Pseudocoelomates Aschelminths

Achelminth Phyla Gastrotricha Rotifera Kinorhyncha Nematoda Nematomorpha Acanthocephala Loricifera Priapulida Entoprocta

Pseudocoelomates Define pseudocoelomate. formed directly from the cavity of the blastula The cavity is small Mostly filled with intestine and oviducts or testes.

Gastrotricha Microscopic Marine and freshwater species Common in lakes, ponds and seashore sands

Rotifera Ciliated crown or corona at the anterior end Carnivorous or parasitic Most common in freshwater environments Body structure: Head has corona Trunk has ridged plates and spines Foot has toes for attachment.

Rotifera

Kinorhyncha About 150 species Lives in marine sediment Uses head as an anchor, pulls body after it. Sexes are separate Feed on algae and bacteria

Nematodes bilaterally symmetrical worm-like surrounded by a cuticle secreted by epidermal cells longitudinal muscles only

Nervous System - Nematodes Simple ring of nervous tissue around pharynx dorsal and ventral nerve cords running the length of the body

Nematode Movement Contract longitudinal muscles High internal pressure causes the body to flex Moves by thrashing back and forth No cilia or flagella

Excretory Systems Some have specialized cells that excrete nitrogenous wastes Others have canals Others have canals plus specialized cells Nematodes do not have flame cells

Nematode Reproduction Most nematodes are dioecious Males use special copulatory spines The sperm move by pseudopodia, like amoebas

Nematode Diversity Close to 500,000 species Some species are generalists Others are much more specialized - one species of nematode is known only from felt coasters placed under beer mugs in a few towns in Germany.

Nematode Lifestyles Many free living Many also parasitic Play critical ecological roles as decomposers and predators on microorganisms

Nematode-Caused Diseases Roundworms - more than ½ the world's humans Hookworms Trichinosis Pinworms infestations - extremely common parasite in the United States can be transmitted from human to human by eggs floating in household dust Filariasis (elephantiasis) Onchocerciasis (river blindness).

Nematomorpha – Horsehair Worms or Gordian Worms Up to 1m long, but very slender animals (1-3mm). Free-living as adults Often find adults in very clean streams

Juveniles are Arthropod Parasites

Acanthocephala - spiny headed worms 2-host parasites Must have invertebrate host Spiny protrusible proboscis About 1150 species Dioecious Both circular and longitudinal muscles

Acanthocephalans - Nutrition Nutrition by diffusion Proboscis attaches to host intestine Cause extensive damage to the intestinal walls Economic importance: Some forms cause serious discomfort and ill-health to domestic livestock

Excretion Reproduction Protonephridia lined with flame cells Reproductive structures are contained in strange ligament sacs. In males two testes are contained within this sheath.

Loricifera Discovered in 1974 Dioecious Have a large brain Little else is known about them.

Priapulida – The Penis Worms Only 9 species All marine worms Found in colder water Predaceous Fossils date back to Middle Cambrian.

Entoprocta (Bryozoa) Ciliary feeding device - LOPHOPHORE Were known as Bryozoa (moss animals) 4000 species Few > 0.5 mm long All aquatic (marine and freshwater)

Ectoproct Feeding

Entoprocta Most are colonial Lives in secreted exoskeleton (zoecium) that may be: Gelatinous Chitinous Stiffened with calcium Impregnated with sand. Some ectoprocts could be mistaken for hydroids but their tentacles are ciliated.

Ectoproct Colony