A Peculiar Type of Spermateleosis in the Spider Beetle Ptinus hirtellus Sturm

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1 76 Cytologia 24 A Peculiar Type of Spermateleosis in the Spider Beetle Ptinus hirtellus Sturm Joseph Jacob1 Institute of Animal Genetics, University of Edinburgh, Edinburgh 9, Scotland Received September 11, 1958 Introduction The highly specialised nature of the spermatozoa of the spider beetle Ptinus tectus Boieldieu has been described earlier (Dlugosz and Harrold 1952) with some observations on spermateleosis also. During the course of work on radioactively labelling the spermatozoa of Ptinus hirtellus (Jacob and Sirlin 1958) it appeared that the spermateleosis in this species was of a type different from that already described, although the mature spermatozoa is specialised as in P. tectus, being 'all head'. The cytology of P. hirtellus has been studied by Sanderson (1956), but no account of the spermateleosis is so far available. The present paper reports briefly the peculiar type of spermateleosis of this beetle. The name P. hirtellus Sturm is used through out in this paper, although Moore (1957) has shown that P. clavipes Panzer is the more valid name for this species. Methods The preparations made in the course of autoradiographic investigation provided ample material for this study. Larval and adult testes were fixed in alcohol-acetic acid (3:1), and sections, and squashes were made. These and the smears were then stained by methyl green-pyronin and studied with the phase microscope. Aceto-orcein squashes and living preparations were also made and proved useful. Observations A just-formed spermatid is shown in Fig. 1, where the relatively large nucleus is centrally situated. The nucleus did not appear quite homogeneous, but the cytoplasm was so, and no conspicuous elements could be detected in the cytoplasm of this spermatid. In the next stage (Fig. 2) the nucleus was situated nearer to one side, which may be referred to as the anterior end of the spermatid. At the opposite or posterior end, the cytoplasm was drawn out into a short tapering 'tail'. The nucleus at this stage was more or less surrounded by a zone of dense cytoplasm, which also appeared to extend to the base of the 'tail'. 1 Present address: Annamalai University, Marine Biological Station, Porto Novo, India.

2 1959 A Peculiar Type of Spermateleosis in the Spider Beetle Ptinus hirtellus Sturm 77 In stage 3, the anterior situation of the nucleus in the spermatid was clearer, as the cytoplasm tended to accumulate posteriorly and the tail in creased in length (Fig. 3). The zone of dense cytoplasm around the nucleus and its extension to the tail were also more evident. The first sign of activity in the nucleus itself appeared at this stage, by the formation of an anteriorly directed beak-like prominence; this, as will be shown below, was the beginning of a process of nuclear elongation. In the next stage (stage 4), a striking change in shape of the spermatid was brought about by an antero-posterior elongation of the entire nucleus, the anterior ends, both of the nucleus and of the spermatid now becoming more pointed, as in Fig. 4. Most of the cytoplasm, except that forming a thin sheath for the nucleus, was pushed posteriorly, and sloughed off in succeeding stages (Figs. 5 and 6). The gradual elongation of the nucleus continued, and in stage 6 it measured about 12ƒÊ, while the cytoplasmic tail had grown considerably and measured over 30ƒÊ in length (Fig. 6). The growth of the 'tall' seemed to have been more or less completed by this stage, as it did not increase in length appreciably in the remaining stages of development. The increase in length of the nucleus was most striking in the succeeding stages, and in stage 7 (Fig. 7) it measured about 20ƒÊ, having almost doubled in length since the previous stage described. Besides mere elongation, there appeared to have been a great increase in nuclear content, although it seemed that the green-staining (DNA) material formed only a 'shell' and stained less intensely than in the earlier stages. The 'tail' now measured a little more than before, being about 35-40ƒÊ in length. The process of elongation continued still further, and immature spermatozoa (Figs. 8 and 9), which were narrower but longer than before, were formed. In stage 8 (Fig. 8) the nuclear portion or 'head' measured about 30ƒÊ, while there was no appreciable change in the length of the 'tail'. Examination of developing spermatozoa in living preparations showed that stage 8 was the earliest stage capable of movement, and some of these cells showed all degrees of curvature according to their form when killed during movement. The fine cytoplasmic investment seen running closely parallel to the 'head' at this stage, appeared in stage 9 to be would round it anteriorly like a delicate membrane (Fig. 9); by this time the 'head', though thinner than before, measured nearly 40ƒÊ in length. Such immature spermatozoa were sometimes observed without the tail, and this might be taken to indicate that the tail usually gets broken off at stage 9. When mature (stage 10; Fig. 10), the spermatozoon con sisted only of the 'head', and measured 50-55ƒÊ in length and less than 0.5 p in thickness. The cytoplasmic investment of the earlier stages now appeared like a delicate membrane running the entire length of the 'all head' spermatozoon, and wound round it as shown in the figure. A few microns (up to 5) of the tail usually remained attached posteriorly; the rest having been lost.

3 78 J. Jacob Cytologia 24 Figs Diagrams of the stages in spermateleosis of Ptinus hirtellus; based mainly on smear preparations-stained with methyl green-pyronin and studied with phase microscopy. 1, a just-formed spermatid (stage 1). 2, a spermatid in stage 2 when the cytoplasm is drawn out into a 'tail'. 3, a spermatid in stage 3, when the nucleus with its beak-like prominence is anteriorly situated and the cytoplasm accumulated posteriorly. The nucleus is surrounded by a zone of dense cytoplasm which also extends to the base of the 'tail'. 4, 5 and 6, later spermatids (stages 4, 5 and 6) showing change in shape of the nucleus, the sloughing off of most of the cytoplasm and the great increase in length of the 'tail'. 7, stage 7 when a marked increase in size of the nucleus occurs. The cytoplasmic invest

4 1959 A Peculiar Type of Spermateleosis in the Spider Beetle Pti nus hirtellus Sturm 79 Discussion Hughes-Schrader (1946, 1948) described a new type of spermiogenesis in iceryine coccids, where the tail developed directly into the m ature sperm. In such instances a nuclear papilla was first formed in the early sperm atid, about which the cytoplasmic anlage of the tail then fo rmed. Later, the Feulgen-positive material of the nucleus moved out into the growing cyto plasmic tail, and on the completion of this migration, the tail broke free and was transformed directly into the functional sperm; the now apparently intact, but empty, nucleus and all formed cytoplasmic constituents were discarded. A somewhat similar situation was suggested to occur i n P. tectus (Dlugosz and Harrold 1952). However, quite unlike these, the course of spermateleosis in P. hirtellus was shown to consist mainly of a progressive elongation of the entire spermatid nucleus, which was finally transformed directly into the mature ' all head' spermatozoon. The cytoplasmic tail, which appeared first in the early spermatid and grew to a considerable length, seemed free of the nucleus at the beginning and isolated from it throughout. Further, no nuclear material was ever noticed in the 'tail'. No centrioles or other cytoplasmic constituents could be discerned with certainty in the spermatids except that zone of dense cytoplasm which appeared around the nucleus in early spermatids. However, it was clear that all the cytoplasm of the spermatid was lost, except that which later formed the delicate membrane of the mature sperma tozoon and the persisting short tail remnant. Summary In the peculiar type of spermateleosis briefly described in 10 stages, the spermatid nucleus progressively elongates and is finally transformed directly into the mature 'all head' spermatozoon. A cytoplasmic 'tail', which appeared in the early spermatid and grew to a considerable length, was later discarded. No nuclear material was ever observed in the 'tail ' and all the cytoplasm of the spermatid was lost except that which later formed the delicate membrane of the mature spermatozoon and the short tail remnant. Acknowledgements I am indebted to Professor C. H. Waddington F. R. S., for providing the facilities and for his interest. My thanks are due to Dr. Ann R. ment of the elongated nucleus is still clear. 8 and 9, immature spermatozoa (stages 8 and 9), showing further increase in length of the 'head'. The fine cytoplasmic investment of stage 8 appears like a membrane partially wound round the 'head ' anteriorly in stage 9. 10, a mature 'all head' spermatozoon (stage 10) showing the delicate cytoplasmic membrane wound round it, and the persisting tail remnant.

5 80 J. Jacob Cytologia 24 Sanderson for helpful criticism and suggestions to Mr. G. E. Woodroffe for the supply of specimens and to Mr. E. D. Roberts for the illustrations. Grateful acknowledgement is also made to the Royal Commission for the exhibition of 1851, London, for a research award. References Dlugosz, J., and Harrold, J. W Proc. Roy. Soc. Edin. (B) 64: 353. Hughes-Schrader, S J. Morph. 78: Adv. in Genetics 2: 127. Jacob, J., and Sirlin, J. L Experientia (Basel) 14(1): 402. Moore, B. P Proc. Roy. Ent. Soc. Lond (B) 26: 199. Sanderson, A. R Proc. Xth Int. Cong. Ent. (In press).