CLASSIFICATION OF SPIRORBIS
PHYLUM :- ANNELIDA (Metamerically segmented, coelomate and laterally symmetrical. )
CLASS :- POLYCHAETA (Many setae, clitellum absent. )
ORDER :- SEDENTARIA (Tubicolous, sedentary and proboscis not-protrusible, without jaws or teeth.)
GENUS :- Spirorbis
- Commonly found in U.S.A., Long Island to Bay of Fundy and northwards.
HABIT AND HABITAT
Spirorbis is minute, tubicolous, sedentary polychaete living in a small calcareous tube, coiled in a flat spiral manner which is incrusted on seaweeds, stones, shells and any hard calcareous object of the sea
GENERAL CHARACTERSTICS OF SPIRORBIS
- Animal measures about 3 mm in length and tube diameter is also nearly 3 mm.
- Body is divided into anterior and posterior regions.
- Anterior end is constituted by prostomium and peristomium.
- Prostomium contains pinnately branched gills.
- One of the gill filaments is enlarged to form stopper or operculum. There are 9 greenish gill filaments.
- Operculum is grooved on one side to serve as brood punch for the developing eggs.
- Peristome is similar to other segments of the thorax, but it forms a collar which secretes the tube.
- Abdominal segments are hermaphroditic. The anterior abdominal segments produce eggs while posterior segments sperms.
Spirorbis has long fossil history. It was abundantly found in Silurian Paleozoic and strata.
The animal contains pinnately branched tentacles and all above characters and hence it is Spirorbis.