Romano Dallai

Population structure and colonization history of the olive fly, Bactrocera oleae (Diptera, Tephritidae).

The olive fly, Bactrocera oleae, is the major pest of olives in most commercial olive‐growing regions worldwide. The species is abundant in the Mediterranean basin and has been introduced recently into California and Mexico, creating problems for quarantine protection and international trade. Here, we use nuclear microsatellite markers and mitochondrial sequences to examine the history of olive fly range expansion and colonization. Sampled populations span the current distribution of the olive fly worldwide, including South and Central Africa, Pakistan, Mediterranean Europe and Middle East, California, and Mexico. The Pakistani populations appear to be genetically well differentiated from the remaining populations, though rooting the origins of the species is problematic. Genetic similarity and assignment tests cluster the remaining populations into two genetic groups — Africa and a group including the Mediterranean basin and the American region. That Africa, and not the Mediterranean, is the origin of flies infesting cultivated olive is supported by the significantly greater genetic diversity at microsatellite loci in Africa relative to the Mediterranean area. The results also indicate that the recent invasion of olive flies in the American region most likely originated from the Mediterranean area.

The mitochondrial genome of the olive fly Bactrocera oleae: two haplotypes from distant geographical locations

The complete sequence of the olive fly (Bactrocera oleae) mitochondrial genome has been determined. Two independent haplotypes, from flies of distant geographical origin (Italy and Portugal) were completely sequenced. The molecule is 15 815 bp long, and shows the gene content and organization typical of insects, namely thirteen protein coding genes (PCGs) encoding proteins involved in oxidative phosphorylation, two rRNAs, twenty‐two tRNAs and a long (949 bp) noncoding region. The genomes of the two fly specimens share the same arrangement, differing by a mere thirty‐one point mutations. The differences are mostly transitions (26) and synonymous substitutions in PCGs (21). The two new sequences are compared with others already present in the database.

The spermatozoon of arthropoda: VI. Ephemeroptera

In this work the spermatozoon of Chloeon dipteron (Ephemeroptera) is examined. The three most important features are that (a) the acrosome is very brief; (b) the mitochondrial derivative is represented by a long mitochondrion with transverse cristae and by a crystalline mass enveloped in a separated membrane; (c) the axial filament of the tail lacks the two principal central units and the central sheath, and is therefore, of the 9 + 9 +0 pattern. This type of flagellum has not previously been described.

Domestication of olive fly through a multi-regional host shift to cultivated olives: Comparative dating using complete mitochondrial genomes

The evolutionary history of the olive fly, Bactrocera oleae, was reconstructed in a phylogenetic and coalescent framework using full mitochondrial genome data from 21 individuals covering the entire worldwide distribution of the species. Special attention was given to reconstructing the timing of the processes under study. The early subdivision of the olive fly reflects the Quaternary differentiation between Olea europea subsp. europea in the Mediterranean area and the two lineages of Olea europea subsp. cuspidata in Africa and Asia, pointing to an early and close association between the olive fly and its host. The geographic structure and timing of olive fly differentiation in the Mediterranean indicates a clear connection with the post-glacial recolonization of wild olives in the area, and is irreconcilable with the early historical process of domestication and spread of the cultivated olive from its Levantine origin. Therefore, we suggest an early co-history of the olive fly with its wild host during the Quaternary and post-glacial periods and a multi-regional shift of olive flies to cultivated olives as these cultivars gradually replaced wild olives in historical times.

Purification and primary structure of ceratotoxin A and B, two antibacterial peptides from the female reproductive accessory glands of the medfly Ceratitis capitata (insecta:Diptera)

In the present article we report the purification and the amino acid sequence of two antibacterial peptides present in the secretion of the female reproductive accessory glands of the dipteran insect Ceratitis capitata. Both peptides consist of 29 amino acid residues, are heat stable, strongly basic and differ from each other for the substitution of two amino acids. Their primary sequence and predicted secondary structure are related to other families of peptides known to have lytic and/or antibacterial activity. We propose the name ceratotoxins (from Ceratitis) for these antibacterial peptides.

Centrosome inheritance in insects: fertilization and parthenogenesis.

Centrosome biogenesis is unclear, although much structural and biochemical research has been performed in several experimental systems. An alternative model to study the assembly of functional centrosomes could be the process of zygotic centrosome formation at the beginning of embryonic development. Although it seems obvious that the sperm cell provides the centrosome at fertilization, some pieces of evidence are not in line with this point of view and give controversial results. Such an analysis could provide useful information if applied to a large variety of organisms. Since insects are a highly diverse group of organisms they provide a variety of models in which to study the process of centrosome reconstitution during fertilization. Moreover, many insect species reproduce by parthenogenesis, a special mode of reproduction in which embryonic development occurs without male contribution. Studies of unfertilized parthenogenetic eggs may therefore teach us much about the process of centrosome assembly in the absence of preexisting centrioles.

Fine structure of the spermatheca of Apis mellifera

Abstract The ultrastructure of the receptacle and duct of the spermatheca of non-fertilized Apis mellifera, of bees a few days after fertilization and of 2- to 3-year-old bees has been investigated. The epithelium of the receptacle does not seem to be involved in the production of secretion. Autolysomes and large amounts of filamentous material of a polysaccharide nature accumulate within the cytoplasm of old bees. The cells of the sperm duct have numerous microtubules which are believed to function as a cytoskeleton since the cells in question are periodically subject to notable compression owing to the muscular contractions of the sperm pump.

The spermatozoon of arthropoda. XXVII. Uncommon axoneme patterns in different species of the cecidomyid flies.

Three different sperm types have been found in the different genera of the gall-midge cecidomyids (Diptera). The first type is here called “9 + 0 immotile” model and is found in the genera Contarinia and Lestodiplosis ; the second, called “9 + 0 plus manchette” model occurs in the genera Gephyraulus, Prolasioptera , and Dryomyia . In these two sperm types the main characteristic is a complete lack of dynein arms on the nine doublet microtubules, and consequently, an immotility of the spermatozoa. The third pattern encountered is the “Sciaralike” model, which is the most common type in the gall-midge family. We have found it in Asphondylia, Aphidoletes, Clinodiplosis, Monarthropalpus , and Diplolaboncus . It is characterized by a variable number of doublets (50–1000) each of them with only one set of arms. Spermatozoa of these species show a rudimentary motility when in the female ducts. The results suggest that flagellar movement is dependent on the presence of dynein arms but is independent of the ninefold symmetry pattern of a sperm tail.

Overview on spermatogenesis and sperm structure of Hexapoda.

The main characteristics of the sperm structure of Hexapoda are reported in the review. Data are dealing with the process of spermatogenesis, including the aberrant models giving rise to a reduced number of sperm cells. The sperm heteromorphism and the giant sperm exceeding the usual sperm size for length and width are considered. The characteristics of several components of a typical insect sperm are described: the plasma membrane and its glycocalyx, the nucleus, the centriole region and the centriole adjunct, the accessory bodies, the mitochondrial derivatives and the flagellar axoneme. Finally, a detailed description of the main sperm features of each hexapodan group is given with emphasis on the flagellar components considered to have great importance in phylogenetic considerations. This study may be also useful to those requiring an introduction to hexapod reproduction.

Bacteria associated with the oesophageal bulb of the medfly Ceratitis capitata (Diptera:Tephritidae)

Extracellular Gram negative bacteria were found to be commonly associated to the oesophageal bulb of Ceratitis capitata with Klebsiella oxytoca and Enterobacter agglomerans as the most common species. All the isolates tested in vitro, except one, were sensitive to the antibacterial material present on the medfly laid egg surface.