Ultrastructure and potential taxonomic importance

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

ZOOMORPHOLOGY (BERLIN. PRINT)

Springer

Lugar: Berlin; Año: 2008

0720-213X

The ultrastructure of mature spermatozoa isinvestigated for the Wrst time in the Volutidae, based on thecommercially signiWcant South American species Zidonadufresnei (Donovan, 1823) (fresh material) and supplementedwith observations on testicular (museum) materialof the deep sea New Zealand species Provocator mirabilis(Finlay, 1926). Euspermatozoa of Z. dufresnei (ex spermduct) consist of: (1) a tall-conical acrosomal vesicle (withshort basal invagination, constricted anteriorly) which isXattened anteriorly and associated with an axial rod, centrallyperforate 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 midpiececonsisting of the axoneme sheathed by 5–6 helicalmitochondrial elements, each exhibiting a dense U-shapedouter 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 Wrst type containsapproximately 14–20 axonemes (arranged peripherally andinterspersed with microtubules) and numerous oblongdense vesicles, numerous less dense (round) vesicles, occasional,large lipid-like vesicles, and scattered mitochondria;the second type contains 25–31 axonemes (peripherallyarranged, interspersed with microtubules), occasional mitochondriaand extensive cytoplasm. Results obtained for P.mirabilis from testis material are essentially as observed inZ. dufresnei, although the euspermatozoan acrosome stillhas to achieve its compressed transverse proWle. Observationson paraspermatozoa were limited by Wxation qualityof available (testis) tissues, but these cells are similar to theWrst type of Zidona paraspermatozoa. Although most of theeuspermatozoal features are also observed in many neotaenioglossansand neogastropods, the U-shaped outer layer ofeach mitochondrial element has not previously beenreported 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)