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A sucker in zoology is a specialised attachment organ of an animal. It acts as an adhesion device in parasitic worms, several flatworms, cephalopods, certain fishes, amphibians, and bats. It is a muscular structure for suction on a host or substrate. In parasitic annelids, flatworms and roundworms, suckers are the organs of attachment to the ...
Most animals called "worms" are invertebrates, but the term is also used for the amphibian caecilians and the slowworm Anguis, a legless burrowing lizard. Invertebrate animals commonly called "worms" include annelids , nematodes , flatworms , nemerteans , chaetognaths , priapulids , and insect larvae such as grubs and maggots .
The nematode model species C. elegans, C. briggsae, and Pristionchus pacificus, among other species, exhibit androdioecy, [53] > which is otherwise very rare among animals. The single genus Meloidogyne (root-knot nematodes) exhibits a range of reproductive modes, including sexual reproduction , facultative sexuality (in which most, but not all ...
A cross section of a post-clitellum segment of an annelid (ringed worm); almost all segments of an annelid contain the same set of organs and parts, a pattern called metamerism. Annelids have no lungs, but rather exchange carbon dioxide and oxygen directly through the moist skin when blood reaches the extremely fine capillaries of the body ...
Annelids are members of the protostomes, one of the two major superphyla of bilaterian animals – the other is the deuterostomes, which includes vertebrates. [68] Within the protostomes, annelids used to be grouped with arthropods under the super-group Articulata ("jointed animals"), as segmentation is obvious in most members of both phyla.
Marine worms can be herbivores, carnivores, parasites, detritivores, or filter feeders, but many strange examples of feeding are seen in this diverse type of animal. The group of Siboglinidae have developed a relationship with symbiotic bacteria within their gut that often perform chemosynthesis from which the worm benefits.
It is a paraphyletic grouping including all animals excluding the chordate subphylum Vertebrata, i.e. vertebrates. Well-known phyla of invertebrates include arthropods, mollusks, annelids, echinoderms, flatworms, cnidarians, and sponges. The majority of animal species are invertebrates; one estimate puts the figure at 97%. [1]
The animal works this cocoon forward and over its head end, whereupon the ends of the cocoon become sealed, with fertilisation and development taking place inside. [ 2 ] [ 3 ] Earthworms and their kin, in the subclass Oligochaeta, lack eyes but have photoreceptor cells in the skin, especially in the dorsal portion of the anterior end.