Diagnosis_Genus: Apodinium Chatton 1907. Ectoparasite of appendicularians, attached by a peduncle. Sporogenesis occurs during the trophont stage by palisporogenesis.
Diagnosis_Species: Apodinium floodi McLean & Galt 1990. Individuals reach 890 µm in length, including dinospores yet to be liberated. Divisions of young trophozoite produce sporogenic cells in a single file; further divisions produce a mass of girdled dinospores that are provided with dinokaryotic chromosomes and trichocysts of dinoflagellate type, and that are liberated apically through a rupture in encompassing membranous envelope. Relatively narrow peduncle originates at sporogenic cytoplasm; diameter increases distally, then decreases gradually until host epidermis and muscle plate are penetrated; peduncle crosses host hemocoel, often accompanied by tube of host cytoplasm, until notochord is reached; within host, peduncle with thin septum that separates lumina of 2 thickly walled elements; lumen of each element continuous with that of principal rhlzoid that invades outer region of notochord, between basement membrane and microfibrils, and later branches; rhizoids with dense inner layer, and absorptive outer layer of tubules (= villosities) on both lateral and medial surface; each principal rhizoid with dense, homogeneous condyle. Tumor-like growths in notochordal lumen, and abnormal cytoplasmic proliferations adjacent to rhizoids. Host, Oikopleura labradonensis Lohmann, 1892 (Phylum Chordata, Subphylum Urochordata, Class Larvacea).
Body_length: 890 µm