(errant polychaete)

(sedentary polychaete)

PHYLUM ANNELIDA (Tree and traits from Nielson 1995 p. 143-4, and most characters from Brusca & Brusca 1990 p. 432.)

(oligochaete)

(leech)

                       ====3==== burrowing "Sedentaria" (slow-moving, sediment-eating worms)
                       |
     ==2=Polychaeta====|   ==5== "Errantia" (active, highly mobile marine worms)
     |                 ==4=|
<<=1=|                     ==6== tube-dwelling "Sedentaria" (sessile, suspension-feeding worms)$
     |
     |   =====8================= Oligochaeta (earthworms & relatives)
     |   |
     =7==|         ====10======= Acanthobdellida (primitive leech-like annelids)
         =====9====|
                   ====11======= Hirudinea (true leeches)

Back to Zool 250 tree for animal phyla or Protostomia

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade):

1= ANNELIDA: a) many similar body segments each bearing a separate coelom** b) simple prostomium & pygidium** c) peristomium: a unique pre-segment surrounding the mouth d) no parapodia** e) multiciliated cells** f) chitinous setae in setal sacs** g) each seta secreted by a single cell h) 4 setal bundles per segment (2 dorsolateral, 2 ventrolateral) i) separate sexes, gametes from body wall (no permanent gonads)** j) segmented ventral nerve cord** k) closed circulatory system with capillaries and contractile vessels or hearts l) nephridia with nephrostome opening in segment anterior to nephridiopore m) trochophore larva** 2: a) extensive setae b) parapodia c) gametes from body wall (no permanent gonads)** d) complex prostomium e) nuchal organs (sensory) f) 1 pair pygidial setae 3= SCOLECIDA: a) 2 or more pairs of cirri on pygidium 4= PALPATA: a) 1 pair of sensory palps on prostomium 5= ACICULATA: a) biramousparapodia well developed b) aciculum in each parapodial lobe c) dorsal and ventral cirri on parapodium d) 2 - 3 pairs of anatennae on prostomium e) pharynx with jaws (most) 6= CANIPALPATA: a) parapodia reduced or absent** b) segments usually differ in form c) jaws usually absent d) grooved feeding palps on prostomium

7= CLITELLATA: a) few setae b) simple prostomium** c) no parapodia** d) hermaphroditic e) clitellum (produces the cocoon in which eggs are laid) f) permanent gonads in a few segments g) trochophore larva los 8= OLIGOCHAETA: a) calciferous glands of esophagus b) typhlosole (earthworms) 9= HIRUDINOMORPHA: a) ectoparasitic lifestyle b) single large coelom due to loss of septae between body segments c) fixed number of body segments d) setae restricted to a few anterior segments e) posterior (and often anterior) sucker f) dorsal anus anterior to posterior sucker g) superficial annuli in body wall h) unpaired, mid-ventral male gonopore 10= ACANTHOBDELLIDA: a) segmented coelom in anterior-most 5 segments (no anterior sucker)** b) prostomium and peristomium lost c) setae restricted to a few anterior segments** d) body of 29 segments 11= HIRUDINEA: a) well-developed anterior sucker b) body of 33 or 34 segments c) coelom unsegmented d) no setae e) unpaired female gonopore