Protoconch

Protoconch

A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell of some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. The protoconch may sometimes consist of several whorls, but when this is the case, the whorls show no growth lines.

The whorls of the adult shell, which are formed after the protoconch, are known as the teleoconch. The teleoconch starts forming when the larval gastropod settles and becomes a juvenile. Quite often there is a visible line of demarkation where the protoconch ends and the teleoconch begins, and there may be a noticeable change in sculpture, or a sudden appearance of sculpture at that point.

In some gastropod groups (such as the Architectonicidae), the teleoconch whorls actually spiral in the opposite direction to the protoconch. In those cases the shell is called heterostrophic.

In species which have a veliger or swimming larval stage which catches out of egg capsules, there are two parts to the protoconch. The first part of the protoconch (which is formed within the embryonic egg capsule) is called protoconch 1, while the part that is formed after the larva has hatched is called protoconch 2. There is often different sculpture or ornamentation on protoconch 1 compared with protoconch 2, and this can be distinguished under the microscope.

The structure of the protoconch has been widely used as a discriminating feature in gastropod systematics.

The homologous structure in bivalves is called the prodissoconch.


Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • Protoconch — Pro to*conch, n. [Proto + conch.] (Zo[ o]l.) The embryonic shell, or first chamber, of ammonites and other cephalopods. [1913 Webster] …   The Collaborative International Dictionary of English

  • protoconch — n. [Gr. protos, first; konche, shell] (MOLLUSCA: Gastropoda) The embryonic shell of a univalve, indicated by the apical whorls of the adult shell being clearly demarcated from later ones; see prodissoconch …   Dictionary of invertebrate zoology

  • protoconch — pro·to·conch …   English syllables

  • protoconch — …   Useful english dictionary

  • Schneckenhaus — Gehäuse der Gefleckten Schnirkelschnecke (Arianta arbustorum) von oben …   Deutsch Wikipedia

  • Cavolinioidea — Taxobox name = Cavolinioidea image caption = An unidentified sea butterfly regnum = Animalia phylum = Mollusca classis = Gastropoda subclassis = Orthogastropoda superordo = Heterobranchia ordo = Opisthobranchia subordo = Thecosomata superfamilia …   Wikipedia

  • Whorl (mollusc) — A whorl is a single, complete 360° turn in the spiral growth of a mollusc shell. A mollusc shell is basically a long tube, usually coiled in a spiral for strength and compactness. The number of whorls in the shell depend on various factors in the …   Wikipedia

  • Odostomiinae — Odostomia pallida, O. conoidea, O. conspicua, O. truncatula Scientific classification Kingdom …   Wikipedia

  • Syrinx aruanus — Apertural view of a shell of Syrinx aruanus Scientific classification Kingdom: An …   Wikipedia

  • Oxygyrus keraudrenii — Temporal range: Pliocene Recent[1] Apical view of the shell of Oxygyrus keraudrenii from the Pliocene Epoch …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”