Many caenogastropods develop notches or even siphonal
canals in this position of the whorl indicating the position of the inhalant stream.
The shell length is measured from the apex of the shell spire to the anterior (abapical) extremity, typically the siphonal
In common with other observers, we found no siphonal
spines (Millar 1960).
DNA was extracted from siphonal
tissue and associated musculature.
green algae possess a blade abandonment strategy linked to rapid proliferation processes, allowing these algae to dominate standing stocks in most calm-water reef habitats in the Caribbean (Littler & Littler, 1999).
Tip pointed, siphonal
capsule asymmetrical, outer arm larger and inner arm smaller.
Primary ribs bear strong spiny umbilical tubercles, less marked inner ventrolateral tubercles and well marked clavate outer ventrolateral and siphonal
canal short and broad, approximately half of aperture width, left edge truncate, right edge wanting, as continuation of outer lip; left edge marked by two strong spiral folds, superior fold smooth, with sharp edge, inferior fold broad, with several arched, strong growth scales (Fig.
They were present at quite a high density (four to five per square metre) projecting by as much as 10 mm above the cobble surface "with bottle-green siphonal
orifices sampling the stream water.
Potamilus amphichaenus have a noticeable opening exposing tissue towards the anterior end of the shell (pedal gape), which is oriented downward into the substrate and another posteriorly (siphonal
gape) which projects upwards into the column of water (Howells et al., 1996).
The only way of visually separating the shells of the two species is the presence of a patch of dark coloration near the siphonal
canal of C.
Unionids move vertically and horizontally in the substrate, open and close their valves and may expel strong siphonal
excurrents (e.g., O'Riordan et al., 1995; Amyot and Downing, 1997; Kadar et al., 2001; Markich, 2003; Schwalb and Pusch, 2007).