Functional morphology of the balanomorph barnacles Tesseropora rosea (Krauss) and Tetraclitella purpurascens (Wood) (Tetraclitidae)

Abstract

Tesseropora rosea of eastern Australia inhabits exposed, wave-washed rocks, is an extension feeder in fast currents, and has monometric growth, with orifice enlargement by erosion. It has a deep, mobile operculum. Tergal depressor muscles are large, scutal depressors moderately large. The opercular valves play an active part in respiratory pumping beat. Tergal depressors effect opercular withdrawal. Rostral scutal depressors assist in pumping beat. Lateral scutal depressors assist in opercular opening. Cim IV-VI of T. rosea unfurl rapidly in response to fast water currents and are captorial, either singly or in concert. The antenniform third maxillipeds (cirrus 111) turn back laterally in the extended position but fold over and hold down the captorial cirri in the curled position. Tetraclitella purpurascens of southern Australia inhabits crevices and overhangs on rocky shores, is an extension feeder in moderate currents, and has diametric growth, with orifice enlargement by circumferential growth of radii and parietes. It has a shallow operculum with only slight mobility. Tergal depressors are large, scutal depressors small. Valve action is mainly hinge-like and slow, with little apicobasal movement. The small scutal depressors assist the large tergal depressors in opercular withdrawal and have only a very minor role in pumping beat. Cirri IV-VI of T. purpurascens are held erect for long periods in moderate water currents. Captorial movements are similar to but slower than those of T. rosea. The third maxillipeds have short rami involved in forward food transfer. Setation correlates with function on the cirri of both species. The oral cone of T. rosea is broader and the mouthparts relatively larger than those of T. purpurascens, possibly mediating a more powerful triturating mechanism. A comparison of structure and function shows that T. purpurascens retains many primitive balanomorph features, whereas T. rosea has a more advanced functional configuration. In the evolution of tetraclitids, it seems likely that the tetraclitellines diverged early, before the austrobalanines gave rise to the tetraclitines. The four-plated wall may have evolved independently in tetraclitellines and austrobalanines.

Structure, function and phylogeny of coral-inhabiting barnacles (Cirripedia, Balanoidea)

“…Rostra1 scutal depressors, also quite large, insert beneath the rostral ends of prominent internal occludent ridges on the scuta. The arrangement and proportions of the depressor muscles are consistent with the vigorous activities of the operculum in rostral uplift and opening, tergal chopping during cirral beating, and carinal rotation during closure and withdrawal (see Anderson & Anderson, 1985). The operculum and its musculature are more modified in A. arcuatus (Figs lC, D, 4D-F).…”

Scanning Electron Microscopy of Mouth Appendages in Six Species of Barnacles (Crustacea Cirripedia Thoracica)

“…Corresponds to the in small groups, on distal two-thirds of the shaft. Apex 'jointed' setae of Anderson & Anderson (1985) the seta to bend while still retaining much rigidity. Setae of types (4b) and (5b) resemble (C14) setae of Lavalli & Factor (1992) to the extent that a similar function is likely.…”

“…But further manipulation and ingestion of captured food takes place within the mantle cavity, so the function of the trophi cannot be observed without special equipment. Accordingly, Anderson & Anderson (1985) remarked that functional interpretations of mouth part morphology are very elusive. This statement, however, refers to observations at the light microscopical level.…”

New names for two well-known shore barnacles (Cirripedia, Thoracica) from Australia and New Zealand

“…Anderson and Anderson 1985, Bennet and Pope 1953, Dakin 1952, Dakin et al 1948, Denley and Underwood 1979, Endean et al 1956, Guiler 1952, Wisely and Blick 1964, Womersly and Edmonds 1958, Underwood 1981 Distribution: Australia; from Double I Point (26°S) south to Tasmania and westwards to about Fremantle (32°S). References to T. purpurascens on tropical Australian shores, or for various Atlantic, Indian or Indonesian localities, probably pertain to various other tetraclitellids with elongate scuta.…”