Green hedgehog worm

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Green hedgehog worm
Bonellia viridis (adult female)

Bonellia viridis (adult female)

Systematics
Trunk : Annelids (Annelida)
Class : Hedgehog worms (Echiura)
Order : Echiuroidea
Family : Bonelliidae
Genre : Bonellia
Type : Green hedgehog worm
Scientific name
Bonellia viridis
Rolando , 1822
Females of Bonellia viridis : Only the grazing trunk with head fork is visible, the trunk is hidden in a cave.
Females of Bonellia viridis , R: proboscis, o: mouth. Brockhaus-Efron, 1905.
Miniature male of Bonellia viridis , greatly enlarged. Brockhaus-Efron, 1905.
Internal anatomy of the female:
a , proboscis (cut off).
b , bristle through the mouth into the pharynx.
c , intestine (coiled).
d , vascular tufts on the anus.
e , ventral nerve cord.
f , ovary, carried by the abdominal vessel (running parallel to e).
g , position of the anus.
h , location of the kidney exit.
i , kidney (nephridium, line does not quite reach inner opening of same).

The green hedgehog worm ( Bonellia viridis ) is a representative of the hedgehog worms (Echiura) from the family Bonelliidae living in the north-east Atlantic and Mediterranean , which is characterized by an extreme sexual dimorphism and phenotypic sex determination : the only 1 to 3 mm long males live in the fallopian tubes of the bis 15 cm long green female that emerges from such a larva that does not meet any adult female as a future sex partner (host).

features

The spherical to sausage-shaped body of the female of Bonellia viridis has a pale to dark green color and is about 5 to 15 cm long. At the front there is a contractible, muscular trunk, at the front end of which sits a forked head flap and which can be extended to over a meter. An eyelash groove on the underside of the trunk transports food particles picked up by the head flap to the mouth on the trunk of the animal. There is only an unpaired nephridium that also serves as a fallopian tube.

According to recent studies, the green porphyrin pigment bonellin is not formed by breaking down the chlorophyll from the green algae consumed, but is produced by the female herself from cobalamin .

The 1 to 3 mm long gutless dwarf male has a flat, unpigmented and eyelashed body that is mainly occupied by the testicles . It lives - usually in large numbers from 20 to 80 individuals - in a blister-shaped enlargement in the fallopian tube of the female.

distribution

The green hedgehog worm is found in the northeastern Atlantic Ocean including the North Sea and the Mediterranean . It also lives in the Red Sea , off the coast of Java and in the Coral Sea , for example in the Great Barrier Reef off the Australian coast.

Habitat and way of life

While the males of Bonellia viridis live hidden in the female's nephridium, which also serves as a fallopian tube, the female stays under gravel, in crevices or abandoned caves of other marine animals and thus avoids daylight. From here it stretches its trunk up to over a meter and grazes with its head fork detritus and microscopic algae, but also small animals, from the seabed. The food particles are fed to the mouth via the eyelashes on the underside of the proboscis, swallowed and digested in the female's intestine. The gutless males living in the female are nourished exclusively by diffusion from the body fluids of the female.

Bonellin as an antibiotic

The adult female of Bonellia viridis produces the bright green pigment bonellin in its skin , which is found in high concentrations in the proboscis and is used both to determine the sex and to protect the animal. It is highly toxic to other organisms, so it paralyzes small animals and kills bacteria. Therefore, possibilities of use as an antibiotic and synthesis are being explored.

Life cycle and sex determination

The Green Hedgehog worm spreads by sexually undifferentiated, free-floating, as zooplankton living larvae . Those larvae that do not meet an adult female, i.e. land on the unoccupied sea floor, metamorphose themselves into young females and grow to female sexual maturity over the years. Most larvae that are not eaten by enemies, however, come into contact with a female, whose bonellin stimulates the larvae to metamorphose into a dwarf male within a few days, which clings to the female and is taken up by the female inside the sexual organs, where it is lives in the genital sac, an extension of the fallopian tube . The egg cells pass from the ovary via the body cavity and the eyelash funnel (nephrostome) into the nephridium, which also functions as the fallopian tube, where they are fertilized by the various males, so that they usually result in half-siblings with different fathers. The development into buoyant larvae takes place in a section of the fallopian tube that is enlarged towards the uterus , so that the larvae come out as a buoyant stage and leave their mother. Approximately 70% of the larvae that come into contact with unpopulated soil or a female metamorphose into females or males, while most of the remaining approximately 30% die off.

Initial description

The genus Bonellia and the type species with the species name Bonellia viridis , which is still valid today , were first described by the Italian anatomist Luigi Rolando in the 1821 annual edition of the Memorie della Reale Accademia delle Scienze di Torino . Rolando honored the Italian zoologist Franco Andrea Bonelli (1784-1830) and referred to the conspicuous green color of this hedgehog with the Latin epithet viridis ("green").

The genus Bonellia comprises a total of nine species (as of 2018). It forms a common clade with the genus Ikeda (systematically also referred to as the subordination Bonelliida). Both are characterized by the peculiar life cycle with dwarf males.

literature

Web links

Commons : Green hedgehog worm ( Bonellia viridis )  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Bonellia viridis, Green Spoonworm: Biogeographic Distribution Invertebrates of the Coral Sea, University of Queensland.
  2. ↑ Franz ‐ Peter Montforts, Ulrich M. Schwartz: Total synthesis of (±) ‐bonellin ‐ dimethylester. Justus Liebig's Annalen der Chemie 1991, pp. 709-725.
  3. ↑ Ludek Berec, Patrick J. Schembri, David S. Boukal (2005): Sex determination in Bonellia viridis (Echiura: Bonelliidae): population dynamics and evolution ( Memento of April 11, 2005 in the Internet Archive ). Oikos 108 (3), pp. 473-484. doi: 10.1111 / j.0030-1299.2005.13350.x
  4. ↑ Lexicon of Biology : Bonellia. Retrieved April 25, 2018.
  5. ↑ Bonellia Rolando, 1822 WoRMS World Register of Marine Species , accessed on 26 April 2018th
  6. ↑ 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