A new species of Acanthobothrium van Beneden, 1849 (Cestoda: Tetraphyllidea) from Rioraja castelnaui (Chondrichthyes: Rajoidei) in coastal waters of Argentina

Abstract

Acanthobothrium marplatensis n. sp. is described from the spiral intestine of the skate Rioraja castelnaui taken off Mar del Plata, Argentina. The new species is compared with those species that it most closely resembles morphologically, to species reported from other skate hosts and to species described from the same geographical region. A. marplatensis is most similar to A. paulum, A. benedeni, A. costarricense, A. fogeli, A. himanturi, A. lintoni, A. monksi, A. olseni, A. puntarenasense and A. mathiasi. All of these species share a similar combination of characters (12–40 proglottids, 20–50 testes and total length of 2–10mm). A. marplatensis can be differentiated from these species and those described from skates by a combination of the following characters: 4.79–8.44 (6.18) mm long, with 18–30 (24) proglottids, spinose cephalic peduncle 160–338 (227) long, bothridial hooks with total length 93-134 (115), 24–39 (32) testes per proglottid, cirrus-sac curved anteriorly, ovarian lobes never reaching the level of the cirrus-sac and vaginal sphincter absent. Geographically, the new species can be distinguished from A. zapterycum and three different species designated as “Acanthobothrium sp.” reported from the coast of Uruguay and Argentina by the size of the worms, number of proglottids, position of the genital pores and size of the bothridial hooks. A. marplatensis showed the greatest preference for chambers 2 and 3 of the eight chambers of the spiral intestine. The mean intensity of infection in individual hosts increased with host size and was greater in spring and summer than in cold seasons. The intensity of infection was unrelated to host sex.