Phylum Nematoda
Body Structure
Bilateral Symmetry
Triploblastic
Flexible, Thick/multi-layered cuticle of chitin
Blastocoelomate
Worm-like, tubular bodies that taper at each end
Hydrostatic skeleton for support and movement
Body System
Digestion and Feeding
Complete digestive system....a tube within a tube design -- need to eat food to move existing food down....
Muscular pharynx
Circulation and Respiration
Lack an actual circulatory system....but use the fluid in their blastocoel to transport gases and nutrients
Gas exchange accomplished by a mixture of diffusion and cutaneous respiration
Excretion and Osmoregulation
Nitrogenous waste from cells is collected in the blastocoel fluid
2 different types of systems may be present to filter fluid
Glandular system -- Rennette glands remove N-waste from fluid
Tubular system -- H-glands and associated excretory canals remove N-waste from fluid
Empty through an excretory pore, near the pharynx
Empty through an excretory pore, near the pharynx
Nervous and Sensory Systems
Nerve ring and ganglia - surround the pharynx and act as a brain
Dorsal and ventral longitudinal nerve cords run the length of the body
Lateral pair of amphids on anterior end....chemo-and mechanosensory
Sensory papillae on anterior and posterior....mostly mechanosensory
Reproduction and Development
Sexual ONLY
Dioecious with internal fert.
External differences between and male and female
Male HOOKED or FANNED END with copulatory spicules
Female has a ventral gonopore toward the anterior
Four Larval Stages -- each separated by molting via ecdysis
Adults sexually produce fertilized eggs
Eggs hatch into the first larval stage *L1
L1 develops and molts into L2
L2 develops and molts into L3
L3 develops and molts into L4
L4 develops and molts into the reproductively mature adult stage