BIO 385 — Invertebrate Zoology

Invertebrate Diversity
Clade Gnathifera:
Rotifers & Relatives

(Click on any image for larger version)

Phylum Rotifera — Wheel Animals

Characteristics Very small, most <1 mm. Varied, complex shapes Anterior end has paired coronas lined with cilia Many forms are sessile, attach via posterior foot Mostly fresh water; a few are parasitic Most are parthenogenic Without Acanthocephalans, the group is paraphyletic Clade that includes rotifers and acanthocephalans sometimes called Syndermata	Fresh-water Rotifer, Philodina sp.; 100x See also labeled photo.	Fresh-water Rotifer, Adineta sp.	Fresh-water Rotifer, Squatinella sp.; collected Toleson, AZ
	Fresh-water Rotifer, Monostyla sp.?; 100x	Fresh-water Rotifer, Euchlanis sp.; 200x	Fresh-water Rotifer, Keratella sp.; Phoenix, AZ
	Fresh-water Rotifer, Brachionus sp.; Rio Salado, AZ; 200x	Fresh-water Rotifer, Synchaeta sp.; Tolleson, AZ; 200x	Fresh-water Rotifer, Polyarthra sp.; Rio Salado, AZ; 200x

Acanthocephala — Spiny-headed Worms

Characteristics Body cylindrical, usually with rings of small spines Fluid-filled proboscis with hooks and spines Lack gut; reduction of most organs Pseudocoelom filled with large gonads Intestinal parasites of vertebrates Derived from within rotifer group Formerly considered a separate phylum, but now is generally treated as a Class of rotifers

Acanthocephalan, stained whole mount

Spiny-headed worm, Neoechinorhynchus sp., preserved specimen

Phylum Chaetognatha — Arrow Worms

Characteristics Elongate, streamlined bodies Lateral & caudal fins supported by rays Mouth surrounded by grasping spines Complete gut Longitudinal but not circular muscles Pelagic marine predators

Sagitta sp., stained whole mount See also labeled photo.

Arrow worm, Sagitta sp., preserved specimen

Sagitta sp., closeup of head; preserved specimen