Beroe abyssicola

Beroe abyssicola is a beroid ctenophore, or comb jelly, in the genus Beroe.[1] It is largely found in deep waters in the North Pacific Ocean, and is common in Japan and the Arctic Ocean. A predator, Beroe feeds mostly on other ctenophores by swallowing them whole. Like other ctenophores, B. abyssicola has a simple nervous system in the form of a nerve net, which it uses to direct its movement, feeding, and hunting behaviors.

Beroe abyssicola
Scientific classification
Kingdom: Animalia
Phylum: Ctenophora
Class: Nuda
Order: Beroida
Family: Beroidae
Genus: Beroe
Species:
B. abyssicola
Binomial name
Beroe abyssicola
Mortensen, 1927

Description

Beroe abyssicola is a pelagic ctenophore species that inhabits the North Pacific.[2] Like other Beroida, B. abyssicola has a very different body plan from other Ctenophores, namely the lack of any tentacles in any life stage.[2] B. abyssicola has a muscular, flat, and cylindrical body. It can grow up to 7 cm long, shorter than other Beroids, but larger than most ctenophores.[3] Its body is more opaque than other ctenophores and can have coloration red or purple. When not feeding, the large mouth is kept closed using adhesive bands of epithelial cells that stick together, holding the mouth closed.[2]

Anatomy and behavior

Beroe abyssicola is a Ctenophore with a flexible, highly muscular body. Being a predator, B. abyssicola uses its muscular body along with its ctene rows to swim and capture its prey, and uses its wide mouth to swallow its prey whole.[2] When not feeding, the mouth is held closed using bands of adhesive epithelial cells paired for each mouth.[4] The mesoglea of Beroe have large smooth muscle fibers, which allows the ctenophore the flexibility to swallow much of its prey whole.[2]

Nervous system

The nervous system of B. abyssicola does not have a central nervous system, but rather consists of a nerve net. The largest concentration of nervous function is concentrated in the aboral organ, located opposite the mouth. Beroe has a defense response that retracts the entire aboral organ inside the body of itself for protection. This organ mediates swimming, gravity sensing and possibly more functions. The nerve net extends out from this organ, covering the surface and pharyngeal surface, as well as a separate system of neurons in the mesoglea.

There is a band of sensory cells surrounding the mouth of abyssicola that can detect chemical and mechanical stimuli. These "lips" can be used by Beroe to detect prey and assist with feeding.[2]

The nervous system of Beroe abyssicola, along with other Ctenophora, is different to those of other animals. Almost no neurotransmitters but glutamate are shared between ctenophore nervous systems and others, as well as lacking many of the same pathways involved in other nervous systems.[5] It has been hypothesized that the nervous systems of Beroe abyssicola, along with other Ctenophores, evolved independently of those of other animals.[5]

Feeding

Beroe abyssicola, like other members of the class Nuda, are predatory ctenophores, whose diet consists mainly of smaller ctenophores.[6] The primary prey of B. abyssicola is Bolinopsis infundibulum.[2] Beroe has a set of large cilia on the inside of its mouth called macrocilia.[7] These macrocilia are large enough to function as teeth, used to keep prey inside and even tear the tissue of the gelatinous prey. Using its "lips" to detect prey, Beroe opens its mouth and swallows its prey whole. B. abyssicola possesses a large pharynx that spans nearly the length of the body to digest its food, using pharyngeal muscles and macrocilia to keep its mouth closed and prey inside. Once digested, the food then moves through the gastrovascular system in canals, which supplies nutrients throughout the mesoglea.

Locomotion

Beroe's swimming is powered by 8 comb rows of joined cilia, swimming mouth-first. They swim constantly and strongly to search for prey, and swallow their prey blindly when they do.[8] Their swimming is controlled largely by the aboral organ.[2]

Distribution

Beroe abyssicola can be found throughout the Northern Pacific Ocean.[1] Abyssicola can be found up to 2000 meters below the ocean surface,[9] and is common in the waters around Japan, as well as the Arctic Ocean,[10] mostly found below 400 meters.[11]

Bioluminescence

Like other ctenophores, B. abyssicola has a rainbow effect on its comb rows caused by light refraction, but it also possesses bioluminescence. Bioluminescence in Beroe is caused by calcium activated photoproteins, similar to hydromedusae. This photoprotein is called berovin, and differs from photoproteins used by hydromedusa in that it is sensitive to visible and UV light, and largely has a different genetic sequence.[12] However both types of photoprotein have a similar EF-Hand structure despite the sequence differences between the two proteins.

Taxonomy

Beroe abyssicola is a ctenophore in the genus Beroe, in the class Nuda. It is classified here because of its lack of tentacles placing it into the Nuda class, and its cylindrical body shape classifying it as Beroe. Ctenophore phylogeny is complicated and not agreed upon entirely. Recent evidence[13] suggests that the Beroida order may be polyphyletic, with Beroe abyssicola being outside of the clade including all other Beroe species. This also suggests B. abyssicola evolved a loss of tentacles independently of other Beroid species.

References
  1. "WoRMS - World Register of Marine Species - Beroe abyssicola Mortensen, 1927". www.marinespecies.org. Retrieved 2020-02-17.
  2. Norekian, Tigran P.; Moroz, Leonid L. (2019-08-15). "Neural system and receptor diversity in the ctenophore Beroe abyssicola". Journal of Comparative Neurology. 527 (12): 1986–2008. doi:10.1002/cne.24633. ISSN 0021-9967. PMID 30632608.
  3. Guha, Hazel (2008-03-28). "The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon (4th ed.)2008133Edited by James T. Carlton. The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon (4th ed.). Berkeley, CA and London: University of California Press 2007. xvii+1001 pp., ISBN: 978 0 520 23939 5 £50; $85". Reference Reviews. 22 (3): 44. doi:10.1108/09504120810859891. ISSN 0950-4125.
  4. Tamm, S.; Tamm, S. (1991). "Macrociliary Tooth Patterns in Beroid Ctenophores". The Biological Bulletin. 181 (2): 355–356. doi:10.1086/BBLv181n2p355. ISSN 0006-3185. PMID 29304610.
  5. Moroz, L. L. (2015-02-15). "Convergent evolution of neural systems in ctenophores". Journal of Experimental Biology. 218 (4): 598–611. doi:10.1242/jeb.110692. ISSN 0022-0949. PMC 4334147. PMID 25696823.
  6. Harbison, G. R.; Madin, L. P.; Swanberg, N. R. (1978-03-01). "On the natural history and distribution of oceanic ctenophores". Deep Sea Research. 25 (3): 233–256. Bibcode:1978DSR....25..233H. doi:10.1016/0146-6291(78)90590-8. ISSN 0146-6291.
  7. Tarmm, Sidney L.; Tamm, Signhild (1987). "Massive actin bundle couples macrocilia to muscles in the ctenophore Beroë: Actin Bundle in Beroë". Cell Motility and the Cytoskeleton. 7 (2): 116–128. doi:10.1002/cm.970070204. PMID 3581184.
  8. "Beroe". 2016-02-20. Archived from the original on 2016-02-20. Retrieved 2020-04-06.
  9. "Beroe abyssicola Mortensen, 1927 - Ocean Biogeographic Information System". obis.org. Retrieved 2020-04-06.
  10. "New technology helps researchers study unknown Arctic comb jellies". UAF news and information. 2016-10-28. Retrieved 2020-02-17.
  11. Lindsay, Dhugal J.; Hunt, James C. (2005). "Biodiversity in midwater cnidarians and ctenophores: submersible-based results from deep-water bays in the Japan Sea and north-western Pacific". Journal of the Marine Biological Association of the United Kingdom. 85 (3): 503–517. doi:10.1017/S0025315405011434. ISSN 1469-7769.
  12. Markova, Svetlana V.; Burakova, Ludmila P.; Golz, Stefan; Malikova, Natalia P.; Frank, Ludmila A.; Vysotski, Eugene S. (2012). "The light-sensitive photoprotein berovin from the bioluminescent ctenophore Beroe abyssicola: a novel type of Ca2+-regulated photoprotein: Recombinant calcium-regulated photoprotein berovin". FEBS Journal. 279 (5): 856–870. doi:10.1111/j.1742-4658.2012.08476.x. PMID 22230281.
  13. Simion, Paul; Bekkouche, Nicolas; Jager, Muriel; Quéinnec, Eric; Manuel, Michaël (2015). "Exploring the potential of small RNA subunit and ITS sequences for resolving phylogenetic relationships within the phylum Ctenophora". Zoology. 118 (2): 102–114. doi:10.1016/j.zool.2014.06.004. PMID 25440713.
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