Nematocyst Types Research Articles

Nematocyst Types and Characteristics in the Tentacles of Gershwinia thailandensis and Morbakka sp. (Cubozoa: Carybdeida) from the Gulf of Thailand.

Nematocysts, specialized stinging cells in cnidarians, play a crucial role in both defense and prey capture, containing venomous, coiled tubes within a capsule. While box jellyfish are recognized as a medical threat, information on the nematocysts of species like Gershwinia thailandensis and Morbakka sp. from Thai waters remains sparse. This study explores the types and morphology of nematocysts found in the tentacles of these species using light and scanning electron microscopy. We identified three nematocyst types: club-shaped microbasic p-mastigophores, oval isorhizas, and oval microbasic p-rhopaloids. Notably, significant differences in capsule sizes were observed, especially in the microbasic p-mastigophores and isorhizas. The discharge tubules tapered from the proximal to the distal ends, featuring arrow-shaped spines in a helical pattern. A distinct lancet structure was present in both microbasic p-mastigophores and p-rhopaloids. These findings suggest that variations in nematocyst size and morphology may be linked to evolutionary adaptations, functional roles, and venom toxicity. Further research into venom discharge mechanisms could offer valuable insights into the ecological and medical importance of these cnidarians.

Nematosit pada Tiga Spesies Karang Scleractinia, Acropora formosa, Seriatopora sp, dan Pocillopora damicornis Di Pantai Nirwana Sumatera Barat

This research was carried out in July - August 2022. The location of coral sampling is in the coral reefs of the Nirwana coast, West Sumatra. The objective by conducting this study is to determine the type of nematocysts in the body tissues of corals scleractinia, Acropora formosa, Seriatopora sp, and Pocillopora damicornis. Method to know the types of nematocysts from A. formosa, Seriatopora sp, and P. damicornis were carried out using an Olympus, microscope with x100 objective lens magnification at the Marine Biology Laboratory, Faculty of Fisheries and Marine Science, University of Riau. Of the 25 major types of nematocysts known in the phylum Cnidarian, two types are found in these three species. The results showed that there were two main types of nematocysts, namely holotrichous isorhizas (HI) and micro basic p-mastigophore (MpM). The three coral species, A. formosa, Seriatopora sp, and P. damicornis, of the holotrichous isorhizas (HI) nematocysts type and the micro basic p-mastigophore (MpM) nematocyst, were found in the coral species A. formosa and P. damicornis. The type of nematocyst is thought to be used to attack and kill prey.

Being Safe, but Not Too Safe: A Nudibranch Feeding on a Bryozoan-Associated Hydrozoan

Nudibranchs have a mostly carnivorous diet, and they prey on a wide variety of other animal taxa. Many species, mainly belonging to the Cladobranchia suborder, feed on cnidarians, including member of the class Hydrozoa. Several hydrozoan species display a symbiotic lifestyle, being associated with other benthic invertebrates, including for instance bryozoans, corals, octocorals, and sponges. In our knowledge, no record of nudibranch predation on symbiotic hydrozoans has been reported so far, possibly thanks to the protective action by the host towards its symbiotic hydrozoan. Here, we show the unexpected case of a nudibranch belonging to the recently described species Sakuraeolis marhe (Fernández-Simón and Moles, 2023) feeding on Zanclea sp. 2, a hydrozoan associated with the cheilostome bryozoan Celleporaria sp. This trophic association is confirmed by the presence and storage of the nematocysts into the nudibranch cnidosacs. Moreover, the nudibranch appears to selectively store mostly a single type of nematocyst, that is large size stenotele. The observation here reported represents the first well-documented record of a nudibranch feeding on a symbiotic hydrozoan and the first confirmed case of predation on Zanclea polyps. Moreover, we provide additional genetic information and the first description of the internal anatomy of S. marhe.

Localization of Multiple Jellyfish Toxins Shows Specificity for Functionally Distinct Polyps and Nematocyst Types in a Colonial Hydrozoan.

Hydractinia symbiolongicarpus is a colonial hydrozoan that displays a division of labor through morphologically distinct and functionally specialized polyp types. As with all cnidarians, their venoms are housed in nematocysts, which are scattered across an individual. Here, we investigate the spatial distribution of a specific protein family, jellyfish toxins, in which multiple paralogs are differentially expressed across the functionally specialized polyps. Jellyfish toxins (JFTs) are known pore-forming toxins in the venoms of medically relevant species such as box jellyfish (class Cubozoa), but their role in other medusozoan venoms is less clear. Utilizing a publicly available single-cell dataset, we confirmed that four distinct H. symbiolongicarpus JFT paralogs are expressed in nematocyst-associated clusters, supporting these as true venom components in H. symbiolongicarpus. In situ hybridization and immunohistochemistry were used to localize the expression of these JFTs across the colony. These expression patterns, in conjunction with known nematocyst type distributions, suggest that two of these JFTs, HsymJFT1c-I and HsymJFT1c-II, are localized to specific types of nematocysts. We further interpret JFT expression patterns in the context of known regions of nematogenesis and differential rates of nematocyst turnover. Overall, we show that JFT expression patterns in H. symbiolongicarpus are consistent with the subfunctionalization of JFT paralogs across a partitioned venom system within the colony, such that each JFT is expressed within a specific set of functionally distinct polyp types and, in some cases, specific nematocyst types.

Venom system variation and the division of labor in the colonial hydrozoan Hydractinia symbiolongicarpus.

Cnidarians (jellyfish, hydroids, sea anemones, and corals) possess a unique method for venom production, maintenance, and deployment through a decentralized system composed of different types of venom-filled stinging structures called nematocysts. In many species, nematocyst types are distributed heterogeneously across functionally distinct tissues. This has led to a prediction that different nematocyst types contain specific venom components. The colonial hydrozoan, Hydractinia symbiolongicarpus, is an ideal system to study the functional distribution of nematocyst types and their venoms, given that they display a division of labor through functionally distinct polyps within the colony. Here, we characterized the composition and distribution of nematocysts (cnidome) in the different polyp types and show that the feeding polyp (gastrozooid) has a distinct cnidome compared to the reproductive (gonozooid) and predatory polyp (dactylozooid). We generated a nematocyst-specific reporter line to track nematocyst development (nematogenesis) in H. symbiolongicarpus, and were able to confirm that nematogenesis primarily occurs in the mid-region of the gastrozooid and throughout stolons (tubes of epithelia that connect the polyps in the colony). This reporter line enabled us to isolate a nematocyst-specific lineage of cells for de novo transcriptome assembly, annotate venom-like genes (VLGs) and determine differential expression (DE) across polyp types. We show that a majority of VLGs are upregulated in gastrozooids, consistent with it being the primary site of active nematogenesis. However, despite gastrozooids producing more nematocysts, we found a number of VLGs significantly upregulated in dactylozooids, suggesting that these VLGs may be important for prey-capture. Our transgenic Hydractinia reporter line provides an opportunity to explore the complex interplay between venom composition, nematocyst diversity, and ecological partitioning in a colonial hydrozoan that displays a division of labor.

Revealing hidden diversity among upside-down jellyfishes (Cnidaria: Scyphozoa: Rhizostomeae:

Morphological variability within Cassiopea is well documented and has led to inaccuracies in the establishment of species boundaries in this taxon. Cassiopea medusae specimens from the Western Pacific (Japan and the Philippines) were analysed using multiple lines of complementary evidence, including types of cnidae, macro-morphology and molecular data. These observations lead to the recognition of two distinct species: Cassiopea mayeri, sp. nov. and a previously synonymised variety now raised to species level (Cassiopea culionensis, stat. nov.). These species can be distinguished from each other using morphological features. Herein, sexually dimorphic traits are included for the first time in the descriptions of Cassiopea species. Nematocyst types not previously observed in the genus are also reported. Molecular analyses, based on individual and combined markers (16S + cytochrome c oxidase I, COI), also support two distinct species; they are not sister taxa, and both are nested together within a clade of other Cassiopea members from the Australian and Indo-Pacific regions. Species richness is underestimated in the Western Pacific region, and integrative approaches are helpful to reveal and describe species. The systematics of Cassiopea is far from completely understood, but the present study represents an important further step. http://www.zoobank.org/References/B1A66787-009D-4465-954A-412C6878FCB4.

Venoms for all occasions: The functional toxin profiles of different anatomical regions in sea anemones are related to their ecological function.

The phylum Cnidaria is the oldest extant venomous group and is defined by the presence of nematocysts, specialized organelles responsible for venom production and delivery. Although toxin peptides and the cells housing nematocysts are distributed across the entire animal, nematocyte and venom profiles have been shown to differ across morphological structures in actiniarians. In this study, we explore the relationship between patterns of toxin expression and the ecological roles of discrete anatomical structures in Telmatactis stephensoni. Specifically, using a combination of proteomic and transcriptomic approaches, we examined whether there is a direct correlation between the functional similarity of regions and the similarity of their associated toxin expression profiles. We report that the regionalization of toxin production is consistent with the partitioning of the ecological roles of venom across envenomating structures, and that three major functional regions are present in T.stephensoni: tentacles, epidermis and gastrodermis. Additionally, we find that most structures that serve similar functions not only have comparable putative toxin profiles but also similar nematocyst types. There was no overlap in the putative toxins identified using proteomics and transcriptomics, but the expression patterns of specific milked venom peptides were conserved across RNA-sequencing and mass spectrometry imaging data sets. Furthermore, based on our data, it appears that acontia of T.stephensoni may be transcriptionally inactive and only mature nematocysts are present in the distal portions of the threads. Overall, we find that the venom profile of different anatomical regions in sea anemones varies according to its ecological functions.

KOMPOSISI NEMATOSIT KARANG FUNGIA, Cycloseris vaugani DARI TERUMBU KARANG PANTAI MALALAYANG, MANADO

The purpose of this study was to determine the composition of nematocysts in the body tissue of the coral fungia, C. vaugani. The location for the collection of C. vaugani colonies was on the coral reefs of the Malalayang coastal area, Manado. This research was carried out in September - December 2020. The observation of nematocysts of C. vaugani was carried out using an Olympus CX41 microscope with a magnification of x100 objective lens which connected to a computer monitor equipped with an optical view 7 application at the Fish Health Environment and Toxicology Laboratory, Faculty of Fisheries and Marine Science, UNSRAT. The present results showed that C. vaugani had a composition of nematocysts, namely type I microbasic p-mastigophore (MpM-I) of 40.00%, small type II microbasic p-mastigophore (sMpM-II) of 31.11%, small holotrichous isorhizas (sHI) of 24.44 %, large type II microbasic p-mastigophore (lMpM-II) of 2.22%, and large holotrichous isorhizas (IHI) of 2.22%. sMpM-II is the most dominant nematocyst type of C. vaugani and this type of nematocyst is thought to be used by coral for aggression and killing prey or predator if there is disturbance from the surrounding aquatic environment where the coral lives. Further research is recommended to study the types and morphology of nematocyst from various species of coral fungia, including C. vaugani to understand the differences in their types and dimension of the nematocyst. Keywords: Composition, Cycloseris vaugani, Fungia, Manado, nematosit

NEMATOSIT KARANG Montipora undata (SCLERACTINIA) DARI PANTAI MALALAYANG TELUK MANADO

The aim of this study was to know the nematocysts composition of Montipora undata (Scleractinia) which was collected in the Malalayang coastal coral reef, Manado Bay. This research was conducted for three months, from October to December 2020. Observation of nematocysts was done under an Olympus CX41 microscope with a magnification of x100 objective lens connected to a computer equipped with the application of Optica view 7 at the Laboratory of Fish Health, Environment and Toxicology, Faculty of Fisheries and Marine Sciences, UNSRAT. The results showed that M. undata had the main nematocyst composition, namely microbasic b-mastigophore (MbM) of 60.0 %, small microbasic p-mastigophore type II (sMpM-II) 26.67 %, small holotrichous isorhiza (sHI) 6 ,67 %, large holotrichous isorhiza (lHI) 4.44 %, and large microbasic p-mastigophore type II (lMpM-II) 2.22 %. MbM is the dominant type of nematocyst for this coral species. Further studies are suggested to investigate the function of MbM and morphology of nematocysts of various types of corals in the genus Montipora.Keywords: Composition, Manado Bay, Montipora undata, nematocyst, Scleractinia

KOMPOSISI TIPE NEMATOSIT KARANG SCLERACTINIA, Pocillopora sp. DARI TERUMBU KARANG PANTAI TONTAYUO, BATUDAA PANTAI, GORONTALO

The objective of this present study is to know the composition of nematocyst types from the coral Scleractinia, Pocillopora sp. The coral colonies of Pocillopora sp. were collected at Tontayuo coastal coral reefs, Batudaa Pantai, Gorontalo. This research was conducted for 3 months, from September-December 2020. The method of testing the type and composition of nematocysts was carried out using an Olympus CX41 type microscope with x100 objective lens magnification connected to a computer ST24 monitor equipped with optical view 7 application (software). Photos of Pocillopora sp. both alive and skeleton form are documented in this journal. The results of the current study showed that Pocillopora sp. has the types and composition of MpM of 91.49%, while HI is 8.51%. MpM is the dominant nematocyst in Pocillopora sp. Future research is recommended to identify this coral at the species level and to study more deeply the various coral species in the genus Pocillopora based on the types and morphology of nematocysts that are useful in the taxonomy of Scleractinia corals.Keywords: Gorontalo, HI, MpM, nematocyst, Pocillopora sp., Scleractinian coral

Cnidome and Morphological Features of Pelagia noctiluca (Cnidaria: Scyphozoa) Throughout the Different Life Cycle Stages

Pelagia noctiluca is considered the most important jellyfish in the Mediterranean Sea, due to its abundance and the severity of its stings. Despite its importance in marine ecosystems and the health problems caused by its massive arrival in coastal areas, little is known about its early life stages and its cnidome has never been described. This study of the morphological and anatomical features throughout the life cycle identifies four early stages: two ephyra and two metaephyra stages. Ephyra stage 1, newly developed from a planula, has no velar canals, gastric filaments or nematocyst batteries. Ephyra stage 2, has velar canals, a cruciform-shaped manubrium and gastric filaments. Metaephyra stage 3 has eight tentacle buds and nematocyst clusters for the first time. Lastly, in metaephyra stage 4, the eight primary tentacles grow nearly simultaneously, with no secondary tentacles. Complete nematocyst battery patterns gradually develop throughout the later life stages. Four nematocyst types are identified: a-isorhiza, A-isorhiza, O-isorhiza and eurytele. Of these, a-isorhiza and eurytele are the most important throughout the entire life cycle, while A-isorhiza and O-isorhiza have a more important role in advanced stages. All nematocysts show a positive correlation between increasing capsule volumes and increasing body diameter of the ephyrae, metaephyrae, young medusae and adult medusae. In the early stages, the volumes of euryteles in the gastric filaments are larger than those in the exumbrella, indicating that the capsule volume is critical in the absence of marginal tentacles, specialized for feeding. This study provides updated information, the most extensive description to date, including high-resolution photographs and schematic drawings of all the developmental stages in the life cycle of P. noctiluca. Additionally, the first cnidome characterization is provided for each stage to facilitate accurate identification of this species when collected in the water column, and to raise awareness of the potential for human envenomation.

The myxozoan minicollagen gene repertoire was not simplified by the parasitic lifestyle: computational identification of a novel myxozoan minicollagen gene

BackgroundLineage-specific gene expansions represent one of the driving forces in the evolutionary dynamics of unique phylum traits. Myxozoa, a cnidarian subphylum of obligate parasites, are evolutionarily altered and highly reduced organisms with a simple body plan including cnidarian-specific organelles and polar capsules (a type of nematocyst). Minicollagens, a group of structural proteins, are prominent constituents of nematocysts linking Myxozoa and Cnidaria. Despite recent advances in the identification of minicollagens in Myxozoa, the evolutionary history and diversity of minicollagens in Myxozoa and Cnidaria remain elusive.ResultsWe generated new transcriptomes of two myxozoan species using a novel pipeline for filtering of closely related contaminant species in RNA-seq data. Mining of our transcriptomes and published omics data confirmed the existence of myxozoan Ncol-4, reported only once previously, and revealed a novel noncanonical minicollagen, Ncol-5, which is exclusive to Myxozoa. Phylogenetic analyses support a close relationship between myxozoan Ncol-1–3 with minicollagens of Polypodium hydriforme, but suggest independent evolution in the case of the myxozoan minicollagens Ncol-4 and Ncol-5. Additional genome- and transcriptome-wide searches of cnidarian minicollagens expanded the dataset to better clarify the evolutionary trajectories of minicollagen.ConclusionsThe development of a new approach for the handling of next-generation data contaminated by closely related species represents a useful tool for future applications beyond the field of myxozoan research. This data processing pipeline allowed us to expand the dataset and study the evolution and diversity of minicollagen genes in Myxozoa and Cnidaria. We identified a novel type of minicollagen in Myxozoa (Ncol-5). We suggest that the large number of minicollagen paralogs in some cnidarians is a result of several recent large gene multiplication events. We revealed close juxtaposition of minicollagens Ncol-1 and Ncol-4 in myxozoan genomes, suggesting their common evolutionary history. The unique gene structure of myxozoan Ncol-5 suggests a specific function in the myxozoan polar capsule or tubule. Despite the fact that myxozoans possess only one type of nematocyst, their gene repertoire is similar to those of other cnidarians.

A new macromedusa from the coast of Mozambique: Aurelia mozambica sp. nov. (Scyphozoa: Ulmaridae).

A new species of the cosmopolitan jellyfish genus Aurelia is described from the coastal waters of Mozambique using a combination of morphological, meristic and genetic information (COI and 18S). The species can be separated from congeners that have been recently described by a combination of bell shape, number of canal origins and anastomoses, and the shape of the manubrium and oral arms. Three types of nematocysts are present in the tissues of both the bell margin and oral arms, and this description of the cnidome will allow for future comparison. Pairwise genetic comparisons showed a mean COI divergence of 4.8% within the group, and a mean divergence ranging between 15% and 22% with all other species of Aurelia.

The Evolutionary History of Siphonophore Tentilla: Novelties, Convergence, and Integration.

Synopsis Siphonophores are free-living predatory colonial hydrozoan cnidarians found in every region of the ocean. Siphonophore tentilla (tentacle side branches) are unique biological structures for prey capture, composed of a complex arrangement of cnidocytes (stinging cells) bearing different types of nematocysts (stinging capsules) and auxiliary structures. Tentilla present an extensive morphological and functional diversity across species. While associations between tentillum form and diet have been reported, the evolutionary history giving rise to this morphological diversity is largely unexplored. Here we examine the evolutionary gains and losses of novel tentillum substructures and nematocyst types on the most recent siphonophore phylogeny. Tentilla have a precisely coordinated high-speed strike mechanism of synchronous unwinding and nematocyst discharge. Here we characterize the kinematic diversity of this prey capture reaction using high-speed video and find relationships with morphological characters. Since tentillum discharge occurs in synchrony across a broad morphological diversity, we evaluate how phenotypic integration is maintaining character correlations across evolutionary time. We found that the tentillum morphospace has low dimensionality, identified instances of heterochrony and morphological convergence, and generated hypotheses on the diets of understudied siphonophore species. Our findings indicate that siphonophore tentilla are phenotypically integrated structures with a complex evolutionary history leading to a phylogenetically-structured diversity of forms that are predictive of kinematic performance and feeding habits.

First record of Salacia tetracythara Lamouroux, 1816 (Hydrozoa, Sertulariidae) as an alien hydroid for the Atlantic Ocean

We present here the first record of Salacia tetracythara as an alien species for the Atlantic Ocean, specifically the coast of the state of Sergipe, northeast Brazil. The species was found attached to an artificial experimental plate installed in the rainy period (July-October 2017), in an estuarine region of the Sergipe River near the Sergipe Harbour. Salacia tetracythara is characterized by a small triangular space below each hydrotheca and two types of microbasic mastigophore nematocysts that differ in shape, size, and location. The species was described from Australia and has been recorded only for tropical to temperate regions of the Indo-Pacific. Salacia tetracythara seems to be a recent introduction into the Atlantic Ocean and, its introduction probably derived from ship transport between the Sergipe Harbour and regions of Oceania and/or Asia. Further investigation should be conducted to determine whether the species is established in the region and how far inside the estuary it has gone.

Updated descriptions of the nematocysts of the scyphozoan jellyfish Cyanea nozakii Kishinouye, 1891 (Cnidaria, Scyphozoa)

Nematocysts are typical cnidarian organelles that can discharge and release venom under physicochemical stimuli for predation and defense. Cyanea nozakii Kishinouye, 1891, a dominant jellyfish-blooming species in Chinese coastal waters, possesses numerous stinging nematocysts on its tentacles, and causes many envenomations every year. However, detailed taxonomic information of nematocysts in C. nozakii is elusive. In the present study, the morphological characteristics of nematocysts from C. nozakii were examined by combined light and scanning-electron microscopy. Five nematocyst types were revealed in the cnidome of C. nozakii, including common nematocyst types identified in Scyphozoa: atrichous isorhizas (a-atrich/O-atrich), microbasic euryteles, and microbasic birhopaloids type II. Importantly, two seldom reported types, microbasic b-mastigophores and microbasic birhopaloids type I, were also found, for the first time, in the cnidome of C. nozakii. This study contributes to understanding of the cnidome of C. nozakii, and the present study strongly suggests that the nematocysts of Scyphozoa are more diverse and complex than previously reported, which sheds new light on the nematocyst types in Scyphozoa species.

Differences in the cnidomes and toxicities of the oral arms of two commercially harvested rhizostome jellyfish species in Thailand

AbstractIn Thailand, two species of rhizostome jellyfish, Rhopilema hispidum and Lobonemoides robustus, are commercially harvested. The cnidomes, nematocyst size and toxicities were compared between these species. Rhopilema hispidum and L. robustus each had four types of nematocysts on their oral arms. For R. hispidum, these nematocyst types included two types of isorhiza and two types of rhopaloid, while in L. robustus, there were three types of isorhiza and one type of rhopaloid. For R. hispidum, tubule lengths of the largest nematocyst type (large round isorhiza; mean ± SD = 313.8 ± 62.2 μm) were significantly longer than those of L. robustus (large ellipsoid rhopaloid; 162.1 ± 38.5 μm). Using the freshwater shrimp, Palaemon paucidens, in a bioassay, we determined that the lethal nematocyst concentrations for R. hispidum and L. robustus were 5705.3 ± 1118.1 and 3408.3 ± 1032.9 unit g−1 wet weight, respectively, and that these concentrations were significantly higher in the former than in the latter.

Nematocyst types and venom effects of Aurelia aurita and Velella velella from the Mediterranean Sea

Natural substances produced by venomous marine organisms are thought to be possible sources of useful compounds and new drugs having the potential to open new ways for pharmacology, nutrition and environmental applications. In this framework, cnidarians are very interesting being widely distributed and all are venomous organisms; so, a deep knowledge of their occurrence, morphology of venomous structures and of effects of venoms at cellular level is fundamental to evaluate the possible utilization of venomous compounds or extracts. In this research, the morphology and occurrence of nematocysts in two cnidarian species (Aurelia aurita, Velella velella), and the preliminary evaluation of the cytotoxicity of V. velella crude extract, of which cytotoxicity on cell cultures at present is unknown, were considered. The specimens were sampled in Güllük Bay, Southwestern coast of Turkey, and in the Gulf of Genova, Northwestern coast of Italy. Six nematocyst types (a-isorhiza, A-isorhiza, O-isorhiza, eurytele, polyspiras, birhopaloid) having different sizes, were observed in A. aurita, and two types (eurytele and stenotele) in V. velella. The crude extract from V. velella showed cytotoxic activity against cultured fibroblasts L929 at high doses, while inducing cell proliferation at low doses. The protein content in the extract increased remarkably after disruption of nematocysts.

Hydra nematocysts in the flatworm Microstomum lineare: in search for alterations preceding their disappearance from the new host.

Nematocysts are characteristic organelles of the phylum Cnidaria. The free-living Platyhelminth Microstomum lineare preys on Hydra oligactis and sequesters nematocysts. All nematocyst types become phagocytosed without adherent cytoplasm by intestinal cnidophagocytes. Desmoneme and isorhiza nematocysts disappear within 2days after ingestion whereas cnidophagocytes containing the venom-loaded stenotele nematocysts migrate out of the intestinal epithelia through the parenchyma to the epidermis. Epidermally localized stenoteles are still able to discharge suggesting that this hydra organelle does preserve its physiological properties. Three to four weeks after ingestion, the majority of stenoteles disappear from M. lineare. To search for alterations of nematocysts that might precede their disappearance, flatworms were stained with acridine orange, a dye that binds to poly-γ-glutamic acid present in hydra nematocysts. The staining properties of all three nematocyst types were indistinguishable during the first 60min after ingestion of hydra tissue whereas 15h later, the majority of desmoneme and isorhiza had lost their stainability in striking contrast to stenoteles. In M. lineare inspected 2, 4 and 10days after feeding, 20-40% of stenoteles had lost their stainability with acridine orange. Non-stained stenoteles had sizes similar to their stained counterparts but some of them were slightly deformed. The presented data indicate that acridine orange staining allows the detection of early alterations of all three ingested nematocyst types preceding their disappearance from M. lineare. Furthermore, they support the notion that the transport of venom-loaded stenoteles to the epidermis provides a strategy of excretion.

The cnidome of Olindias muelleri (Cnidaria: Hydrozoa: Limnomedusae) from South Adriatic Sea

Olindias muelleri is a hydromedusa distributed in the Mediterranean Sea and tropical Atlantic Ocean. Although this species is frequently reported in the Mediterranean Sea and its sting can cause serious human health problems, no data are currently available on its nematocysts. Therefore, the aim of the present investigation is to provide the description of its cnidome. Three types of nematocysts (microbasic b-mastigophores, pseudostenoteles and microbasic euryteles) and two unidentified types were identified in O. muelleri hydromedusa. For each nematocysts type, the location and abundance were recorded from tentacles, bell margin and manubrium. The three types of nematocysts identified in O. muelleri match with the types observed in the Brazilian Olindias sambaquiensis, the only species of the same genus for which information about the cnidome is available. However, the two species are clearly distinguished in terms of nematocyst size and location. No nematocysts have been observed in the exumbrella and subumbrella of O. muelleri, indicating that only its tentacles, bell margin or manubrium are responsible of envenomation, while the contact with all structures of O. sambaquiensis could be stinging. In addition, the unidentified medium-size capsules represent a character exclusive of O. muelleri.