Spermatogenesis and Sperm Ultrastructure in Some Cyst Nematodes, Heterodera Spp

Abstract

In both round (Heterodera s.g. Globodera Skarbilovich) and lemon-shaped (H. s.g. Heterodera Skarbilovich) species of cyst nematodes studied, the early stages of spermatogenesis were completed in the 4th-stage larva and no further cell divisions took place after the last moult. Only spermatids and spermatozoa were present in adult males; in old males the whole gonad was occupied by mature sperm. Evidently the sperm output of the non-feeding, adult male is limited, possibly conserving reserves of energy for mate-finding, Resources are also conserved when, during maturation of the spermatozoa, the discarded cytoplasm and organelles of the so-called 'residual bodies' are engulfed by cells of the testis wall. Heterodera sperm resemble other described nematode sperm in being aflagellate and amoeboid, in lacking a nuclear membrane during all stages except the spermatogonium and in having a fibrillar storage product in the spermatids which in H. rostochiensis disperses during the transition to sperm but in H. schachtii is retained. They differ from other nematode sperm in lacking the polarity, the secretory granules and the so-called 'membrane specialisations' found in one or other of the four main types of nematode sperm, and in possessing a layer of cortical microtubules lining the whole surface of the sperm, including the pseudopodia. In round-cyst nematodes the state of condensation of the sperm nucleus changes several times during spermiogenesis and insemination, the chromatin passing through a compact homogeneous, a finely stranded, another compact and finally a coarsely stranded phase. These changes have not been recorded in other nematode sperm. The sperm nucleus in lemon-shaped cyst nematodes does not pass through the finely stranded phase in the testis, a further difference distinguishing the two main groups of cyst nematodes.