aposematic coloration provides a selective advantage against fish predators. Field and laboratory assays with artificial aeolids were employed to test the effects of different factors (number of cerata, colour pattern, nematocysts), or a combination of factors, on fish learning. Fish learned to avoid unpalatable models with the colour pattern of C. peregrina. After three to four training sessions with unprofitable models, fish avoided profitable models with the same colour pattern. Our results suggest that the colour pattern of C. peregrina combined with the presence of dorsal appendages and nematocysts make fish avoid aeolids. [ABSTRACT FROM AUTHOR]

The reproductive organs of Coryne epizoica (Stechow 1921) are described for the first time. The gonophores are sessile sporosacs of the styloid type developing in the axils of the tentacles. The characteristic sac‐like outgrowths of the hydrocaulus, previously suspected to be incipient gonophores, are actually an adhesive organ likely used to translocate hydranths to other gastropod shells and thus promote vegetative growth and spreading. [ABSTRACT FROM AUTHOR]

The article presents abstracts of biological research. They include "Nanosecond-scale kinetics of nematocyst discharge," "Total antioxidant power in sled dogs supplemented with blueberries and the comparison of blood parameters associated with exercise," and "Simple rules guide dragonfly migration."

Isolated nematocysts of the Scyphozoan Pelagia noctiluca became diaphanous when incubated at low pH for 1 h or left at room temperature for a few hours. Diaphanous nematocysts were unable to undergo discharge when triggered by proper physico-chemical stimuli. The aim of the present study was to investigate the relationship between the morphological features of diaphanous nematocysts and the haemolytic power of their crude venom, obtained by sonication on ice. Nematocysts stored at-20 ° C in neutral medium were used as a control. Our results show that the haemolytic power of crude venom from isolated nematocysts kept at low pH or at room temperature decreased significantly with respect to the control. From this study, it can be deduced that a neutral pH and low temperature conditions are recommended to store nematocysts properly in order to use them in toxicological investigations. [ABSTRACT FROM AUTHOR]

In the sea anemone Bartholomea annulata, four different types of cnidocysts, basitrichous isorhizas, microbasic p-mastigophores, microbasic amastigophores and spirocysts were identified. In relation to the efficacy of different substances to induce discharge of nematocysts we observe that distilled water induced more than 70% of microbasic p-mastigophores to discharge, whereas spirocysts were discharged in a lesser extent (≈20%). The median lethal dose (LD50) in mice was found after injection of 700.7 mg protein per kg of body weight from the crude extract. The protein with neurotoxic effect was isolated using low-pressure liquid chromatography. The neurotoxic activity was determined using sea crabs ( Ocypode quadrata), injecting 15 μg of crude extract or isolated fraction into the third walking leg, and violent motor activity followed by progressive loss of sensibility to external stimuli, further leading to full paralysis were observed. The active fraction (called V) eluted at 43.9 min. [ABSTRACT FROM AUTHOR]

The nematocyst capsules of the cnidarians are specialized explosive organelles that withstand high osmotic pressures of ≈ 15 MPa (150 bar). A tight disulfide network involving cysteine-rich capsule wall proteins, like minicollagens and nematocyst outer wall antigen, characterizes their molecular composition. Nematocyst discharge leads to the expulsion of a long inverted tubule that was coiled inside the capsule matrix before activation. Spinalin has been characterized as a glycine-rich, histidine-rich protein associated with spine structures on the surface of everted tubules. Here, we show that full-length Hydra spinalin can be expressed recombinantly in HEK293 cells and has the property to form disulfide-linked oligomers, reflecting its state in mature capsules. Furthermore, spinalin showed a high tendency to associate into dimers in vitro and in vivo. Our data, which show incomplete disulfide connectivity in recombinant spinalin, suggest a possible mechanism by which the spine structure may be linked to the overall capsule polymer. [ABSTRACT FROM AUTHOR]

This paper describes two neurotoxic proteins obtained from the Caribbean sea anemone Lebrunia danae. To assess the neurotoxic activity of the venom of L. danae, several bioassays were carried out, and to evaluate the effect of the toxin, Median Lethal Doses (LD50) were determined in vivo using sea crabs ( Ocypode quadrata) and Artemia salina nauplii with the crude extract of the proportion of 2.82 mg/m. The proteins with neurotoxic effects were isolated using low-pressure liquid chromatography. The fractions containing the neurotoxic activity were analyzed by SDS-PAGE and showed protein bands with an apparent molecular weight of 62.50 kDa (LdNt1) and 58 kDa (LdNt2). To demonstrate that these proteins were indeed responsible for the neurotoxic activity observed, we injected a small fraction of the purified protein into the third walking leg of a crab and observed the typical convulsions, paralysis and death provoked by neurotoxins. Hemolytic activity was also tested for 0.238 mg of crude extract; the hemolytic value was 39.5, 49.6 and 50.1% for cow, sheep and pig erythrocytes, respectively. [ABSTRACT FROM AUTHOR]

This paper describes one neurotoxin and three cytolysins isolated from the venom of the Caribbean box jellyfish Carybdea marsupialis. To assess the cytolytic and neurotoxic activity of the nematocyst venom, several bioassays were carried out, and to evaluate the effect of the toxin, the dose causing 50% lethality (LD50) was determined in vivo using sea crabs ( Ocypode quadrata). The proteins with neurotoxic and cytolytic effects were isolated using low-pressure liquid chromatography. The fraction containing the neurotoxic activity was analyzed by SDS-PAGE and showed a single protein band with an apparent molecular weight of 120 kDa (CmNt). To demonstrate the neurotoxic activity of this protein, a small fraction of the purified protein was injected into a crab, and the typical convulsions, paralysis, and death provoked by neurotoxins were observed. Three fractions containing cytolysins had protein bands in SDS PAGE with apparent molecular weights of 220, 139, and 36 kDa, and their cytolytic activity was confirmed with the haemolysis assay. [ABSTRACT FROM AUTHOR]

In Hydra, developmental processes are permanently active to maintain a simple body plan consisting of a two-layered, radially symmetrical tube with two differentiated structures, head and foot. Foot formation is a dynamic process and includes terminal differentiation of gastric epithelial cells into mucous secreting basal disc cells. A well-established marker for this highly specialized cell type is a locally expressed peroxidase (Hoffmeister et al. ). Based on the foot-specific peroxidase activity, the gene PPOD1 has been identified (Hoffmeister-Ullerich et al. ). Unexpectedly, this approach led to the identification of a second gene, PPOD2, with high sequence similarity to PPOD1 but a strikingly different expression pattern. Here, we characterize PPOD2 in more detail and show that both genes, PPOD1 and PPOD2, are members of a gene family with differential complexity and expression patterns in different Hydra species. At the genomic level, differences in gene number and structure within the PPOD gene family, even among closely related species, support a recently proposed phylogeny of the genus Hydra and point to unexpected genomic plasticity within closely related species of this ancient metazoan taxon. [ABSTRACT FROM AUTHOR]

The mechanisms involved in cnidocyst discharge among cnidarians are not well understood. In this study we examined the discharge mechanism in an anthozoan. We examined the effect of the Ca 2+ antagonists (Mg 2+ , Co 2+ and La 3+ ), a Ca 2+ agonist (Sr 2+ ), and two cations (Ca 2+ and K + ) upon cnidocyst discharge, using electrical stimulation applied directly to sea anemone tentacles. In our experiment we used the sea anemone Heteractis crispa (Class: Anthozoa, Family: Stichodactylidae), a known host for anemonefishes, as a model organism. Our results show that the Ca 2+ antagonists effectively inhibit, while all the other cations enhance the cnidocyst discharge of H. crispa . These results are comparable to those from a similar study on the hydrozoan, Hydra vulgaris , which also used the electrostimulation method. Our results demonstrate for the first time that the discharge mechanisms in Anthozoa and Hydrozoa are comparable, and support existing hypotheses concerning the importance of Ca 2+ in cnidocyst discharge. [ABSTRACT FROM AUTHOR]

Aeolid nudibranchs maintain functional nematocysts, which are sequestered from the nudibranchs' cnidarian prey and provide protection against predators. Some species exhibit extensive variation in incorporated nematocysts, while others maintain a limited number of types. This study examines the apparent diversity in uptake and patterns of nematocyst incorporation among related species. Nematocyst complements were described for four Gulf of Maine nudibranch species in the genus Flabellina exhibiting a variety of feeding strategies and prey specificities. Diet manipulations were performed to examine the response to changing nematocyst availability using a generalist consumer, Flabellina verrucosa, to assess nematocyst uptake based on diet. The flabellinid species examined exhibited significant differences in nematocyst incorporation, reflecting differences in their specificity as predators and nematocyst types available in their natural prey. The nematocyst complement of F. verrucosa was the most variable and differed among collection regions. When diet was manipulated, nematocyst uptake depended on the prey the nudibranchs consumed, but when offered a variety of prey, F. verrucosa selectively preferred nematocysts from scyphistomae. The observed variation in nematocyst uptake among species and regions probably relates to environmental disparities among populations. [ABSTRACT FROM AUTHOR]

We examined the cnidomes (total complement of nematocysts) of medusae of the zooxanthellate and azooxanthellate jellyfishes Phyllorhiza punctata and Catostylus mosaicus (Rhizostomeae, Scyphozoa), and compared the assemblage of zooplankton captured on the oral arms of each species to determine whether differences in the types or amount of zooplankton captured were consistent with possible differences in the cnidomes. Cnidomes were described using light and scanning electron microscopy. Each species had a distinct cnidome and, in general, specimens of P. punctata appeared to have far fewer nematocysts than those of C. mosaicus. Four types of nematocysts were identified in medusae of C. mosaicus; 2 types of holotrichous isorhizae, rhopaloids, and birhopaloids. In C. mosaicus, the oral arms and bell margins possessed all of these types, but the cnidomes of the 2 regions differed in relative abundances and sizes of isorhizae and rhopaloids. Five types of nematocysts were identified in medusae of P. punctata, although not all types were found in all specimens. Round holotrichous isorhizae were found only in the bell, while oval holotrichous isorhizae, rhopaloids of 2 distinct size ranges, and birhopaloids were found in the bell and oral arms. Cnidomes of the bell and oral arms in specimens of P. punctata also differed in the relative abundance and sizes of oval isorhizae and rhopaloids. Although there were clear differences in the overall cnidomes and absolute abundances of nematocysts in each species, the oral arms (feeding appendages) of specimens of both C. mosaicus and P. punctata had similar types and relative abundances of nematocysts. Zooplankton sampled from the oral arms of each species showed that both species preyed predominantly on copepod nauplii and larvae of gastropods and bivalves. Medusae of C. mosaicus captured∼10× more gastropod larvae and 5× more bivalve larvae than those of P. punctata. Specimens of P. punctata captured approximately twice as many copepod nauplii as those of C. mosaicus. Differences in the relative abundance of types of zooplankton captured by each species could not be adequately explained by differences in the cnidomes of the oral arms. [ABSTRACT FROM AUTHOR]

Chrysaora quinquecirrha (sea nettle) nematocyst venom is lethal to rainbow killifish (Adina xenica) when injected intraperitoneally or topically applied to the exposed brain or denuded epithelium. The lethal activity is thermostable requiring 100°C heat for inactivation. This paper reports here for the first time that the venom also activates the complement system with the subsequent formation of the C5b-9 terminal complement complex. The events are associated with both a strong chemoattractant release and the tissue damage. These are also, at least in part, responsible for the pathogenesis of some clinical signs and symptoms associated to the jellyfish stings. [Copyright &y& Elsevier]

The nematocyst is a unique extrusive organelle involved in the defense and capture of prey in cnidarians. Minicollagens and the glycoprotein NOWA are major components of the nematocyst capsule wall, which resists osmotic pressure of 15 MPa. Here we present the recombinant expression of NOWA, which spontaneously assembles to globular macromolecular particles that are sensitive to reduction as the native wall structure. Ultrastructural analysis showed that the Hydra nematocyst wall is composed of several layers of globular particles, which are interconnected via radiating rodlike protrusions. Evidence is presented that native wall particles contain NOWA and minicollagen, supposed to be linked via disulfide bonds between their homologous cysteine-rich domains. Our data suggest a continuous suprastructure of the nematocyst wall, assembled from wall proteins that share a common oligomerization motif. [ABSTRACT FROM AUTHOR]

Abstract: Crude extracts of the coelenterate Aiptasia mutabilis (Anthozoa, Aiptasiidae) nematocysts have been tested for their cytotoxicity of Vero and HEp-2 cells monolayers. The results indicate that the nematocyte venom contains one or more toxins with an extremely powerful cytolytic activity. An extract containing the equivalent of as little as 0.6 nematocysts/μL is sufficient to induce significant cellular necrosis, and IC50 can be estimated to be ca. 2 nematocysts/μL on Vero cells. These values are 1–2 orders of magnitude lower than those reported so far for other sea anemone venoms. The extreme potency is accompanied by poor stability of the venom that is readily inactivated by moderate heat and by buffers at non-neutral pH values. The extract is unstable even when kept for short times at 4 °C, or after storage at −20 °C. Separation of crude venom by affinity chromatography on ConA-Sepharose allowed us to identify two main components with molecular masses of 95 and 31 kDa, respectively, as responsible for the cytolytic properties of A. mutabilis nematocyst extract. [Copyright &y& Elsevier]

Abstract: Stings of fire corals, potent hydroids common in the Red Sea, are known to cause severe pain and they develop burns and itching that lasts few hours after contact. Nematocyst venom of Millepora platyphylla (Mp-TX) was isolated according to a recent method developed in our laboratory to conduct a previous investigation on the nematocyst toxicity of Millepora dichotoma and M. platyphylla. In this study, Mp-TX was fractionated by using both gel filtration and ion exchange chromatography. Simultaneous biological and biochemical assays were performed to monitor the hemolytic (using washed human red blood cells, RBCs) and phospholipase A2 (using radiolabeled sn-2 C14-arachidonyl phosphatidylcholine as a substrate) active venom fractions. The magnitude of both hemolysis and phospholipase A2 activity was found in a fraction rich of proteins of molecular masses ∼30,000–34,000 Daltons. The former fraction was purified by ion exchange chromatography, and a major bioactive protein factor (approx. 32,500 Daltons , here named milleporin-1) was recovered. Milleporin-1 enzymatic activity showed a significant contribution to the overall hemolysis of human RBCs. This activity, however, could not be completely inhibited using phospholipid substrates. Melliporin-1 fraction retained about 30% hemolysis, until totally rendered inactive when boiled for 3 min. The overall mechanism of action of milleporin-1 to impact the cellular membrane was discussed; however, it is pending more biochemical and pharmacological future studies. [Copyright &y& Elsevier]

Chiropsalmussp. medusae collected in this study ranged from 3 to 71 mm diagonal bell width and displayed growth best described by the following equation size (mm)?=?74.9 ×?exp (?exp(0.041 (time since metamorphosis (day) ?35.6674))). Growth rates of up to 7?mm?week?1 increase in diagonal bell width are theoretically possible, with animals able to reach sexual maturity in approximately 70?days. Correlation of the number of rings on the statoliths with the predicted age of the individual from the field produced a relationship that indicates the growth rings are laid down daily and as such could be used to infer age of the medusae. Over the 1998-1999 season, there were four influxes of juvenile cohorts, each occurring approximately 14?days after a major rainfall event. [ABSTRACT FROM AUTHOR]

Statistical phylogenetic analyses of 111 5.8S and partial-28S ribosomal DNA sequences (total aligned length=434 nucleotides) including jellyfishes representing approximately 14 of known scyphozoan morphospecies (21 genera, 62 families, and 100 orders) are presented. These analyses indicate stauromedusae constitute a fifth cnidarian class (Staurozoa) basal to a monophyletic Medusozoa (=Cubozoa, Hydrozoa, and Scyphozoa). Phylogenetic relationships among the medusozoans are generally poorly resolved, but support is found for reciprocal monophyly of the Cubozoa, Hydrozoa, Coronatae, and Discomedusae (=Semaeostomeae?+ Rhizostomeae). In addition, a survey of pairwise sequence differences in Internal Transcribed Spacer One within morphospecies indicates that scyphozoan species diversity may be approximately twice recent estimates based on morphological analyses. These results highlight difficulties with traditional morphological treatments including terminology that obfuscates homologies. By integrating molecular phylogenetic analyses with old and new morphological, behavioural, developmental, physiological, and other data, a much richer understanding of the biodiversity and evolution of jellyfishes is achievable. [ABSTRACT FROM AUTHOR]

New preparations of the medusaBougainvillea principisshow features corresponding to those inB. superciliarisas described by Louis Agassiz in 1850 and are presented in context with his account. Allowing for some simplification, and one possible error, Agassiz’s drawings give a good picture of the layout of the hydromedusan nervous system. On present evidence, Agassiz was the first person to discover a nervous system in any member of the Cnidaria. [ABSTRACT FROM AUTHOR]

Structure of nematocysts fromPolypodium hydriformewas studied by scanning and transmission electron microscopy. Two nematocyst types were observed: holotrichous isorhizas with minute spines, and true atrichous isorhizas. Among holotrichous isorhizas four morphological categories were distinguished based on differences in morphology of their discharged stinging tubules. The cnidom ofP. hydriformepossesses no specialized penetrant types. Instead,Polypodiumuses holotrichous isorhizas as penetrants during prey capture. Stinging tubules of holotrichous isorhizas display two helical rows of tiny spines in the discharged state and possess two helical folds in the undischarged state, thus corresponding to double-helical symmetry. Double-helical symmetry has never been described for nematocysts of any cnidarians, thus being a peculiar feature ofP. hydriforme. [ABSTRACT FROM AUTHOR]

In addition to their role in orchestrating body and tentacle contractions, hydra’s nerves control the behavior of nematocysts; precisely how is still a work in progress. There are strong indications that the classical neurotransmitters, glutamate and GABA (?-amino-butyric acid), play an essential role in effecting stenotele and desmoneme discharge. In experiments on isolated tentacles ofHydra vulgaris, in which cnidocils were mechanically deflected with a piezo-electrically-driven glass micropipette, stenoteles and desmonemes respond to differences in applied force in a dose-dependent manner. GABA, working through its metabotropic receptor, appears to be involved with the recruitment of desmonemes. Desmonemes in distant battery cells or in another part of a given battery cell were discharged by stimulating a desmoneme cnidocil in the presence of bath-applied GABA or its metabotropic agonist, baclofen. The effect was blocked by phaclofen, its metabotropic antagonist. Neither GABA nor baclofen affected stenotele discharge. GABAA agonists had no effect on nematocyst discharge. Glutamate caused a significant increase in number of stenoteles responding to direct mechanical stimuli, but did not effect desmoneme discharge. The effect was mimicked by NMDA (n-methyl-d-aspartate) together with kainate, or by NMDA plus AMPA (amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid), but not with any ionotropic agonist alone. The effect was blocked by D-AP 5 (d- (?)-2-amino-5-phosphopentanoic acid), a specific NMDA antagonist, or CNQX (6-cyano-7-nitroquinoxaline-2,3-dione), a specific kainate/AMPA antagonist. A glutamatergic mechanism working through ionotropic glutamate receptors appears to lower the firing threshold of stenoteles, perhaps?by permitting the entry of Ca2+ into the cell through the early evolved NMDA/kainite/AMPA mechanism. [ABSTRACT FROM AUTHOR]

The stinging hydromedusaOlindias 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 sambaquiensisoccurred 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.sambaquiensisspawn 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). [ABSTRACT FROM AUTHOR]

Three colony fragments of the scleractinian coralMycetophyllia feroxWells from Florida were observed in flow-through seawater aquaria under light and dark conditions. The colonies were then anesthetized and fixed for microscopic examination. Small vesicles formed across the epidermis in response to light as gastrodermis containing approximately 1.9 × 106 zooxanthellae cm-2 migrated into them. The vesicles flattened in the dark and the gastrodermis retreated to a clumped position. The epidermis is dominated by mucus cells with more than 6300 per mm2. In contrast, there are very few epidermal cnidae. The polyps lack tentacles entirely, though small tentacles do occur, albeit sporadically, along the colline walls. Colline tentacles are expanded both day and night, and there is considerable intracolonial variability in the number of cnidae within them, ranging from as few as 316 to more than 3200 per mm2 tentacle. There may be several small cnidocyst batteries containing both spirocysts and nematocysts (all microbasic p-mastigophores), but the principal battery is at the tentacle tip where cnidae are much more densely packed. There is considerable variation in the ratio of the two cnidae among tentacles in the same colony. Since the tentacles occur inconsistently and do not appear to expand, their functional role is unclear. Comparisons of epidermal characters are made with other members of the genusMycetophyllia. [ABSTRACT FROM AUTHOR]

The taxonomic value of nematocyst size in sea anemones is still being assessed. We evaluate size distribution of nematocysts of one type in a single individual anemone. Length of unfired nematocysts was measured along the column, tentacles, and actinopharynx of a preserved specimen ofActinodendron arboreum(Quoy&Gaimard, 1833). Mean, range, minimum, and maximum length of nematocysts vary along the column, those in the middle region being least variable. The length of nematocysts in mature (split) acrospheres is less variable than in immature (unsplit) acrospheres. There is significant variability between nematocysts in tentacles of the primary and quaternary cycles, and along a tentacle, the middle being least variable. Size distribution of actinopharynx nematocysts is complex. The results of this study suggest that assembling data on nematocysts from multiple individuals for taxonomic purposes should be used with an awareness that sampling site can be an important variable. Ideally, the position of tissue sampled should be documented, an attempt should be made to be consistent in sampling from the same position in individuals being compared, and the variability of nematocyst length at each sampled site should be assessed. Inferences can also be made on ontogeny from these data; we conclude that an actinodendrid tentacle grows from the base and at the tips of its branches. [ABSTRACT FROM AUTHOR]

Seven different types of nematocyst are detailed and illustrated from the Zoanthidea. We studied the size population structure of nematocyst capsules: how they are affected by preservation, and how and what should be measured. Populations of two types, large holotrichs andp-mastigophores, from the mesenterial filaments ofProtopalythoa heliodiscusandPr. mutukihave been compared using length, width, and (forp-mastigophores) shaft length. The analysis employed bivariate scattergrams and discriminant analysis. The two species are strongly differentiated by their holotrichs, less well by theirp-mastigophores. The problem of bimodal size distributions is considered and resolved. It is recommended that nematocyst capsule population descriptors should always be included in species’ descriptions, in addition to or instead of the customary minimum-maximum range. [ABSTRACT FROM AUTHOR]

Our previously published studies are here reviewed detailing neuro-cnidocyte synapses, demonstrating putative neurotransmitter substances, and identifying complex neural pathways in sea anemones. Synapses were traced to their contacts on nematocytes and spirocytes by transmission electron microscopy of serial thin sections of tentacles. In five animals, cells containing microbasicp-mastigophores had synapses with clear vesicles, whereas cells containing basitrichous isorhizas had synapses with dense-cored vesicles, providing preliminary evidence for a selectivity of neurotransmitter types for different nematocysts. Either clear or dense-cored synaptic vesicles were also present at neuro-spirocyte contacts. Antho-RFamide immunoreactivity occurred in some anthozoan synaptic vesicles and immunogold labeling of serotonin was found at a neuro-spirocyte synapse. Neural pathways included direct innervation of spirocytes by sensory cells, sequential neuro-neuro-spirocyte and neuro-neuro-nematocyte synapses and reciprocal synapses involving axons of both sensory cells and ganglion cells. Such synaptic patterns resemble neuro-effector pathways found in higher animals and lay to rest the independent effector hypothesis for cnidocyte discharge in tentacles of sea anemones. [ABSTRACT FROM AUTHOR]

Mechanoelectric transduction and its ultrastuctural basis were studied in the cnidocil apparatus of stenotele nematocytes of marine and freshwater Hydrozoa (CapitataandHydra) as a paradigm for invertebrate hair cells withconcentrichair bundles. The nematocytes respond to selective deflection of their cnidocil with phasic-tonic receptor currents and potentials, similar to vertebrate hair cells but without directional dependence of sensitivity. Ultrastructural studies and the use of monoclonal antibodies allowed correlating the mechanoelectric transduction with structural components of the hair bundle. Two other types of depolarising current and voltage changes in nematocytes arepostsynaptic, as concluded from their ionic and pharmacological characteristics. One of these types is induced by mechanical stimulation ofdistantnematocytes and sensory hair cells. It is graded in amplitude and duration, but different from the presynaptic receptor potential. Adequate chemical stimulation of the stenoteles strongly increases the probability of discharge of their cnidocyst, if the chemical stimulus precedes the mechanical one. Simultaneously, the probability of synaptic signalling induced by mechanical stimulation is increased, reaching nearly 100%. The chemoreception of the phospholipids used could be localized in the shaft of the cnidocil, because of the water-insolubility of the stimulant. This chemical stimulation itself does not cause a receptor potential; its action is classified as a modulatory process. Electron microscopy of serial sections of the tentacular spheres ofCorynerevealed synapses that areefferentto nematocytes and hair cells besides neurite-neurite synapses, each containing 3-10 clear and/or dense-core vesicles of 70-150 nm diameter. The only candidates to explain thegraded afferentsignal transmission of nematocytes and hair cells are regularly occurring cell contacts associated with 1(-4) clear vesicles of 160-1100 nm diameter.Transientfusion andpartialdepletion ofstationaryvesicles are discussed as mechanisms to reconcile functional and structural data of many cnidarian synapses. [ABSTRACT FROM AUTHOR]

The nematocysts ofChiropsalmusquadrigatus(Cubozoa; Cubomedusa; Chirodropidae) were examined to determine if their composition changes with an increase in body size. Fixed tentacles of specimens collected in Okinawa, Japan, were homogenized and their nematocysts were observed under a differential interference contrast microscope. Six nematocyst types were observed in medusae of all sizes microbasic mastigophores (MM), large and small trirhopaloids (lTR and sTR), holotrichous isorhizas (HI), ellipsoidal isorhizas (eI), and ovoid isorhizas (oI). Two other nematocysts, large ovoid isorhizas (loI) and microbasic euryteles (ME), were observed only in small individuals. There was also marked difference in proportion of tentacular nematocysts between small and large individuals. HI was the dominant type in small specimens, while MM and eI were predominant in large specimens. Nematocyst composition in the bell and pedalia also differed between small and large individuals. Bells of small medusae contained oI and sTR, while only oI were observed in most large individuals. The pedalia of small medusae had clusters of MM, ME, sTR, and oI. Such single clusters on pedalium bases were characteristic of small individuals. The pedalia of large individuals contained scattered oI. Tentacles of medusae are used for prey capture, so the changes in the major type of nematocysts in tentacles may reflect changes in prey type. [ABSTRACT FROM AUTHOR]

Abstract: Comparative studies on cnidocysts, involving adequate statistical treatment, are very scarce. Classical statistical tests are frequently used assuming normal frequency distributions of capsule lengths, but many distributions are non-normal in acontiarian sea anemones. A traditional choice in these situations are non-parametric tests, although they are not as powerful as parametric tests. An extension of classical methods was developed by some authors; these models, called Generalized Linear Models (GLM), can be used under certain conditions with non-normal data. In view of the properties of our data, that are positive, skewed and with constant coefficient of variation, a GLM with gamma distribution and inverse link function was chosen to analyse the cnidae of acontia from the species Haliplanella lineata, Tricnidactis errans and Anthothoe chilensis. Graphical analysis of residuals showed that these assumptions were reasonable. This method allowed us to avoid transformation of data set and controversial cases in the limit of significance level. For this task, appropriate subroutines in GLIM language were written. In all cases highly significant differences were found between the specimens considered for every species and nematocyst type (b-rhabdoids, p-rhabdoids B1b and p-rhabdoids B2a). [Copyright &y& Elsevier]

Tentacles from representatives of all four classes of the phylum Cnidaria were examined using antibodies against the neuropeptides FMRFamide and RFamide to reveal the organization of neurons and nerve nets associated with cnidocytes. The tentacles of all species examined contained FMRFamide- or RFamide-immunoreactive neurons, in varying densities. In representatives from the Scyphozoa, Hydrozoa, and Cubozoa, the FMRFamide-immunoreactive neurons formed plexuses at the base of the cnidocyte assemblages; in anthozoans, the absence of discrete assemblies of cnidocytes precluded visual co-localization of cnidocytes and immunoreactive neurons. In all four classes, immunoreactive sensory cells connected these peptidergic nerve nets to the surface of the tentacle. These findings suggest that members of all four cnidarian classes share a common organizational pattern, and it is proposed that this peptidergic innervation may be involved in the chemosensory regulation of cnidocyte discharge. [ABSTRACT FROM AUTHOR]

Previous studies suggest that large body size reduces the risk of predation for acontiate sea anemones. For two species of Metridium, we found significant increases in the length of the acontial threads and in the mean lengths of the unfired acontial nematocyst capsules, with increasing body size. This supports the hypothesis that more damaging acontial defenses protect larger acontiate anemones from their predators. Metridium is planktivorous, and food size does not increase substantially with body size; so we expected smaller increases in nematocyst size for the feeding tentacles. In fact, scaling exponents were significantly smaller for the tentacle nematocysts than for acontial nematocysts of the same types in 3 out of 4 cases. This suggests that nematocyst scaling responds predictably to selection pressure. When specimens of the same size were compared, the non-clonal, subtidal species, M. farcimen, had significantly larger acontial nematocysts than did its clonal congener, M. senile, which lives at the upper tidal limits for major subtidal predators in the northeastern Pacific. Therefore, larger acontial nematocysts may be particularly advantageous where predation levels are high. These data demonstrate that closely related anemone species can be distinguished on the basis of ecologically and functionally relevant differences in nematocyst scaling. [ABSTRACT FROM AUTHOR]

Scaling analysis provides a quantitative method for describing and comparing how qualities of organisms vary as a function of body size. However, cell level phenomena have been notoriously hard to analyze because animal cells and organelles have such irregular shapes. The intracellular cnidae make good models of scaling at the cell level because they are durable and easy to image and measure. The mean length of unfired tentacle cnidae (spirocysts) varies continuously, and reversibly, with body size for three macrophagous anemone species. Significant differences in spirocyst shape and size relative to body mass are related to differences in tissue functions and species ecologies, strongly suggesting that cnida size, shape, and scaling patterns respond to natural selection. Cnida scaling patterns can be treated as features of cnidarian life histories. Spirocyst scaling exponents (slopes of log cnida dimension vs. log body weight) are similar to each other (0.05-0.09) and to reported values for animal somatic cells (0.017-0.17), but are much smaller than reported values for anemone basal diameters (0.30-0.38). I propose, here, a general, mechanical explanation for microscaling of structural secretory cells and their secretions, including the cnidae. Larger bodies require thicker, pliant sheets of sluggishly respiring extracellular support materials such as mesoglea and basement membrane. Thicker mesoglea can support larger, taller epithelial cells, which in turn provide additional maintenance services for these progressively thicker acellular layers. Ultimately, larger, taller cells can secrete and support larger, longer cnidae. [ABSTRACT FROM AUTHOR]

Various comparative studies into the biological activity and relative toxicity of cubozoan venoms have been investigated, in particular the venom from the potentially lethal cubozoan Chironex fleckeri. Efficient and reliable extraction of venom from nematocysts is essential before any research into venom toxicity can be conducted and previous cited methods of extraction have varied greatly, each with their own associated problems. A new standardised technique for the recovery of venom from nematocysts of cubozoans is investigated to decrease the variation displayed between authors due to differing extraction techniques. The use of a mini bead mill beater, as investigated in this trial, allows for the rapid extraction of venom from nematocysts and is devoid of the previously isolated problems experienced with other methods of venom isolation, such as excessive heat build up. [Copyright &y& Elsevier]

The minicollagens found in the nematocysts of Hydra constitute a family of invertebrate collagens with unusual properties. They share a common modular architecture with a central collagen sequence ranging from 14 to 16 Gly-X-Y repeats flanked by polyproline/hydroxyproline stretches and short terminal domains that show a conserved cysteine pattern (CXXXCXXXCXXXCXXXCC). The minicollagen cysteine-rich domains are believed to function in a switch of the disulfide connectivity from intra- to intermolecular bonds during maturation of the capsule wall. The solution structure of the C-terminal fragment including a minicollagen cysteinerich domain of minicollagen-1 was determined in two independent groups by ¹H NMR. The corresponding peptide comprising the last 24 residues of the molecule was produced synthetically and refolded by oxidation under low protein concentrations. Both presented structures are identical in their fold and disulfide connections (Cys²-Cys18, Cys6-Cys14, and Cys10-Cys19) revealing a robust structural motif that is supposed to serve as the polymerization module of the nematocyst capsule. [ABSTRACT FROM AUTHOR]

Specimens of actiniarians from the Gulf of California having a column densely covered with vesicles or verrucae have been attributed to one of three species: Anthopleura dowii, Bunodactis mexicana, or Bunodosoma californica. These three species are difficult to distinguish and are at least partly synonymous: Bunodosoma californica is a pro parte synonym of A. dowii and Bunodactis mexicana is a junior synonym of A. dowii. However, based on anatomy, coloration patterns, types of cnidae in the column, and habitat preferences, I discern three distinct species. I describe specimens attributed to Bunodactis mexicana not belonging to A. dowii as Isoaulactinia hespervolita, n. sp. I redescribe Bunodosoma californica and A. dowii and designate a lectotype for Bunodosoma californica to resolve taxonomic confusion. [ABSTRACT FROM AUTHOR]

Discusses the origins of myxozoans in terms of their phylogenetic relationships and the evolution of their life cycles. Classification of the phylum myxozoa; Myxozoan lineages and evolution of parasitism; Myxozoan polar capsules and cnidarian nematocyst.

The aim of this paper was to focus on the toxinological aspects of microbasic-mastigophore nematocysts isolated from acontia of Aiptasia mutabilis, an Anthozoan collected in the Strait of Messina, by performing hemolytic assay on human, chicken, and rabbit red blood cells in suspension. The hemolytic effects of single isolated nematocysts were achieved by checking the lytic pattern after discharge. Crude extract from a population of isolated nematocysts was obtained by sonication on ice. Hemolysis induced by crude extract was detected spectrophotometrically. The results of the extraction method used show that crude venom that can be obtained is effective in inducing hemolysis of erythrocytes from the different sources. Rabbit erythrocytes in particular seem to be more sensitive to this crude venom. The hemolytic activity is dose-dependent and is inhibited if heated to 70°C. Further investigations will better focus these results leading to venom characterization. [ABSTRACT FROM AUTHOR]

Cnidae have been used in hexacoral taxonomy since 1900 but their value at species-level remains controversial. Data given in descriptions have generally been cnida types, their distribution, and capsule sizes presented as ranges (maxima and minima). More recently, measurements of cnida capsules, treated as populations, have been employed. Sampling cnidae extracted from zooids ranging from buds to full-grown polyps, we have analysed 28 300 random measurements of capsule length and width in 133 samples taken from two colonies of the zoanthid Acrozoanthus australiae , one from Queensland, Australia, and one from Indonesia. Using image analysis we measured large holotrichs, microbasic b -mastigophores and p -mastigophores, basitrichs being absent. Length has a lower coefficient of variation than width. Up to 12% of sample distributions were non-normal, depending on the test employed, but there was no consistent pattern of departure from normality. Sample sizes of 50 are regarded as adequate for the calculation of means and variances but need to be larger (contrary to current practice) for an accurate estimation of range. Moreover, some ranges were asymmetrical with respect to the sample mean. Statistical methods for comparing ranges are lacking, so sample size, mean and a measure of variance must always be included. Capsule sizes often differed significantly along the length of tentacles and filaments; they also showed significant differences between polyps within a colony, sometimes clearly correlated with polyp size. It is suggested (based on size frequency distributions that are right skewed or bimodal) that new buds may contain residual cnidae derived from the parent polyp as well as others that have differentiated in situ . Though length appears to be the most useful capsule descriptor, bivariate (width: length) scattergrams provide a concise summary of capsule size, also displaying cnida type and source. We make several recommendations for future practice. [ABSTRACT FROM AUTHOR]

We have previously reported immunocytochemical, biochemical, behavioral, and electrophysiological evidence for glutamatergic transmission through (±)-α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA)/kainate receptors in hydra. We now report specific localization of the N-Methyl-D-aspartic acid receptor subunit 1 (NMDAR1) in epithelial, nerve, nematocytes, and interstitial cells of hydra. Macerates of tentacle/hypostome pieces of Hydra vulgaris were prepared on agar-coated slides, fixed with buffered formaldehyde/glutaraldehyde, and fluorescently labeled with monoclonal antibodies against mammalian NMDAR1. Negative controls omitted primary antibody. Digital images were recorded and analyzed. Specific localized and intense labeling was found in ectodermal battery cells, other epithelial cells, nematocytes, interstitial cells, and sensory and ganglionic nerve cells, and in battery cells was associated with enclosed nematocytes and neurons. The labeling of myonemes was more diffuse and less intense. In nerve and sensory cells, punctate labeling was prominent on cell bodies. These results are consistent with our earlier evidence for glutamatergic neurotransmission and kainate/NMDA regulation of stenotele discharge. They support other behavioral and biochemical evidence for a D-serine-sensitive, strychnine-insensitive, glycine receptor in hydra and suggest that the glutamatergic AMPA/kainate-NMDA system is an early evolved, phylogenetically old, behavioral control mechanism. [ABSTRACT FROM AUTHOR]

Nudibranchs that feed on cnidarians must defend themselves from the prey's nematocysts or risk their own injury or death. While a nudibranch's mucus has been thought to protect the animal from nematocyst discharge, an inhibition of discharge by nudibranch mucus has never been shown. The current study investigated whether mucus from the aeolid nudibranch Aeolidia papillosa would inhibit nematocyst discharge from four species of sea anemone prey. Sea anemone tentacles were contacted with mucuscoated gelatin probes, and nematocyst discharge was quantified and compared with control probes of gelatin only. Mucus from A. papillosa inhibited the discharge of nematocysts from sea anemone tentacles. This inhibition was specifically limited to the anemone species on which the nudibranch had been feeding, When the prey species was changed, the mucus changed within 2 weeks to inhibit the nematocyst discharge of the new prey species. The nudibranchs apparently produce the inhibitory mucus rather than simply becoming coated in anemone mucus during feeding. Because of the intimate association between most aeolid nudibranchs and their prey, an adaptable mucus protection could have a significant impact on the behavior, distribution, and life history of the nudibranchs. [ABSTRACT FROM AUTHOR]

The Okinawan sea anemone Actineria villosa causes severe cases of stinging. We isolated the 60 kDa A. villosa toxin (AvTX-60A) as the major toxin from the isolated nematocysts of this species. AvTX-60A showed fatal toxicity to mice with intraperitoneal injection at a minimum lethal dose of less than 250 μg/kg. The N-terminal amino acid sequence was determined and the corresponding cDNA encoding AvTX-60A was sequenced. The deduced amino acid sequence of AvTX-60A showed high similarity with PsTX-60A, which had been isolated as one of the major toxins from the venomous sea anemone Phyllodiscus semoni. These sea anemone toxins are new members of the family of proteins containing membrane-attack complex/perforin (MACPF) domains, best known in pore forming proteins such as perforin. These are the first examples of MACPF domain proteins as toxins for prey acquisition or repelling predators in nature. [Copyright &y& Elsevier]

An epidermal growth factor (EGF)-like toxin (gigantoxin I) and two sodium channel toxins (gigantoxins II and III), previously isolated from the sea anemone Stichodactyla gigantea, were cloned for their cDNAs. The precursor protein of gigantoxin I is composed of a signal peptide, propart and mature peptide, similar to those of gigantoxins II and III, and is much simpler in structure than those of mammalian EGFs. In addition, gigantoxin I as well as gigantoxins II and III was demonstrated to be contained in nematocysts, suggesting that gigantoxin I functions as a toxin in S. gigantea. [Copyright &y& Elsevier]

Discharge stimuli and cell structure of polar capsules and cnidae are reviewed for both Cnidaria and Myxozoa. The discharge process in Cnidaria (especially Anthozoa) can be summarized as follows: 1) cnidae can discharge either independently or under the influence of adjacent cells. There are at least three types of cell complexes: one responding to mechanical stimuli, one to mechanical stimuli only after chemosensitization, and another responding to vibrational frequencies. 2) Supporting cells for the complex requiring chemosensitization bear chemoreceptors to mucins, N-acetylated sugars, and certain proteins. Binding of these ligands modifies the length of sensory cilia, sensitizing the cnidocyte to mechanical stimuli. 3) Mechanical stimuli from prey triggers the sensitized cnidocyte and cnidae discharge; spirocyst tubes stick to prey and penetrating nematocysts puncture prey. 4) Body fluids from prey provide additional ligands, further influencing cnidocytes. 5) Venom from nematocyst increases struggling of prey, mechanically triggering more nematocysts. Chemical signaling between cells is reviewed. Discharge in Myxozoa is less studied, but can occur after treatment with strong bases, urea, concentrated hydrogen peroxide, potassium salts, and in some species, mucus. Similarities between Cnidaria and Myxozoa include radial symmetry, development of specialized structures containing inverted, helically coiled filament,; that are sticky and capped with a "stopper," and the filament discharge response of these structures to pressure, potassium ion, and extreme pH. Myxozoans differ from cnidarians in the lack of a nerve net, less cellular organization, different life cycle stages, and in the response to chemosensitizers, neurochemicals, and external Ca&sup2+; removal. [ABSTRACT FROM AUTHOR]

Abstract. Haliclona sp. 628 (Demospongiae, Haplosclerida, Chalinidae), a sponge found on the reef slope below 5 m depth on the Great Barrier Reef, has two unusual characteristics. It contains a symbiotic dinoflagellate, Symbiodinium sp., similar in structure to the dinoflagellate found within Acropora nobilis (S. microadriaticum), and it contains coral nematocysts randomly distributed between the ectosome and endosome and usually undischarged in intact sponge tissue. Given the unusual occurrence of nematocysts in Haliclona sp. 628, the focus of this study was to determine the distribution of this species of sponge on the reef slope at Heron Island Reef in relation to the distribution of potential coral donors. A combination of line and belt transects was used to estimate the abundance of Haliclona sp. 628 and a co-occurring congener, Haliclona sp. 1031, which does not contain nematocysts, at three widely separated sites on the reef slope at Heron Island Reef. The abundance of different types of substratum (sand, sand-covered coral rubble, dead A. nobilis, live A. nobilis, other live coral, and other dead coral) along the transects and the substratum to which each sponge colony was attached were also recorded. Despite the predominance of live A. nobilis and sand-covered rubble at all sites, between 30 and 55% of Haliclona sp. 628 colonies were attached to dead A. nobilis which comprised less than 8% of the available substratum along any transect. In contrast, Haliclona sp. 1031 was found significantly more frequently on other dead corals and less frequently on live A. nobilis than would be expected based on the availability of the different substrata in the sites. Potential explanations to account for the distribution of Haliclona sp. 628 in relation to potential coral donors are discussed. [ABSTRACT FROM AUTHOR]

Nematocysts were isolated from individuals of Calliactis tricolor maintained under different feeding schedules or in different salinities in an attempt to determine how these culture conditions influence the discharge of isolated nematocysts. In addition, the discharge frequencies of nematocysts isolated from two different populations of sea anemones found in two different environments were also compared. Undischarged acontial nematocysts were isolated by extrusion into 1 M sodium citrate and were then treated with 5 mM EGTA to initiate discharge. Nematocysts isolated from anemones maintained under three different feeding schedules showed significantly different responses to the test solution. Nematocysts isolated from anemones maintained in two different salinities did not differ significantly in discharge frequency. Nematocysts isolated from individuals from two separate populations of C. tricolor responded significantly differently to 5 mM EGTA and to deionized water, and these responses also depended upon the isolation solution used. Environmental conditions are known to have an impact on the physiological state of most organisms, but this is the first study providing evidence that the environment or feeding state of an anemone affects discharge of isolated nematocysts. Inherent differences in ionic and osmotic characteristics among nematocysts could explain some of the ambiguities when comparing past studies of isolated nematocyst discharge. [Copyright &y& Elsevier]