Hydractiniidae

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Hydractiniidae
Hydractinia epiconcha

Hydractinia epiconcha

Systematics
Trunk : Cnidarians (Cnidaria)
Class : Hydrozoa (Hydrozoa)
Subclass : Leptolinae
Order : Anthomedusae
Subordination : Filifera
Family : Hydractiniidae
Scientific name
Hydractiniidae
Agassiz , 1862

The Hydractiniidae are a family of marine hydrozoa (Hydrozoa) found worldwide . The family currently includes around 100 species. The oldest records of the family come from the Lower Cretaceous; reports from the Jura are questionable.

features

The hydroid polyps are sessile, the hydrants are often polymorphic. The hydrorhiza is formed either from stolonal tubes that are covered with perisarc or as an encrusting mat that is formed by the coalescence of the stolonal system. This encrusting mat can be covered with perisarc or bare coenosarc. In some types, the hydrorhiza mat is reinforced by layers of aragonite . Chitinous or chalky thorns often grow out of the mat and can grow together to form branched or unbranched pillars. Occasionally the hydrants sit in protective tubes. The feeding polyps have one to several rings of filiform tentacles below the cone of the mouth (hypostome), or the numerous tentacles are more or less randomly distributed over the upper half of the body. Very rarely only one or two tentacles are formed. The defense polyps, on the other hand, have no tentacles. The gonophores are typically located on special sexual polyps. These have one or more wreaths of filiform tentacles or can also be tentacle-free. The latter usually do not have a mouth either. Spore sacs, eumedusoids or free medusas can be formed on them. The umbrella of the medusa, when free medusa is formed, is more or less bell-shaped and has a more or less pronounced apex that rises above the exumbrella. The manubrium is tubular or sack-shaped and does not extend beyond the edge of the screen. The mouth has four simple or branched lips, which can be elongated to form arms, and which can have nettle cells at the tip. A gastral stalk may be present or absent. Four, eight or more tentacles are attached to the edge, but they are not grouped together. There are four radial channels and one ring channel. The gonads sit on the manubrium, interradially, or sometimes extend along perradial protrusions at the base of the manubrium. Ocelli can be present or absent.

Geographical occurrence and way of life

The family is spread around the world. The main area of ​​distribution is in the cooler waters of the northern hemisphere. The colonies often live as epizoa on the shells of living snails , but also as a coating on stones.

Systematics

The size of the family is very inconsistent in the literature. While Bouillon & Boero (2000) only list the genus Hydractinia under the family and the genus " Kinetocodon Kramp, 1921" (recte Kinetocodium Kramp, 1921) under "Hydractiniidae incertae sedis", Peter Schuchert lists six genera in the "Hydrozoa Directory" of the family to. Daly, et al. (2007) state that the family contains seven genera. The "World Register of Marine Species" lists eleven valid genera (and seven more recent synonyms). Miglietta et al. (2009) also list Hansiella Bouillon 1980 and Tregoubovia Picard, 1958, and the generic names Stylactaria Stechow, 1921 and Podocoryna Sars, 1846, which are treated as younger synonyms of Hydractinia in the other publications .

The family thus includes up to 12 valid genres, depending on the publication.

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literature

  • Marymegan Daly, Mercer R. Brugler, Paulyn Cartwright, Allen G. Collin, Michael N. Dawson, Daphne G. Fautin, Scott C. France, Catherine S. McFadden, Dennis M. Opresko, Estefania Rodriguez, Sandra L. Romano & Joel L. Stake: The phylum Cnidaria: A review of phylogenetic patterns and diversity 300 years after Linnaeus. Zootaxa, 1668: 127-182, Wellington 2007 ISSN  1175-5326 Abstract - PDF
  • Jean Bouillon and Fernando Boero: Synopsis of the families and genera of the hydromedusae of the world, with a list of worldwide species. Thalassia Salentina, 24, 47-296, Galatina 2000 ISSN  0563-3745 PDF .

On-line

Individual evidence

  1. ↑ Michael J. Benton (Ed.): The Fossil Record 2. Chapman & Hall, London a. a., 1993 ISBN 0-412-39380-8
  2. ↑ [1]
  3. ^ Maria Pia Miglietta, Peter Schuchert and Clifford W. Cunningham: Reconciling genealogical and morphological species in a worldwide study of the Family Hydractiniidae (Cnidaria, Hydrozoa). Zoologica Scripta, 38: 403-430, Leiden 2009 doi : 10.1111 / j.1463-6409.2008.00376.x
  4. ↑ The genus Clava is classified by Bouillon & Boero (2006) in a separate family Clavidae together with the genera of the Oceaniidae .
  5. ↑ cf. also Atlas of Living Australia  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / data.ala.org.au  
  6. ↑ cf. also Atlas of Living Australia  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / data.ala.org.au  
  7. ↑ cf. also MarBEF Data System