Bulla gizzard plates

July 11, 2001
From: Paula M. Mikkelsen

In a recent discussion of Bulla ampulla (Cephalaspidea), Bob Bolland (http://rfbolland.com/okislugs/bullampu.htm) made reference to a Sea Slug Forum posting from Bill Rudman {Dec 18, 1998), which says that:
"the gizzard [of Bulla] has four large crushing plates. All other cephalaspids with gizzards (other than the runcinids), have three gizzard plates."

This is in error. All Bulla species in my experience have three near-equal corneous gizzard plates plus additional, smaller, corneous gizzard spines both in front of and behind the plates. The only shelled opisthobranch group with four gizzard plates is the Runcinoidea, and they are indeed still of uncertain phylogenetic affinities. While Bulla's configuration of plates and spines, as well as the shape of its radular teeth, are rather unique among cephalaspids, the evolutionary statements made by Rudman in this posting also need to be adjusted. Bulla, Haminoea and Smaragdinella form a well-defined monophyletic group (Bulloidea) according to my 1996 phylogenetic analysis (Malacologia, 37(2): 375-442).

I am further puzzled by this posting because the Rudman paper cited (1971, J. Nat. Hist. 5: 647-675) clearly discusses three gizzard plates in Quibulla quoyi...

Paula M. Mikkelsen


Mikkelsen, P.M., 2001 (Jul 11) Bulla gizzard plates. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4797

Dear Paula,
Clearly my statement on the website is incorrect and the Rudman paper cited is correct - Bulla has three gizzard plates. What puzzles me is how long it has taken for someone to notice this error on my part. I can give no reason why I said Bulla has 4 gizzard plates - other than the excitement of preparing a collection of bubble shell pages for Xmas 1998 caused some misfirings in my brain. I have made the necessary changes.

Concerning the evolutionary relationships of these animals - I agree, and provided a lot of evidence to show the close relationship between Haminoea, Smaragdinella, Phanerophthalmus and Atys, but I still have strong doubts about relating Bulla to that group. Many features of the alimentary canal, and the reproductive system just do not fit well with the Haminoeoidea. I may be wrong, you may be wrong, but that's the nature of hypothesising about phylogeny. Basically our disagreement highlights the need for further investigation of these interesting animals.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Jul 11). Comment on Bulla gizzard plates by Paula M. Mikkelsen. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4797


Bulla ampulla

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