Invertebrates 2

I. Annelids (segmented worms); I. Annelids (segmented worms); This phylum includes earthworms, marine worms, and leeches. A. Body Structure; bilateral symmetry 1. Bodies are segmented (divided) 2. They have a developed nervous system. Some marine worms have a primitive brain, and eyes with lenses and retinas. 3. closed circulatory system – blood vessels and hearts

4. complete digestive tract with mouth, crop, gizzard, 4. complete digestive tract with mouth, crop, gizzard, intestine, and anal opening 5. coelomate- coelom is surrounded by mesoderm. a. divided by septa (partitions)

6. muscles run laterally and in rings (segments), around the body. By muscular contraction in each segment, the fluid in the septa is squeezed, resulting in the movement of the worm.

B. Reproduction; May be sexual, or asexual. 1. earthworms and leeches are hermaphrodites, but reproduction generally involves 2 parents (sexual reproduction). 2. Sexual reproduction among marine worms. There are male and female worms C. Nutrition; 1. earthworms and marine worms; consume organic waste material. a. Earthworms- Soil is taken into the mouth. Food within the soil is ground in the gizzard, then passed into the intestine. Soil and undigested food pass as waste through the anus.

Giant earthworms from Gippsland, Australia can be over a meter long (3 feet).

Marine worms (bristle worms)

Christmas tree worms on a coral reef.

Zombie worms feeding on whale bones.

The skin of zombie worms produces an acid that dissolves bone so that they can reach the fats and protein on the inside. They do not have a mouth or stomach. The worms rely on a root system of sorts (their setae). They drill into the bone, and symbiotic bacteria living on the roots (setae) help them digest their food. Exactly how the nutrients make their way into the worm still isn't clear to scientists.

Female zombie worms are the only ones that we see; male zombie worms are microscopic and live inside the female. Hundreds of tiny male specimens have been found in one female worm, which removes the stress of attempting to find a mate on scattered bones in the deep ocean.

The largest bristle worm is called the sand stalker, or Bobbit worm. It can reach 10 feet in length, most being about an 1 inch in diameter. It buries itself in the sand, and catches fish that swim by.

Palolo worms produce gamete segments each spring. These are eaten by Samoans in palolo worm festivals each spring.

a. predatory- eating small aquatic organisms. 2. leeches; a. predatory- eating small aquatic organisms. b. parasitic- feed from the blood of a host animal. Saliva contains chemicals that act as an anesthetic, and an anticoagulant. Hirudo medicinalis European medical leech

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