A cercaria (plural cercariae) is the larval form of the
trematode
Trematoda is a class of flatworms known as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive h ...
class of parasites. It develops within the germinal cells of the sporocyst or redia.
A cercaria has a tapering head with large penetration glands.
It may or may not have a long swimming "tail", depending on the species.
[ The motile cercaria finds and settles in a host where it will become either an adult, or a mesocercaria, or a metacercaria, according to species.
Rotifers ('' Rotaria rotatoria'') produce a chemical, Schistosome Paralysis Factor, suppressing cercaria swimming and reducing infections.][{{cite journal , editor1-last=Khosla , editor1-first=Chaitan , last1=Gao, first1=Jiarong, last2=Yang, first2=Ning, last3=Lewis, first3=Fred A., last4=Yau, first4=Peter, last5=Collins, first5=James J., last6=Sweedler, first6=Jonathan V., last7=Newmark, first7=Phillip A., title=A rotifer-derived paralytic compound prevents transmission of schistosomiasis to a mammalian host, journal=PLOS Biology, volume=17, issue=10, year=2019, pages=e3000485, issn=1545-7885, doi=10.1371/journal.pbio.3000485, pmid=31622335 , pmc=6797223 , doi-access=free]
References
Larvae
Reproduction in animals
Digenea