Ikeda (genus)
| Ikeda | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Ikedidae | ||||||||||||
| Bock, 1942 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Ikeda | ||||||||||||
| Wharton , 1913 |
Ikeda is the name of a small genus of large hedgehog worms (Echiura), which at the same time forms the monogeneric family of the Ikedidae andincludes2 described, but probably even more species in the Indo-Pacific .
features
The hedgehog worms of the genus Ikeda are large with body lengths of up to 40 cm and widths of up to 2 cm. The Proboscis is very long and can be extended to over a meter. The nephridia are unpaired and, compared to other hedgehog worms, numerous: In Ikeda pirotansis there are at least 30, in Ikeda taenioides around 200 to 400 nephridia. In contrast to other hedgehog worms, the nephrostomata are not arranged basally, but distally. The closed blood vessel system is well developed. The animals have large anal vesicles. While Iwaji Ikeda, in his first description of Ikeda taenioides, saw an arrangement of the longitudinal muscles of the skin muscle tube outside the cricoid and transverse muscles, Teruaki Nishikawa observed an external circular musculature in fresh specimens as well as those preserved by Iwaji Ikeda, including the longitudinal muscles and finally the transverse muscles on the inside, as is the case with other hedgehog worms.
The Ikeda hedgehog worms live with their trunk hidden in their caves, which they do not leave, which is why people only get to see their proboscis, with which the worms graze microscopic food particles from the substrate. The food is conveyed through an eyelash groove on the concave side of the proboscis to the mouth at the front end of the trunk.
Life cycle
Of the Ikeda hedgehog worms, only females have been described so far. Since molecular biological investigations suggest a closer relationship between the Ikedidae and the Bonelliidae family , a sexual dimorphism is suspected in view of the males not found , in which dwarf males live inside the giant female.
Species and their distribution
The 1907 Iwaji Ikeda as taenioides Thalassema described Ikeda taenioides is in the western Pacific Ocean to Japan to find. Their proboscides have often been found by Japanese fishermen and thought to be complete worms. Ikeda pirotansis , described by Menon & Datta Gupta in 1962 as Ikedosoma pirotansis , was found on the Indian island of Pirotan . In 1987, in Gulf Saint Vincent , South Australia , SJ Edmonds found the torso of a hedgehog worm, which he believes is another species of Ikeda .
External system
More recent molecular biological investigations of nuclear and mitochondrial DNA in 49 species of hedgehog worms classify the family Ikedidae with the Bonelliidae in a clade of sexually dimorphic hedgehog worms, which is compared to a group of sexually monomorphic hedgehog worms with the families Echiuridae , Urechidae and Thalassematidae . The sexual dimorphism is said to have evolved in shallow waters.
literature
- Stanley J. Edmonds: Fauna of Australia, Volume 4A. Polychaetes & Allies. The Southern Synthesis 4. Commonwealth of Australia, 2000. Phylum Echiura. P. 25, Family Ikedidae.
- Iwaji Ikeda (1907): On Three New and Remarkable Species of Echiuroids (Bonellia miyajimai, Thalassema taenioides and T. elegans). Journal of the College of Science of the Imperial University of Tokyo 21, pp. 1-64.
- Teruaki Nishikawa (2002): Comments on the taxonomic status of Ikeda taenioides (Ikeda, 1904) with some amendments in the classification of the phylum Echiura. Zoological Science 19 (10), pp. 1175-1180.
- SJ Edmonds (1987): Echiurans from Australia (Echiura). Records of the South Australian Museum 32, pp. 119-138, here pp. 135-136.
Individual evidence
- ↑ a b Ryutaro Goto (2016): A comprehensive molecular phylogeny of spoon worms (Echiura, Annelida): Implications for morphological evolution, the origin of dwarf males, and habitat shifts. Molecular Phylogenetics and Evolution 99: 247-260. doi: 10.1016 / j.ympev.2016.03.003