Hyalopale Perkins, 1985

Watson, Charlotte & Faulwetter, Sarah, 2017, Stylet jaws of Chrysopetalidae (Annelida), Journal of Natural History 51 (47 - 48), pp. 2863-2924 : 2881-2882

Genus Hyalopale Perkins, 1985

( Figure 10a–f ; Tables 1, 2)

Type species: Hyalopale bispinosa Perkins, 1985

Material examined

One specimen Hyalopale bispinosa: SIO-BIC (specimen used for molecular analyses after photography and not retained), Belize, Caribbean Sea, Western Atlantic; 1 specimen Hyalopale cf . bispinosa: NTM W.25603, Crete, Mediterranean Sea (mCT-00039).

Distribution

Hyalopale is a pan-tropical taxon found between ~ 35°N and 35°S. At present, Hyalopale represents a monotypic genus but new species are being described (Watson and Rouse, in prep.)

Habitat

Hyalopale bispinosa is very small and rarely seen; when found it is most frequently in algal samples ranging from filamentous greens to leafy reds or coralline maerl (CW pers. obs.); it has also been recorded from polychaete tube colonies, e.g. Dendropoma colonies in the Red Sea (as Paleanotus chrysolepis ; Ben Eliahu 1976). Most individuals from the tropics have been recorded from shallower waters, intertidal to 5 m; eastern Mediterranean collections were from algae on rocky substrates in 15–20 m (Watson and Chatzigeorgiou, Forthcoming).

General morphology

Hyalopale individuals are very small bodied, <3 mm in length, attaining maximally 20 segments, and possess hyaline, asymmetric-shaped main paleae that cover the dorsum ( Figure 10a ) and simple lateral and medial spines. Sensory structures include a prostomium, fused with the anterior segments, two pairs of complex eyes, moderate sized oval palps and lateral organs. The nuchal organ is composed of a very small glandular fold that appears to be diminished or absent ( Perkins 1985; Watson and Chatzigeorgiou, Forthcoming).

Pharynx and jaws

Hyalopale species possess a short, broad proboscis and a broad barrel-shaped to slightly more elongate pharynx, with large horizontal septa. Small caeca are visible in microscope photos but not in CT scans. The pharynx is undifferentiated and a small calcified pharyngeal ring is present ( Figure 10b, c ). Jaws are short and appear to overlap a little in the posterior section, then diverge outwards mid-way with a slight swelling present on the inner margins at this point ( Figure 10d ). Microscope photos show in detail the very broad, inner groove present in each jaw and the roughened, tanned distal jaw tips ( Figure 10e, f ).

Figures

Figure 10. Hyalopale cf. bispinosa (mCT-00039), imaged through micro-CT and rendered in 3D. (a) dorsal view, entire body; (b and c) dorsal view, virtually dissected at different levels to expose pharyngeal structures; (d) jaws, dorsal view and cross sections through the jaw along its length; Hyalopale bispinosa microscope figures: (e) anterior end of animal, dorsal view; (f) jaws, dorsal view.