Themiste hennahi

Themiste hennahi is a species of unsegmented benthic marine worm in the phylum Sipuncula, the peanut worms. It is native to shallow waters on the Pacific coast of North and South America. This worm was first described in 1828 by the British zoologist John Edward Gray as Themiste hennahi, the type specimen having been collected by the Rev. W. Hennah, with the type locality being Peru.[2]

Themiste hennahi
Scientific classification
Kingdom:
Animalia
Phylum:
Sipuncula
Class:
Sipunculidea
Order:
Golfingiida
Family:
Themistidae
Genus:
Themiste
Species:
T. hennahi
Binomial name
Themiste hennahi
Gray, 1828[1]
Synonyms[1]
  • Dendrostoma mytheca Chamberlin, 1919
  • Dendrostoma perimeces Fisher, 1928
  • Dendrostoma peruvianum Collin, 1892
  • Dendrostoma ramosum (Quatrefages, 1865)
  • Dendrostoma zostericolum Chamberlin, 1919
  • Dendrostomum lissum Fisher, 1952
  • Dendrostomum peruvianum Collin, 1892
  • Dendrostomum ramosum Quatrefages, 1865
  • Dendrostomum schmitti Fisher, 1952
  • Dendrostomum zostericolum Chamberlin, 1919
  • Phascolosoma rapa (Quatrefages, 1865)
  • Sipunculus rapus Quatrefages, 1865
  • Themiste lissa (Fisher, 1952)
  • Themiste perimeces (Fisher, 1928)
  • Themiste ramosa (Quatrefages, 1865)
  • Themiste schmitti (Fisher, 1952)
  • Themiste zostericola (Chamberlin, 1919)

Description

The body of this worm is cylindrical. The introvert (the retractable anterior part of the worm) is tipped by a crown-like structure of six branching tentacles which surround the mouth. The collar (immediately behind the tentacles) is not reddish-purple as it is in Themiste dyscrita, and the introvert is devoid of spines.[3]

Distribution and habitat

Themiste hennahi is native to the tropical and subtropical eastern Pacific Ocean, its range including the western coast of the United States, and the coasts of Peru and Chile. It burrows into sandy, gravelly, silty and muddy substrates in the intertidal zone, including eelgrass beds, and conceals itself under loose rocks.[4]

Ecology

This worm often lives in a burrow or other low-oxygen environment, extending its introvert into the water column to feed. The skin of the trunk is thick and unsuitable as a respiratory surface. Research has shown that the tentacular crown is the main respiratory surface, leading to this worm being described as a "tentacle breather".[5] Oxygen diffuses into the fluid inside the tentacular system where it is taken up by the pigment hemerythrin in the blood cells. The oxygen further diffuses through an elaborate septum into the coelomic cavity where it is retained because there is a greater capacity for oxygen in the coelom than in the tentacular cavity. This respiratory system makes the worm resistant to a lack of oxygen as it can call on the oxygen already bound to the hemerythrin when the oxygen in its environment is insufficient.[5]

References
  1. Saiz-Salinas, José (2009). "Themiste (Themiste) hennahi Gray, 1828". WoRMS. World Register of Marine Species. Retrieved 28 February 2019.
  2. Zoological Society (London) (1868). Proceedings of the Zoological Society of London: 1868. p. 98.
  3. Light, Sol Felty (2007). The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon. University of California Press. pp. 288–289. ISBN 978-0-520-23939-5.
  4. "Themiste hennahi Gray, 1828". SeaLifeBase. Retrieved 28 February 2019.
  5. Australian Biological Resources Study (2000). Polychaetes & Allies: The Southern Synthesis. CSIRO Publishing. p. 383. ISBN 978-0-643-06571-0.
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