Hydroid Polyps Research Articles

Bryozoans in fouling communities on artificial substrates in Kazachya bay of the Black Sea

Study of the formation of fouling communities on artificial substrates is actual due to the development of mariculture in the Black Sea. Some representatives of macrofoulers are able to influence the process of colonization and development of cultivated organisms. Purpose of work. The main tasks of the study are the revealing the peculiarities of the formation of the fouling community on the experimental plates of the various materials in the environment of the Kazachya bay in the Black Sea and the role of bryozoans in the fouling community. Materials and methods. The experimental plates which were made from the different materials (plastic, aluminum, rubber, galvanized iron) were installed in September 2017 at a depth of 5 m in Kazachya bay (Black Sea). The plates were lifted every month during the year, a total of 480 plates were examined. Results. The peculiarities of the formation of the fouling community on the experimental plates of different materials in the Kazachya bay (Black Sea) were studied. Totally, 22 species were found in the macrofouling community formed on the experimental plates in the Kazachya bay during the year, comprising the following 8 taxa: hydroid polyps - 1, barnacles - 1, sea anemones - 1, bryozoans - 4, polychaetes - 4, bivalve mollusks - 1, tunicates - 2, macrophytes - 8. During the year, the succession of the fouling community of the experimental plates developed through the stage of dominance of microorganisms - barnacle Amphibalanus improvisus , and then - bryozoan Cryptosula pallasiana. Conclusion: the bryozoan Cryptosula pallasiana is the dominant species in the fouling community at four to twelve months old at a depth of five meters.

Transposon-derived transcription factors across metazoans.

Transposable elements (TE) could serve as sources of new transcription factors (TFs) in plants and some other model species, but such evidence is lacking for most animal lineages. Here, we discovered multiple independent co-options of TEs to generate 788TFs across Metazoa, including all early-branching animal lineages. Six of ten superfamilies of DNA transposon-derived conserved TF families (ZBED, CENPB, FHY3, HTH-Psq, THAP, and FLYWCH) were identified across nine phyla encompassing the entire metazoan phylogeny. The most extensive convergent domestication of potentially TE-derived TFs occurred in the hydroid polyps, polychaete worms, cephalopods, oysters, and sea slugs. Phylogenetic reconstructions showed species-specific clustering and lineage-specific expansion; none of the identified TE-derived TFs revealed homologs in their closest neighbors. Together, our study established a framework for categorizing TE-derived TFs and informing the origins of novel genes across phyla.

Consortiums «tumbleweeds» of the Amurskii liman

For the first time, the «tumbleweeds» – consortia of the Amur estuary were studied. The determinants of consortia are fragments of brown algae-macrophytes thalli and colonies of hydroid polyps, rolled up into a ball by currents, and the consorts are amphipods inhabiting it. It was show that the reason for the emergence of consortative relationships is the hydrological conditions of the estuary and features of it bottom landscape, under which amphipods are forced to seek shelter. In the diet of the kaluga Huso dauricus and Amur sturgeon Acipenser schrenckii in the Amur Estuary, amphipods were found together with plant remains, which indicates the feeding of sturgeons by consortia. Kaluga, in comparison with the Amur sturgeon, consumes such type food much more often and in greater quantities. Animals associated with the aggregation of dead algae and polyps play a significant role in the formation of the food base for sturgeons in the Amur Estuary.

Green Fluorescence of Cytaeis Hydroids Living in Association with Nassarius Gastropods in the Red Sea.

Green Fluorescent Proteins (GFPs) have been reported from a wide diversity of medusae, but only a few observations of green fluorescence have been reported for hydroid colonies. In this study, we report on fluorescence displayed by hydroid polyps of the genus Cytaeis Eschscholtz, 1829 (Hydrozoa: Anthoathecata: Filifera) found at night time in the southern Red Sea (Saudi Arabia) living on shells of the gastropod Nassarius margaritifer (Dunker, 1847) (Neogastropoda: Buccinoidea: Nassariidae). We examined the fluorescence of these polyps and compare with previously reported data. Intensive green fluorescence with a spectral peak at 518 nm was detected in the hypostome of the Cytaeis polyps, unlike in previous reports that reported fluorescence either in the basal parts of polyps or in other locations on hydroid colonies. These results suggest that fluorescence may be widespread not only in medusae, but also in polyps, and also suggests that the patterns of fluorescence localization can vary in closely related species. The fluorescence of polyps may be potentially useful for field identification of cryptic species and study of geographical distributions of such hydroids and their hosts.

Symmetry in colonies of thecate hydroids (Cnidaria, Hydroidomedusa, Leptomedusae): Transition from radial to bilateral symmetry

Hydroid polyps (Cnidaria, Hydrozoa) are characterized by predominantly radial symmetry. On the basis of the Berking’s model (Berking 2003, 2006), which is based on the positional information and “self-activation and lateral inhibition” hypotheses, transition from radial symmetry of the primary module to bilateral symmetry or glide-reflection symmetry of compound shoots of thecate hydroids (subclass Leptomedusae) is analyzed. It is shown that ordering of three-dimensional structure and changes in the symmetry type are byproduct of mechanisms regulating the developemnt of modular organisms based on the cyclic morphogenesis.

Эстафетный способ перемещения гидроплазмы в колониях гидроидных полипов

In this study, we continued the investigation of the distribution system of colonial hydroids in the course of its development, starting with its emergence during the planula metamorphosis and ending with the formed colony. The hydroplasmic stream system of two species of colonial hydroids--Perigonimus abyssi G.O. Sars, 1874, and Stauridia producta Wright, 1858--was studied. W found that the main principle by which hydroplasma moves in these colonies, which form no shoots, is the relay-race from one hydranth to another through a stolon fragment connecting them or directly from one hydranth to the next one, etc. W show that the efficiency of the conducting (distribution) system does not depend on the level of complexity of the colonial structure. The results of this study confirm the absence of general colonial processes of integration and self-regulation in hydroid polyps.

Shiny spheres of placozoans (Trichoplax) function in anti‐predator defense

Abstract. When individual placozoans, Trichoplax adhaerens, were fed to polyps of the hydroid Podocoryna carnea, the polyps became paralyzed in all 27 trials. In one instance the hydroid polyp died and in five instances a fragment of the placozoan survived. The time to recovery from paralysis varied with the relative size of the polyp and the placozoan. Placozoans were disassociated into separate cells and then reaggregated by centrifugation to produce pellets of tissue lacking the vesicles called shiny spheres, normally abundant in the upper epithelium. We fed pellets of two size classes to the hydroid polyps. When the placozoan pellet was smaller than the hydroid, paralysis was eliminated in nine of ten trials. When the placozoan pellet was comparable in size to the polyp, paralysis occurred but the recovery time was substantially reduced, compared with trials in which polyps were fed intact placozoans possessing shiny spheres. These results support a function of shiny spheres in anti‐predator defense.

Hydrozoan nematocytes send and receive synaptic signals induced by mechano-chemical stimuli

Nematocytes, the stinging cells of Hydrozoa, can be considered as prototypic mechanosensory hair cells bearing a concentric hair bundle, the cnidocil apparatus. These cells produce typical mechanoreceptor potentials in response to deflection of their cnidocil. Here we show that mechanosensory signals are relayed to neighbouring nematocytes via chemical neurotransmission and that nematocytes receive synaptic input from surrounding nematocytes, hair cells and probably from epithelial cells. Intracellular voltage recordings from stenotele nematocytes of capitate hydroid polyps showed two distinct types of responses when other nematocytes within the same tentacle were mechanically stimulated: (i) graded depolarizations of variable duration ('L-potentials'), and (ii) uniform impulse-like, often repetitive depolarizations ('T-potentials') that occurred in correlation with contractions of epitheliomuscular cells. Voltage clamp experiments showed that despite the stereotyped time course of T-potentials, their generation did not involve electrically excitable conductances. Instead, time course, post-stimulus delay, susceptibility to blockers of neurotransmission and gap junctions, and induction by electrical stimulation of other nematocytes indicate that L- and T-potentials are postsynaptic, most likely glutamatergic potentials. Both result from different presynaptic pathways: L-potentials are induced monosynaptically by presynaptic receptor potentials, T-potentials are most likely triggered by presynaptic action potentials propagating through the ectodermal epithelium via gap junctions. Moreover, contact-chemosensory (phospholipid) stimulation of the presynaptic nematocyte is a positive modulator of the nematocyte's afferent synaptic efficacy and of cnidocyst discharge, both triggered by mechanoreceptor potentials. The results reveal that hydrozoan nematocytes act as bimodal sensory cells, signalling coincident chemical and mechanical stimuli indicative of prey, and receive signals from other nematocytes and sensory cells.

Multicellular Redox Regulation in an Early‐Evolving Animal Treated with Glutathione

Redox signaling has emerged as a unifying theme in many seemingly disparate disciplines. Such signaling has been widely studied in bacteria and eukaryotic organelles and is often mediated by reactive oxygen species (ROS). In this context, reduced glutathione (GSH) acts as an important intracellular antioxidant, diminishing ROS and potentially affecting redox signaling. Complementing this cell-level perspective, colonial hydroids can be a useful model for understanding organism-level redox signaling. These simple, early-evolving animals consist of feeding polyps connected by tubelike stolons. Colonies treated exogenously with GSH or reduced glutathione ethyl ester (GEE) were expected to show a morphological change to sheetlike growth typical of low levels of ROS. Contrary to expectations, diminished stolon branching and polyp initiation was observed. Such runnerlike growth is associated with higher levels of ROS, and surprisingly, such higher levels were found in GSH- and GEE-treated colonies. Further investigations show that GSH triggered a feeding response in hydroid polyps, increasing oxygen uptake but at the same time relaxing mitochondrion-rich contractile regions at the base of polyps. Diminished gastrovascular flow and increased emissions of mitochondrial ROS also correlated with the observed runnerlike growth. In contrast to cell-level, "bottom-up" views of redox signaling, here the phenotype may arise from a "top-down" interaction of mitochondrion-rich regions and organism-level physiology. Such multicellular redox regulation may commonly occur in other animals as well.

Autotomy and self-amputation of nerve processes in tissue culture and in vivo

Self-amputation of body appendages, such as severing of the tail by lizards or a leg by long-legged harvestmen (Phalangida), is widespread in nature. This phenomenon is observed in hydroid polyps, actinia, nemertines, annelids, starfishes, mollusks, and crustaceans and is regarded as a physiological protective mechanism [1]. However, the first data on the amputation of neuronal processes [2] were debated, although natural separation of fragments from the nucleus-containing soma and vice versa was described in other cells. The cell fragments separated from megakaryocytes were referred to as platelets [3]. Mammalian erythrocytes separate the nucleus-containing cell fragment and continue to live and function for a long time. Viable cytosomes (cytoplasts) were separated in experiments with the use of cytochalasin in all cells studied [4]. Although self-amputation as a physiological process has not been studied in neurons, we have no doubts that it can be observed in these cells. In this work we studied the autotomy and self-amputation of neurites under normal conditions in cell culture and in vivo. We discovered and analyzed the autotomy of neuronal processes and self-amputation of terminals of nonsynaptic dendrites in the tissue culture and in vivo. It was found that development of both processes is determined by the contractile activity of the processes in combination with adhesion of the terminals to a substrate or to other neurons. We showed that these processes take place continuously during activity of neurons and alternate with protruding growth processes. Self-amputation proceeds by the apocrine mechanism. The data obtained suggest that the dendrites that undergo self-amputation of cytoplasts filled with activated lysosomes have a certain trophic function. The study was performed with the tissue culture of isolated neurons of the pond snail ( Lymnaea stagnalis ). Single neurons were isolated via enzymatic and mechanical processing of the peripharyngeal nerve ring of mature pond snails (for details, see [5]). The cells were cultured for 5‐6 days in a serum-free medium (RPMI-1640 or Eagle’s MEM). The dynamics of regenerating neurons was recorded with an automated microvideoinstallation using time-lapse photography (shooting speed, 1 frame per 10 min) under an inverted phase-contrast microscope (objectives, 20 × , 40 × ; eyepiece, 10 × ). The illustrations are presented as a series of frames from the films. A comparison of the results of in vitro and in vivo studies was performed with the use of Dogel’s type II cells of the enteric plexus of healthy mature cats. The neurons were impregnated according to Bil’shovskii and Gros. The sensor terminals of nonsynaptic dendrites were studied with the use of the conventional electron microscopy.

A Geometro-mechanical Model for Pulsatile Morphogenesis

A model is proposed which imitates the morphogenesis of several species of the lower invertebrate animals, the hydroid polyps and permits the derivation of the geometry (surface curvature) of each developmental stage from that of the preceding stage. The model is based upon two experimentally verified assumptions. First, neighbouring cells are assumed to compress each other laterally in a regular and species-specific pulsatile manner. It is this pressure, and/or an active cell reaction to it, which changes the curvature of a cell layer. Secondly, cell layers are assumed to have quasi-elastic properties tending to smooth out their curvature. With our model, the different pulsatile patterns of cell-cell pressure are reproduced and the elasticity parameters are modulated. As a result, within a large zone of parameter values (a so-called "morphogenetic zone", MZ) realistic shapes of the rudiments are reproduced. The main principles of the model can also be used for interpreting the morphogenesis of other groups of animals. A suggested model emphasizes the self-organizing properties of a "stressed geometry" of embryonic rudiments.

Effects of discharging nematocysts when an eolid nudibranch feeds on a hydroid

The exposure to discharging nematocysts of the eolid nudibranch Cratena peregrina feeding on polyps of the hydroid Eudendrium racemosum was examined. The smaller size-class of microbasic eurytele mastigophor nematocysts is located on the tentacles of the hydroid polyps, while the larger size-class of holotrichous isorhiza nematocysts is located on long cnidophores and basal rings of some polyps. Discharging nematocysts of the tentacles do not appear to have damaging effects on the dorsal appendages of the snail, the cerata. In contrast, contact of a cnidophore with a ceras elicits massive discharge of nematocysts, which results in adherence, membranolysis and local destruction of the epidermis within seconds. The differential locations and effects indicate that the small tentacle nematocysts serve for capturing prey, while the large cnidophore nematocysts serve for the hydroid's defence. Both small and large, discharged and intact nematocysts were found in the pharynx and stomach of the snail after feeding. Thus, the alimentary tract appears to be efficiently protected against discharging nematocysts. Small and large intact nematocysts, which were capable of discharge, were also found in the cnidosacs.

Redescription and biology ofStenothoe brevicornisSars (Amphipoda: Crustacea), an obligate associate of the sea anemoneActinostola callosa(Verrill)

The amphipod Stenothoe brevicornis Sars, 1883 (Crustacea: Amphipoda: Stenothoidae) is redescribed using material from the Tromsø area, northern Norway. It is characterized by a reduced armament of antennae and legs and very small secondary sexual differences. S. brevicornis is an obligate and host-specific associate of the actiniid sea anemone Actinostola callosa (Verrill). The amphipods spend their entire life-cycle among the tentacles of their host and feed mostly on host tissue. A short review of associations involving Stenothoe species is given. Most species live among hydroid polyps or algae, a few i or on sponges, ascidians, hydro-corals, and sea anemones.

Differences in fine-scale structure and composition of zooplankton between mixed and stratified regions of Georges Bank

Transects were made with the Video Plankton Recorder (VPR) in different water masses on the southern flank of Georges Bank in May 1992. CTD-data, chlorophyll fluorescence, and attenuation were measured simultaneously. Images were recorded at a rate of 60 fields per second, as the instrument was towed at 2 m s−1 (4 knots). Tapes from high and low magnification cameras (imaging volumes of 0.62 ml and 33 ml, respectively) were analyzed with respect to the distribution of copepods and other grazers, as well as invertebrate predators. This paper describes the differences in patterns of occurrence of important zooplankters in well-mixed and stratified waters on the Bank and in Slope Water south of these stations. Planktonic taxa were sampled over the same range of scales as the fluorescence and hydrography, allowing direct visual comparisons of the spatial distributions of these variables. Late copepodites of Calanus finmarchicus were strongly concentrated near the surface in the stratified area, while a dense belt of Limacina sp. and Oikopleura sp. occurred below the pycnocline. Other fragile forms were also found to be dominant. Colonies of hydroid polyps were very abundant at the mixed station, especially deeper in the water column, indicating that they may have been transported up from the bottom. Colonies of the diatom Chaetoceros socialis were abundant in the cold bottom water in the stratified region and also in the mixed area. These colonies may have been in the process of sedimenting out of the water column, as similarly sized and shaped marine snow was abundant in the same area. In the Slope Water, acantharia and Trichodesmium were found in the chlorophyll maximum above the pycnocline. Other important genera encountered were: Pseudocalanus, Oithona, Centropages, Obelia, Pleurobrachia and Sagitta. Taxa that occurred in all three areas were often differently distributed with respect to depth and physical parameters, indicating that vernal stratification is an important structuring factor of plankton populations.

X-ray microanalysis of ion contents in vacuoles and cytoplasm of the growing tips of a hydroid polyp as related to osmotic changes and growth pulsations

Growth pulsations (GP) in hydroid polyps are associated with changes in vacuolar patterns which can be imitated by altering external osmolarity. With the use of X-ray spectroscopy we measured the elemental contents in the vacuoles and cytoplasm of the growing tips of a hydroid polyp, Podocoryne carnea, under various tonicity conditions. Under hypertonic condition which arrested the samples at the retraction phase of normal GP, the elemental content within the vacuolar compartment appeared to be similar to that of the external medium, confirming our previous conclusion about the dehermetization of the vacuolar compartment under these conditions. Under hypotonical condition which arrested samples at the extension GP phase (vacuoles isolated) element ratio data displayed an obvious bimodality. At least one of the data groups could be characterized by a significant increase in the concentrations of sodium and potassium, as related to Cl, Ca and Mg, and in comparison to the same ratios in hypotonical samples and those in the external medium. We suggest that under hypotonical conditions the isolated vacuolar compartment is formed by influx of sodium and potassium ions. These cations are accompanied by anions other than chloride. Potassium appears to be transferred into the vacuoles from the cytoplasm while the sodium derives from the external environment.

Cytophysiology of growth pulsations in hydroid polyps

AbstractCell orientation and intercellular changes accompanying growth pulsations (GP) have been studied in the marine hydroids Obelia longissima, O. loveni, and Dynamena pumila with the use of time‐lapse filming, mechanography, optical microscopy, and electron microscopy. The extension phase of the GP was correlated with an increase in cell volume and the rotation of cells to a transverse orientation. Tip cells return to an oblique orientation during the retraction phase via a rapid (about 1 μm/second) distalward sliding of external cell poles. In most samples, a proximodistal wave of transversad cell rotations was observed within a period of 30–90 μm/minutes. In contrast, return to the oblique orientation is almost synchronous. The extension GP phase is correlated with extensive cell vacuolization and the retraction phase with fusion of these vacuoles into elongated channels opening into external space.The extension phase was stabilized in hypotonic medium, isotonic medium with increased NaCl concentration, and by ionic transport inhibitors (which increase cytoplasmic concentration of Na+ and Cl−). GP are arrested in the retraction phase in hypertonic medium, isotonic medium with decreased Na+ and Cl− concentration, and by inhibitors whose decreasing cytoplasmic concentrations of Na+ and Cl− arrest GP in the retraction phase. These data point out the participation of osmotic mechanisms in the regulation of GP.

Numerical simulations of the effects of retinoids on pattern formation in a hydroid.

Retinoids have been shown to influence pattern formation in hydroid polyps (Hydractinia echinata) at various levels. These effects are counteracted by an inhibitor isolated from Hydra. The present study provides a theoretical attempt to elucidate the role of retinoids by computer simulations based on a simple model of pattern formation in Hydractinia. The elements of this model are morphogens of the Gierer-Meinhardt type, namely a long-range inhibitor and a short-range activator. From the calcualtions, a reducing effect of retinoids on the propagation of the inhibitor seems most probable.

Antisera to the sequence Arg-Phe-amide visualize neuronal centralization in hydroid polyps

Antisera to the sequence Arg-Phe-amide (RF-amide) have a high affinity to the nervous system of fixed hydroid polyps. Whole-mount incubations of several Hydra species with RFamide antisera visualize the three-dimensional structure of an ectodermal nervous system in the hypostome, tentacles, gastric region and peduncle. In the hypostome of Hydra attenuata a ganglion-like structure occurs, consisting of numerous sensory cells located in a region around the mouth opening and a dense plexus of processes which project mostly radially towards the bases of the tentacles. In Hydra oligactis an ectodermal nerve ring was observed lying at the border of hypostome and tentacle bases. This nerve ring consists of a few large ganglion cells with thick processes forming a circle around the hypostome. This is the first direct demonstration of a nerve ring in a hydroid polyp.

Retinoids and pattern formation in a hydroid

The retinoids (retinol, retinal, retinoic acid) cause alterations in the pattern of limb elements in vertebrates (Summerbell & Harvey, 1983). As shown here, retinoids also influence pattern specification in hydroid polyps (Hydractinia echinata) in a way suggesting interference with the generation and transmission of signals responsible for the dimension and spacing of structures. A pulse-type application of low doses (e.g. retinoic acid 10(-6) to 10(-10) M, 4 h) causes metamorphosing primary polyps to develop more tentacles but fewer stolons per unit circumference, to shorten the length of the hydranth while the stolon elongates, and to bud secondary hydranths at high frequency 2-3 days after treatment (Fig. 3). Dose-response curves display optimum peaks. It is argued that the increase in budding rate is due to a reduction of the range of spacing signals emitted by the primary hydranth. In regenerating hydranths, low doses (10(-10) to 10(-9) M) improve the rate of head formation, whilst medium doses (10(-8) to 10(-6) M) result in more tentacles being regenerated. However, prolonged treatment with high doses (10(-6) to 10(-5) M) causes the animals to reduce all head structures and to transform eventually into stolons, in contravention of the rule of distal transformation that they normally obey (Fig. 8). The effects of the retinoids are counteracted by a putative morphogen, the endogenous inhibitor isolated from Hydra by Berking (1977). The Hydra-derived 'head-activator' displayed no stimulating effect on the number of tentacles and buds formed.

Ökologische Untersuchungen an Hydroiden des Felslitorals von Santa Marta (Kolumbien)

The ecology of tropic hydroids on the rocky shore of Santa Marta, Colombia, was studied from January 1971 to April 1972. Main interests concentrated on vertical distribution, temporal succession, activity, maturity, population density, shape and growth of colonies, and on type of settlement. These aspects have been related to quantitative data and to variations in biotic and abiotic factors. The results are compared with those obtained on other types of shores, viz. artificial and sandy shores. They indicate that local abiotic differences in water quality are influenced, above all, by the sequence of dry and rainy seasons. In a rapidly changing abiotic environment, life cycles and ontogenetic stages (settlement, growth, maturity) follow each other faster than in a static environment. With increasing water depth, the density of the hydroid populations decreases, while the size of single colonies increases. In addition, with increasing depth, the length of the maturity period increases. For the same species, the time of attainment of maturity may be different in different localities. Hydroid species with short life cycles settle faster than species with long life cycles. Hydroid polyps may counteract environmental perturbations by changes in activity. Distribution and zonation of hydroid populations depend to a high degree on water movement, sun orbit, and shade-spending coastal profiles.