Spadix (zoology)

Diagram of the mouth of an adult male Nautilus pompilius. AS, antispadix; B, buccal mass; CS, cephalic sheath composed of the fused sheaths of the digital tentacles; O', preocular tentacle; O'', postocular tentacle; S, spadlx; SLL, superior labial lobe; V, Van der Hoeven's organ.

In the field of zoology, a spadix (pl.: spadices) is a secondary sexual organ found in some cephalopods and hydrozoans. In the genus Nautilus, the spadix is a composite erectile organ in the male located in the oral region which is composed of four highly modified tentacles and which is paired with a somewhat smaller antispadix that is also composed of four tentacles. The spadix is normally a concealed organ but quickly becomes distended upon the animal's death. The exact function of the spadix and antispadix in Nautilus is not yet known.[1]

## See also

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* Spadix (botany)

## References

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1. ^ Arthur Giese (2 December 2012). Reproduction of Marine Invertebrates V4: Molluscs: Gastropods and Cephalopods. Elsevier Science. p. 233\. ISBN 978-0-323-15305-8.

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Cephalopod anatomy

Shell|

| Types|

| External|

* Ammonoid shell
* Argonautid eggcase
* Nautiloid shell
* Orthocone

|

Internal|

* Belemnoid guard
* Cirrate shell
* Cuttlebone
* Gladius (pen)
* Spirula shell
* Stylet

Features|

| External|

* Aperture
* Apex
* Callus
* Lirae
* Periostracum
* Sculpture
* Spire
* Sutures
* Umbilicus

|

Internal|

* Body chamber
* Camerae
* Nacre
* Phragmocone
* Septa
* Siphuncle
* Whorls

Mantle &
funnel|

| External anatomy|

* Dermal structures
* Fins (wings)
* Flotation devices ("secondary fins")
* Funnel–mantle locking apparatus
* Tail

|

Internal anatomy|

* Branchial hearts
* Ctenidia (gills)
* Hepatopancreas (digestive gland)
* Ink sac and ink
* Needham's sac
* Nephridia ("kidneys")
* Nidamental glands
* Osphradium
* Pericardial glands

Head &
limbs|

| Brachial crown|

* Arms
* Hectocotylus
* Tentacles
* Carpus
* Dactylus
* Manus
* Suckers and hooks

|

Buccal region|

* Aptychus
* Beak
* Odontophore
* Radula
* Spadix and antispadix

Occipital region|

* Nuchal crest (occipital crest)
* Nuchal folds (occipital folds)
* Occipital membrane
* Olfactory organ
* Nuchal organ

Other parts|

* Eyes
* Statocysts

General|

* Chromatophores
* Photophores
* Nervous system
* Squid giant axon
* Squid giant synapse

Developmental stages: Spawn → Paralarva (Doratopsis stage) → Juvenile → Subadult → Adult • Egg fossils • Protoconch (embryonic shell)

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