Hydra Oligactis Research Articles

Chronic exposure of Brown (Hydra oligactis) and green Hydra (Hydra viridissima) to environmentally relevant concentrations of pharmaceuticals

Low concentrations of pharmaceuticals in the environment (ng/L to μg/L) are an environmental concern. We used the invertebrates, Hydra oligactis and Hydra viridissima, as freshwater models for primary toxicity testing to study effects of chronic low concentrations of pharmaceuticals in the environment. H. oligactis were exposed to three concentrations (0.1, 1.0 and 10 μg/L) of either fluoxetine, carbamazepine, or triclosan; H. viridissima were exposed to three concentrations (0.1, 1.0 and 10 μg/L) of triclosan. Ecologically relevant endpoints including morphology, budding rate, feeding behaviour, and regenerative capacity were examined during the 14 days exposure period. The interstitial:epithelial stem cell ratios was also examined in H. oligactis. There were no significant effects on the morphology, budding rate and feeding behaviour of the H. oligactis across all concentrations of fluoxetine, carbamazepine, and triclosan. However, regenerative capacity significantly decreased in comparison to the controls when H. oligactis was exposed to 10 μg/L of triclosan and fluoxetine, although there was no significant difference when exposed to carbamazepine. Neither fluoxetine nor carbamazepine treatment altered stem cell ratios. Exposure to triclosan at any concentration did not impact H. viridissima morphology, budding rate, regeneration or feeding behaviour. These results show there are limited effects in Hydra after exposure to chronic, low concentrations of fluoxetine, carbamazepine, and triclosan, except for regeneration in H. oligactis. These endpoints can be used effectively (and cost effectively) to study the effects of environmentally relevant concentrations of pharmaceuticals in Hydra species.

The diversity of the Baikal lineage of Hydra oligactis Pallas, 1766: molecular and morphological evidence.

In this paper, molecular analyses of Baikal hydras from the ‘oligactis group’, based on COI and ITS1–5.8S–ITS2, and morphological analysis of their holotrichous isorhizas, were performed. Low genetic diversity and shared haplotypes were found between Hydra oligactis Pallas, 1766 and Hydra baikalensis Swarczewsky, 1923 specimens, which is evidence of the mixing of these lineages. Genetic distances among all Baikal hydras (0.006) were less than the interspecific distances of other hydras. The size of hydras and proportions of their holotrichous isorhizas varied depending on microhabitat and environmental conditions. Our combined molecular and morphological approach proves that H. baikalensis is synonymous with H. oligactis

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 diversity of hydras (Cnidaria: Hydridae) in the Baikal region

We have studied the fauna of Hydra the waters of the Baikal region using morphological and molecular genetic methods. By the external morphological features of the structure of the polyp and the microscopic study of nematocysts, we have identified four species belonging to three different genetic groups: “oligactis group” (Hydra oligactis, H. oxycnida), “braueri group” (H. circumcincta) and “vulgaris group” (H. vulgaris). Molecular phylogenetic analysis has confirmed the species status of the hydras studied. The intraspecific genetic distances between the Baikal and European hydras are 1.5–4.2% and 0.4–2.7% of the substitutions in COI and ITS1–5.8S–ITS2 markers, respectively, while, interspecific distances for different species significantly exceed intraspecific and amount to 9.8−16.1% and 6.4−32.1% of substitutions for the markers COI and ITS1–5.8S–ITS2, respectively. The temperature regime of the water and the availability of food resources, which play a key role in the reproduction of hydras, determine the habitats of the identified species. The research performed has replenished the regional fauna with species whose findings were previously considered presumptive or doubtful. The first record of H. vulgaris in the artificial reservoir near the Angara River (Lake Kuzmikhinskoye) will help to clarify the distribution of this species.

Observaciones ecológicas, corológicas y taxonómicas de hídridos dulceacuícolas (Cnidaria, Hydrozoa: Hydridae) en la Cuenca del Duero

Se describe la presencia de cuatro taxones de hidras de agua dulce (Cnidaria, Hydrozoa: Hydridae) en zonas someras epicontinentales de la cuenca del Duero (NO de España). En la subcuenca del Tera se encontraron individuos aislados sobre macrófitos sumergidos de tres taxones: Hydra vulgaris Pallas, 1766, Hydra (Pelmatohydra) oligactis Pallas, 1766 e Hydra (Chlorohydra) viridissima Pallas, 1766, y además en el Carrión grupos coloniales sobre bloques de cuarcita de la forma H. vulgaris var. aurantiaca Ehrenberg, 1838. En todos los casos se corresponde con ecosistemas de media montaña de aguas frías, transparentes y oligotróficas, de pH ligeramente ácido y con escasa mineralización. Todas las especies fueron localizadas en simpatría estricta, aunque en el lago de Sanabria se pudo citar tres taxones en diferentes hábitats. Se documenta la predación en cautividad de H. oligactis sobre gusanos oligoquetos y los periodos de formación de pólipos por gemación.

Reproductive mode, stem cells and regeneration in a freshwater cnidarian with postreproductive senescence

Abstract In many basal metazoans, both somatic and reproductive functions are performed by cellular derivatives of a single multipotent stem cell population. Reproduction can drain these stem cell pools, imposing a physiological cost with subsequent negative effects on somatic maintenance functions. In the freshwater cnidarian Hydra oligactis, both asexual (budding) and sexual reproductive modes (production of resting eggs) are present, and both of these are dependent on a common pool of interstitial stem cells. Resting eggs tolerate harsh abiotic conditions which neither the parental animals, nor asexual offspring can survive (e.g., freezing). Therefore, when facing unfavourable conditions and increased mortality risk, hydra polyps are expected to show higher level of differentiation of interstitial stem cells into germ cells (i.e., sexual reproduction) than other cell types needed for self‐maintenance or asexual reproduction. Here, by comparing sexually and asexually reproducing individuals to nonreproductives, we studied the physiological costs of reproduction (size of interstitial stem cell pools, their somatic derivatives and regeneration rate, which is dependent on these cell types) in H. oligactis polyps from a free‐living Hungarian population prior to the onset of winter. Sexual individuals were characterized by significantly smaller interstitial stem cell pools, fewer nematoblasts involved in food capture and lower regeneration ability compared to nonreproductives, but asexuals did not differ from nonreproductive animals. We also found a negative correlation between germ cell counts and stem cell numbers in males (but not in females). We suggest that the lower numbers of these cell types and lower regenerative ability in sexual individuals reflect a somatic cost of sexual reproduction. Our results also suggest that increased differentiation of stem cells into gametes might limit investment into somatic functions in hydra polyps. Exhaustion of cellular resources (stem cells) could be a major mechanism behind the extreme postreproductive senescence observed in this species. A plain language summary is available for this article.

Organelle survival in a foreign organism: Hydra nematocysts in the flatworm Microstomum lineare

Nematocysts are characteristic organelles of the phylum cnidaria. They are designated kleptocnidae when sequestered in animals that feed on cnidaria. Kleptocnidae are known for more than a century. Nevertheless it is still enigmatic how selected nematocyst types survive in the predator and how they reach their final destination in the foreign body. In the free-living Platyhelminth Microstomum lineare the fate of nematocysts of the prey Hydra oligactis was analyzed at the ultrastructural level and by fluorescence microscopy using hydra polyps that had been stained in vivo with the fluorescent dyes TROMI and TRITC. M. lineare digested hydra tissue in its intestine within 30 min and all nematocyst types were phagocytosed without adherent cytoplasm by intestinal cnidophagocytes. Desmoneme and isorhiza nematocysts were digested whereas cnidophagocytes containing the venom-loaded stenotele nematocysts started to migrate out of the intestinal epithelia through the parenchyma to the epidermis thereby traversing the subintestinal and subepidermal muscle layer. Within one to two days, M. lineare began to form a muscle layer basolateral around epidermal cnidophagocytes. Epidermal stenoteles survived in M. lineare for at least four weeks. The ability of epidermal stenotele nematocysts to discharge suggest that this hydra organelle preserved its physiological properties in the new host.

Phytophilous Fauna of a Small and Artificial Urban Lake

Abstract Phytophilous community on Myriophyllum spicatum was studied in a small artificial urban lake in the city of Osijek (eastern Croatia), during the spring and summer season in 2010. In the eutrophic conditions, macrophyte stands were well developed and in the formed periphyton representatives of the following invertebrate taxa were found: Hydrozoa, Nematoda, Gastropoda, Cladocera, Copepoda, Insecta larvae - including families Chironomidae and Coleoptera. They displayed differences in temporal abundance patterns. Two separate phases in macrophyte colonization with differences in invertebrate composition and abundance were recorded. Insect larvae, particularly Chironomidae, were most abundant in the first phase, through the spring period, and Hydra oligactis (brown hydra) was most abundant in the second phase, i.e. summer period. Concurrently, microcrustacean abundance declined towards the end of the summer. Results of the analyses indicated that water temperature and perihyton biomass were the variables exerting the main influence on the invertebrate assemblage, while interestingly, macrophyte size and biomass were negatively correlated with most of the fauna abundance. On the other hand, brown hydra was negatively correlated with all other invertebrate taxa, except gastropods. Larger surface of submersed macrophytes is the main parameter supporting the increase of invertebrate abundance due to providing protection from predators and growth for periphyton, an important food source for these phytophilous organisms. Macrophyte length was positively correlated with Hydra abundance, while Chironomids were more influenced by periphyton biomass. These organisms can indicate water quality conditions and a potential increase in primary and secondary production.

Meiobenthic Invertebrates Community Associated with Aquatic plant Ceratophyllum demersum Salamiyat irrigation canal / north Baghdad

The aim of the present study is to study the meiobenthic invertebrate's community associated with the aquatic plant Ceratophyllum demersum in Al-Salamiyat irrigation canal / north Baghdad, with the chemical and physical parameters of the canal water, during the study period from September 2015 to May 2016. Two sites were chosen for sample collection, the first site (S1) at the beginning of the canal near it's connection with Tigris river, and the second site (S2) after 10 km from the first site. The chemico-physical analysis results revealed that the water temperature ranged from 10-30oC, and pH values ranged between 6.9-7.8, and the dissolved oxygen concentration and the BOD values from 7.2-9.2 mg/l, and 1.2-5.4 mg/l, respectively. The salinity values were ranged between 0.45 and 0.86 ‰, and the total suspended solids were changed 357-674mg/l. A total of 9089 individuals of meiobethic invertebrates were sorted out from C. demersum during the study perid , representing 34 species including Hydra oligactis (Hydrozoa , Cnidaria); two species of Turbellaria ( Platyhelminthes); five species of Nematoda; seven species of Rotifera; 14 species of aquatic Oligochaeta (Annelida); four Crustacea, and one species of chironomid larva species, in addition to recording one individual of Tardigrada from (S2). The highest total number of meiobenthic invertebrates of 5600 individuals were recorded at (S2), while at (S1) less number of (3489) individuals were reported. Four species were recognized as a new records for Iraqi fauna, including Hydra oligactis (Hydrozoa:Cnidaria); Macrostomum tuba (Platyhelminthes: Turbellaria(, Dero cooperi (Annelida:Oligochaeta,) and Stenocypris hislopi )Crustacea: Otracoda(.

Life history traits and previous exposure predict resistance to UV irradiation in the freshwater cnidarianHydra oligactis

Abiotic stress is an important source of mortality for cnidarians and is likely to be a major factor shaping their life histories. In freshwater hydra, the ability to withstand exogenous sources of stress varies between species and populations, but little is known about the factors responsible for this variation. Here, we investigated resistance to UV irradiation in Hydra oligactis, a common temperate freshwater cnidarian. We collected polyps from 12 populations and propagated these asexually under standard conditions in the laboratory to obtain 69 laboratory clonal lines with a total of 324 polyps of different age. We measured the size of polyps and recorded their budding rate. In addition, a subset of animals was exposed to hormetic treatment, where experimental animals received a short, sublethal irradiation 2 d before testing their resistance to a higher dose. We investigated how life history traits (age, size, and budding rate), hormetic treatment, and the interaction between life history traits and hormetic treatment relate to the ability of hydra polyps to tolerate high doses of UV irradiation. In multivariate models controlling for the effect of other variables, stress tolerance was positively related to age (lower tolerance in freshly detached buds compared to adult hydra) and size (higher tolerance in polyps with a large body column). Budding rate was negatively associated with stress tolerance. Hormetic treatment increased resistance to UV irradiation, but we found no evidence for an interaction between hormetic response and any of the life history traits, suggesting that the ability to upregulate physiological defense mechanisms after exposure to mild stress does not depend on the life history background of the individuals.

A comparative study of mobility in threeHydraspecies with different reproductive strategies

Sessility or isolated habitat can significantly reduce the number of encounters with potential mating partners and thus favour evolution and maintenance of self-fertilisation. Mobility analysis of phylogenetically related species that differs in reproductive mode and self-fertilisation ability could support the widely accepted but not clearly validated theory of selfing being favoured by sessility. Here, we compare mobility in three species of Hydra (Cnidaria, Hydridae) that differ in reproductive strategy: a simultaneous hermaphrodite able to self-fertilise, a sequential hermaphrodite, and a gonochoric species. The results indicate that mobility expressed as distance traversed by individuals is significantly reduced in Hydra circumcincta, a species that is able to self-fertilise, compared to sequential hermaphroditic Hydra vulgaris and gonochoric Hydra oligactis. Differences in mobility were not correlated to individual body size. It is likely that habitat isolation and limited mobility is associated wit...

Meiobenthic Invertebrates Community Associated with Aquatic plant Ceratophyllum demersum Salamiyat irrigation canal / north Baghdad

The aim of the present study is to study the meiobenthic invertebrate's community associated with the aquatic plant Ceratophyllum demersum in Al-Salamiyat irrigation canal / north Baghdad, with the chemical and physical parameters of the canal water, during the study period from September 2015 to May 2016. Two sites were chosen for sample collection, the first site (S1) at the beginning of the canal near it's connection with Tigris river, and the second site (S2) after 10 km from the first site. The chemico-physical analysis results revealed that the water temperature ranged from 10-30oC, and pH values ranged between 6.9-7.8, and the dissolved oxygen concentration and the BOD values from 7.2-9.2 mg/l, and 1.2-5.4 mg/l, respectively. The salinity values were ranged between 0.45 and 0.86 ‰, and the total suspended solids were changed 357-674mg/l. A total of 9089 individuals of meiobethic invertebrates were sorted out from C. demersum during the study perid , representing 34 species including Hydra oligactis (Hydrozoa , Cnidaria); two species of Turbellaria ( Platyhelminthes); five species of Nematoda; seven species of Rotifera; 14 species of aquatic Oligochaeta (Annelida); four Crustacea, and one species of chironomid larva species, in addition to recording one individual of Tardigrada from (S2). The highest total number of meiobenthic invertebrates of 5600 individuals were recorded at (S2), while at (S1) less number of (3489) individuals were reported. Four species were recognized as a new records for Iraqi fauna, including Hydra oligactis (Hydrozoa:Cnidaria); Macrostomum tuba (Platyhelminthes: Turbellaria(, Dero cooperi (Annelida:Oligochaeta,) and Stenocypris hislopi )Crustacea: Otracoda(.

Thrombospondin Type-1 Repeat Domain-Containing Proteins Are Strongly Expressed in the Head Region of Hydra.

The head region of Hydra, the hypostome, is a key body part for developmental control and the nervous system. We herein examined genes specifically expressed in the head region of Hydra oligactis using suppression subtractive hybridization (SSH) cloning. A total of 1414 subtracted clones were sequenced and found to be derived from at least 540 different genes by BLASTN analyses. Approximately 25% of the subtracted clones had sequences encoding thrombospondin type-1 repeat (TSR) domains, and were derived from 17 genes. We identified 11 TSR domain-containing genes among the top 36 genes that were the most frequently detected in our SSH library. Whole-mount in situ hybridization analyses confirmed that at least 13 out of 17 TSR domain-containing genes were expressed in the hypostome of Hydra oligactis. The prominent expression of TSR domain-containing genes suggests that these genes play significant roles in the hypostome of Hydra oligactis.

Intensity-dependent response to temperature in hydra clones.

The intensity of environmental factors differs in natural habitats and could shape the response of an animal that is able to assess a factor's gradient. However, intensity-dependent response to environmental factors has been only occasionally reported in animals. In laboratory experiments, I studied changes in sexual induction in response to a series of temperature decreases in different clones of Hydra oligactis. The percentage of sexually-induced clone-mates was related to the temperature gradient intensity. This intensity-dependent response was observed independently of the H. oligactis clone and gender. The magnitude of the response differed significantly between the clones originated from the distinct sites. The possible significance of the intensity-dependent response in the Hydra clones is discussed in evolutionary terms.

Hydra as a tractable, long-lived model system for senescence

Hydra represents a unique model system for the study of senescence, with the opportunity for the comparison of non-aging and induced senescence. Hydra maintains three stem cell lineages, used for continuous tissue morphogenesis and replacement. Recent work has elucidated the roles of the insulin/IGF-1 signaling target FoxO, of Myc proteins, and of PIWI proteins in Hydra stem cells. Under laboratory culture conditions, Hydra vulgaris show no signs of aging even under long-term study. In contrast, Hydra oligactis can be experimentally induced to undergo reproduction-associated senescence. This provides a powerful comparative system for future studies.

Predation and cyanobacteria jointly facilitate competitive dominance of small-bodied cladocerans

The hypothesis that the joint effects of predation and cyanobacteria favor the performance of small-bodied cladocerans relative to large-bodied species was tested using three competition experiments in a two-factor full-factorial design. The largebodied Daphnia pulex outcompeted the medium-bodied Simocephalus vetulus when fed a green alga Chlorella pyrenoidosa. However, the presence of the toxic cyanobacterium Microcystis aeruginosa and the coelenterate predator Hydra oligactis reversed the competitive outcome. Their joint effect was significant and contributed to the strongest dominance of S. vetulus. Similar dominance shifts were also observed in the competition between D. pulex and the small-bodied Bosmina longirostris, and in the competition between S. vetulus and B. longirostris. Life table and predation experiments showed that the order of sensitivity of three cladoceran species to Microcystis and to Hydra was the same as the order of competitive superiority in the absence of cyanobacteria. Therefore, cyanobacteria, predation and their joint effects are important drivers for competitive outcomes among cladocerans, potentially creating new opportunities for small-bodied species to dominate in a community. The present study underscores the importance of considering the combined effects of dietary palatability and predation on competitive dominance among herbivores, when predicting zooplankton responses to frequent cyanobacterial blooms.

Is larger better in sit-and-wait predators? Competitive superiority in Hydra

Contrary to a generalisation arising from many studies, a larger body size is not always the key to competitive superiority amongst animals. An analysis of competition between pairs of Hydra oligactis, Hydra vulgaris and Hydra circumcincta, that simultaneously encountered a single prey item, showed that competitive success in these sessile predators depended on species and clone in inter- and intraspecific competition, respectively. H. oligactis appeared to be competitively superior, even to the larger H. vulgaris individuals. Phenotypic traits important for prey capture, such as the fraction of the nematocyst that penetrates the prey (penetrants), were positively related to success in intraspecific competition. Body size appeared to be a positive key factor in determining foraging success in the competition between pairs of conspecifics from single or different clones. In contrast to the results of the intraspecific competition, body size was not significantly related to the foraging success of competing heterospecifics.

Hydra, the everlasting embryo, confronts aging

Existing data imply that the cnidarian Hydra vulgaris does not undergo senescence. In contrast, the related species Hydra oligactis shows increased mortality and physiological deterioration following sexual reproduction. Hydra thus offers the chance to study a striking difference in lifespan in members of the same genus. Adult Hydra possess three well-characterized stem cell populations, one of which gives rise to both somatic cells and gametes. The lack of senescence in Hydra vulgaris raises the question of how these stem cell populations are maintained over long periods of time. Investigation of the roles in Hydra of proteins involved in cellular stress responses in other organisms should provide insight into this issue. Proteins of particular interest include the Hsp70 family proteins and the transcription factor FoxO.

Maturation costs affect maturation timing: sexual reproduction in a heterogonic hydra

If maturation is more costly for females, they may need more distinct environmental cues to induce sexual reproduction than males. We verified this hypothesis by comparing the indirect costs of maturation to males and females of the heterogonic Hydra oligactis, reproducing both asexually and sexually. The laboratory experiments revealed that males mature 2 weeks earlier than the first females at falling temperatures simulating the natural conditions that precede sexual reproduction. The difference between the energy costs of maturation for males versus females has been considered a likely factor responsible for the observed difference in maturation time. Available food supply positively affected the percentage of sexually mature females, indicating that females are more sensitive to food limitation than males. The number of gonads was correlated positively with the size of mature hydra for both males and females. However, males produced twice as many testes as ovaries produced by females. We postulate that females are induced later than males in order to prevent gonadal development after an unseasonable drop in temperature. As sexual reproduction in H. oligactis interferes with asexual budding, under favorable conditions for asexual proliferation unnecessary gonadal development decreases an individual’s fitness through reduction of the number of produced offspring.

Effects of Norflurazon on Green and Brown Hydra

For the first time effects of norflurazon on green (Hydra viridissima Pallas, 1766) and brown hydra (Hydra oligactis Pallas, 1766) in high- and low-light conditions were investigated in order to establish the extent of damage that this substance inflicts, with special emphasis on the "bleaching effect" and the effect on hydra-algae symbiosis. Green hydra is a typical example of an endosymbiotic organism. The gastrodermal myoepithelial cells of green hydra contain endosymbiotic algae. Norflurazon is a selective translocational herbicide that induces a "bleaching effect" on newly developed chloroplasts, resulting in a decrease of photosynthetic activity and viability of the organism. In the experiment, morphological (binocular), cytological and histological (Bouin fixative, dehydration, paraplast embedding, Hämalaun-eosine staining, light microscope) and conventional transmission electron microscopy (cTEM) (glutaraldehyde, dehydration, raisin, uranyl-acetate, Pb-citrate) were used. Depending on the concentration and light conditions, norflurazon caused mortality, deformations, changes in behavior, locomotion and asexual reproduction, changes in the structure of all 3 layers in hydras, changes in the position and shape of endosymbiotic algae inside the hydra body as well as ultrastructural changes of treated hydras and endosymbiotic algae. Under low concentrations of norflurazon the effects on hydra were similar to the controls, while in the highest concentrations especially manifested were antichloroplastal and antimitochondrial effects. Norflurazon caused a great extent of damage and induced deleterious effects also upon other cellular components such as cellular membranes, ER, Golgi apparatus, ribosomes. Newly developed buds in symbiotic green hydras were not bleached. After a recovery period, the green hydra individuals that had survived re-established regular endosymbiosis with algae and recovered completely, whereas brown hydras recovered only partially.