Sepia trygonina
{{Short description|Species of cuttlefish}}
{{Speciesbox
| image =
| status = LC
| status_system = IUCN3.1
| genus = Sepia
| parent = Sepia (Doratosepion)
| species = trygonina
| authority = (Rochebrune, 1884)Doratosepion trygoninum Rochebrune, 1884, Bulletin des Sciences par la Societe Philomatique de Paris, 7(8): 97
| synonyms = *Doratosepion trygoninum Rochebrune, 1884
| synonyms_ref = {{cite web | url = http://www.marinespecies.org/aphia.php?p=taxdetails&id=220311 | title = Sepia trygonina (Rochebrune, 1884) | access-date = 8 April 2017 | publisher = World Register of Marine Species | author = J. Finn | year = 2016}}
}}
Sepia trygonina, the trident cuttlefish, is a species of cuttlefish in the genus Sepia from the Red Sea and the western Indian Ocean. They are also a major source of food for larger marine life like dolphins, seals, and even birds.{{Cite journal|last1=Sajikumar|first1=K.K|last2=Ragesh|first2=N.|last3=Said Koya|first3=K. P.|last4=Venkatesan|first4=V.|last5=Joseph|first5=Mathew|last6=Remya|first6=R.|last7=Mohamed|first7=K.S.|date=2013-10-15|title=Paralarva of the sharpear enope squid Ancistrocheirus lesueurii (Oegopsida: Ancistrocheiridae) in the southeastern Arabian Sea|journal=Journal of the Marine Biological Association of India|volume=55|issue=2|pages=79–82|doi=10.6024/jmbai.2013.55.2.01796-12|issn=0025-3146|url=http://eprints.cmfri.org.in/10058/1/Article-12.pdf}}
Description
It is characterized by 10 appendages, two tentacles and eight arms that surround the mouth, which are covered in suckers. The difference between arms and tentacle clubs are that tentacles are an elongated arm that ends in a point, while tentacle clubs are a long appendage that has a rounded end. On its tentacle clubs, it has 8 different suckers in distinct rows and then 5 larger sized ones. Some of the arms have a hollowed-out section that replaces suckers.{{Cite book |title=Yearbook of the United Nations 1995 |date=1995-12-31 |isbn=9789210574907 |pages=1469–1472 |chapter=Food and Agriculture Organization of the United Nations (FAO) |doi=10.18356/d6ce0776-en}} Their legs are placed below their eyes and are held together like a swimming keel.{{Cite journal|title=Cephalopods of the World . Vol. 3|last=Patrizia|first=Jereb|date=2014|doi = 10.18356/0c7b0c29-en|s2cid=201770112 }} They also have free fins on their head, which are used to maneuver the cuttlefish in the water in whichever way they choose.{{Cite journal|last1=Sasikumar|first1=Geetha|last2=Mohamed|first2=K.S.|last3=Bhat|first3=U.S.|date=2013-07-22|title=Inter-cohort growth patterns of pharaoh cuttlefish Sepia pharaonis (Sepioidea: Sepiidae) in Eastern Arabian Sea|journal=Revista de Biología Tropical|volume=61|issue=1|pages=1–14|doi=10.15517/rbt.v61i1.10871|pmid=23894959|issn=2215-2075|doi-access=free}} They are able to propel themselves through the water by pumping water through and out of a siphon in their body.{{Citation|last=Guerra|first=Ángel|chapter=Functional Anatomy: Macroscopic Anatomy and Post-mortem Examination|date=2019|pages=11–38|publisher=Springer International Publishing|isbn=9783030113292|doi=10.1007/978-3-030-11330-8_3|title=Handbook of Pathogens and Diseases in Cephalopods|doi-access=free|hdl=10261/180240|hdl-access=free}} The eyes are covered with a transparent membrane and false eye lids. Their eyes are laterally placed, which allow them to see 177 degrees and use binocular vision to help them hunt and camouflage.{{Cite journal|last1=Schnell|first1=Alexandra K.|last2=Bellanger|first2=Cécile|last3=Vallortigara|first3=Giorgio|last4=Jozet-Alves|first4=Christelle|title=Visual asymmetries in cuttlefish during brightness matching for camouflage|journal=Current Biology|language=en|volume=28|issue=17|pages=R925–R926|doi=10.1016/j.cub.2018.07.019|pmid=30205059|year=2018|doi-access=free|bibcode=2018CBio...28.R925S }} They contain only one set of gills. This cuttlefish can be recognized by its small body, slender tentacles, and lanceolate, or leaf-like, shape.{{Cite book|title=Cephalopod bionomics, fisheries and resources of the exclusive economic zone of India|last=Silas, E. G.|date=1986|publisher=Central Marine Fisheries Research Institute|oclc=19660837}}
There are some characteristic differences between male and female trident cuttlefish, especially in their arms. For males, one set of their arms are significantly shorter than the others. Additionally, the suckers are in rows of four on their tentacles. In female cuttlefish, the suckers on two pairs of arms are in rows of four. Then on the other pair of arms, the suckers are in rows of four only on the distal third of the arms. Additionally, the area that surrounds the cuttlefish's beak, called the buccal membrane, is covered with longitudinal ridges.{{Cite book|title=Cephalopods of the world : an annotated and illustrated catalogue of cephalopod species known to date|editor=Jereb, Patrizia |editor2=Roper, Clyde F. E. |date=2005|publisher=Food and Agriculture Organization of the United Nations|isbn=9251053839|oclc=493888222}} Overall, the female trident cuttlefish is generally larger than the male.
Distribution
Sepia trygonina is known from the Indian Ocean, including the Saya-de-Malha Bank, region of the Mascarene Ridge and Zanzibar, the Red Sea, the Persian Gulf and southern India.Sarvesan R. (1976); On the Occurrence of Sepia trygonina (Rochebrune) (Cephalopoda: Sepiidae) in Gulf of Mannar; Indian Journal of Fisheries Vol 23, No 1 & 2
Habitat
The trident cuttlefish occurs at depths of 20 to 410 m. Just like other cephalopods, all cuttlefish go through vertical migration. During the day, they will be at depths around 400m or more and then will travel to up to around 20m or shallower during the night.
Fisheries
This species is an occasional catch for trawlers in India,{{cite web|url=http://eprints.cmfri.org.in/2858/1/Article_19.pdf|title=NATIONAL SYMPOSIUM ON RESEARCH AND DEVELOPMENT IN MARINE FISHERIES|website=Eprints.cmfri.org.in|access-date=13 March 2022}} but is listed as heavily exploited by native fishermen in Yemen.Abubakr, M.M. 2004 The Republic of Yemen Marine Biotic Ecosystem (Resources, Habitats and Species)The Republic of Yemen, Ministry of Water and Environment, Environment Protection Authority.
Camouflage
The trident cuttlefish is able to change the color of its skin in 270-730 milliseconds in response to what is going on around them in their environment. They do this by the use of chromatophores, which are organs in their skin that are used for pigmentation. They are able to respond to any conflicting patterns on either side of their body and will replicate those conflicting patterns on their body. They do this by their laterally placed eyes that can see the surrounding environment on either side of them. They also seem to favor their right eye over their left for adjusting camouflage patterns on their body. Then, they use their left eye to scan their surroundings for any potential predators.{{Cite journal|last1=Schnell|first1=Alexandra K.|last2=Bellanger|first2=Cécile|last3=Vallortigara|author-link3=Giorgio Vallortigara|first3=Giorgio|last4=Jozet-Alves|first4=Christelle|title=Visual asymmetries in cuttlefish during brightness matching for camouflage|journal=Current Biology|language=en|volume=28|issue=17|pages=R925–R926|doi=10.1016/j.cub.2018.07.019|pmid=30205059|year=2018|doi-access=free|bibcode=2018CBio...28.R925S }} The trident cuttlefish will camouflage in the presence of absence of any predators.