Comprehensive Description

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General Description

The worms are large, 10-15 cm in length and 7-9 mm wide across the widest anterior segments, with hundreds of crowded segments. The body is widest anteriorly, gradually tapering posteriorly, with distinct regions not apparent. There are branchiae throughout the body, but branched and most conspicuous in the first one-fourth of the body. The parapodia are highly vascularized adjacent to the branchiae, with numerous branching blood vessels.

The prostomium is narrow, elongate and usually directed ventrally. It is bluntly rounded along the anterior margin, with a shape resembling that of a capitellid. Eyes are absent. Eversible nuchal organs are present on the anterior lateral margin of the peristomium. The peristomium is a single, narrow, incomplete achaetous ring.

Chaetiger 1 and the subsequent segments have long, cirriform noto- and neuropodial lamellae superficially resembling tentacular cirri. The noto- and neuropodia are close together, arising from a single point of origin. After about 10-15 segments the podia separate, but never very far; this continues for the length of the body. Posteriorly, both lamellae become shorter, with the neuropodial lamella eventually reduced, short and pointed and about one-fourth the length of the dorsal one.

Chaetal fascicles of the noto- and neuropodia arise very close to one another over the first few chaetigers, then gradually separate, but never far from each other. The notochaetae of the anterior chaetigers are longer and more numerous than the neurochaete. They consist of long, orbiniid-like capillaries bearing transverse rows of bristles and 8-10 narrow spines with bluntly pointed tips, some of which have a subapical spur or secondary tooth oriented forward along the shaft of the spine. The spines of the middle and posterior chaetigers are reduced to 4-6 per fascicle, and are without a spur. The neurochaetae of the anterior chaetigers have 3-4 elongate, thin spines with a straight shaft and blunted tips accompanied by a few threadlike capillaries. There are 3-4 short, protruding, curved aciculae or spines at the base of the fascicle. The spines are lost by the middle body of the chaetigers, and the acicular spines are reduced to two per neuropodium in posterior chaetigers. The neuropodial spines and aciculae are thicker than the notopodial spines.

There are branchiae from chaetiger 5, occurring dorsal to the notopodium. The branched branchiae in the anterior segments have numerous dichotomies, which are reduced to a single branched branchia posteriorly. All the branchiae have a central blood vessel connected to a lateral blood vessel by numerous connecting capillaries. Each branch has a paired row of cilia extending along its length. The branchiae are superficially appearing to be striated due to elongate cells in the integument.

The pygidium has a terminal anus surrounded by several long, tapering cirri.

(Blake, 2000).


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