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A few marine annelids that live in tubes lack cuticles, but their tubes have a similar structure, and mucus-secreting glands in the epidermis protect their skins. [8] Under the epidermis is the dermis , which is made of connective tissue , in other words a combination of cells and non-cellular materials such as collagen.
Trochophores exist as a larval form within the trochozoan clade, which include the entoprocts, molluscs, annelids (including echiurans and sipunculans) and nemerteans. Together, these phyla make up part of the Lophotrochozoa; it is possible that trochophore larvae were present in the life cycle of the group's common ancestor.
Acetabulum / æ s ɪ ˈ t æ b j ʊ l ə m / (pl.: acetabula) in invertebrate zoology is a saucer-shaped organ of attachment in some annelid worms (like leech) and flatworms. It is a specialised sucker for parasitic adaptation in trematodes by which the worms are able to attach on the host. [1] In annelids, it is basically a locomotory organ ...
Molluscs are generally regarded members of the Lophotrochozoa, [28] a group defined by having trochophore larvae and, in the case of living Lophophorata, a feeding structure called a lophophore. The other members of the Lophotrochozoa are the annelid worms and seven marine phyla. [31] The diagram on the right summarizes a phylogeny presented in ...
Lamellibrachia luymesi is a cold seep tube worm that reaches lengths of over 3 m and may be the most long-lived annelid, being over 250 years old. A still unclassified multilegged predatory polychaete worm was identified only by observation from the underwater vehicle Nereus at the bottom of the Challenger Deep , the greatest depth in the ...
Molluscs are generally regarded members of the Lophotrochozoa, [53] a group defined by having trochophore larvae and, in the case of living Lophophorata, a feeding structure called a lophophore. The other members of the Lophotrochozoa are the annelid worms and seven marine phyla. [61]
The prostomium (From Ancient Greek, meaning "before the mouth"; pl.: prostomia; sometimes also called the "acron") is the cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not include) the mouth, being usually a small shelf- or lip-like extension over the dorsal side of the mouth.
The lophophore surrounds the mouth and is an upstream collecting system for suspension feeding. Its tentacles are hollow, with extensions of a coelomic space thought to be a mesocoel. The gut is U-shaped with the anterior mouth at the center of the lophophore. The anus, where present, is also anterior, but is dorsal to the mouth.