Lecture 14: Introduction to Ecdysozoa and Phyla Nematoda and Nematomorpha

Ecdysozoa

Group of protostomes with external cuticles, most speciose animal group (due to arthropods), make up 83% of all animal taxa

Protostomes

Major group of animals characterized by having the mouth develop before the anus during embryonic development along with spiral and determinate cleavage

Ecdysis

Molting, as they grow ecdysozoans shed their outer cuticle and grow a larger one

Clade Nematoida

Nematodes and nematomorphs (roundworms and horsehair worms), cuticle mostly without chitin, males posses a cloaca

Cloaca

Common chamber of reproductive and digestive system

Phylum Nematoda

Consists of roundworms, diverse, typically outnumber other species in the same habitat, widespread/ can live anywhere

Amphids

Olfactory, chemoreceptive, and thermoreceptive centers of nematode located in depressions on anterior end of worm

Cryptobiosis

Can go completely inactive until conditions become favorable again

River blindness

Filarial worm causes eyes disease in humans, transmitted by black flies in latin ameria/ africa, infect vitreous chamber, retina, and optic nerve, causing visual impairment and blindness

Trichinosis

Caused by trichinella spiralis, ingested by eating raw or undercooked pork/ wild game, develop in intestines and then travel through lymphatic vessels into muscles, make muscle cells elastic to house nematode, blood vessels supply parasite with nutrients

Elephantiasis

Condition caused by Wuchereria bancrofti, transmitted via mosquitoes, nematodes block lymphatic vessels and cause fluid accumulation (edema), causes enlargement of body parts

Stylet

Specialized oral structure used to pierce root cells and suck out contents

Gonochoristic

A species where individuals are either male/ female, with separate sexes

Spicule

Male nematodes have this copulatory structure that transfers sperm

Pseudogamy

Asexual reproduction strategy in which females use sperm of males (different species) to activate their oocytes, sperm isn’t used, embryos derived from maternal DNA to give rise to females

Caenorhabditis elegans

Model organism for research, 1 mm long, self-fertilizing hermaphroditic worm, easy to care for, short life cycle, transparent (can observe all cells), large number of offspring

Phylum Nematomorpha

Horsehair worms, known for thread-like shape, most occur in freshwater, body covered in thick cuticle

Areoles

Outer layer of nematomorpha covered in bumps, warts, or papillae