Abstract

On the basis of comparative anatomy, Darwin proposed that the catophragmid C. polymerus, representing the basic form among balanomorphs, had evolved from a scalpellid lepadomorph ancestry. This hypothesis has since been supported by fossil evidence, but has not been tested by the techniques of comparative functional morphology. Functional studies of C. polymerus and Calantica villosa have now shown that an evolution of catophragmid balanomorphs from calanticine scalpellids is functionally feasible, upholding Darwin's proposal. C. polymerus retains the scalpellid mode of planktivorous extension feeding, except for further modification of the first two pairs of cirri as short maxillipeds acting in forward food transfer in a limited space. The basic adaptive significance of the foreshortened form and flattened operculum of C. polymerus lies in allowing a species with this mode of feeding to inhabit a high energy intertidal environment. Protection against certain kinds of predation may also have been important. The development of the opercular valves from capitular plates and their changed orientation relative to the wall is accommodated by further modification of a hinge mechanism already present in calanticine scalpellids. The closure mechanism of the operculum involves supplementation of the action of the adductor scutorum by the downward pull of large tergal depressor muscles, evolved as a modification of the peduncular longitudinal muscles of calanticines. Massive tergal and small scutal depressor muscles, a basic balanomorph condition, are functionally associated with a large prosoma and paired branchiae occupying the rostral part of the limited mantle cavity.

 
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Bibliographic Data

Short Form
Anderson, 1984, Aust. Mus. Mem. 18(2): 7–20
Author
D. T. Anderson
Year
1984
Title
Catomerus polymerus and the evolution of the balanomorph form in barnacles (Cirripedia)
Serial Title
Australian Museum Memoir
Volume
18
Issue
2
Start Page
7
End Page
20
DOI
10.3853/j.0067-1967.18.1984.369
Language
English
Date Published
31 March 1984
Cover Date
31 December 1983
ISSN
0067-1967
CODEN
AUNMA5
Publisher
The Australian Museum
Place Published
Sydney, Australia
Digitized
09 September 2009
Reference Number
369
EndNote
/Uploads/Journals/17626/369.enw
Title Page
/Uploads/Journals/17626/369.pdf
File size: 128kB
Complete Work
/Uploads/Journals/17626/369_complete.pdf
File size: 1807kB