Fish nose

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Most fish, like this grouper ( Epinephelus bruneus ), have two nostrils on each side of the head.
The large nostrils of a sturgeon ( Acipenser sinensis )

The nose (from Latin nasus ) or olfactory pit of the fish is anatomically the organ of cartilaginous fish and bony fish , which usually includes four outer nostrils and the two nasal cavities. This structure forms the seat of a chemical sensory organ, which is also known in fish as the sense of smell . In none of the fish living today is the nose used for breathing. In addition, most fish species lack the connection between the nose and the mouth or throat . In the lung fish in which such a connection exists, no respiratory flow via the nose was observed, neither when breathing in the water nor when breathing air. Breathing through the nose did not develop until the amphibians . The jawless lampreys and hagfish have only one nostril that leads into a paired but connected nasal cavity.

General

The fish's sense of smell is a chemical sense that responds to the substances dissolved in the water. In addition to the olfactory organ located in the nose, there are other chemical sensory organs in fish, namely the taste buds in the mouth or on the nearby structures such as barbels and on the skin and the general chemical skin senses, consisting of single-celled sensory organs ( solitory chemosensory cells ) and free nerve endings, which mainly allow attackers or conspecifics to smell. The diversity and exact function of these different senses has not yet been adequately researched.

For many fish, the sense of smell as a chemical remote sense is more important than the sense of sight for the perception of food sources or enemies . The light intensity in the water decreases rapidly with increasing depth; at shallower depths, turbidity caused by turbulent sediments can obstruct the view. The shark's good sense of smell, together with sound waves, allows it to track down its prey. Since the specific composition of sound has a short range, the sense of smell is also ascribed an important role in the settlement of fish in coral reefs . Although the fish larvae are drifted by the currents and the tides, a large part of them return to their home reef, and even to the population from which they came.

anatomy

The nasal organ is typically developed in most ray fins (Actinopterygii), the other fish groups differ little. The olfactory membrane forms an oblong, round rosette of folds around a longitudinal middle raphe in each nasal sac . Only with Lepisosteus from the family of gars the medial half of the rosette missing. The wrinkles increase in number over the course of life. In microsmats , vertebrates with relatively few olfactory receptors, in which odor perception plays a minor role, e.g. B. the pike only a few olfactory folds are formed. In a few Teleostei like Belone and Syngnathus they are completely absent. On each fold ( plica ) z. B. In salmon , cod and perch, additional lamellae that enlarge the olfactory epithelium are often missing. In the bald pike ( Amia calva ), which with over 100 folds does not count among the microsmats, these lamellae are missing, as are the female fish (genus Elops ) and moon-eyes (genus Hiodon ) , which are not closely related to Amia .

A placode is the embryonic structure of a sensory epithelium, which soon thickens and bulges or bulges. The embryonic olfactory placodes are always paired in the jaw mouths , which include all vertebrates with the exception of the lampreys and hagfish . This feature also led to the name Diplorhina or Amphirhina for the jaw mouths and contributed to the view that the jaws can only form after the two nasal organs. The monorhina , i.e. the jawless ones, have only one nostril.

In the Actinopterygii the nasal primordia soon migrate to the top of the snout, in the Dipnoi , however, they remain ventral, like in the sharks and rays . They then sink into a cranial fossa each and the nasal capsules arise. A flap of skin grows over it mediad - in this way, two nostrils are created on both sides, also called narins (from Latin naris "nostril"). The largest probably have the sturgeon ( acipenser ), with 20–30 folds. In 1994, Chen and Arratia even found tertiary lamellae in the Atlantic sturgeon ( Acipenser oxyrinchus ).

At least in fish, this pairing of the olfactory organs is often interpreted functionally. The direction of an odor stream could be perceived with the two olfactory organs, but this has not been proven with certainty. For sharks, for example, it is possible to determine from which direction a chemical stimulus has come by perceiving the flow conditions with the help of the lateral line organ . Only in hammerheads , in which the nostrils sit on the hammer-shaped widening of the head, the cephalofoil , is the distance large enough to be able to perceive a gradient in the concentration of chemical fragrances between left and right. A corresponding reaction has been demonstrated in tests. Hammerhead sharks have short, lobed nasal flaps, and the distance between the nostrils on the front edge of the cephalofoil is 7 to 14 times the nostril diameter.

particularities

Two pairs of nostrils (Narinen), interspersed with low sail, while Hecht .
Rhinomuraena - male with funnel-shaped anterior narins. The females have similar funnels.

In most fish, other devices help to move the medium over the olfactory epithelium : cilia stroke (e.g. with eels ), the swimming movement of the animal itself, the strengthening of the current through a transverse skin sail on the outside between the anterior and posterior narine (in many carp-like species, etc.), or pumping movements through muscle movements on neighboring bones. These facilities are found in many Acanthopterygii , but they are still completely absent in the Osteoglossiformes . Quite a few Teleostei such as Gasterosteidae , Hexagrammidae , Cichlidae , Anarhichadidae , Zoarcidae only have one nostril each. In many percoidei, each nasal sac forms two soft-skinned blind tubes , one below the nasal, it extends beyond the rostral cartilage, and one medial to the lacrimal. In many paracanthopterygii, among others, there is only one each. Rarely, mainly in benthic fish, there are also three or four. They are difficult to prepare and can practically only be made visible by means of injection. They are put into function by movements of the maxillary apparatus or, in the absence of this, via the lacrimal, etc., thus indirectly by the masticatory muscle or even separate divisions from it as in Amia - ie even with somewhat stronger breathing movements. Cilia are often still active as well. It is possible that the frequent “ yawning ” also serves to “smell ”. Mostly, mucosal flaps can be identified as valves for the accessory nasal sacs.

The rear of the two narines is usually wider in order to obstruct the flow as little as possible. The front nostrils can be placed on tubes ("tentacles") in order to take in water from the vicinity of the mouth. B. in Polypterus , Amia , Notopterus , Anguilla , Muraena , Mastacembelus , Tetraodon . In Rhinomuraena there is a large, funnel-shaped flap of skin on each of the two front nostrils. The rear nostrils can be moved to the edge of the eyes and slit-shaped z. B. in Anguilla , similar in Pollimyrus . The slits could have a valve function, but there is no corresponding function for the anterior nostrils cf. Mastacembelidae or even, with stomatorhinus , towards the corner of the mouth.

breathing

Although it seems obvious to use the respiratory water flow for chemical perception as well, as happens with the air in terrestrial vertebrates, a connection between the nasal organ and the oral cavity is seldom and secondary (argument against Bjerring 1968, who even used the nose of a pair of gill slits): in sharks and rays (nasolabial folds to the mouth), in sea ​​cats and lungfish (rear narine in the mouth, but no choane , because this is not a narine homologous), and in some teleostei such as snake eels (Ophichthidae) and sky gazers (genus Astroscopus ). In these fish, the posterior narine opens medial to the premaxillary into the oral cavity. They live mostly buried, e.g. B. Astroscopus guttatus as well as Gymnodraco and Psilodraco (see M. Jakubowski 1976). Whether or not "real choans" are present here depends on whether one wishes to derive and define them from the secondary confluence of accessory nasal sacs into the oral cavity.

The unique connection of the (here "unpaired") nose with the pituitary duct opening into the throat , in the case of the Hyperotreti (Myxini), has not yet been clarified morphologically and functionally. Physiologically are hagfishes any case macro Maten , especially since they are blind rely on chemical perception. The last-mentioned seven taxa would therefore be the only ones among the "fish" that can breathe through the nose in order to take in the weather.

Magnetoreceptors

Single -celled magneto receptors have been found in the nasal mucous membrane of some fish species that are apparently able to orient themselves in the earth's magnetic field (e.g. Oncorhynchus with magnetite granules; Walker et al. 1997). These salmon in particular, like Salmo salar, are famous for their far-reaching homing behavior in the sea , which “switches” to olfaction (smell) near the coast.

Individual evidence

  1. ↑ James W. Atz: Narial Breathing in Fishes and the Evolution of Internal Nares. In: The Quarterly Review of Biology. 27, 4 The University of Chicago Press, 1952, pp. 366-377. ( Abstract at JSTOR)
  2. ↑ Kurt Kotrschal: Solitary chemosensory cells: why do primary aquatic vertebrates need another taste system? In: TREE. 11, 3, Elsevier Science, 1996, pp. 110-114.
  3. ^ TJ Hara: Mechanism of olfaction. In: TJ Hara (Ed.): Fish chemoreception. Chapman and Hall, London 1992, pp. 150-170.
  4. ^ Davies-Colley, DG Smith: Turbidity, Suspended Sediment, and Water Clarity: A Review. In: Journal of the American Water Resources Association. 37, 2001, pp. 1085-1101.
  5. ^ AC Utne-Palm: Visual feeding of fish in a turbid environment: Physical and behavioral aspects. In: Marine and Freshwater Behavior and Physiology. 35, 2002, pp. 111-128.
  6. ↑ Wolfgang Legrum: Fragrances, between stench and fragrance. Vieweg & Teubner Verlag, 2011, ISBN 978-3-8348-1245-2 , p. 43.
  7. ↑ Gabriele Gerlach, Jelle Atema, Michael J. Kingsford, Kerry P. Black, Vanessa Miller-Sims: Smelling home can prevent dispersal of reef fish larvae. In: Proceedings of the National Academy of Sciences of the USA. 104, 3, 2007, pp. 858-863.
  8. ↑ placard. 5th edition. In: Roche Lexicon Medicine. Urban & Fischer, 2003.
  9. ↑ Sabine Goldhahn: Nose creates jaw . Deutschlandfunk, Forschungs aktuell dated August 18, 2011 (accessed January 23, 2013)
  10. ↑ Timothy C. Tricas, Stephen M. Kajiura, Adam P. Summers: Response of the hammerhead shark olfactory epithelium to amino acid stimuli. In: Journal of Comparative Physiology. A, 195, 2009, pp. 947-954.
  11. ^ XY Chen, GF Arratia: Olfactory Organ of Acipenseriformes and Comparison With Other Actinopterygians: Patterns of Diversity. In: Journal of Morphology. 222, 3, 1994, pp. 241-267.
  12. ^ GA Nevitt: Do fish sniff? A new mechanism of olfactory sampling in pleuronectid flounders. In: Journal of Experimental Biology. 157, 1991, pp. 1-18.
  13. ^ RH Burne: The anatomy of the olfactory organ of teleostean fishes. In: Proceedings of the Zoological Society of London. 2, 1909, pp. 610-663.
  14. ^ O. Stabell: Homing and olfaction in Salmonids: a critical review with special reference to the Atlantic Salmon. In: Biological Reviews. 59, 3, 2008, pp. 333-388.

literature

  • Wilfried Westheide, Reinhard Rieger: Special Zoology. 2nd Edition. Volume 2: Vertebrates or Skull Animals. Elsevier - Spektrum Akademischer Verlag, Munich 2010, ISBN 978-3-8274-2039-8 .
  • Alfred Sherwood Romer, Thomas S. Parsons: The Vertebrate Body. Holt-Saunders International, Philadelphia 2007, ISBN 978-0-03-910284-5 , pp. 453-458.

Web links

  • Don Glass: Can fish smell? A Moment in Science, November 29, 2004 (accessed January 24, 2013)