Reproductive anatomy and gametogenesis inShipleya inermis(Cestoda: Dioecocestidae)

Abstract

Study of the reproductive anatomy in 65 strobilae of the dioe cious cestode Shipleya inermis Fuhrmann, 1908 (Acoleata: Dioe cocestidae) showed that a common genital duct, probably arising through fusion of the vas deferens and the proximal portion of the vaginal duct, compensated functionally for the loss of a patent vagina. Gonochorism was characteristic, but rudimentary genital organs of the opposite sex were present in 26 % of males and 9 % of females; two strobilae (3 %) were hermaphroditic. Her maphrodites had normally developed male organs and were capable of cross-fertilization as males; their female organs were much reduced in size but were functional, and eggs or fertilized ova in the uteri indicated that self-fertilization occurred. Gametoge nesis was traced, mainly in chromosomal preparations. The diploid chromosomal complement in embryos and germ-line cells consisted of four pairs of homologues (2n = 8, n = 4, FN = 14). Based on observation in female cestodes of one pair of chromosomes having non-homologous or non-pairing segments due to influence of heterochromatin, the authors suggest that females produce gametes of two types relative to heterochromatic DNA, while males are homogametic, and that sex-determining effects are associated therein. In males, meiosis included chromosomal pairing and recom bination, after which heterochromatin was eliminated from germ line cells through fragmentation. Other biological characteristics of S. inermis in the hosts, Limnodromus spp. (Charadriiformes), are briefly discussed. The genera of dioecious cestodes in the order Cyclophyllidea have been arranged in either one or two families in the suborder Acoleata Skriabin, 1940. In a recent revision of the Acoleata, Ryzhikov and Tolkacheva (1981) Accepté le : 27 décembre 1990.Une étude a été faite sur 65 strobiles du cestode dioïque Shi pleya inermis Fuhrmann, 1908 (Acoleata : Dioecocestidae) concer nant l'anatomie reproductrice et la gamétogenèse. Elle a montré que le conduit génital commun (résultant vraisemblablement de la fusion du canal déférent et de la partie proximale du conduit vaginal) sert à compenser la perte d'un vagin séparé. Chez ce ces tode, le gonochorisme est typique, mais les auteurs ont observé des organes génitaux rudimentaires de l'autre sexe dans 26 % des mâles et dans 9 % des femelles. Deux des 65 strobiles (3 %) sont hermaphrodites, avec l'appareil mâle fonctionnel et capable de fécondation réciproque; les organes femelles sont réduits en taille. Les oeufs des spécimens hermaphrodites ont atteint la maturité après autofécondation. La gamétogenèse a été observée principa lement dans des préparations chromosomiques. La garniture chro-

Classical and molecular cytogenetics of Khawia sinensis (Cestoda: Caryophyllidea), invasive parasite of carp, Cyprinus carpio

“…In general, the accumulation of a small amount of AT-rich DNA repeats primarily in the centromeric regions of almost all chromosomes is the most commonly reported feature in tapeworms (Rausch and Rausch 1990;Mutafova and Gergova 1994;Hanzelová et al 1995;Špakulová and Scholz 1999;Kráľová-Hromadová et al 2010;Orosová et al 2010a, b). In K. sinensis and K. saurogobii, small heterochromatin blocks were observed on all chromosomes, except for the biggest metacentric chromosome pair (present data, Orosová et al 2010a).…”

Ultrastructure of the cirrus sac of the male strobila of Shipleya inermis (Fuhrmann, 1908) (Cestoda: Cyclophyllidea)

“…with some exceptions there is a pairing of males and females in each host. Five types of strobilae with well-developed cirrus sacs were distinguished in S. inermis on the basis of functional and morphological characteristics by Rausch and Rausch (1990). Didyk and Burt (1998) also noted five types of strobilae in this species and suggested that these tapeworms are protogynous hermaphrodites that usually become regionally dioecious, possibly in response to some form of interaction between individuals.…”