39 — Hairy trumpet shell, Monoplex parthenopeus

Monoplex parthenopeus, Tauranga Harbour
Bridge, 1/10/16.

Monoplex parthenopeus, Tauranga Harbour
Bridge, 1/10/16.

Monoplex parthenopeus, Tauranga Harbour
Bridge, 1/10/16.

This is a hairy trumpet shell, Monoplex parthenopeus * . Its hairy appearance and common name are due to an outer covering which the animals secretes, called a periostracum. The periostracum can have several uses: from protecting the shell, to acting as a camouflage aid. This one was photographed in between rocks along the causeway at the base of the Tauranga Harbour bridge.

This is quite an interesting species because not only does it have a global distribution in temperate seas, but it also dates back in the fossil record ~15 million years.

One of the reasons for it's success is the long time its veliger larvae spend in the water column. Trumpet shells (Family: Ranellidae) are not direct-developers and have a planktonic larval stage. The planktonic larval duration for hairy trumpets is thought to be around 300 days and it has been estimated that this amount of time enables a possible larval distribution of about 4000 km. This would go a long way to explaining way they're found in so many places.

In New Zealand they are often washed up after storms on northern east coast beaches. However, they're not that commonly seen in the intertidal zone. The shell pictured below is about 100mm long; they can get as large as 180mm.

* (Salis Marschlins, 1793)




More info:

https://commons.wikimedia.org/wiki/Category:Monoplex_parthenopeus

More pictures: http://www.mollusca.co.nz/speciesdetail.php?speciesid=860&species=Monoplex%20parthenopeus