A search for predators and food selectivity of two native species of Hydra (Cnidaria: Hydrozoa) from Brazil

Massaro, Fernanda Cristina; Negreiros, Natália Félix

doi:10.1590/s1676-06032013000200003

Cited by 7 publications

(4 citation statements)

References 20 publications

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“…The choice for the invertebrate Hydra viridissima was based in the increasing attention that this cnidarian has attracted in aquatic ecotoxicology as a sensitive species of the epibenthonic community and as a bioindicator species [19][20][21]. Together with its small size, simple anatomy, and easy maintenance of the culture, the multiple physiological targets that can be evaluated during tests with this organism are very attractive characteristics, which include asexual reproduction, feeding behavior (predators), and morphological and regenerative characteristics [13,19,[22][23][24][25], which may provide a broader understanding on the effects of both Round ® Ready and the active ingredient.…”

Section: Introductionmentioning

confidence: 99%

Glyphosate and Roundup® Ready Effects in Hydra viridissima: New Data in an Old Issue

2023

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Herbicides are used worldwide to protect agricultural crops, glyphosate being among the most frequently applied. In 2019 the European Commission approved the use of this herbicide for another 5 years and is now preparing its re-authorization for marketing. It is known that glyphosate (an active ingredient—AI) is usually less toxic than its commercial formulations, which may be related to adjuvants presents in such formulas. In this context, this work aimed to evaluate and compare the effects of glyphosate, as the commercial formulation Roundup® Ready (RR), and the AI in the Hydra viridissima life cycle, namely: mortality, morphology, feeding, reproduction, and regeneration. To attain this goal, H. viridissima was exposed to an environmentally relevant concentration of glyphosate (5.2 mg AI/L, both for RR and the AI) and to its culture medium (control). The mortality was lower than 0.03% for both RR and AI. Regarding morphological alterations, these were more severe on organisms exposed to RR, while a high recovery capacity in hydras exposed to AI was observed. No hydra was able to completely regenerate its body parts when exposed to RR, while 95% of the organisms exposed to AI were able to regenerate completely. The feeding rates of hydras exposed to RR decreased by from ~20% to ~50% compared to AI. As for reproduction, hydras exposed to RR released ~70% less buds than those exposed to AI. These timely results suggest that adjuvants present in the commercial formulation of glyphosate may cause higher toxicity to biota than the AI at environmentally relevant concentrations. Though the commercial formulation exerted higher toxicity in hydra, the effects AI induced in the morphology of the hydra cannot be disregarded, suggesting that a deeper understanding on the long-term toxicity of this AI is still needed to further support the decision on its marketing authorization and environmentally safe use.

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Section: Introductionmentioning

confidence: 99%

Glyphosate and Roundup® Ready Effects in Hydra viridissima: New Data in an Old Issue

2023

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“…personal observation). This, in turn, could have major consequences for the population dynamics of their prey (mainly cladocerans and copepods, but also small fish; Cuker & Mosley, 1981 ; Deserti et al, 2017 ; Elliot et al, 1997 ; Massaro et al, 2013 ; Rivera‐de la Parra et al, 2016 ; Schwartz et al, 1983 ) in a manner that amplifies with climate change. However, whether warming temperatures affect sexual or asexual fitness, and thereby population dynamics in hydra is still unclear.…”

Section: Introductionmentioning

confidence: 99%

Warming increases survival and asexual fitness in a facultatively sexual freshwater cnidarian with winter diapause

Tökölyi

2023

Ecology and Evolution

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Temperature is a key abiotic factor controlling population dynamics. In facultatively sexual animals inhabiting the temperate zone, temperature can regulate the switch between asexual and sexual modes of reproduction, initiates growth or dormancy, and acts together with photoperiod to mediate seasonal physiological transitions. Increasing temperature due to recent global warming is likely to disrupt population dynamics of facultatively sexual animals because of the strong temperature dependence of multiple fitness components. However, the fitness consequences of warming in these animals are still poorly understood. This is unfortunate since facultatively sexual animals—through their ability for asexual reproduction resulting in quick population growth and sexual reproduction enabling long‐term persistence—are key components of freshwater ecosystems. Here, I studied the fitness effects of warming in Hydra oligactis , a freshwater cnidarian that reproduces asexually throughout most of the year but switches to sexual reproduction under decreasing temperatures. I exposed hydra polyps to a simulated short summer heatwave or long‐term elevated winter temperature. Since sexual development in this species is dependent on low temperature, I predicted reduced sexual investment (gonad production) and elevated asexual fitness (budding) in polyps exposed to higher temperatures. The results show a complex effect of warming on sexual fitness: While gonad number decreased in response to warming, both male and female polyps exposed to high winter temperature were capable of multiple rounds of gamete production. Asexual reproduction and survival rate, on the contrary, clearly increased in response to higher temperature, especially in males. These results predict increased population growth of H. oligactis in temperate freshwater habitats, which will likely affect the population dynamics of its main prey (freshwater zooplankton), and through that, the whole aquatic ecosystem.

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“…They are passive predators waiting for potential prey touching cnidocytes on tentacles ( Hydra ) or the head of the polyp ( Craspedacusta ; [ 34 ]). Both polyps feed on crustacean zooplankton species, rotifers, oligochaete worms, nematodes, chironomids, and other insect larvae [ 35 , 36 , 37 , 38 , 39 , 40 ].…”

Section: Introductionmentioning

confidence: 99%

Trophic Positions of Polyp and Medusa Stages of the Freshwater Jellyfish Craspedacusta sowerbii Based on Stable Isotope Analysis

Gießler

Strauß²,

Schachtl

et al. 2023

Biology

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When species spread into new regions, competition with native species and predatory–prey relationships play a major role in whether the new species can successfully establish itself in the recipient food web and become invasive. In aquatic habitats, species with a metagenetic life cycle, such as the freshwater jellyfish Craspedacusta with benthic polyps and planktonic medusae, have to meet the requirements of two distinct life stages occurring in two habitats with different food webs. Here, we examined the trophic position of both life stages, known to be predatory, and compared their niches with those of putative native competitors using stable isotope analysis. We found that δ13C and δ15N signatures of medusae overlapped with those of co-occurring Chaoborus larvae and juvenile fish (Rutilus rutilus) in a well-studied lake, implying high competition with these native predators. The comparison of δ15N signatures of Hydra and Craspedacusta polyps in four additional lakes revealed their similar trophic position, matching their predatory lifestyle. However, their δ13C signatures differed not only across all four of the lakes studied but also within one lake over time, suggesting a preference for pelagic or benthic food sources. We conclude that invasive and native polyps differ in their niches due to different food spectra, which favors the invasion success of Craspedacusta.

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A search for predators and food selectivity of two native species of Hydra (Cnidaria: Hydrozoa) from Brazil

Cited by 7 publications

References 20 publications

Glyphosate and Roundup® Ready Effects in Hydra viridissima: New Data in an Old Issue

Glyphosate and Roundup® Ready Effects in Hydra viridissima: New Data in an Old Issue

Warming increases survival and asexual fitness in a facultatively sexual freshwater cnidarian with winter diapause

Trophic Positions of Polyp and Medusa Stages of the Freshwater Jellyfish Craspedacusta sowerbii Based on Stable Isotope Analysis

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