Ultrastructure and potential taxonomic importance of euspermatozoa and paraspermatozoa in the volutid gastropods Zidona dufresnei and Provocator mirabilis (Caenogastropoda, Mollusca).

J. GIMENEZ; J. HEALY; G. HERMIDA; F. LO NOSTRO; P. PENCHASZADEH

ZOOMORPHOLOGY (BERLIN. PRINT)

SPRINGER

Lugar: Berlin; Año: 2008 vol. 127 p. 161 - 173

0720-213X

The ultrastructure of mature spermatozoa is investigated for the first time in the Volutidae, based on thecommercially significant South American species Zidona dufresnei (Donovan, 1823) (fresh material) and supplemented with observations on testicular (museum) material of the deep sea New Zealand species Provocator mirabilis(Finlay, 1926). Euspermatozoa of Z. dufresnei (ex spermduct) consist of: (1) a tall-conical acrosomal vesicle (with short basal invagination, constricted anteriorly) which is Xattened anteriorly and associated with an axial rod, centrally perforate basal plate and short accessory membrane;(2) a rod-shaped, solid and highly electron-dense nucleus (with short basal fossa containing centriolar complex andinitial portion of a 9 + 2 axoneme); (3) an elongate mid piece consisting of the axoneme sheathed by 5–6 helicalmitochondrial elements, each exhibiting a dense U-shape douter layer; (4) an elongate glycogen piece (axonemesheathed by nine tracts of putative glycogen granules); (5) adense annulus at the junction of the midpiece and glycogenpiece and (6) a short free tail region (axoneme surroundedonly by plasma membrane). Paraspermatozoa of Z. dufresneiare vermiform and dimorphic: the first type contains approximately 14–20 axonemes (arranged peripherally and interspersed with microtubules) and numerous oblong dense vesicles, numerous less dense (round) vesicles, occasional, large lipid-like vesicles, and scattered mitochondria; the second type contains 25–31 axonemes (peripherally arranged, interspersed with microtubules), occasional mitochondria and extensive cytoplasm. Results obtained for P.mirabilis from testis material are essentially as observed in Z. dufresnei, although the euspermatozoan acrosome still has to achieve its compressed transverse prole. Observations on paraspermatozoa were limited by fixation qualityof available (testis) tissues, but these cells are similar to the first type of Zidona paraspermatozoa. Although most of the euspermatozoal features are also observed in many neotaenioglossans and neogastropods, the U-shaped outer layer ofeach mitochondrial element has not previously been reported and may prove a diagnostic feature of the Volutidae, the subfamily Zidoniinae or possibly only the Zidonini (in which Z. dufresnei and P. mirabilis are currently placed).