Treptopale Perkins, 1985

Watson, Charlotte & Faulwetter, Sarah, 2017, Stylet jaws of Chrysopetalidae (Annelida), Journal of Natural History 51 (47 - 48), pp. 2863-2924 : 2892

Genus Treptopale Perkins, 1985

( Figure 17a–f ; Tables 1, 2)

Type species: Treptopale rudolphi Perkins, 1985

Material examined

One specimen Treptopale homalos Watson, 2010 : NTM W . 22892, Great Barrier Reef, Queensland, South West Pacific (mCT-00085); 1 specimen Treptopale paromolos Watson, 2010 : NTM W .23701, Darwin, Northern Territory, Arafura Sea (mCT-00403).

Distribution

Treptopale is a pan-tropical taxon found between 24°N and 33°S.

Habitat

Treptopale species are relatively common on mainland fringing and offshore coral reefs throughout the Indo-Pacific. A review of species from northern Australia found a partitioning of the coral reef habitat, with Treptopale homalos inhabiting cleaner rubble habitats often associated with Halimeda J.V. Lamouroux, 1812 and coralline algae and Treptopale paromolos occurring in rubble from silty reefs, muddier sands, Halimeda and seagrasses: depth range low water mark to ~ 40 m ( Watson 2010). A newly described Treptopale species from the Mediterranean occurs in a shell matrix habitat dominated by turfing green algae (Watson and Chatzigeorgiou, Forthcoming).

General morphology

Treptopale species comprise elongate, slender individuals that possess pale golden to silvery coloured, symmetrical-shaped main paleae and a median paleae fascicle that form flattened fans that entirely cover the dorsum ( Figure 17a ). Sensory structures include a prostomium, fused with the anterior segments, two pairs of complex eyes, oval palps, glandular nuchal fold and lateral organs ( Watson 2010).

Pharynx and jaws

Treptopale species possess a short, broad proboscis and a short, broad pharynx which appears to narrow slightly at the posterior end. The pharynx appears undifferentiated and a calcified muscular ring is present. Caeca are not discernible on CT scans ( Figure 17b–d ). A pair of relatively small, elongate, slender jaws sits deep in the pharynx and occupies over half its length ( Figure 17c, d ). Stylets possess a slight swelling present on their inner margins at the point where the jaws diverge anteriorly outwards; the posterior elongate sections of the stylets sit close to one another but do not interlink ( Figure 17e, f ).

Figures

Figure 17. Anterior end of Treptopale homalos (mCT-00085), imaged through micro-CT and rendered in 3D. (a) dorsal view; (b and c) dorsal view, virtually dissected at different levels and with different opacity levels to expose pharyngeal structures; (d) lateral view, virtually dissected to expose pharyngeal structures; (e) jaws, anterolateral view; (f) dorsal view and cross sections through the jaw along its length.