Acta Parasitologica, Vol. 51, No. 4, 2006, 264-272 Aneta Yoneva(1)*, Jordi Miquel(2), Zdzislaw Swiderski(3,4), Katia Georgieva(1), Yana Mizinska(1) and Boyko B. Georgiev(5,6) - Ultrastructure of spermiogenesis and mature
spermatozoon of Angularella beema (Clerc, 1906) (Cestoda, Cyclophyllidea, Dilepididae)
(1)Institute of Experimental Pathology and Parasitology, Bulgarian Academy of Sciences, Acad. G. Bonchev Street, Block 25, 1113 Sofia, Bulgaria; (2)Laboratori de Parasitologia, Departament de Microbiologia i Parasitologia Sanitaries, Facultat de Farmacia, Universitat de Barcelona, Av. Joan XXIII, sn, 08028 Barcelona, Spain; (3)W. Stefanski Institute of Parasitology, Polish Academy of Sciences, 51/55 Twarda Street, Warsaw, Poland; (4)Department of General Biology and Parasitology, Warsaw Medical University, Warsaw, Poland;
(5)Central Laboratory of General Ecology, Bulgarian Academy of Sciences, 2 Gagarin Street, 1113 Sofia, Bulgaria; (6)Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
*Corresponding author: ayoneva@iepp.bas.bg
ABSTRACT
The ultrastructure of the spermiogenesis of a dilepidid cestode species is described for the first time. The spermiogenesis of Angularella beema is characterised by absence of both flagellar rotation and proximodistal fusion. The differentiation zone is surrounded by cortical microtubules and is delimited by a ring of arching membranes. It contains two centrioles, one of which develops the axoneme that grows directly into the elongating cytoplasmic protrusion. This pattern of spermiogenesis was described as the Type IV spermiogenesis of cestodes. Among cestodes, similar pattern of spermiogenesis is known in the family Hymenolepididae and in some representatives of the family Anoplocephalidae. The mature spermatozoon of A. beema consists of five regions differing in their ultrastructural characteristics. It is characterised by the presence of cortical microtubules (spirally arranged at angle of 30-40° to the spermatozoon axis) and a single crested body. There is a periaxonemal sheath in certain parts of the spermatozoon as well as glycogen-like granules between the periaxonemal sheath and the cortical microtubules.
The comparisons of the mature spermatozoon of A. beema with those of other two dilepidid species (Dilepis undula and Molluscotaenia crassiscolex) demonstrate some variation within the family: presence of periaxonemal sheath in A. beema and
D. undula and its absence in M. crassiscolex; presence of electron-dense rods in D. undula and their absence in A. beema.
KEY WORDS: Cestoda, Cyclophyllidea, Dilepididae, Angularella beema, spermiogenesis, spermatozoon, ultrastructure