Zoology 250

Clade for ANNELIDA


Tree and most traits from (Nielson 1994 p. 143-4), and Brusca & Brusca (1990 p. 432).


                        ====3=== "SubCl." Errantia (errant marine segmented worms)
       ==2==Polychaeta==|
<<=1===|                ====4=== "SubCl." Sedentaria (sedentary marine segmented worms)
       |
       |   =====6=============== Oligochaeta (earthworms & relatives)
       |   |
       =5==|         ==8======== Acanthobdellida (primitive leech-like annelids)
           =====7====|
                     ==9======== Hirudinea (true leeches)

Traits supporting each clade (** plesiomorphic- a primitive state, not unique to clade):

1:a) many similar body segments each bearing a separate coelom**, b) simple prostomium**, c) no parapodia**, d) multiciliated cells**, e) chitinous setae in setal sacs**, f) separate sexes, gametes from body wall (no permanent gonads)**, g) segmented ventral nerve cord**, h) closed circulatory system with capillaries and contractile vessels or hearts, i) nephridia with nephrostome opening in segment anterior to that of the nephridial tubule
2: a) extensive setae, b) parapodia, c) gametes from body wall (no permanent gonads)**, d) complex prostomium
3: a) parapodia well developed, b) pharynx with jaws (most)
4: a) parapodia reduced or absent**, b) segments usually differ in form, c) jaws usually absent
5: a) few setae, b) simple prostomium**, c) no parapodia**, d) hermaphroditic, e) clitellum that produces the cocoon in which eggs are laid, f) permanent gonads
6: a) calciferous glands of esophagus, b) typhlosole (earthworms)
7: a) single large coelom due to loss of septae between body segments, b) fixed number of body segments, c) setae restricted to a few anterior segments, d) posterior (and often anterior) sucker, e) superficial annuli in body wall
8: a) segmented coelom in anterior-most 5 segments (no anterior sucker)**; b) setae restricted to a few anterior segments**, c) body of 30 segments
9: a) anterior sucker, b) body of 34 segments, c) coelom unsegmented, d) no setae

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Copyright © 1998 by A. Richard Palmer. All rights reserved. (revised March 8, 1998)