Atrichous Isorhizas Research Articles

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.

Nematocyst discharge in Hydra vulgaris: Differential responses of desmonemes and stenoteles to mechanical and chemical stimulation

The effects of mechanical and chemical stimulation on desmoneme and stenotele discharge in Hydra vulgaris were quantified, in situ, in isolated tentacles and single tentacles with attached hypostomes . Cnidocils of desmonemes and stenoteles were stimulated 24 h after tentacle ablation. Single impacts with maximum calculated forces of 3.7 × 10 − 3 to 3.8 × 10 − 2 Newtons were delivered by piezoelectrically-driven glass capillary probes. Video analysis revealed that desmonemes discharged at forces of 3.7 × 10 − 3 N; stenoteles required forces of 1.9 × 10 − 2 N. Desmonemes not directly stimulated discharged if another desmoneme was adequately stimulated; the effect was carried through to at least two adjacent battery cells. Tentacles responded to desmoneme stimulation, by bending at the stimulation site. These findings imply afferent excitatory pathways between nematocytes onto other nematocytes and myonemes. Locomotory nematocysts (atrichous isorhizas) discharged only in hypostome-attached tentacles contacting a substrate; desmonemes and stenoteles did not discharge during substrate attachment, implying differential neuronal inhibition. At low concentrations, bath-applied mucin, a prey-associated glycosylated protein, lowered desmoneme and stenotele firing thresholds, abolishing the force dose-dependency in stenoteles, and allowing them to discharge at previously below threshold forces. At higher concentrations, mucin inhibited discharge, suggesting an involvement in prey-induced feeding inhibition.

A new species of large and highly contractile hydroid in the genus Candelabrum (Hydrozoa: Anthoathecatae) from southern Oregon, U.S.A.

A new species of hydroid, Candelabrum fritchmanii, is described from Cape Arago, Oregon, U.S.A. Specimens were collected from the intertidal region underneath boulders. This new species' standing with respect to other members of the genus is discussed. The claspers in the blastostylar region of the new species show similarities to the North Atlantic Candelabrum cocksii. However, three specimens had multiple, connected polyps at varying stages of development and the cnidome differs between C. cocksii and the new species, leading to the erection of a new species. The polyp cnidome consists of desmonemes, heteronemes (microbasic mastigophores and homotrichous microbasic euryteles), and stenoteles and the actinula cnidome consists of desmonemes, haplonemes (atrichous isorhizas), and stenoteles. Emendations to the family, subfamily, and genus diagnoses are presented to accommodate these findings. Observations are also presented on actinula development and the ensnaring, predatory feeding behavior of the highly contractile polyp.

Morphogenesis of the atrichous isorhiza, a type of nematocyst, in Hydra observed with a monoclonal antibody.

We produced a monoclonal antibody, AE03, which recognized mucous granules in the basal disk gland cells in Hydra and the secreted mucus with which they stick onto substrate. AE03 also recognized atrichous isorhizas, one of the four types of nematocyst present in tentacles, and their nematoblasts present in the body column. With this monoclonal antibody, we could observe the detailed morphogenesis of the atrichous isorhiza from the beginning of its formation. The elongation and invagination processes of external tubes and correspondence between the external tubes and the thread of discharged nematocysts were confirmed.

Protection of human skin against jellyfish (Cyanea capillata) stings

In tropical and subtropical regions of the world, jellyfish stings cause fatalities by means of venom injecting nematocysts. For nematocyst discharge an adequate combination of chemical and mechanical stimulation is required. In order to test whether skin care products can protect against nematocyst discharge, we tested two sunscreens and one lotion applied to pieces of live human skin and exposed them to Cyanea capillata tentacles. (Test specimens were collected in 1990 along the shore of Romo, Denmark and in the Flensburger Forde.) The fine structure analysis of the cnidom of C. capillata showed a high grade of variation in shape and size. The basic distinctive characteristic for stomocnides and astomocnides, the terminal opening at the tubule tip, could not be found. The identification of spines at the basal tubule of atrichous isorhizas suggested that these should be characterized as basitrichous isorhizas. An association between nematocyst morphology and a special function such as penetration or entanglement was not observed. All nematocyst types penetrated unprotected skin. Parafilm (an inert material) and unprotected skin substrates served as controls. The discharged nematocysts on the skin and Parafilm surfaces were counted using scanning electron microscopy. The percentage of discharged nematocysts on test substance protected skin surfaces ranged from only 7.7 to 38.2%, compared to 100% on the unprotected control skin. In addition to this marked reduction in nematocyst discharge, the relatively few discharged nematocysts on protected skin showed malfunctions, and the injection of venom would have failed because the tubules of the nematocysts did not penetrate the skin. The results indicate a general possibility that human skin may be protected against nematocyst discharge of jellyfish with the application of sunscreen or lotion.

The Electrophysiology of Cnidocytes

ABSTRACT Electrical properties of cnidocytes isolated from the hydroid Cladonema and the scyphomedusa Chrysaora were examined using current- and voltage-clamp recording techniques. The stenoteles of Cladonema produced action potentials when depolarized above 0mV. The inward current that produced the action potential was a Na+ current. These cells also possessed an A-current and a K-current. Atrichous isorhizas from Chrysaora did not spike and did not have any inward currents. All cells examined had K-currents, some had A-currents also. Very few cnidocytes discharged during the course of the recordings, irrespective of the degree to which they were depolarized or hyperpolarized, or the presence or selective blockade of any ionic currents. When discharge did occur it could never be correlated with any obvious electrophysiological event. Recordings from cnidocytes in situ in tentacles of the siphonophore Physalia indicate that these cells do not spike. Their current/voltage relationships were linear. They too did not discharge in response to changes in membrane potential, suggesting that the failure of isolated cnidocytes to discharge cannot be attributed to the isolation procedure.

Ultrastructural observations on prey capture and digestion in the scyphomedusa Aurelia aurita

Aurelia aurita medusae are able to catch their prey with their entire body surface. Catch efficiency in medusae caught in Kiel harbour in May 1985 was found to be highest at the tentacles and lowest at the subumbrella. Surface structures of the medusa as well as the cnidom are described by SEM observations. Microbasic heterotrichous euryteles and atrichous isorhizas were found. Discharged nematocysts on the prey's skin indicate different functions of the two types. The villi in the gastral cavity show a characteristic morphological differentiation that consists of a ciliated distal and a basal area covered by vesicles. Four types of glandular cells were identified by TEM observations. Mucous cell types preferably occur in densely ciliated areas. The presence of serous cells is restricted to the basal region of the gastral villi and gastral cavity where the extracellular predigestion takes place. The time of food passage in young medusae of A. aurita decreases from 19 h at 4°C to 4 h at 22°C.

BIOLOGY OF HYDRACTINIID HYDROIDS. 4. ULTRASTRUCTURE OF THE PLANULA OFHYDRACTINIA ECHINATA

The fine structure of the ectodermal surface of the planula larva of Hydractinia echinata is described and the spatial distribution of cell types quantified. The larval ectoderm contains five cell types: nematocytes, gland cells, epitheliomuscular cells, neurosensory cells, and nerve cells. Nematocytes (atrichous isorhizas and desmonemes) and neurosensory cells are clustered at the tapered posterior end of the larvae. Mucous cells occur over the surface of the planula, but are particularly common at the anterior end. The larva is similar to others described from marine hydroids, except that (a) gland cells display a ring of microvilli emerging from a cavity encircling the cilium and (b) nerve cells appear to lack a cilium.

The structure and function of the nematocysts of Chironex fleckeri Southcott, 1956.

Microbasic p-mastigophores, euryteles of two size groups, holotrichous isorhizas and atrichous isorhizas, comprise the cnidom of Chironex fleckeri, a cubozoan that has been responsible for several human fatalities. In its undischarged state each microbasic mastigophore of C. fleckeri consists of a capsule containing matrix and an inverted tube possessing a smooth-walled butt which is loosely coiled helically and which narrows to form a thread that is tightly coiled helically and markedly pleated. Both butt and thread carry three helices of spines and contain a granular matrix. During discharge, the proximal butt spines form initially a piercing stylet. Granular material from the butt and thread is released prior to the release of capsular material. Each eurytele possesses a tube with a butt composed of three bulbs, the middle bulb bearing long spines. Each holotrichous isorhiza possesses a coiled tube bearing small spines along its length. Each atrichous isorhiza exhibits a tube that is devoid of spines and loosely folded in the undischarged condition. The probable role of each type of nematocyst is inferred from its structure and features that enable the ready separation of the nematocysts of C. fleckeri from those of scyphozoan jellyfish are discussed.

Distribution and dynamics of nematocyte populations in Hydra Attenuata

The distribution and dynamics of the 4 nematocyte populations of Hydra attenuata were investigated. Ninety-seven per cent of all nematocytes, including all 4 types, are mounted in the battery cells of the tentacles. The remaining 3%, including 2 types (stenoteles and holotrichous isorhizas) are mounted in the ectoderm of the body column. Eight-two per cent of all nematocytes are desmonemes; 11%, atrichous isorhizas; 5%, stenoteles; and 2%, holotrichous isorhizas. The density of each nematocyte population increases along the length of the tentacle towards the tip. The percentages of the total nematocytes per quarter of tentacle for each of the 4 quarters starting at the base is 15, 18, 25 and 42% respectively. The turnover time of the nematocyte populations in the tentacles was measured with 2 methods. First, the transit time for a carbon-marked battery cell from the base to the tip of the tentacle was measured. Secondly, the time required to replace the unlabelled nematocytes in the tentacles with [3H]proline-labelled nematocytes was measured. In both cases the time was 7--9 days. Based on these data (distribution and turnover time) a model was constructed for the dynamics of the nematocyte populations in the tentacles. The numbers of nematocytes produced dialy in the body column as predicted by the model are in reasonable agreement with the measured values.

Laboratory observations on the life history of Rhopilema verrilli (Scyphozoa: Rhizostomeae)

The life history of the scyphozoan Rhopilema verrilli is described from the planula to the young medusa stages. Planulae are retained within the gonadal tissue of the medusa until fully developed. On liberation, most planulae set and developed into small scyphistomae within 7 to 10 days. The scyphistoma differs from those of other described species in having an unusually large, clavate manubrium. The only means of asexual reproduction observed in the scyphistoma cultures involved the formation of podocysts. Strobilation was usually of the monodisc variety, although polydics strobilation was not infrequent. The process of strobilation was completed within 7 days at 20°C. Newly liberated ephyrae typically had 8 pairs of lappets, and 8 rhopalia. Ephyral development resembled that of the closely related rhizostome Rhizostoma pulmo. The cnidome of the planula and scyphistoma consisted of atrichous isorhizas (“a” atrichs) and microbasic heterotrichous euryteles, while that of the strobila and ephyra consisted of “a” atrichs, euryteles, and holotrichous haplonemes

OBSERVATIONS ON THREE SPECIES OF JELLYFISHES FROM CHESAPEAKE BAY WITH SPECIAL REFERENCE TO THEIR TOXINS. II. CYANEA CAPILLATA.

1. The human body exhibits little or no response to contact with the tentacles of specimens of Cyanea capillata from Chesapeake Bay. 2. Three types of nematocysts were identified: atrichous isorhizas, holotrichous isorhizas, and heterotrichous microbasic euryteles. 3. The tubes of nematocysts discharged into 2% agar take a sinuous course, often coiling on themselves. Most tubes penetrated less than 350µ. 4. Although faradic shock and FAA caused discharge of nematocysts from living tentacles, they failed to produce discharge of isolated nematocysts. 5. Homogenization of thoroughly washed frozen nematocysts causes rupture, releasing the toxic principle which is a single protein. 6. The LD 50 of the toxin was of the order of magnitude of µg/g of mouse body weight. 7. Mice were unaffected by intraperitoneal injections of washed capsular debris and tubes, or lipids, or of washed undischarged nematocysts in moderately heavy suspensions.

Observations on three species of jellyfishes from Chesapeake Bay with special reference to their toxins. I. Chrysaora (Dactylometra) quinquecirrha.

1. The response of the human body to the toxin of the summer nettle, Chrysaora quinquecirrha, is allergic in nature.2. Four types of nematocysts were identified: atrichous isorhizas; holotrichous i...

On the Functions and Mode of Action of the Nematocysts of Hydra.

Summary.(1) The threshold for discharge in response to mechanical stimulation of the stenoteles and desmonemes of Hydra is lowered by food extracts, in the same way as has been shown by Pantin to occur in sea anemones.(2) The tentacles are attached during locomotion by discharge of the atrichous isorhizas. Food extracts have the effect of inhibiting the discharge of this type of nematocyst. The duration of mechanical stimulation necessary to bring about discharge is greater for atrichous isorhizas than for stenoteles.(3) The holotrichous isorhizas have only been found to be discharged when stimulated by animals which are not normally eaten by Hydra and evoke no feeding reaction. Their threshold is unaffected by food extracts. Their function is concluded to be defensive.(4) Normal feeding and locomotion in Hydra are described, and the relation of the reactions of the nematocysts to chemical and mechanical stimuli in their normal functions is discussed.My thanks are due to Professor H. Munro Fox, F.R.S. in whose laboratory this work was carried out, to Dr. C. F. A. Pantin, F.R.S., for helpful discussions and advice, and to Messrs. George Newnes Ltd., for permission to reproduce fig. 1.