Uma raça cromossômica natural de Tityus bahiensis (Scorpiones-Buthidae)

A natural chromosomal race of Tityus babiensis (Scorpiones Buthidae) is described in the present paper. Five males and seven females received from St. Joaquim, State of S. Paulo, gave the following interesting results: All the spermatogonia of the five males were provided with 9 chromosomes of different sizes. All primary spermatocytes showed at metaphase one independent bivalent of normal shape and a complex group formed by 7 chromosomes which have exchanged parts. Some of the chromosomes associated in the complex group, to Judge by their behavior, were composed of fragments of three different chromosomes, being thus paired with three other members of the compound group. The manner in which all the 7 components of the group have paired with each other showed to be very constant. They gave always origin to a double-cross configuration, the longst branch of which being formed by a long chromosome paired with two components of the group and with a third chromosome that did not belong to the group. The chromosomes of the independent bivalent separate regularly, going to different poles. From the 7 elements of the compound group, 4 go to one pole and 3 to the opposite one. Consequently, secondary spermatocytes with 4 and 5 chromosomes are produced. The females, so far as it can be inferred from the study of the follicular cells of the ovariuterus, have 10 chromosomes. These females are, therefore, considered as being monogametic, that is, as producing eggs with 5 chromosomes. A sex-determining mechanism arose in this manner, the spermatozoa with 5 chromosomes giving origin to females and those with 4 to males. The fact that the sex chromosome is one of the elements taking part in the formation of the group, seems highly interesting to the author. Tetraploid cysts have been occasionally found in the testis. In one individual the chromosomes of the tetraploid primary spermatocytes behaved as expected, forming a group of 14 elements, and two independent pairs or a tetravalent group In another individual, the chromosomes of the tetraploid cells have formed two independent groups of 7, and two independent pairs, as if both chromosomal sets were by their turn entirely independent frcm one another. This fact is certainly not devoid of special interest. The males as well as the females studied in this paper differed in nothing from the typical members of the species. The unique differential character of the new race is found in the umber and behavior of its chromosomes. It is highly remarkable that the occurrences which have transformed the 6 chromosomes normally present in the species into a new set of 9 elements, 7 of which have been profoun- dly altered in their structure, do not show any influence on the morphology of the organism. This fact, together with those found in the salivary-chromosomes races of Drosophila and Sciara. compromises strongly the genetical concept of position effects.

Breve notícia sôbre a espermatogênese de Lutosa brasiliensis Brunner (Tettigoniodea-Stenopelmatidae)

Lutosa brasiliensis, an Orthopteran Tettigonioidean belonging to the family Stenopelmatidae is referred to in this paper The spermatogonia are provided with 15 chromosomes, that is, 7 pairs of autosomes and a single sex chromosome. One pair of autosomes is much larger than the rest, two pairs are of median sized elements, and four pairs are of small ones. The daughter sex chromosomes show at anaphase great difficulty in reaching the poles, being left for a long while in the region of the equator where they are seen stretched one after the other on the same line or lying side by side in different positions. When the spermatogonium divides each daughter cell gets passively its sex chromosome. Though slowly, the sex chromosome finishes by beins enclosed in the nucleus. Its behavior may be attributed to a very weak kinetic activity of the centromere. In view of se pronouced an inertness of the sex chromosomes, two things may be expected : primary spermatocyte nuclei with two sex chromosomes, and primary spermatocytes with the sex chromosome lying outside the nucleus. Both situations have been discovered. The latter, together with the delay of the spermatogonial sex chromosome in reaching the poles suggested to the anther the mechanism which might have given origin to the cases in which the sex chromosome normally does not enter the nucleus to rejoin the autosomes, remaning outside in its own nucleus. It may well be supposed that accidents like that found in the present individual have turned to be a normal event in the course of the evolution of some species. Trie primary spermatocytes are provided with chromatoid bodies which remain visible all over the whole history of the cells and pass to one of the resulting secondary spermatocytes, the larger of them being found later in the area occupied by the tails of the spermatozoa. No relation of these bodies to nucleoli con?d be established. Pachytene and diplotene nuclei are normal Metaphase nuclei show 7 autosomal tetrads, one of which being much larger than the rest. At this stage the chromosomes have a pronounced tendency to form clumps. Even when they are separated from each other they generally appear competed by chromosomal substance. The sex chromosome Hes always in one of the poles, being enclosed in the nucleus formed there. The stickness of the chromosomes can also be noted at anaphase. Telophase chromosomes distend them- selves for giving origin to secondary spermatocyte nuclei in a state comparable to a beginning prophase. As the secondary spermatocytes approach metaphase the autosomes appear entirely divided except at the kinetochore where the chromatids remain united. In the division of the secondary spermatocytes nothing else merits special reference.

Comportamento dos cromossômios no gênero Hypselonotus (Hemiptera -Coreidae)

The three species studied have 19 chromosomes, being one heterochromosome, one pair of microchromosomes and 8 pairs of autosomes. The microchromosomes of Hypselonotus fulvus are amongst the largest we know. During the synizesis, in Hypselonotus fulvus, we can see in several strands that scape from the chromatic knot a place in which they are widley open. As, in that phase the chromosomes have both ends converging to the same place, the openings suggest a side-to-side pairing of the chromosomal threads. The tetrads are like that studied by Piza (1945-1946). The bivalents are united side by side at their entire length. The unpaired part at the midle of the bivalents gives origin to the arms of the cross-shapede tetrads. The chromosomes have a kinetochore at each end. The bivalents sometimes unite their extremities to form ring-shaped figures, which open themselves out before metaphase. The tetrads are oriented parallelly to the spindle axis. At telophase the kinetochores repeli one another, the chiasmata, if present, slip toward the acentric extremities and the chromosomes rotate in order to arrange themselves parallelly to the axis of the new spindle. Separation is therefore through the pairing plane. In the spermatogonial anaphase of Hypselonotus subterpunctatus the chromosomes are curved to the poles, like those described by PIZA (1946) and PIZA and ZAMITH (1946). The sex chromosomes in Hypselonotus interruptus and Hypselonotus fulvus appears longitudinally divided. It is oriented with the ends in the plane of the equator and its chomatids separate by the plane of division. In the second division the sex chromosome, provided as it is with an actve klnetochore at each end, orients itself with its length parallelly to the spindle axis and passes undivided to one pole. Sometimes it is distended between the poles. This corresponds to case (a) established by PIZA (1946) for the sex chromosomes of Hemiptera In Hypselonotus subterpunctatus the sex chromosome, in the first division of the spermatocytes, orients like the tetrads and divides transversaly. In the second division, as its kinetochore becomes inactive, it remans monocentric, does not orient in the spindle, and is finally enclosed in the nearer nucleus. In the secondary telophase it recuperates its dicentricity like the autosomal chromatids. This behavior corresponds to case (c) of PIZA (1946).

Meiose em Rhinocricus Padbergi Verhoeff, 1938

In the present paper the behaviour of the chromosomes in the spermatogenesis of the Myriapod Rhinocricus Padbergi Verhoeff, 1938 is studied. The primary spermatocytes are provided with 10 independent bivalents which separate normally giving rise to equivalent secondary spermatocytes. No indication of sex chromosomes has been found. Fusion of two bivalents or of four, two by two, has been observed, giving origin to secondary spermatocytes with 9 and 8 chromosomes respectively, in which fused chromosomes could be discovered. For analysing the facts the chomosomes of both, primary and secondary metaphases were separately counted from a total of 190 celis of four individuals and statistically treted. The X2-test gave insignificant results. Twenty chomosomes were counted in somatic tissues. The heterochròmatic parts of the leptotene threads were usually arranged in the periphery of the nucleus. In resting nuclei chromocenters can be observed in varyng number. Their chromosomal nature is revealed by the fact that when treated by KCÑ or KNOS they begin uncoiling.

Nota sôbre cromossômios de alguns Ortópteros do Brasil

A short, report on the chromosomes of three species of Brasilian Orthoptera is given in the present paper. Meroncidius intermedins Brunner, belonging to the Pseu-dophyllidae, differs from the species already studied in the Family in having 30 instead of 34 autosomes and a metacentric sex chromosome. "Of the autosomes, 4 showed to be metacentric. The author believes that the present species may be originated from one having 34 acrocentric autosomes by means of centric fusions. The origin of ths metacentricity of the X is not discussed. Oxyprora flavicornis Redtb.,belonging to the Copiphori-dae, has spermatogonia with 29 chromosomes. Of the autosomes, 4 seemed to be metacentric. The X has the form of a V of subae-qual arms. Neoconocephálus injuscatus (Scudd.), also belonging to the Copiphoridae, is provided with secondary spermatocytes of 13 -j- X and 13 chromosomes. The heterochromosome is metacentric. In the spermatogonia, whose chromosome number has not been counted, there are a lot of metacentric elements. In the opinion of the present writer species provided with 31, 33 and 35 chromosomes should exist in the Copiphoridae.

Bases para o estudo da genética de populações dos Hymenoptera em geral e dos Apinae sociais em particular

This paper deals with problems on population genetics in Hymenoptera and particularly in social Apidae. 1) The studies on populations of Hymenoptera were made according to the two basic types of reproduction: endogamy and panmixia. The populations of social Apinae have a mixed method of reproduction with higher percentage of panmixia and a lower of endogamy. This is shown by the following a) males can enter any hive in swarming time; b) males of Meliponini are expelled from hives which does not need them, and thus, are forced to look for some other place; c) Meliponini males were seen powdering themselves with pollen, thus becoming more acceptable in any other hive. The panmixia is not complete owing to the fact that the density of the breeding population as very low, even in the more frequent species as low as about 2 females and 160 males per reproductive area. We adopted as selection values (or survival indices) the expressions according to Brieger (1948,1950) which may be summarised as follows; a population: p2AA + ²pq Aa + q2aa became after selection: x p2AA + 2pq Aa + z q²aa. For alge-braics facilities Brieger divided the three selective values by y giving thus: x/y p2 AA + y/y 2 pq Aa + z/y q²aa. He called x/y of RA and z/y of Ra, that are survival or selective index, calculated in relation to the heterozygote. In our case all index were calculated in relation to the heterozygote, including the ones for haploid males; thus we have: RA surveval index of genotype AA Ra surveval index of genotype aa R'A surveval index of genotype A R'a surveval index of genotype a 1 surveval index of genotype Aa The index R'A ande R'a were equalized to RA and Ra, respectively, for facilities in the conclusions. 2) Panmitic populations of Hymenoptera, barring mutations, migrations and selection, should follow the Hardy-Weinberg law, thus all gens will be present in the population in the inicial frequency (see Graphifc 1). 3) Heterotic genes: If mutation for heterotic gene ( 1 > RA > Ra) occurs, an equilibrium will be reached in a population when: P = R A + Ra - 2R²a _____________ (9) 2(R A + Ra - R²A - R²a q = R A + Ra - 2R²A _____________ (10) 2(R A + Ra - R²A - R²a A heterotic gene in an hymenopteran population may be maintained without the aid of new mutation only if the survival index of the most viable mutant (RA) does not exced the limiting value given by the formula: R A = 1 + √1+Ra _________ 4 If RA has a value higher thah the one permitted by the formula, then only the more viable gene will remain present in the population (see Graphic 10). The only direct proof for heterotic genes in Hymenoptera was given by Mackensen and Roberts, who obtained offspring from Apis mellefera L. queens fertilized by their own sons. Such inbreeding resulted in a rapid loss of vigor the colony; inbred lines intercrossed gave a high hybrid vigor. Other fats correlated with the "heterosis" problem are; a) In a colony M. quadrifasciata Lep., which suffered severely from heat, the percentage of deths omong males was greater .than among females; b) Casteel and Phillips had shown that in their samples (Apis melifera L). the males had 7 times more abnormalities tian the workers (see Quadros IV to VIII); c) just after emerging the males have great variation, but the older ones show a variation equal to that of workers; d) The tongue lenght of males of Apis mellifera L., of Bombus rubicundus Smith (Quadro X), of Melipona marginata Lep. (Quadro XI), and of Melipona quadrifasciata Lep. Quadro IX, show greater variationthan that of workers of the respective species. If such variation were only caused by subviables genes a rapid increasse of homozigoty for the most viable alleles should be expected; then, these .wild populations, supposed to be in equilibrium, could .not show such variability among males. Thus we conclude that heterotic genes have a grat importance in these cases. 4) By means of mathematical models, we came to the conclusion tht isolating genes (Ra ^ Ra > 1), even in the case of mutations with more adaptability, have only the opor-tunity of survival when the population number is very low (thus the frequency of the gene in the breeding population will be large just after its appearence). A pair of such alleles can only remain present in a population when in border regions of two races or subspecies. For more details see Graphics 5 to 8. 5) Sex-limited genes affecting only females, are of great importance toHymenoptera, being subject to the same limits and formulas as diploid panmitic populations (see formulas 12 and 13). The following examples of these genes were given: a) caste-determining genes in the genus Melipona; b) genes permiting an easy response of females to differences in feeding in almost all social Hymenoptera; c) two genes, found in wild populations, one in Trigona (Plebéia) mosquito F. SMITH (quadro XII) and other in Melipona marginata marginata LEP. (Quadro XIII, colonies 76 and 56) showing sex-limited effects. Sex-limited genes affecting only males do not contribute to the plasticity or genie reserve in hymenopteran populations (see formula 14). 6) The factor time (life span) in Hymenoptera has a particular importance for heterotic genes. Supposing one year to be the time unit and a pair of heterotic genes with respective survival indice equal to RA = 0, 90 and Ra = 0,70 to be present; then if the life time of a population is either one or two years, only the more viable gene will remain present (see formula 11). If the species has a life time of three years, then both alleles will be maintained. Thus we conclude that in specis with long lif-time, the heterotic genes have more importance, and should be found more easily. 7) The colonies of social Hymenoptera behave as units in competition, thus in the studies of populations one must determine the survival index, of these units which may be subdivided in indice for egg-laying, for adaptive value of the queen, for working capacity of workers, etc. 8) A study of endogamic hymenopteran populations, reproduced by sister x brother mating (fig. 2), lead us to the following conclusions: a) without selection, a population, heterozygous for one pair of alleles, will consist after some generations (theoretically after an infinite number of generation) of females AA fecundated with males A and females aa fecundated with males a (see Quadro I). b) Even in endogamic population there is the theoretical possibility of the presence of heterotic genes, at equilibrium without the aid of new mutations (see Graphics 11 and 12), but the following! conditions must be satisfied: I - surveval index of both homozygotes (RA e Ra) should be below 0,75 (see Graphic 13); II - The most viable allele must riot exced the less viable one by more than is permited by the following formula (Pimentel Gomes 1950) (see Gra-fic 14) : 4 R5A + 8 Ra R4A - 4 Ra R³A (Ra - 1) R²A - - R²a (4 R²a + 4 Ra - 1) R A + 2 R³a < o Considering these two conditions, the existance of heterotic genes in endogamic populations of Hymenoptera \>ecames very improbable though not - impossible. 9) Genie mutation offects more hymenopteran than diploid populations. Thus we have for lethal genes in diploid populations: u = q2, and in Hymenoptera: u = s, being u the mutation ratio and s the frequency of the mutant in the male population. 10) Three factors, important to competition among species of Meliponini were analysed: flying capacity of workers, food gathering capacity of workers, egg-laying of the queen. In this connection we refer to the variability of the tongue lenght observed in colonies from several localites, to the method of transporting the pollen in the stomach, from some pots (Melliponi-ni storage alveolus) to others (e. g. in cases of pillage), and to the observation that the species with the most populous hives are almost always the most frequent ones also. 11) Several defensive ways used for Meliponini to avoid predation are cited, but special references are made upon the camouflage of both hive (fig. 5) and hive entrance (fig. 4) and on the mimetism (see list in page ). Also under the same heading we described the method of Lestrimelitta for pillage. 12) As mechanisms important for promoting genetic plasticity of hymenopteran species we cited: a) cytological variations and b) genie reserve. As to the former, duplications and numerical variations of chromosomes were studied. Diprion simile ATC was cited as example for polyploidy. Apis mellife-ra L. (n •= 16) also sugests polyploid origen since: a) The genus Melipona, which belongs to a" related tribe, presents in all species so far studied n = 9 chromosomes and b) there occurs formation of dyads in the firt spermatocyte division. It is su-gested that the origin of the sex-chromosome of Apis mellifera It. may be related to the possible origin of diplo-tetraploidy in this species. With regards to the genie reserve, several possible types of mutants were discussed. They were classified according to their survival indices; the heterotic and neutral mutants must be considered as more important for the genie reserve. 13) The mean radius from a mother to a daghter colony was estimated as 100 meters. Since the Meliponini hives swarm only once a year we may take 100 meters a year as the average dispersion of female Meliponini in ocordance to data obtained from Trigona (tetragonisca) jaty F. SMITH and Melipona marginata LEP., while other species may give different values. For males the flying distance was roughly estimated to be 10 times that for females. A review of the bibliography on Meliponini swarm was made (pg. 43 to 47) and new facts added. The population desity (breeding population) corresponds in may species of Meliponini to one male and one female per 10.000 square meters. Apparently the males are more frequent than the females, because there are sometimes many thousands, of males in a swarm; but for the genie frequency the individuals which have descendants are the ones computed. In the case of Apini and Meliponini, only one queen per hive and the males represented by. the spermatozoos in its spermateca are computed. In Meliponini only one male mate with the queen, while queens of Apis mellijera L. are fecundated by an average of about 1, 5 males. (Roberts, 1944). From the date cited, one clearly sees that, on the whole, populations of wild social bees (Meliponini) are so small that the Sewall Wright effect may become of great importance. In fact applying the Wright's formula: f = ( 1/aN♂ + 1/aN♀) (1 - 1/aN♂ + 1/aN♀) which measures the fixation and loss of genes per generation, we see that the fixation or loss of genes is of about 7% in the more frequent species, and rarer species about 11%. The variation in size, tergite color, background color, etc, of Melipona marginata Lep. is atributed to this genetic drift. A detail, important to the survival of Meliponini species, is the Constance of their breeding population. This Constance is due to the social organization, i. e., to the care given to the reproductive individuals (the queen with its sperm pack), to the way of swarming, to the food storage intended to control variations of feeding supply, etc. 14) Some species of the Meliponini are adapted to various ecological conditions and inhabit large geographical areas (e. g. T. (Tetragonisca jaty F. SMITH), and Trigona (Nanno-trigona testaceicornis LEP.) while others are limited to narrow regions with special ecological conditions (e. g. M. fuscata me-lanoventer SCHWARZ). Other species still, within the same geographical region, profit different ecological conditions, as do M. marginata LEP. and M. quadrifasciata LEP. The geographical distribution of Melipona quadrifasciata LEP. is different according to the subspecies: a) subsp anthidio-des LEP. (represented in Fig. 7 by black squares) inhabits a region fron the North of the S. Paulo State to Northeastern Brazil, ,b) subspecies quadrifasciata LEP., (marked in Fig. 7 with black triangles) accurs from the South of S. Paulo State to the middle of the State of Rio Grande do Sul (South Brazil). In the margined region between these two areas of distribution, hi-brid colonies were found (Fig. 7, white circles); they are shown with more details in fig. 8, while the zone of hybridization is roughly indicated in fig. 9 (gray zone). The subspecies quadrifasciata LEP., has 4 complete yellow bands on the abdominal tergites while anthidioides LEP. has interrupted ones. This character is determined by one or two genes and gives different adaptative properties to the subspecies. Figs. 10 shows certains meteorological isoclines which have aproximately the same configuration as the limits of the hybrid zone, suggesting different climatic adaptabilities for both genotypes. The exis-tance of a border zone between the areas of both subspecies, where were found a high frequency of hybrids, is explained as follows: being each subspecies adapted to a special climatic zone, we may suppose a poor adaptation of either one in the border region, which is also a region of intermediate climatic conditions. Thus, the hybrids, having a combination of the parent qualities, will be best adapted to the transition zone. Thus, the hybrids will become heterotic and an equilibrium will be reached with all genotypes present in the population in the border region.

Provas cruciais da dicentricidade dos cromossômios dos hemipteros

Studying the meiosis of two Hemiptera, mamely, Lybindus dichrous (Coreidae) and Euryophthalmus humilis (Pyrrhocoridae), the author has found new proofs in favor of the existence of a centromere at each end of the chromosomes of the insects belonging to that order. Following the behaviour of a pair of large autosomes of Lybindus, he was able to verify that in the first division of the spermatocytes, the tetrad they form divides transversely by the middle, giving rise to two V-shaped anaphase chromosomes that go to the poles with the vertex pointing forwardly. From the end of the first division till the metaphase of the second one, the centromeres occupying the vertex of the V go apart from one another, making the chiasmata existing there slip to the opposite extremities, what changes the V into an X. When the chiasmata reach the acentric ends, the X is again converted into a V. The V of the secondary metaphase, therefore, differs from the V of the primary anaphase, in being inverted that is, in having the centromeres in the extremity of its arms, and no longer in the vertex as in the latter. The opening out of the chromosomes starting at the centric extremities in order to recuperate the dumbbell shape they show in the secondary anaphase, just in the manner postulated by PIZA, is thus demonstrated. In Euryophthalmus humilis it was verified once more, that the heterochromosome, in the secondary spermatocytes, orients parallelly to the spindle axis, accompanying with its ends the anaphase plates as they move to the poles. The author is in disagreement with NORONHA-WAGNER & DUARTE DE CASTRO's interpretation of the behaviour of the chromosomes in meiosis of Luzula nemorosa.

Organization of the cysts in bee (Hymenoptera, Apidae) testis: number of spermatozoa per cyst

The morphology of the cyst cells in Apis mellifera Linné, 1758, Scaptotrigona postica Latreille, 1804, and Melipona bicolor bicolor Lepeletier, 1836 testis, as well as the average number of spermatic cells are reported. The data indicates a supporting and nourrishing role of the cyst cells to the developing cystocytes. The counts of immature spermatozoa in the cysts show an average of 202.8 ± 21.2 spermatozoa for A. mellifera, 117.4 ± 8.68 for S. postica and 88.8 ± 15.57 for M. bicolor, which predict the occurrence of 8 mitotic cycles in the cystocytes of A. mellifera and 7 in the meliponines, considering that only one spermatozoom originates of each final spermatogonium.

Chromosomal characterization of Pseudonannolene strinatii (Spirostreptida, Pseudonannolenidae)

The chromosomes of the cave millipede Pseudonannolene strinatii Mauriès, 1974 were investigated. The diploid chromosome number was found to be 2n=16, XX/XY; the C-banding technique revealed a large amount of heterochromatin while the silver staining technique (Ag-NOR) evidenced the presence of heteromorphism of the NORs in some cells.

Chromosome studies of Brazilian vespertilionids Lasiurus cinereus and Lasiurus ega (Mammalia, Chiroptera)

Cytogenetical studies based on conventional coloration by Giemsa, C-banding and Ag-NOR were performed on 2 species of bats from the vespertilionid family: Lasiurus cinereus (Beauvois, 1796) and Lasiurus ega (Gervais, 1856). The 2n was 28 and FN was 48 in both species. The constitutive heterochromatin is located in centromeric regions in the two species and in the short arm of the subtelocentric X chromosome in L. ega. NORs were observed in the secondary constriction of the smaller autosome in both species.

Cytogenetic study in natural hybrids of Callithrix (Callitrichidae: Primates) in the Atlantic forest of the state of Rio de Janeiro, Brazil

In the Atlantic forest of Rio de Janeiro, Callithrix aurita (É. Geoffroy in Humboldt, 1812) is a native species vulnerable to extinction and C. jacchus (Linnaeus, 1758) and C. penicillata (É. Geoffroy, 1812) are invasive species. The major threats to the native species are habitat degradation and hybridization, although there are currently no genetic data about natural hybrids available. Previous studies have revealed that species of the Callithrix genus are extremely homogeneous in their karyotypes with the exceptions of the morphology and size of the Y chromosome and its nucleolar organizer region (NOR) banding pattern. Three male marmosets captured in the wild in Guapimirim municipality, Rio de Janeiro, Brazil, considered as possible hybrids between C. aurita and C. jacchus or C. penicillata on the basis of pelage pattern, were cytogenetically studied. Metaphase chromosomes were obtained by using short-term lymphocyte cultures and Ag-NOR staining was performed. The hybrids karyotypes were 2n=46, 14 uni- and 30 bi-armed autosomes, a median size submetacentric X and NOR bearing autosomes, being compatible with that observed for the genus. In the three individuals studied, Y chromosomes were similar to those found for C. aurita, without NORs. The data obtained suggest the involvement of C. aurita in natural hybridization with one of the invasive species. We discuss the possible consequences of this hybridization.

Comparative cytogenetics in different populations of the cavernicolous diplopod Pseudonannolene strinatii (Diplopoda, Pseudonannolenidae)

Different populations of Pseudonannolene strinatii Mauriès, 1974 collected from three caves in Iporanga, state of São Paulo, were cytogenetically compared using techniques of conventional coloration, C-banding and silver nitrate impregnation. Specimens were morphologically similar and small cytogenetic differences were observed between the populations with relation to the distribution of constitutive heterochromatin.

Observações citológicas no gênero Hydnocarpus Gaertner: determinação do número de cromósomas de Hydnocarpus laurifolia (Dennst. ) Sleumer

The autor determined the number of chromosomes of Hydnocarpus laurifolia (Dennst). Sleumer and found 2n = 48. He ventures the hypothesis that this species is a natural tetraploid.

Estudos sobre a regeneração do figado - variação do volume nuclear das celulas hepáticas em repouso divisional

Surgical removal of large amounts of hepatic tissue in male albino rats results in a rapid and conspicuous raise in cellular nuclear volumes. Measurements were made exclusively in resting nuclei. This volume variation is transitory. Nuclear volumes return to the normal value withins 6 days of restoration. The higher value are abserved 48 hours after the hepatic removal, indicating probably that this effect is due to hydration of the nucei, as occurs in the cytoplasm. This hydration could be correlated to the mitotic activity of the renmant tissue since a peak of mitoses parallels the changes in the nuclear volumes.

Effects of juvenile hormone analogue on ecdysis prevention induced by precocene in Rhodnius prolixus (Hemiptera: Reduviidae)

Precocene II, added to the meal of fourth-instar larvae of Rhodnius prolixus (25 mug/ml of blood), induced an in crease in the duration of the molting cycle. This effect was related to the decrease of both the nuclear area of the prothoracic gland cells and the mitotic activity in epidermal cellS. juvenile hormone analogue applied topically (60 mug/insect) together with Precocene II treatment avoided atrophy of the prothoracic glands and induced a higher number of epidermal mitosis accelerating the time of subsequent ecdysis. A possible relationship between juvenile hormone and production of ecdysone is discussed.