prostomium


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prostomium

[prō′stō·mē·əm]
(invertebrate zoology)
The portion of the head anterior to the mouth in annelids and mollusks.
References in periodicals archive ?
Interestingly, a similar plasticity is hypothesized for the ontogeny of the operculum, being derived from a radiole in the SerpulalHydroideslCrucigera clade in serpulins but a de novo development from the prostomium in spirorbins (Brinkmann and Wanninger, 2009).
Prostomial, peristomial appendages and dorsal cirri are all non-articulated; peristomial cirri reach to the mid prostomium.
a) Dorsal view of the iront end of the polychaete Pherecardia striata; b) prostomium, dorsal view; c) parapodium 4, anterior view; d) notochaeta and capillary neurochaeta, parapodium 4.
Descriptions of this species, prostomium elongate are rounded anteriorly, flanked laterally by peristomial ridges leading to ventral mouth.
This statement disagrees with that outlined by Eliason (1920) and Thulin (1921), according to Jones (1956), who mentioned that the prostomium had a transverse furrow, giving the erroneous impression that the proximal part was an asetigerous segment.
adventitium crawled anteriorly on the earthworm and "capped" the prey's prostomium, peristomium and anterior segments with its own head and anterior body.
During metamorphosis, the once-planktonic larva's body elongates, trochal cilia are shed, the prostomium elongates, and capillary setae protrude (Biggers et al.
The prostomium is smooth, conical, more or less acutely pointed, globular, broad, or spatulate; without any sensory appendages or palps, but nuchal slits or depressions are sometimes present; with a pair of small eyes sometimes present.
Prostomium transverse, short, longitudinally striated; dorsal setae of anterior body region single, ventral setae doubled, no setae in posterior body region; ventral tuberculum single.
The specific name naso is a noun derived from the Latin word nasus (nose) and the Roman personal name Naso, emphasizing the nose-like prostomium of this worm.