Hydra oligactis
Pallas, 1766 · speciesAt a glance
Sources11 archives
Databases and archives Hydra oligactis's data was compiled from.
WikipediaWikimedia Foundation9 languages↗
Animal Diversity WebUniv. of Michigan MZspecies account↗
BioWikiNetmultilingual Wikipediamultilingual↗
GBIFGlobal Biodiversity Information Facility234 records↗
OBISOcean Biodiversity Information System60 records↗
ENAEuropean Nucleotide Archive · EMBL-EBI372 eDNA detections↗
BOLD SystemsCentre for Biodiversity Genomics220 specimens↗
Open Tree of LifeOpenTreephylogeny backbone↗
GoaTGenomes on a Tree · Sangergenome & karyotype↗
NCBIUS National Library of Medicinegenome & karyotype↗
Catalogue of LifeCOLtaxonomy↗Every layer below draws on the sources above — open one to explore it, or use ← → to move between tabs.
Hydra oligactis, also known as the brown hydra, is a species of hydra found widely dispersed in the northern temperate zone. It is a common organism found in still waters from early Spring to late Autumn. It is commonly found attached to the stems of water plants, the undersides of leaves, submerged twigs and on the surface of stones. When disturbed it retracts to a small brown blob which is easily overlooked. Gently sweeping through a clean weedy pond and allowing the collected water and leaves to stand in a jar will often reveal Hydra emerging after only a few minutes. When in feeding mode, the fully extended tentacles are very long and may exceed 1 in in length. In this condition the tentacles are very difficult to see with the naked eye and are often only revealed when a prey animal such as Daphnia is caught. The relative length of the tentacles compared to the body is characteristic of the species and serves to differentiate it from any other brown Hydra of cool temperate waters. When a cold sensitive strain of H. oligactis is subjected to temperature stress, it undergoes a shift from asexual budding to sexual reproduction.Sun S, White RR, Fischer KE, Zhang Z, Austad SN, Vijg J. Inducible aging in Hydra oligactis implicates sexual reproduction, loss of stem cells, and genome maintenance as major pathways. Geroscience. 2020 Aug;42(4):1119-1132. doi: 10.1007/s11357-020-00214-z. Epub 2020 Jun 23. PMID 32578072; PMCID: PMC7394996 This shift involves an upreglation of genes involved in gametogenesis, cellular senescence, apoptosis and DNA repair, and a downregulation of genes involved in stem cell maintenance. Hydra oligactis is preyed upon by the flatworm Microstomum lineare, which incorporates Hydra stenoteles into its own epidermis.
No narrative description available for this taxon yet.
Habitat & environment3
A DNA barcode is a short, standardised stretch of genes that works like a fingerprint — enough to tell one species from another. Below is the molecular trace Hydra oligactis has left across the world's sequence archives.
At a glance
★ the standard DNA barcode for this group — the short region actually read to tell this species apart. The rest are extra genes sequenced along the way.
Besides the big genome in the nucleus, cells carry a small, circular loop of DNA inside the cell's energy factories — the mitochondria. It is inherited almost only from the mother and is a leftover from ancient bacteria that moved into the cell. The mitochondrial markers above (ND*, COX, CYTB…) are read from exactly this loop. Outer ring = one strand, inner ring = the other.
The complete instruction manual Hydra oligactis carries — its genome. We read it from three angles — how big it is, how the DNA is packed into chromosomes, and how completely it has been sequenced — and explain how to read each value as you go.
Genome sizehow big the whole instruction manual is
Measured in base pairs (bp) — the individual letters of DNA (human ≈ 3.2 Gb, a bacterium a few million). The chart places this genome on a logarithmic scale — each step to the right is ten times bigger — among reference organisms. Across species a bigger genome loosely tracks with larger cells, slower growth and lower-energy lifestyles (powered flight favours small genomes) — yet it does not imply more genes or a more advanced organism (the long-standing C-value paradox).
Chromosomes & ploidyhow the DNA is packaged
2n is the full chromosome count in a normal body cell; n is a gamete (egg or sperm), which carries half. Ploidy is how many complete chromosome sets each cell holds — 2× (diploid) is typical for animals, while higher levels (polyploidy) are common in plants. Click any value below to see the underlying records and sources.
2n 121×GoaT · Animal Chromosome Counts Database
Sequencing statusassembly quality — how far to trust these numbers
Assembly level tells you how finished the sequence is — from fragmented contigs, through scaffolds, up to a full chromosome-level assembly. BUSCO % estimates completeness: the share of genes expected to be present that were actually found. These describe the data quality, not the organism.
How far back this lineage goes — and how we know. Everything here is measured in Ma, short for “mega-annum”: millions of years ago. The chart reads left to right like a calendar of the Earth, from the deep past on the left to today at the right edgetop to bottom like a core drilled through the Earth, from the deep past at the top down to today at the bottom.
At a glance
When this lineage existed
How to read this: the coloured strip along the bottomdown the left is the geological calendar — the standard epochs (Pliocene, Pleistocene…) every museum uses, shown so you can see which chapter of Earth's history this lineage lived in. This lineage is a young one, so the strip is zoomed in to epochs — the finer subdivisions inside a period. The orange marker is the DNA clock: DNA accumulates mutations at a roughly steady rate, so comparing this species' DNA with its relatives estimates when the lineage split off — independently of any fossil.
Record type294 records
Range
Depth
Wildobservation + sensor
Human sightings and records, or camera-trap / sensor detections — someone (or a device) saw or captured the species in the wild.
Museum / Voucheredphysical evidence
Backed by a physical specimen — a herbarium sheet, sample or voucher held in a collection. “Vouchered” means supported by material evidence, not just an observation.
Wildobservation + sensor
Human sightings and records, or camera-trap / sensor detections — someone (or a device) saw or captured the species in the wild.
Holding institutions1 of 3 geolocated
Institutions and collections holding physical, vouchered specimens of this species — click a row to fly to it on the map.
| Institution | Specimens |
|---|---|
| Stockholm, SE | 3 |
| University of Guelph, Centre for Biodiversity Genomicslocation not on record | 2 |
| Royal Ontario Museumlocation not on record | 1 |
Where the DNA of Hydra oligactis was picked up in samples of water, soil or air — nobody saw the organism, only its DNA left behind. A trace is a clue that the species was near, not a confirmed sighting.
Signal
Where its DNA was found
How strong is each trace?
Modelled climatemodelled
How to read this: each dot is one detection of this species' DNA in an environmental sample. The confidence meter weighs how many independent studies and places back up the signal — one detection in one study is a hint; many across several studies is solid. Records dated before 2008 (when eDNA methods began) are treated as likely mislabeled and left off the map.