VCSU Macro-Invertabrate Lab

Phylum Annelida - The Segmented Worms

The Annelids are segmented worms. Common examples are the leeches (bloodsuckers) and aquatic earthworms (oligochaetes). In addition to leeches and oligochaetes, we also occasionally collect branchiobdellids, which are leech-like parasites on crayfish. All annelids feature a segmented body and soft muscular body wall.

General Life cycle - Leeches may take blood meals from living organisms or feed on dead animals. Only a few actually feed on warm-blooded animals such as humans or livestock. The aquatic earthworms feed much as terrestrial earthworms do, consuming sediment and extracting nutrients from it. Annelids are generally hermaphroditic, meaning individuals have both male and female sexual glands. However they do need a partner to reproduce. Some oligochaetes can reproduce by budding, an asexual method of reproduction that does not require a partner.

Identification - To identify the type of leech you collect, you may need to count segments between the sexual pores, locate the eyespots, or identify characteristics of the suckers. When identifying taxa of aquatic earthworms, the location and number of small hairs is important so a strong microscope will be necessary. Other features such as the location of the budding zone may be important. To identify the genera of branchiobdellid you would need to view the reproductive organs carefully.

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