In this presentation, phylum Phylum Xenoturbellida is described. Phylum Onychophora known as velvet or walking worms. After watching this you will learn the characteristics and Xenoturbella bocki and Xenoturbella westbladi .The brief description of Phylum Phylum Xenoturbellida along with reproduction and fertilization also described. The concept of phylum Xenacoelomorpha. It is part of BS Zoology Course, Animal diversity.

1. Phylum Xenoturbellida Dr. Muhammad Moosa Abro
@Zoology by Miler and Harley

2. Example Two species: Xenoturbella bocki and Xenoturbella
westbladi
Xenoturbella is a genus of worm-like (up to 4 cm)
Bilaterian animals that live in North Sea mud.
These animals have no brain, an incomplete gut, no excretory
system, and no organized gonads.
Sexual reproduction does occur, as gametes are produced from
unstructured gonadal tissue.
Xenoturbellids possess cilia and a diffuse nervous system.
Phylum Xenoturbellida Dr. Muhammad Moosa Abro

3. Their larval stage develops as an internal parasite of certain molluscs.
The adults feed on bivalves and bivalve eggs.
Phylogenetic Relationships
There are two radically different interpretations of phylogeny for
Xenoturbellida.
Morphological and molecular studies suggest a close relationship with
Acoelomorpha near the base of the bilaterian tree, thus they may be
united with the acoels in a phylum Xenacoelomorpha.
Other molecular studies suggest that Xenoturbella is a primitive basal
deuterostome or in a sister-group relationship with the echinoderms and
hemichordates.
Phylum Xenoturbellida Dr. Muhammad Moosa Abro

4. References
4
1. Miller, A.S. and Harley, J.B. ; 1999 , 2002., 2007, 2009, 2012 & 2016 Zoology, 4th , 5th, 6th, 7th,
8th , 9th& 10th Edition (International), Singapore : McGraw Hill.
2. Hickman, C.P., Roberts, L.C/, AND Larson, A., 2018. INTEGRATED PRINCIPLES OF ZOOLOGY,
15th Edition (International), Singapore: McGRAW-Hill