65 — Deep-sea moon snail, Globisinum sp.

Globisinum sp. ~12mm.

Globisinum sp. ~12mm.

New species are discovered in the deep-sea almost daily. But there more species being discovered than there are people to officially describe them and give them names. Therefore, there is quite a lag between the time a species gets discovered and when it gets named. As a consequence there are many species which don't yet have official scientific names (called undescribed species), and this is one of those.

This is a moon snail, belonging to the family Naticidae. Naticids tend to be predators and bore holes in the shells of their prey (often bivalves). The holes have bevelled sides, so if you find a shell with such a hole, it was probably predated by a moon snail.

This moon snail belongs in the genus Globisinum. There is a species of this genus (called a cogener) already known from New Zealand waters: Globisinum drewi (Murdoch, 1899), but this one is a new undescribed species. It has a higher spire (and other less obvious differences) than G. drewi and also lives in much deeper water.

The brown colour of the shell possibly either an outer covering (periostracum), or the result of coming into contact with the digestive juices inside the guts of a deep-sea fish.

Rough-head rattail

Fishes can make very good collectors of marine samples, particularly when it comes to hard-shelled invertebrates like gastropods and bivalves. This undescribed Globisinum species came from the intestines of a rough-head rattail (Coelorinchus trachycarus McMillan & Shcherbachev, 1999), which was caught in 1062m of water on the north eastern Chatham Rise.

Fishes can go into areas which trawls or grab samples can't and therefore their gut contents can often reveal more than mechanical sampling methods.

Rattails (Pisces: Macrouridae) are a common group of deep-sea fishes and there are many species found in New Zealand waters. They possess a gas-filled swim bladder (to regulate buoyancy) and when they are brought to the surface, this bladder expands rapidly, killing the fish and voiding all of it's stomach contents. As a consequence the only way to directly ascertain the diet (and their position in deep-sea food webs) is to look in their intestines.

More info:

Jones, M. R. L., 2008. Dietary analysis of Coryphaenoides serrulatus, C. subserrulatus and several other species of macrourid fish (Pisces: Macrouridae) from northeastern Chatham Rise, New Zealand. New Zealand Journal of Marine and Freshwater Research, 42, 73–84.