Kinorhyncha (mud dragons) the head is completely retractable

“moveable snout” head also with retractile proboscis for burrowing

(once also called echinodera) around head is up to 7 circlet of spines (stylets)

179 species Body Wall tiny, free living marine worms body wall covered by a cuticle, secreted by syncitial epidermis usually <1mm long

only a little larger than most covered with spines found in oceans throughout the world à pole to pole epidermis with numerous mucous glands

benthic: important part of interstitial fauna no cilia on body burrow in silt & mud beneath the epidermis are several bands of some have been found in algal mats longitudinal, circular and diagonal muscles

a few are commensal inside or other body cavity a pseudocoelom marine Feeding & Digestion Body Form feed on (algae) and organic matter found in short worm-like, somewhat flattened body divided in mud 13 spiny segments mouth on protrusible mouth cone with powerful has head, neck and trunk pumping no limbs complete digestive tract : Phylum Kinorhyncha; Ziser Lecture Notes; 2015.9 1 Animals: Phylum Kinorhyncha; Ziser Lecture Notes; 2015.9 2

two pairs of salivary glands and pancreatic glands paired genital organs secrete digestive enzymes into throat area internal fertilization with specialized penial spines a midgut acts as a stomach and an intestine development includes minute free-living anus at posterior end of progressive larval molts No circulatory system

Excretory system of 2 protonephridia

Nervous System circumpharyngeal ganglia and one ganglion in each segment senses:

simple eyespots

spines and bristles with chemoreceptors and mechanoreceptors

Excretory system paired protonephridia

Reproductive System dioecious but no dimorphism Animals: Phylum Kinorhyncha; Ziser Lecture Notes; 2015.9 3 Animals: Phylum Kinorhyncha; Ziser Lecture Notes; 2015.9 4