The Animal Kingdom: The Protostomes. Protostomes 4/16/2012. Chapter 30

Transcription

1 Porifera Acoelomates ates The Animal Kingdom: The Protostomes Chapter 30 Protostome Bilateral Protostomes Acoelomates ates Characterized by spiral cleavage determinate cleavage (fixed fate of cells) of mouth from blastopore Protostome Bilateral Phylum (Flatworms) - 20,000 spp. Acoelomate animals with: bilateral cephalization 3 definite tissue layers well-developed organs Many are hermaphrodites single animal produces both sperm and eggs Phylum (Flatworms) Ladder-type nervous system sense organs simple brain composed of two ganglia 2 nerve cords that extend the length of body Protonephridia function in osmoregulation and disposal of metabolic wastes 1

2 Protonephridia Flame bulb 3 Classes of Phylum Class Turbellaria free-living flatworms, including planarians Classes Trematoda and Monogenea parasitic flukes Class Cestoda parasitic tapeworms Fig Class: Turbellaria Carnivorous???? Ganglia Auricle Eyespot Nerve Gastrovascular cavity Auricle Class turbellaria e.g. planarians Food in Undigested out Sexual (hermaphrodites) + asexual Gasses via diffusion Pharynx Sheath surrounding pharynx Mouth Fig Protonephridia 1 mm Fig. 30-1ab, p. 642 Class: Trematoda (Monogenea) Flukes Look like free living flatworms - BUT Modified body plan - suckers for clinging to host Complex life cycle that may involve several hosts Large number of eggs Liver Fluke 2

3 1. Larvae burrow through the skin. Do not post photos on Internet 2. Larvae make their way to the circulatory system. During reproduction, which takes place in the intestinal veins, the male holds the female in a long groove. 7. Finally, fork-tailed larvae (cercariae) develop and leave the snail. 3. Eggs pass into the intestine. 6. The larvae must enter a second host, a freshwater snail. After burrowing into the tissues of the snail, larvae develop into a form that reproduces asexually. This process greatly increases the number of larvae. Blood Fluke 4. Eggs containing developing embryos are excreted with the feces. 5. If they find their way to fresh water, the eggs hatch, releasing free-swimming larvae (miracidia). Fig Slide 19 Trematoda Class: Cestoda (tapeworms) 5,000 species Long, flat ribbon like animals Head (scolex) that attaches to intestine and absorbs digested food Body a long chain of proglottids No mouth no digestive system Proglottids 3

4 Tapeworm Acoelomates ates Protostome Bilateral Phylum: Nemertea (ribbon worms or proboscis worms) 900 species Free living critters marine habitats Characterized by proboscis Coelom (rhynchocoel) carnivorous!!! Separate sexes Evolutionary milestones!! 4

5 Nematoda Phylum: Nemertea Acoelomates ates 1st blood vessels????!!!!! Complete digestion???!!!!!!!!! Protostome Bilateral Nematoda - The Roundworms (20,000 spp.) New major grouping - ate animals Decomposition and nutrient recycling Free living and parasitic acts as a hydroskeleton Complete digestive tract (mouth and anus) Three germ tissue layers No circulatory system Sexes separate Body covered by tough cuticle helps prevent desiccation Phylum Nematoda (Roundworms) Parasitic nematodes in humans Ascaris hookworms trichina worms pinworms Ascaris 5

6 Nematoda Rotifera Acoelomates ates Phylum Rotifera ~ 2000 spp. Most Marine Recycling of nutrients Characteristic crown of cilia Brain sense organs eye spots Protonephridia cell constant Dormancy!!! For months/years Protostome Bilateral 6

7 Nematoda Rotifera Tardigrada Onychophora Acoelomates ates Coelom is a fluid-filled body cavity completely lined by mesoderm between digestive tube and outer body wall Protostome Bilateral Allows tube-within-a-tube body plan body wall is outer tube inner tube is digestive tubea space in which internal organs develop including gonads! Helps transport materials Protects internal organs Phylum: Tardigrada Tiny with unbranched clawed legs Phylum Onychohoran Paired appendages not jointed Jaws are derived from appendages 7