Astomes are a group of ciliate

Ciliate

The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella...

 protozoans commonly found in the guts of annelid

Annelid

The annelids , formally called Annelida , are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches...

 worms, especially oligochaetes, and other invertebrate

Invertebrate

An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s. As their name implies, these parasites are characterized by an absence of mouth. The cell is covered by uniform cilia; in addition, some astomes attach themselves to their hosts by sucker

Sucker (parasitic worms anatomy)

The sucker is an attachment organ of parasitic worms.-In Platyhelminths:In Platyhelminths , the sucker is called bothridium....

s, while others use various hooks or barbs.

Asexual reproduction

Asexual reproduction

Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...

 is by transverse fission. In some cases, chains of individuals form by repeated fission without separation of the cell

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

s. The sexual phenomenon of conjugation

Bacterial conjugation

Bacterial conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells...

 also occurs. Representative genera include Cepedietta, which lives in the amphibian

Amphibian

Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

 digestive system, and Radiophrya.