THE EFFECTS OF COLCHICINE ON SPERMATOGENESIS IN NITELLA

Abstract

Treatment of Nitella antheridia with colchicine results in various sperm abnormalities, depending upon duration of exposure and subsequent recovery . Early effects of treatment include disappearance of spindle fibers and a cessation of ordered cell wall formation in dividing cells . Sperm released from antheridia treated for 24 hr and allowed to recover for 4-5 days possess branched flagella . After a recovery period of 6-10 days the sperm appear normal ; however, following longer recovery periods, the sperm exhibit variations in size and number of flagella . Branched flagella contain a variety of microtubule patterns ranging from branches containing a single microtubule to flagella with an excess of microtubules . Spermatids which differentiate in the presence of colchicine lack flagella and a microtubular sheath . Nuclear contents undergo condensation stages ; however, the nucleus as a whole does not undergo the orderly elongation and coiling characteristic of untreated Nitella spermatids . Long-term colchicine treatment followed by a recovery period produces atypical microtubules and microtubular aggregations in the spermatid . The results indicate that colchicine affects not only polymerization of microtubule subunits but also factors responsible for their ordered spatial relationships in the cell . The presence of microtubules is a prerequisite for normal morphological changes during spermiogenesis .

Motile Gametes of Land Plants: Diversity, Development, and Evolution

“…Already formed microtubule arrays of the spline, basal bodies, and flagella are stable and hence are unaltered by inhibitors. In the green alga Nitella, treatment with colchicine also prevents the spline from forming and results in misshapen nuclei, supporting the involvement of microtubules in nuclear shaping in this alga as in archegoniates (Turner, 1970).…”

Le cytosquelette des gamètes mobiles des végétaux

“…L'intervention des rnicrotubules dans le contrôle de l'élongation nucléaire est amplement démontrée par l'action des inhibiteurs de polymérisation de la tubuline. Lorsque ces substances sont employées en cours de gamétoge-nèse, en effet, le noyau reste amoeboïde et la cellule ne subit pas la mise en forme habituelle (Turner, 1970 ;Cave et Bell, 1979 ;Myles et Hepler, 1982). Cependant les modalités d'intervention des microtubules restent mal comprises.…”

Giant nebenkern produced by colcemid treatment of the spermatocysts of the silkworm,Bombyx mori

“…This indicates that spermiogenesis occurs in the spermatocytes with a nebenkern no matter in what stage of meiosis the nebenkern is formed. Turner (1970) reported the appearance of branched flagella following colchicine treatment during spermatogenesis in male plants of the dioecious charophytes Nitella spp. He proposed that extra centrioles which are incorporated into the maturing spermatid eventually give rise to excess flagella.…”

“…Numerous studies have been conducted to examine the effect of colcemid on the behavior of the mitotic apparatus or chromosomes during meiosis and also on the transformation of nuclear shape during spermiogenesis (Handel 1979, with mouse; Liebrich 1982, with Drosophila hydei; Abe and Uno 1984, with newt;LaFountain 1985, Czaban andForer 1985, with crane fly). However, the only experiment that followed further stages of spermiogenesis after blocking meiosis by colchicine is Turner's (1970) with NitelIa rnissouriensis and N. rnirabilis.…”