Ommatokoita elongata

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Ommatokoita elongata
Systematics
Sub-stem : Crustaceans ( Crustacea )
Subclass : Copepods ( Copepoda )
Order : Siphonostomatoida
Family : Lernaeopodidae
Genre : Ommatokoita
Type : Ommatokoita elongata
Scientific name of the  genus
Ommatokoita
Leigh-Sharpe, 1926
Scientific name of the  species
Ommatokoita elongata
( Grant , 1827)

Ommatokoita elongata is a species from the subclass of copepods that preferentially attach to the cornea of bowhead sharks ( Somniosus microcephalus ) and Pacific sleep sharks ( Somniosus pacificus ). Ommatokoita elongata is the only known species of the monotypic genus Ommatokoita (Leigh-Sharpe, 1926) and wasfirst scientifically describedby the Scottish doctor and zoologist Robert Edmond Grant in 1827 under the name Lernaea elongata .

features

Ommatokoita elongata shows how many representatives of the Lernaeopodidae have a pronounced sexual dimorphism . Unless otherwise stated, the following descriptions are essentially based on the descriptions by Kabata, 1988.

Adult females of Ommatokoita elongata , including the attached egg sacs, reach a length of 4–6 cm and are therefore unusually large for representatives of copepods . The cephalothorax is short and flat with only a weak spinal shield. The abdomen is much longer than it is wide and has an approximately parallel lateral border. There is no armor at the end of the abdomen. The perianal area is clearly set off. The second antennas serve as gripping tools. The mandibles have 3 secondary teeth. The first maxillae have a lateral floating branch and three terminal papillae on the walking branch . The second maxillae are elongated like a tentacle with two finger-shaped projections in the area of ​​the tips. The tips themselves are fused with one another and anchored in the cornea of the shark via the actual adhesive organ, the bulla . The bulla is plano-convex and sessile. The inner edge of the corpus maxillipedis is covered with numerous thorns. The body length (without second maxillae and egg sacs) is 2–2.5 cm.

Adult males are much smaller than the females and only reach a total length of 2.5 mm. The cephalothorax is longer than the abdomen and connects to its longitudinal axis at an obtuse angle. On the abdominal side there are large second maxilles and maxillipedas . At the end of the abdomen are the external genitals and uropods . Two rudimentary pairs of legs in the front part of the abdomen.

Way of life

Sexually mature females and larvae in the Copepodite stage parasitize on the eyeball of Greenland Sharks ( Somniosus microcephalus ) and Pacific Sleeping Sharks ( Somniosus pacificus ) where they cause severe tissue damage that can lead to blindness of the infected animal. The infestation rate is unusually high at 98.9% for the Greenland Shark and 97% for the Pacific Sleeping Shark .

The previously known distribution area of Ommatokoita elongata accordingly essentially coincides with the distribution areas of the two host species. The only exception to this seems to be a population of Greenland sharks in the mouth of the St. Lawrence River, where no infestation by Ommatokoita elongata could be determined.

Due to the high infestation rate, the hypothesis was put forward that the relationship between Ommatokoita elongata and the infected host animals is more mutualistic than purely parasitic . Specifically, it has been speculated that the bioluminescent , eye-dangling cancer would help the shark attract potential prey. However, bioluminescence could not be detected in Ommatokoita elongata .

Synonyms

" Lernaea elongata " ( Grant , 1827): (invalid)

First described by Grant in 1827

" Lernaeopoda elongata ": (invalid)

" Ommatokoita superba ng et sp." (Leigh-Sharpe, 1926): (invalid)

The genus newly established by Leigh-Sharpe in 1926 was found to be valid due to significant differences from other members of the Lernaeopodidae family , but the species " Ommatokoita superba " established by him was considered identical to " Lernaea elongata ". According to the priority rules of the biological nomenclature , Ommatokoita elongata is the valid species name

" Ommatokoita elongata " ( Grant , 1827): (valid)

Possible further representatives of the genus Ommatokoita

In 1986, a parasitic copepod was described on a specimen of the great black dogfish ( Etmopterus princeps ), which was very similar to Ommatokoita elongata . However, the animal was not attached to the shark's eyeball, but to the body behind the second dorsal fin. Furthermore, differences in body shape and size as well as in the structure of the first maxillae were found. However, the existing evidence was not sufficient to define a new, separate species and the genus Ommatokoita is therefore still regarded as monotypical for the time being .

Individual evidence

  1. ↑ a b c d R. E. Grant, MD, FRSE: On the Structure and Characters of the Lernaea elongata, Gr. a New Species from the Arctic Seas . In: The Edinburgh Journal of Science , Vol. VII, No. XIII, pp. 147–154 & Plate II, Fig. 5, 1827. (online at archive.org)
  2. ↑ GW Benz, Z. Lucas & LF Lowry: New host and ocean records for the copepod Ommatokoita elongata (Siphonostomatoida: Lernaeopodidae), a parasite of the eyes of sleeper sharks . In: The Journal of Parasitology , Vol. 84, No. 6, pp. 1271-1274, 1998. PMID 9920328 .
  3. ↑ a b W. H. Leigh-Sharpe: Ommatokoita superba ng et sp., A Parasitic Copepod of Somniosus microcephalus . In: Parasitology , Vol. 18, Issue 2, pp. 224–229, 1926. (Abstract at cambridge.org)
  4. ↑ a b c Z. Kabata: Copepoda and Branchiura In: L. Margolis & Z. Kabata (eds.): Guide to the Parasites of Fishes of Canada. Part II - Crustacea . - Canadian Special Publication of Fisheries and Aquatic Sciences 101, pp. 3–127, Ottawa, 1988. (online)
  5. ↑ MacNeil, BC McMeans, NE Hussey, P. Vecsei, J. Svavarsson, KM Kovacs, C. Lydersen, MA Treble, GB Skomal, M. Ramsey & AT Fisk: Biology of the Greenland shark Somniosus microcephalus . In: Journal of Fish Biology , 80, pp. 991-1018, 2012. (available at researchgate.net)
  6. ↑ a b J.D. Borucinska, GW Benz & EH Whiteley: Ocular lesions associated with attachment of the parasitic copepod Ommatokoita elongata (Grant) to corneas of Greenland sharks, Somniosus microcephalus (Bloch & Schneider) . In: Journal of Fish Diseases , Vol. 21, Issue 6, pp. 415-422, 1998. doi : 10.1046 / j.1365-2761.1998.00122.x
  7. ↑ a b c G. W. Benz, JD Borucinska, LF Lowry, EH Whiteley: Ocular Lesions Associated with Attachment of the Copepod Ommatokoita elongata (Lernaeopodidae: Siphonostomatoida) to Corneas of Pacific Sleeper Sharks Somniosus pacificus Captured off Alaska in Prince William Sound . In: Journal of Parasitology . tape 8 , no. 3 , 2002, p. 474-481 , doi : 10.1645 / 0022-3395 (2002) 088 [0474: OLAWAO] 2.0.CO; 2 (English).
  8. ↑ a b B. Berland: Copepod Ommatokoita elongata (Grant) in the eyes of the Greenland Shark - a possible cause of mutual dependence . In: Nature , 191, pp. 829-830, 1961.
  9. ↑ Ch. J. Harvey-Clark, JJ Gallant & JH Batt: Vision and its Relationship to Novel Behavior in St. Lawrence River Greenland Sharks, Somniosus microcephalus . In: Canadian Field-Naturalist , Vol. 119, Issue 3, pp. 355-359, 2005. (online)
  10. ^ SA Bullard: In Memoriam: George William Benz (January 1, 1954– February 9, 2015) . In: Acta Ichthyologica et Piscatoria . tape 46 , no. 2 , 2016, p. 141–162 , doi : 10.3750 / AIP2016.46.2.12 (English, (online) [PDF]).
  11. ↑ a b W. E. Hogans & J. Brattey: Ommatokoita sp. (Copepoda: Lernaeopodidae) parasitic on a demersal shark, Etmopterus princeps, from the northwest Atlantic Ocean . In: Canadian Journal of Zoology , Vol. 64, No. 4, pp. 833-835, 1986. doi : 10.1139 / z86-124