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Rostrum (anatomy)

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Anatomy term

Rostrum (fromLatinrostrum, meaningbeak) is a term used inanatomy for several kinds of hard,beak-like structures projecting out from the head or mouth of an animal. Despite some visual similarity, many of these arephylogenetically unrelated structures in widely varying species.^{[citation needed]}

Diagram ofNebalia bipes showing the rostrum at2

Invertebrates

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In spiders, the rostrum is a part of the mouth of which it borders the opening in front. Homologous of an upper lip, this outgrowth is especially characterised by the presence of a pocket-shaped secreting organ, the rostral gland, only accessible by the sole means of histology and electron microscopy (external link "archentoflor").
Incrustaceans, the rostrum is the forward extension of thecarapace in front of the eyes.^[1] It is generally a rigid structure, but can be connected by a hinged joint, as seen inLeptostraca.^[2]
Amonginsects, the rostrum is the name for the piercingmouthparts of the orderHemiptera as well as those of thesnow scorpionflies, among many others. The long snout ofweevils is also called a rostrum.^[3]
Gastropod molluscs have a rostrum orproboscis.^[4]
Cephalopod molluscs have hardbeak-like mouthparts referred to as the rostrum.^[5]

Invertebrate rostrums
Crustacean: the rostrum of the shrimpMacrobrachium rosenbergii isserrated along both edges.
Insect:assassin bug piercing its prey with its rostrum
Cephalopod: the two-part beak of agiant squid
Proboscis of hawk-moth (Agrius convolvuli)

Vertebrates

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Diagram of a wolf skull with key features labelled

In mammals, the rostrum is that part of thecranium located in front of thezygomatic arches, where it holds the teeth, palate, and nasal cavity.^[6] Additionally, thecorpus callosum of the human brain has a nerve tract known as the rostrum.

The beak orsnout of avertebrate may also be referred to as the rostrum.

Somecetaceans, includingtoothed whales such asdolphins^[7]^[8] andbeaked whales, have rostrums (beaks) which evolved from their jawbones. Thenarwhal possesses a large rostrum (tusk) which evolved from a protruding canine tooth.
Somefish have permanently protruding rostrums which evolved from theirupper jawbones.Billfish (marlin,swordfish andsailfish) use rostrums (bills) to slash and stun prey.Paddlefish,goblin sharks andhammerhead sharks have rostrums packed withelectroreceptors which signal the presence of prey by detecting weak electrical fields.Sawsharks and the critically endangeredsawfish have rostrums (saws) which are both electro-sensitive and used for slashing.^[9] The rostrums extendventrally in front of the fish. In the case of hammerheads the rostrum (hammer) extends both ventrally andlaterally (sideways).

The upper jawbones of some fish have evolved into rostrums
Sailfish, like allbillfish, have a rostrum (bill) which is an extension of their upper jawbone.
Thepaddlefish has a rostrum packed withelectroreceptors.
Sawfish have an electro-sensitive rostrum (saw) which is also used to slash at prey.

References

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^Charles Drew (November 17, 2003)."Crustacea".University of Bristol.Archived from the original on July 3, 2012. RetrievedNovember 7, 2010.
^Todd A. Haney, Joel W. Martin & Eric W. Vetter (2007)."Leptostraca". In James T. Carlton (ed.).The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon (4th ed.).University of California Press. pp. 484–495.ISBN 978-0-520-23939-5.Archived from the original on 2020-09-12. Retrieved2020-09-12.
^George Gordh, Gordon Gordh & David Headrick (2003)."Rostrum".A Dictionary of Entomology.CAB International. p. 792.ISBN 978-0-85199-655-4.
^Douglas Grant Smith (2001)."Mollusca (gastropods, pelecypods)".Pennak's freshwater invertebrates of the United States: Porifera to Crustacea (4th ed.).John Wiley and Sons. pp. 327–400.ISBN 978-0-471-35837-4.Archived from the original on 2020-09-12. Retrieved2020-09-12.
^Burt Carter."Cephalopods". Invertebrate Paleobiology.Archived from the original on 2012-04-02. Retrieved2011-09-22.
^Elbroch, Mark "Animal Skulls: A Guide to North American Species", Stackpole Books 2006, p9
^William F. Perrin; Bernd Würsig; J.G.M. Thewissen (26 February 2009).Encyclopedia of Marine Mammals. Academic Press.ISBN 978-0-08-091993-5.Archived from the original on 2 September 2020. Retrieved12 September 2020.
^"Basic anatomy of Cetaceans – Dolphins".Robin's Island. Archived fromthe original on November 17, 2010. RetrievedNovember 7, 2010.
^Wueringer, Barbara E.; Squire, Lyle; Kajiura, Stephen M.; Hart, Nathan S.; Collin, Shaun P. (2012)."The function of the sawfish's saw".Current Biology.22 (5):R150 –R151.Bibcode:2012CBio...22.R150W.doi:10.1016/j.cub.2012.01.055.PMID 22401891.