ZOO 115 Invertebrate Zoology Phylum Echiura

Phylum Echiura (Viper tail)- General Characteristics “Peanut worms” ~ 250 species Similar to Annelids but NO segmentation All marine benthic Sand, mud, with boring clams Some as deep as 10,000m From 1 cm to 2 m in length

Phylum Echiura- external anatomy http://content.answers.com/main/content/img/McGrawHill/Encyclopedia/images/CE211200FG0010.gif Two main body parts Trunk Proboscis (non-retractable) Some have a pair of chaetae similar to Annelids http://www.quadernsdigitals.net/datos_web/proyectos/p_307/bonelia.jpeg

Phylum Echiura- Locomotion Hydrostatic skeleton (coelom) Peristalsis - Similar to Sipunculids

Phylum Echiura- Feeding and Digestion http://content.answers.com/main/content/img/McGrawHill/Encyclopedia/images/CE211200FG0010.gif http://www.17slon.org/potapljanje/lokacije/hr/istra2/marina016-500.jpg Most surface feeders (detritivore) mucus and cilia on proboscis gutter for transporting food particles Suspension feeding mucus net (Urechis caupo) Trunk hidden http://www2.ucsc.edu/seymourcenter/images/urechis4.JPG

Phylum Echiura- Feeding and Digestion Note the relatively straight, but coiled, digestive tract (not U-shaped) Hindgut gut has a ciliated groove for moving food. http://bio.classes.ucsc.edu/bio136/echiura/echiura.html

Phylum Echiura– Gas Exchange and Circulation Anal vesicle (sac) used for gas exchange. Body causes water to be pumped in and out of anus. Closed circulatory system powered by body movements http://bio.classes.ucsc.edu/bio136/echiura/echiura.html

Phylum Echiura- Excretion Metanephridia one pair two pair in Echiuris hundreds in Ikeda Anal vesicles pick up coelomic waste and transport it to anus http://bio.classes.ucsc.edu/bio136/echiura/echiura.html

Phylum Echiura– Nervous system Simple – similar to annelids Brain around gut http://bio.classes.ucsc.edu/bio136/echiura/echiura.html Ventral nerve cord Almost no sensory receptors

Phylum Echiura- Reproduction Urechis caupo has good wound healing but asexual reproduction not known Sexual Reproduction Dioecious Gonad produce gametes Gametes brought into nephridia and ejected to the outside http://bio.classes.ucsc.edu/bio136/echiura/echiura.html

Phylum Echiura – Reproduction Bonellia sp. Have parasitic males Sex determined by proximity of larvae to female proboscis – if close becomes male Controlled by hormones from proboscis Males enter female body through nephridia Male

Phylum Echiura – Development Trochophore larvae Spiral holoblastic cleavage

Urechis caupo (Fat Inkeeper) http://www.elkhornslough.org/critters/fatworm.htm Commensal species Permanent Pea crab (Scleroplax granulata) Scale worm (Hesperonoe adventor) Clam (Cryptomya sp.) Temporary Goby (Clevelandia ios) http://academic.evergreen.edu/g/goefre12/symbiosis/commensals.htm http://www.amonline.net.au/collections/marineinverts/record.cfm?id=128 http://en.wikipedia.org/wiki/Image:Pinnotheres_pisum.jpg