The trunk or metasome is the posterior and largest part of the body.The trunk bears a mid-dorsal and a mid-ventral ridge, each accomodating nerve and blood vessel.The trunk is further differentiated into three regions: an anterior branchiogenital,a middle hepatic and a poaterior post-hepatic, abdominal or caudal region.
Branchiogenital region-The anterior or branchiogenital region of trunk is marked by a pair of lateral, thin,flat and longitudinal flaps,the genital wings,containing the gonads.The numbers of gillpores increases with the age of the animal..
Hepatic region-The middle or hepatic region of trunk is smaller than the genital region.It is greenish in colour and its dorsal surface has numerous irregular intestinal sacculations or hepatic caeca.
Posthepatic region-It is the posterior-most and the longest part of the trunk also called the abdomen or caudal region.
Branchiogenital region-The anterior or branchiogenital region of trunk is marked by a pair of lateral, thin,flat and longitudinal flaps,the genital wings,containing the gonads.The numbers of gillpores increases with the age of the animal..
Hepatic region-The middle or hepatic region of trunk is smaller than the genital region.It is greenish in colour and its dorsal surface has numerous irregular intestinal sacculations or hepatic caeca.
Posthepatic region-It is the posterior-most and the longest part of the trunk also called the abdomen or caudal region.
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