Polypocephalus rhinobatidis

Polypocephalus sp. is a genus of larval tapeworms that live inside its host’s central nervous system of decapod crustaccans. Residing within the nervous system provides a great occasion for the parasites to control the behavior of their hosts. These parasites attack shrimp (Litopenaeus setiferus) and rays. One example of the ray would be the Atlantic stingray (Dasyatis Sabina). Polypocephalus rhinobatidis is an example of Polypocephalus sp.

Members of the Polypocephalus species are characterized by tentacles and suckers located on the head. The level of the contraction and the degree of retraction of the tentacles describe the different stages of scolex. There is a funnel shaped opening located at the tip of the tentacle which results in creation of a highly convoluted narrow cavity taking up the anterior 4th of the tentacle. The spinal intestine is where the adult rays are found.

Polypocephalus rhinobatidis sp. n. has different stages of development ranging from very immature to gravid stages.

The larvae of the cestode attacks the central nervous system and appears to continue living within there. This provides a great opportunity for the parasite to control the behavior of their hosts. Ingestion of a free-swimming larval stage causes the intermediate host to become infected, even though there is not a clear identification of its route of transmission to the intermediate host. Studies revealed that if a shrimp contains lots of larval tapeworms, they will spend more time walking on the substrate instead of sitting still or other activities such as swimming. Their overall increased activity level is sufficient to allow transmission to occur in these parasites.

The life cycle of Polypocephalus (Lecanicephalidae) is not yet known. Diagnosis Infection by P. rhinobatidis can only be recognized with characters of the genus that are up to 72 mm. in length including each segment overlapping the subsequent one; testes of 6 in number; ovary dumbbell shaped; and uterus lying on the ventral side of all parts of the segment.

Call, G. A survey of the tapeworms fauna of the cownose ray, Rhinoptera bonasus, from the northern Gulf of Mexico with comments on intermediate hosts. M.A. Thesis. University of Kansas, Lawrence, Kansas, 2007 141 p.

Carreon, N., Faulkes, Z. and Fredensborg, B. L. Polypocephalus sp. infects the nervous system and increases activity of commercially harvested shrimp. Journal of Parasitology. 2011 (97):755-759.

Subhapradha, C. K. and Hindle F.R.S., F.Z.S., E. On the genus Polypocephalus Braun, 1878 (Cestoda), together with descriptions of six new species from Madras. Proceedings of the Zoological Society of London. 1951 (121) 2:205-235.