PROC. BIOL. SOC. WASH. 100(4), 1987, pp. 700-712 ANTARCTIC RECORDS OF ASTEROID-INFESTING ASCOTHORACIDA (CRUSTACEA), INCLUDING A NEW GENUS OF CTENOSCULIDAE Mark J. Grygier Abstract.— The following Ascothoracida parasitizing Antarctic asteroids are described and illustrated: an immature female Dendrogaster sp. cf antarctica Grygier, and females and brooded offspring of Gongylophysema asetosum, new genus and species, all parasitic in Odontaster validus Koehler; several females and males of Z). usarporum, new species, from Porania antarctica glabra Sladen. Females of both species of Dendrogaster have setose thoracopods, a new mor-phological feature for this genus. Gongylophysema is the most apomorphic genus of the Ctenosculidae and has numerous similarities witih the dendro-gastrid genus Ulophysema. Its embryological development omits the nauplius, and the ascothoracid larva's medial penis originates as paired embryonic limb buds, a finding with implications for the entire Ascothoracida and Cirripedia. The sexes are separate by ascothoracid larva I. The opportunity is also taken to identify tentatively an historically enigmatic parasite of a Canadian brisingid asteroid as a ctenosculid ascothoracidan. Ascothoracidans of the order Dendrogas-trida are all crustaceans that parasitize echi-noderms. Two members of this group have been described from Antarctica, Dendro-gaster antarctica Grygier, 1980, a coelomic parasite of the asteroid Acodontaster con-spicuus Koehler in McMurdo Sound, and Ascothorax gigas Wagin, 1 968, a bursal par-asite of the large ophiuroid Ophionotus vic-toriae Bell along the Antarctic Peninsula (and in the South Sandwich Islands) (Gry-gier 1981b, Grygier and Fratt 1984). Also, A. M. Clark (1962, 1977) mentioned an as-cothoracidan, apparently a member of the family Ctenosculidae, in the asteroid Aco-dontaster hodgsoni forma stellatus (Koeh-ler) from off MacRobertson Land. New rec-ords of Dendrogaster from two Antarctic asteroids are given in the present report as well as a new dendrogastridan genus, here assigned to the Ctenosculidae, from one of these same asteroids. Class Maxillopoda Dahl, 1956 Subclass Thecostraca Gruvel, 1905 Superorder Ascothoracida Lacaze-Duthiers, 1880 Order Dendrogastrida Grygier, 1987b Family Dendrogastridae Gruvel, 1905 Dendrogaster Yjiiipoyich, 1890 Dendrogaster sp. cf. antarctica Grygier, 1980 (nom. correct, pro D. antarcticus) Fig. 1 Material. —^on-hrooding 9 (USNM 228260) from coelom oi Odontaster validus Koehler also infested with Gongylophysema asetosum, new genus and species (see be-low), coll. G. Hendler, 25 Mar 1982, Hero Cr 824, Sta 30-1, 64°14.15'S, 62°33.60'W, 90-135 m. Description. —Tv3.ns\QrsQ span of mantle 21.4 mm (Fig. lA, B). Middle piece dis-torted, but longer than wide and tapered
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