Nov 13, 2013

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I've read many researchers' interpretations and they are not all quite consistent, but generally, here's the difference.

Paucispiral literally means "spiral with few turns."

Protoconchs can be classified into two groups:

1. Direct development - where the larval stage is completed in the egg (usually within an egg mass or casing) and teleoconch growth has started by the time the animal/shell is expelled and the animal "crawls away."

2. Lecithotrophic development - where the larva is dispersed into and remains in the water column of the aquatic environment before the larval stage is completed, usually with a yolk sac to provide nutrition for the completion of larval development, but may also be able to feed. Lecithotrophic developers may spend a short or long time in the water column. Lecithotrophic developers that remain in the water column for a fairly long duration (2-3 months) until larvel development is completed are referred to as Planktotrophic. Planktotrophic protoconchs have more numerous whorls, often with distinctive protoconch 1 and protoconch 2 parts of differing sculpture. Planktotrophic protoconchs tend to be tiny, light-weight and translucent.

The number of protoconch whorls in both "direct" and "lecithotrophic" developers is variable, but most often "direct" developers and "lecithotrophic" developers that spend a short time in the water column have protoconchs with only a few whorls, tend to be large, bulbous, heavy, rapidly increasing in width, and opaque [or with the first whorl translucent and subsequent whorl(s) opaque] and are often described as Paucispiral .

Just keep in mind that words like "few," "short time," "numerous" are interpretive and relative, and that Mother Nature has evolved all kinds of variations that often defy clear classification.

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