---
title: "What the sources say about the Hydra | AnimalTracks.wiki"
description: "47 claims from the Hydra profile, each beside the words of the source that backs it."
image: "https://animaltracks.wiki/images/animals/hydra-1.webp"
canonical: "https://animaltracks.wiki/animals/hydra/sources/"
---

# What the sources say about the Hydra (*Hydra vulgaris*)

> 47 claims from the Hydra profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Hydra](https://animaltracks.wiki/animals/hydra/)

## Auclair et al. (2024). Ecotoxicity of a Representative Urban Mixture of Rare Earth Elements to Hydra vulgaris. Toxics.

https://doi.org/10.3390/toxics12120904

| The page says | The source says |
| :--- | :--- |
| Small prey such as copepods and other zooplankton | They feed on small prey, such as copepods and other zooplankton. (note: stats.diet) |
| Hydra is a freshwater polyp, an animal with a tube-shaped body. | Hydras are relatively small organisms (between 2 and 10 mm in length) with a tubular body (note: freshwater from the Klymenko line 'small predatory fresh-water polyp' and temperature-2025 'freshwater polyps') |
| It measures between 2 and 10 mm in length | between 2 and 10 mm in length |
| Hydra feeds on small animals such as copepods and other zooplankton | They feed on small prey, such as copepods and other zooplankton. |

## Klymenko & Lutz (2026). From Hydra to Humans: Head Activator in Neurogenesis and Neurorepair. Cells.

https://doi.org/10.3390/cells15070616

| The page says | The source says |
| :--- | :--- |
| A small freshwater polyp | The hydra is a small predatory fresh-water polyp (note: tagline. The size figure moved out of the tagline: sources disagree (Auclair 2-10 mm, Klymenko up to 30 mm), the body states both.) |
| a freshwater polyp | The hydra is a small predatory fresh-water polyp |
| though the body can reach up to 30 mm | The body can reach up to 30 mm in length. |
| Its head is ringed by tentacles. | A hypostome with an oral opening, surrounded by a radially symmetrical crown of tentacles forming the head region. |
| The tentacles are packed with cnidocytes, cells that hold stinging parts and are rich in neurotoxic substances that paralyse prey. | harbouring stinging organelles (nematocysts) [ 7 ]. The cnidocytes densely populate the tentacle areas of hydra, being enriched in neurotoxic substances, ready for a rapid injection to paralyse different kinds of prey. |
| Once the tentacles have caught a meal, it is moved to the hypostome | Captured by the tentacles, the immobilised prey is propelled towards the hypostome. |
| It reproduces mostly without a partner, by budding, which makes genetically identical clones. | The reproduction of hydra occurs primarily asexually through budding, resulting in genetically identical clones. |

## Destry, Cochran & Macias-Muñoz (2025). The effect of temperature on asexual reproduction in Hydra vulgaris. microPublication Biology.

https://doi.org/10.17912/micropub.biology.001508

| The page says | The source says |
| :--- | :--- |
| Fresh water | vulgaris are freshwater polyps (note: stats.habitat) |
| Not Evaluated | Hydra vulgaris is a model cnidarian used for interdisciplinary studies in biology (note: stats.conservationStatus. GBIF's copy of the Red List has no category for Hydra vulgaris and the prefetch found no assessment DOI (Crossref searches for synonyms returned HTTP 429), so no IUCN reference is cited. The quote names the species only. Precedent: great-scallop.) |
| It belongs to the phylum Cnidaria, the group that also holds jellyfish, sea anemones and corals. | belong to the phylum Cnidaria, which encompasses jellyfish, sea anemones, and corals |
| the hypostome, the mouth opening | Photograph of a Hydra polyp with tentacles, hypostome (mouth opening) (note: Figure 1 caption of the same paper.) |
| Warmth boosts budding. | Our findings indicate that Hydra populations exhibit increased growth through asexual budding at higher temperatures. |
| By the end of one lab test, an average of 45 polyps were budding at 25 degrees Celsius, against 4 at 15 degrees | By the end of experimental weeks, an average of 45 polyps were budding at 25°C compared to 4 at 15°C. |
| It can reproduce sexually, but it also buds. | H. vulgaris are also capable of reproducing both sexually and asexually by budding. |
| Under favorable conditions, a bud forms in the lower section of the body | Under favorable conditions, a bud develops in the lower section of the H. vulgaris body. |
| passes through 10 stages of growth and tentacle formation, then detaches as a new polyp | The bud proceeds through 10 stages of growth and tentacle formation, then detaches from the parent polyp |

## Schaible et al. (2015). Constant mortality and fertility over age in Hydra. Proceedings of the National Academy of Sciences.

https://doi.org/10.1073/pnas.1521002112

| The page says | The source says |
| :--- | :--- |
| whose death rate in lab studies stayed flat as it got older | have extremely low, constant rates of mortality (note: tagline; two closely related Hydra species, lab cohorts) |
| every animal that breeds repeatedly would see its death rate rise and its fertility fall with age after maturity | Senescence, the increase in mortality and decline in fertility with age after maturity, was thought to be inevitable for all multicellular species capable of repeated breeding. (note: 'scientists thought' keeps the source's 'was thought to be inevitable'.) |
| A 2015 study put that to the test on 2,256 Hydra from two closely related species. | 2,256 Hydra from two closely related species in two laboratories in 12 cohorts (note: Year 2015 is the schaible-2015 reference year (PNAS, first published online 7 December 2015 per the MPIDR press release).) |
| Spread across 12 groups in two labs, they had extremely low, constant rates of mortality. | in two laboratories in 12 cohorts, with cohort age ranging from 0 to more than 41 y, have extremely low, constant rates of mortality (note: Reviewer cut the 0-41 year range: it is cohort age, not the age of any individual polyp, and read as a 41-year-old hydra.) |
| The researchers say features such as a high proportion of stem cells and rapid cell turnover may make that flat death rate possible. | A high proportion of stem cells, constant and rapid cell turnover, few cell types, a simple body plan, and the fact that the germ line is not segregated from the soma are characteristics of Hydra that may make nonsenescence feasible. |

## Forever young. Max Planck Institute for Demographic Research, press release.

https://www.demogr.mpg.de/en/news_press/news/press/forever_young_4396.htm

| The page says | The source says |
| :--- | :--- |
| Replaces all of its cells within four weeks | as Hydra replaces all of their cells within only four weeks (note: stats.superpower) |
| In a lab in Rostock, Germany, researchers cared for about 1,800 polyps over almost ten years | For almost ten years they have cared for of about 1,800 of the Hydras in a laboratory in the basement of the institute in Rostock. (note: Rostock, Germany is the dateline: 'Rostock, Germany.') |
| each in its own small glass dish at a constant 18 degrees Celsius | Each polyp lives in its own small glass dish exposed to a natural day-and-night cycle in special cabinets that are kept at a constant temperature of 18 degrees Celsius. |
| fed three times a week | Three times a week they are fed exactly the same amount of food. |
| Their yearly chance of dying stayed at a low 0.6 percent. | For Hydra, however, it remains constant at a low 0.6 percent. (note: 'it' is the probability of dying within one year, per the previous sentence.) |
| For humans, it reaches levels as high as 50 percent at advanced ages. | For humans the probability of dying within one year is reaching levels as high as 50 percent for advanced ages. |
| Its stem cells can develop into any part of the body. | Stem cells are capable of developing into any part of the body at any time. |
| Hydra replaces all of its cells within four weeks | as Hydra replaces all of their cells within only four weeks |
| it regularly expels cells that mutations have changed | it regularly and quickly expels all cells that have been changed genetically by mutations |
| It can completely replace body parts that are damaged or lost, and it can fully regenerate if its body is almost completely destroyed. | Hydra are capable of completely replacing parts of the body that are damaged or are somehow lost. It can even fully regenerate if its body is destroyed almost completely |
| A hydra replaces all of its cells within four weeks, and in the lab its death rate stayed flat as it aged. | as Hydra replaces all of their cells within only four weeks (note: vibe.reason; the rest of the sentence restates body claims: Spread across 12 groups in two labs, they had extremely low, constant rates of m) |

## Martı́nez (1998). Mortality Patterns Suggest Lack of Senescence in Hydra. Experimental Gerontology.

https://doi.org/10.1016/S0531-5565(97)00113-7

| The page says | The source says |
| :--- | :--- |
| followed three groups of hydra for four years and tracked deaths and reproduction | mortality and reproductive rates for three hydra cohorts have been analyzed for a period of four years (note: 1998 is the martinez-1998 reference year.) |
| Death rates stayed extremely low and reproduction showed no apparent sign of falling. | mortality rates have remained extremely low and there are no apparent signs of decline in reproductive rates |

## Sahm et al. (2024). Hydra has mammal-like mutation rates facilitating fast adaptation despite its nonaging phenotype. Genome Research.

https://doi.org/10.1101/gr.279025.124

| The page says | The source says |
| :--- | :--- |
| In the wild, Hydra's average life span is counted in weeks rather than years, because of high extrinsic mortality | In the wild, due to a high extrinsic mortality, Hydra ’s average life span is counted in weeks rather than in years (note: Genus scope. Also Schaible 2015: 'the short life expectancy of Hydra in the wild'. Lifespan claim. 'because' is the source's own 'due to'.) |
| which is the death rate from outside causes | due to a high extrinsic mortality (note: Definition of the term; no quote defines it. Cut if the reviewer prefers.) |
| The lab is a kind place, though. | The nonsenescent phenotype is observable only under benign laboratory conditions (note: Framing sentence; 'only' is the source's.) |

## Schenkelaars et al. (2020). The polymorphism of Hydra microsatellite sequences provides strain-specific signatures. PLOS ONE.

https://doi.org/10.1371/journal.pone.0230547

| The page says | The source says |
| :--- | :--- |
| Hydra strains collected from around the world | Hydra strains collected worldwide (note: stats.habitat; the body names the range with the same claim. Scope: genus strains, no finer geographic range is stated in any cached source (2 audit searches and 3 Europe PMC queries found none).) |
| Researchers have collected Hydra strains from around the world. | Hydra strains collected worldwide |

## Dupre & Yuste (2017). Non-overlapping Neural Networks in Hydra vulgaris. Current Biology.

https://doi.org/10.1016/j.cub.2017.02.049

| The page says | The source says |
| :--- | :--- |
| It was long described as a simple nerve net. | the nervous system of Hydra is traditionally described as a simple nerve net |
| researchers used calcium imaging to record the activity of essentially all of its neurons | using calcium imaging of genetically engineered animals to measure the activity of essentially all of its neurons (note: 2017 is the dupre-2017 reference year.) |
| found a series of networks that do not overlap, each tied to a specific behavior | a series of functional networks that are anatomically non-overlapping and are associated with specific behaviors |
| One network is active when the body contracts lengthwise, another when it stretches in response to light. | activated selectively during longitudinal contractions, elongations in response to light, and radial contractions |