ALBERT

Notes: Zusammenfassung Druck- und Bewegungsregistrierungen haben gezeigt, dass die Kiemenventilation beim plectognathen FischBalistes capriscus primär denselben doppelten Pumpmechanismus benützt, wie andere Knochenfische. Messungen des Ventilationsvolumens wurden durch Zufuhr von Wasser unter konstantem Druck zur Mundöffnung durch einen Gummischlauch, der an der steifen Haut des Fisches festgekblet wurde, vorgenommen. Es wurden Sauerstoffausnützungen von 90% beobachtet.

Notes: Abstract The sex chromosomes segregate precociously in prometaphase I of male meiosis, without prior synapsis or any physical connection, in 4 species of American mantispids (Neuroptera: Mantispidae). Segregational movements are interpolar, and are implemented through chromosomal fibers. Univalent autosomes, present from diakinesis on in several species, are capable of a similar distance segregation in prometaphase. The sex chromosomes are XX ♀ —XY ♂, as is characteristic of the Order, with the exception of Entanoneura phthisica in which both elements are compound —X1X2X3Y1Y2Y3in the male, and X1X1X2X2X3X3 in the female. In tetraploid sectors of gonial origin in testes of this species no sex bivalents are formed; a distance segregation of 6 sex univalents to each pole is effected, but — as observed in the one individually identifiable pair — segregation separates complete homologues, Y1 from Y1, X1 from X1, etc. In all species the male meiotic spindle is formed by the collocation of individual chromosomal spindle units within which bivalents become deformed; the timing and degree of deformation vary with the species. In karyotype the American species conform to a common pattern with the known Japanese and European species; diploid numbers range only from 18 to 22, and each complement carries the family insigné of one pair of disproportionately large autosomes in a set of small and rather uniformly sized chromosomes.

Notes: Abstract In the Panamanian iceryine coccid Icerya zeteki Cockerell (Family Margarodidae Morrison) all females become hermaphroditic early in the first instar; occasional males arise from unfertilized eggs, but self-fertilization is assured by the protandry of the hermaphrodite. In the development of the ovotestis, initiation of the male phase is brought about by haploidization of those germ cells destined for spermatogenesis. In both Icerya zeteki and Icerya purchasi this gonial reduction results from the degeneration and elimination of one genome during prophase. Except for minor variations in the coiling cycle of spermatocytes, the chromosomes (n=2) of I. zeteki correspond closely to those of all other haplo-diploid iceryines known. The present status of the species Icerya zeteki Cockerell is reviewed, and on both taxonomicand cytological grounds is judged to be uncertain.

Notes: Abstract The chromosome complement of Gueriniella serratulae (F.) Fernald, Tribe Iceryini, Subfamily Monophlebinae of the primitive coccid Family Margarodidae, is 2 n ♀=6; males are unknown. Reproduction is by thelytokous parthenogenesis. Meiosis is normal; polar bodies do not contribute to the formation of a zygote-substitute nucleus; and development is initiated by a haploid cleavage of the female pronucleus. Diploidy is restored by the fusion of the 2 nuclei resulting from this division. With the exception of Gueriniella, all cytologically known Iceryini are haplo-diploids, with a chromosome complement of n=2. The hypothesis is proposed that Gueriniella is a persistent primitive stemming from the ancestral iceryine stock prior to the loss of the sex chromosomes and the evolution of haplo-diploidy within the tribe. A review of the available evidence from cytology, taxonomy, endosymbiosis, behavior and distribution shows good agreement with this interpretation.

Notes: Abstract Meiosis is described in a thelytokous strain of the anoetid mite Histiostoma feroniarum (Dufour) and in both sexes of the arrhenotokous strain of this species. Oogenesis in the thelytokous strain is accomplished by ameiotic mitosis with only one pseudo-maturation division. During this division one or more chromosomes may move to the poles precociously and while in this position can be mistaken for centrioles. Fourteen chromosomes are found at metaphase of the pseudo-maturation division and in cleaving eggs of this strain. In the arrhenotokous strain, male meiosis consists of a single mitotic division. Oogenesis is regular and 7 bivalents are observed at the first maturation division. Metaphases of the first cleavage division in fertilized eggs show 14 chromosomes and 7 chromosomes in unfertilized eggs. It is postulated that the thelytokous strain has arisen from the arrhenotokous strain. This assumption is in agreement with that suggested for several insect species previously reported. The evolution in the Acari and the variability in the modes of reproduction in this suborder are discussed in light of the findings in this paper on the Anoetidae.

Notes: Summary In excised roots of barley and tomato plants, lowering the water potential of nutrient solutions to-10.4 and-20.4 atm decreased the uptake of bromide and phosphorus while increasing the loss of these ions to the external solutions. Lowering the water potential greatly increased the rate of loss of potassium and bromide from the cytoplasm, but the increases in loss from the vacuoles were much smaller. The results suggest that the mechanisms of ion uptake are not affected by low water potential and that the decrease in ion accumulation is caused by the increased leakage from the cells.

Notes: Summary 1. The germ cells of the hermaphrodite embryos ofIcerya purchasi contain the diploid number of chromosomes (four) from the time of the first segregation of the germ cells up to the time of the emergence of the nymphs from the eggs. 2. During the early part of the first nymphal instar, usually before the attachment of the nymph to the host plant has occurred, haploid nuclei appear among the diploid nuclei of the gonad. 3. The chromosomes of these haploid nuclei are recognisable by size and shape as comprising one member of each pair of the diploid chromosome complex. It follows that a reduction from the diploid to the haploid condition has taken place, but no evidence on the cytological mechanism underlying this reduction is available. 4. The haploid nuclei usually give rise to the central core of the gonad and often to a variable amount of more or less isolated lateral masses of tissue. From this haploid tissue the spermatozoa of the hermaphrodite gonad are derived. 5. In the spermatogenesis only one meiotic division occurs. This is equational in character. The processes of spermatogenesis correspond exactly with those described for the haploid males of this species. 6. In two aberrant cases spermatids were produced from diploid cells. Two divisions were undergone and reduction to the haploid state accomplished, although without synapsis. Cytology of these aberrant cases is incomplete. 7. The diploid nuclei of the gonad proliferate slowly throughout the male phase, and usually come to form the outer or peripheral zone of the young gonad. The diploid nuclei give rise to the follicular epithelium of the gonad, the egg cells, the nurse cells, and to the greater part of the interstitial tissue of the gonad. 8. Oogonia are differentiated from the primary diploid germ cells by a peculiar type of mitosis which involves the formation of a continuous spireme and its early longitudinal splitting. The split spireme segments into four lenghts which condense to form the chromosomes. This type of mitosis is restricted to the early proliferation of oogonia and to the three divisions of each oogonium by means of which the eight cells (seven nurse cells and one egg) of each ovariole are produced. 9. Coincident with or slightly before the first appearance of haploid nuclei in the hermaphrodite gonad, degeneration of certain germ cell nuclei occurs. This continues to a variable extent throughout the development of the gonad and is particularly evident in regions where haploid and diploid nuclei meet, in diploid regions during the male phase, and in haploid regions during the diploid or female phase of the gonad. With the final establishment of the female phase degeneration usually ceases. Evidence is given that this nuclear disintegration is not directly involved in the original reduction of the spermatogonial-mother cells. 10. InIcerya purchasi collected at various places, including one collection from Italy, the same types, diploid hermaphrodites and haploid males, are present as in the American stock first described. No pure females have been found. 11. Breeding data indicate that separate strains or races differing in respect to the presence or absence of the facultative parthenogenesis by means of which the haploid males are produced, do not exist.