Streptoneury or chiastoneury is a plesiomorphic condition present in all gastropods which is a result of an evolutionary event called torsion in which the intestines, heart, nephridia, gills, and nerve cords "twist" causing some organs to migrate from the animal's left to its right in order to accommodate the relocation of the mantle cavity close to the animal's head. Specifically, streptoneury is the crossing of the cerebrovisceral connectives caused by this torsion.[1][2]
An illustration of the evolutionary process of streptoneury among gastropods. A. bilateral, B. asymmetrical, C. streptoneurous condition. The reference letters are placed upon the organs of the primitive left side. a. anus; c. cerebral ganglion; g. ctenidium; l. auricle; m. mouth; n. nephridial opening; o. osphradium; pa. parietal ganglion; pe. pedal ganglion; pl. pleural ganglion; v. ventricle.
In a streptoneurous animal, the right visceral nerve becomes a supraintestinal nerve (i.e., moving up from its former position along the intestines on the right side) and the left visceral nerve becomes a subintestinal nerve (i.e., moving down below the intestines and shifting to the right).
The extant gastropod molluscs can be described as streptoneurous. However, some lineages, especially the opisthobranchs,[2] have reversed this twist secondarily. The term for this event is detorsion, and the condition in a detorted animal— a state in which these nerves no longer cross— is called euthyneury.[3]
Referencesedit
^Hertwig, Richard; Kingsley, John Sterling (1905). A manual of zoology. H. Holt and company. p. 373.
^ abChase, Ronald (2002). Behavior and Its Neural Control in Gastropod Molluscs. Oxford University. p. 6. ISBN9780195354485.
^Barker, G. M. (2001). The biology of terrestrial molluscs. CABI. p. 185. ISBN9780851997186.
This gastropod-related article is a stub. You can help Wikipedia by expanding it.
streptoneury, chiastoneury, plesiomorphic, condition, present, gastropods, which, result, evolutionary, event, called, torsion, which, intestines, heart, nephridia, gills, nerve, cords, twist, causing, some, organs, migrate, from, animal, left, right, order, a. Streptoneury or chiastoneury is a plesiomorphic condition present in all gastropods which is a result of an evolutionary event called torsion in which the intestines heart nephridia gills and nerve cords twist causing some organs to migrate from the animal s left to its right in order to accommodate the relocation of the mantle cavity close to the animal s head Specifically streptoneury is the crossing of the cerebrovisceral connectives caused by this torsion 1 2 An illustration of the evolutionary process of streptoneury among gastropods A bilateral B asymmetrical C streptoneurous condition The reference letters are placed upon the organs of the primitive left side a anus c cerebral ganglion g ctenidium l auricle m mouth n nephridial opening o osphradium pa parietal ganglion pe pedal ganglion pl pleural ganglion v ventricle In a streptoneurous animal the right visceral nerve becomes a supraintestinal nerve i e moving up from its former position along the intestines on the right side and the left visceral nerve becomes a subintestinal nerve i e moving down below the intestines and shifting to the right The extant gastropod molluscs can be described as streptoneurous However some lineages especially the opisthobranchs 2 have reversed this twist secondarily The term for this event is detorsion and the condition in a detorted animal a state in which these nerves no longer cross is called euthyneury 3 References edit Hertwig Richard Kingsley John Sterling 1905 A manual of zoology H Holt and company p 373 a b Chase Ronald 2002 Behavior and Its Neural Control in Gastropod Molluscs Oxford University p 6 ISBN 9780195354485 Barker G M 2001 The biology of terrestrial molluscs CABI p 185 ISBN 9780851997186 nbsp This gastropod related article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Streptoneury amp oldid 1063330087, wikipedia, wiki, book, books, library,
