Contributo all'embriologia delle tamaricaceae

Riassunto

L'Autore stabilisce, con osservazioni effettuate su oltre 4500 ovuli prelevati tutti da una medesima pianta, che lo sviluppo del gametofito femminile in Tamarix gallica L. si effettua secondo i seguenti quattro tipi di costruzione e con le rispettive percentuali di frequenza: 1) tipo Euphorbia dulcis, S-nucleato, 90%; 2) tipo Pyrethrum cierariaefolium 12- e 10-nucleato, 5%; 3) tipo Pyrethrum parthenifolium sottotipo Ulmus 10-nucleato, 3%; 4) tipo Adoxa 8-nucleato, 2%. L'A. mette pure in luce che la triploidia dei nuclei calazali caratteristica dei gametofiti di tipo Euphorbia dulcis può determinarsi nella stessa pianta secondo due distinte modalità: o per un processo di vera e propria cariogamia dei tre nuclei sporiali quiescenti durante lo stadio di polarizzazione 143 con conseguente formazione durante la storia dello sviluppo di uno stadio binucleato secondario, o per coalescenza dei tre fusi calazali durante la terza divisione dello sviluppo.

L'A. stabilisce, con osservazioni effettuate su ca. 1000 ovuli prelevati tutti da una stessa pianta, che lo sviluppo del gametofito femminile di Tamarix africana Poir. si effettua secondo tre tipi di costruzione, con le seguenti percentuali di frequenza: 1) tipo Euphorbia dulcis 8-nucleato, 43%; 2) tipo Pyrethrum cinerariaefolium 12- e 10-nucleato, 47%; 3) tipo Pyrethrum parthenifolium 16- e 14-nucleato, 10%.     

Sulla Terminologia dei Processi Mitotici

Summary

The Author has proposed to establish a general plan for the best known modality of the mitosis discovered in these last years in the higher organism animals and vegetables. Two facts are taken in consideration: the distribution of the chromosomes in the anaphase and the chromosome structure. When the distribution of the chromosomes is unever, the mitosis is called with the phrase “mitosis with irregular distribution” (case of the distribution of the chromosomes non regular between the two poles), or “restitutional mitosis” (case of the forming of the restitution nucleus in metaphase or in the anaphase), or “endorestitutional mitosis” (case of the return of the resting stage before the end of the prophase).

A special case is given when is present the accessory phenomenon of the somatic pairing, in which case the mitosis is called precisely “mitosis with somatic pairing”. The Author regards to the mechanism of the mitosis, observes that the determination of the structure gone beyond the chromatid has not value because the anaphase distributes as a rule whole chromatids. From this point of view the types of chromosomes experimentally observed in an undoubted manner are exactly: monochromosomes, diplochromosomes, polychromosomes, univalents, bivalents, polivalents, diplounivalents and diplobivalents. These two last types of the chromosomes are observed during the first mitosis of the spore, in cases in which the meiosis respectively fails in the interkinesis or before the heterotypic anaphase. The term diplounivalent is originated by the author to distinguish this type of chromosome (that though present in the mitosis is however of meiotic origin) from the other type (the diplochromosome) that has same structure but not of meiotic origin. (The diplochromosome is owing to a supernumerary reproduction of the usual mitotic chromosome).

It is also describes, as far as it can be said accuracy, the course of the different types in metaphase and in anaphase. Keeping thus in mind the chromosome structure (the chromatid is considered as a unity) the mitosis is subdivided in the following types: 1° Mitosis with monochromosomes; 2° Mitosis with diplochromosomes; 3° Mitosis with polychromosomes; 4° Mitosis with diplounivalents; 5° Mitosis with diplobivalents.

The terms proposed considering the chromosome distribution or the chromosome structure can be combinable so that the mitosis with monocromosomes (etc). can be called “restitutional mitosis with monochromosomes” (as for instance in the case of the action of the colchicine), or endorestitutional mitosis with monochromosomes (as for istance in the case of the tapetal cells of Spinacia). Not adding either the term restitutional or endorestitutional, it is understood that the course of the mitosis is regular right up to the end.

In the course of his research the Autor shows a personal explanation for the “later divisions ” in Culex (Berger 1938, Grell 1946) and points out the necessarity of new researches on the mitotic, supramitotic, etc. chromosomes type of Trillium (Matssuura e Haga 1940).     

Sulla Terminologia dei Processi Apomittici

Summary

The Author observing the great disagreement of the terminology usually adopted for the apomictic phenomena, examines the whole series of the phenomena noted both in regards of the formation of the gametophyte and of the embryo. The forming of the gametophyte is fixed on the base of nature of its original cell, normally a haploid spore or »haplospore« (phenomenon of the »haplospory« following the regular meiosis), rarely a diploid spore or »diplospore« (phenomenon of the »diplospory« following the irregular meiosis, as for instance in the case of restitution nucleus, etc.). The original cell can be at least represented by the same cell that usually is the spore mother cell, whether for the outward causes, or for inward causes is lacking the usual reductional process. For the failure of the meiotic process, such a cell cannot be called »spore«.

A cell of the somatic tissue of the sporophyte can even become the original cell of the gametophyte always in case of the absence of the meiosis. These two last cases of apospory are respectively called: »somatic apospory« and »gonial apospory« (= germinal apospory) (Chiarugi 1926).

The formation of the embryo is fixed on the base of the nature of the fecundation. The principal phenomena of the fecundation are represented by the following cases: »amphigamy« (or eugamy, or gamy), »semigamy, »pseudogamy«, »apogamy« »parthenogenesis«. The A. uses the term »apogamy« both for the diploid eggs and for the haploid eggs in which the stimulation of the division is produced by the pollen-tube or by male nuclei, in absence of the gamy.

The term »parthenogenesis« is restricted to the division of the haploid or diploid eggs in which the stimulation is not caused by pollen-tube nor even for the great reason, by the male nuclei existing in it.     

Multiple oviposition and larval feeding strategies in Euphydryas maturna (Linné, 1758) (Nymphalidae) at two disjoint European sites

Globally, Euphydryas maturna is a polyphagous butterfly species. At our study sites in Italy and Germany however, the plant used for egg-laying was almost exclusively Fraxinus excelsior. Nevertheless, in Germany, two egg-batches were found on Ligustrum vulgare and one on Viburnum opulus. Females lay their egg-batches at low heights and mostly on small trees (but not <1 m). At the end of the flight season, small egg-batches are laid and we conclude that these are late batches laid by “old females”. Egg-batches and pre-diapause larval webs are often clustered on certain trees and even leaves. This was shown to be a result of female behaviour and not of habitat quality, since the trees chosen were different in subsequent years. Individual females may return for laying further egg-batches to the place of the first egg-deposition and other females follow, since the survival of pre-diapause larvae is higher when more larval webs are on one tree. A further possible advantage during hibernation is discussed. In Italy, post-hibernation larvae form two distinct cohorts: larvae feeding on herbaceous plants (Plantago major, P. minor, Veronica hederifolia), and larvae feeding on Fraxinus excelsior. Although the latter group starts feeding later and pupates later, it reaches the same pupation weight. At our German site, post-hibernation larvae were found almost exclusively on F. excelsior. In fact, we observed larvae searching for food on F. excelsior while the buds of this tree were still closed. We also found larvae searching for food in the herbal layer without finding suitable plants. In some areas, larvae have to wait for the buds of the ash tree to open. Our data suggest that conservation strategies for E. maturna must be site specific according to food plant use of pre- and post-hibernation larvae and habitat type.     

MHC Class II haplotypes of Colombian Amerindian tribes

We analyzed 1041 individuals belonging to 17 Amerindian tribes of Colombia, Chimila, Bari and Tunebo (Chibcha linguistic family), Embera, Waunana (Choco linguistic family), Puinave and Nukak (Maku-Puinave linguistic families), Cubeo, Guanano, Tucano, Desano and Piratapuyo (Tukano linguistic family), Guahibo and Guayabero (Guayabero Linguistic Family), Curripaco and Piapoco (Arawak linguistic family) and Yucpa (Karib linguistic family). for MHC class II haplotypes (HLA-DRB1, DQA1, DQB1). Approximately 90% of the MHC class II haplotypes found among these tribes are haplotypes frequently encountered in other Amerindian tribes. Nonetheless, striking differences were observed among Chibcha and non-Chibcha speaking tribes. The DRB1*04:04, DRB1*04:11, DRB1*09:01 carrying haplotypes were frequently found among non-Chibcha speaking tribes, while the DRB1*04:07 haplotype showed significant frequencies among Chibcha speaking tribes, and only marginal frequencies among non-Chibcha speaking tribes. Our results suggest that the differences in MHC class II haplotype frequency found among Chibcha and non-Chibcha speaking tribes could be due to genetic differentiation in Mesoamerica of the ancestral Amerindian population into Chibcha and non-Chibcha speaking populations before they entered into South America.     

A Missense Mutation in the Rabbit Melanocortin 4 Receptor (MC4R) Gene is Associated with Finisching Weight in a Meat Rabbit Line

In this study we resequenced 1729 bp of the rabbit melanocortin 4 receptor (MC4 R) gene in 31 rabbits from different breeds/lines and identified ten polymorphisms: one was an indel and 9 were single nucleotide polymorphisms (SNPs). The indel and 5 SNPs were in the 5′-flanking region, 3 were synonymous SNPs and one was a missense mutation (c.101G>A; p.G34D), located in a conserved position of the extracellular tail of the MC4 R protein. The missense mutation was analyzed in a panel of 74 rabbits of different breeds and in 516 performance tested rabbits of a commercial paternal line under selection for growth efficiency. Association analysis indicated that rabbits with the less frequent genotype in this population (DD) had a lighter weight at 70 postnatal days than animals with genotype GD (P < 0.10) and animals with genotype GG (P < 0.05). This is the third study on candidate genes, after those on GH1 and IGF2 that reported a marker associated with finishing weight. Therefore, it seems that a candidate gene approach in rabbit based on previous information accumulated in other livestock species could be useful to identify genes explaining a fraction of variability of performance traits with potential application on rabbit breeding and selection.     

Deconstructing the control of the spotted alfalfa aphid Therioaphis maculata

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