Question

Q- describe general organisation and affinities of sacaulina

Answer 1

Balanoglossus also called the tongue worm is a marine tuberculous or burrowing hemichordate inhabiting shallow coastal waters. It leaves inside of its own burrow in sand or mud. The body of tapeworm is soft, elongated, worm-like a cylinder and bilaterally symmetrical measuring 10 to 15 cm in length.It is bright or drab with reddish or orange tints. The body is divided into 3 distinct parts, proboscis, collar and trunk, and is unsegmented.Proboscis is also called proteosome,which is anterior part of the body. It is short conical and circular in cross section. It has the thick muscular wall and hollows within. Its cavity is called proboscis coelom, which communities outside through proboscis pore.Posteriorly proboscis narrow as a neck which is attached to the collar. Below this there is preoral ciliary organs which test the taste of the water entering the mouth. The collar is also called mesosome, which is middle, short and cylinder part. The flap-like collarette surrounds the neck and a part of the proboscis.Ventrally there is the mouth opening to the buccal cavity inside.The collar has collar code which communicates to outside through a pair of collar pore. The trunk or metasoma is posteriorly and larger part of the body and it has a cuticular constriction. Trunk bears mid-dorsal and mid-ventral ridge at its surface. The trunk is further subdivided into branch genital, hepatic and caudal regions. The branchiogenic region contains gonad, gonopore, and gill pore which is the region of reproduction and respiration.The hepatic region has numerous hepatic caeca.Posterior tapering caudal region gas the anus. Due to the peculiar anatomical organisation and embryology of tapeworm, it has been considering closer to the Chordates well as non-chordate phyla by different scientists from time to time, some of these views regarding affinities are summarised below.
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