World Congress of Malacology Antwerp ... - Unitas Malacologica

Hyalogyrinidae. Their rhipidoglossate radula and the lack of cartilages suggest that the
Heterobranchia as a whole emerged from the rhipidoglossate rather than from the taenioglossate level
of gastropod evolution. Accordingly, a change of function in the supporting apparatus (replacement
of cartilages by a muscular mass) predates the change of the radular type itself at the beginning of
heterobranch evolution.
Molluscan evidence of woodland disturbance in the Irish Holocene
Speller, George R.; Preece, Richard C.
Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK,
Email: gspeller@gmail.com; rcp1001@cam.ac.uk
Radiocarbon dated molluscan sequences from three extensive Irish Holocene tufa deposits have
provided information relating to human impact on the environment. Work at Newlands Cross,
situated in the outskirts of Dublin in the east of Ireland, builds on an earlier study, which
demonstrated that this thin deposit of tufa (only about 1 m thick) covered much of the early to mid
Holocene, providing the most detailed succession of land snails known from Ireland. The new work
includes the analyses of five further profiles, with a much-improved sampling resolution (down to 1
cm). These have amplified aspects of faunal history and enabled further light to be shed on a
Mesolithic disturbance horizon previously identified at the site. The new records suggest that the area
affected by the disturbance was extremely limited (perhaps less than 50 m 2 ) and of relatively brief
duration (a few hundred years). Two sites (Graffy and Cartronmacmanus) located only 3 km apart in
Co Mayo in western Ireland provided less complete records for the very early Holocene but furnished
excellent sequences from about 8200 yrs BP to 2000 yrs BP. The faunal successions were less
dynamic than those at Newlands Cross but they too yielded evidence of woodland disturbance, this
time dating from the late Bronze Age and early-middle Iron Age. The registration of at least five such
events differed significantly from the characteristic faunal signatures associated with comparable
impacts in southern Britain. This results from the relative scarcity in Ireland of species such as
Vallonia costata, although the impacts are clearly indicated by declines in shade-demanding species,
such as Discus rotundatus.
Scallops visually respond to simulated particles in flow
Speiser, Daniel I; Johnsen, Sönke
Duke University Department of Biology, Box 90338, Durham, NC 27708, USA,
Email: dis4@duke.edu; sjohnsen@duke.edu
Scallops’ eyes are abundant in number and positioned along the mantle at the edges of the valves.
The optical properties of these eyes have been well-studied and they are known to form relatively
high-resolution images. However, the function of scallop vision remains open to debate. We tested
whether scallops, which are filter feeders, use their eyes to detect suspended particles. Specimens of
the Common Bay Scallop Argopecten irradians were placed in an operating flow tank and shown
simulated images of moving particles. Their mantle gapes were then observed at 24 second intervals
over ten minute trials. We found that 25 scallops were open in 52% ± 6% of observations when
particles were shown, while 24 scallops viewing a blank screen were open in 29% ± 5% of
observations. The difference between these treatments was found to be significant (P