Courtship behavior of male white perch, Morone americana: evidence for control by androgens

Courtship behaviors are androgen-dependent in many vertebrates and castration often decreases courtship. We examined the effectiveness of castration in reducing courtship behaviors and 11-ketotestosterone (KT) and testosterone (T) in restoring them in male white perch. Castrates were given implants containing KT, T or no hormone. Sham-operated males received implants without hormone. Three weeks later, males were exposed to an ovulated female for 1 h and two courtship behaviors were quantified. Attending behavior involves close and continuous following of a female with occasional contact. Circling involves rapid transits around the female in a circular pattern or back and forth in front of her. In plasma samples taken immediately after observations, KT and T were below detectable levels in castrated males but at high physiological levels in males implanted with KT or T. Castrated males given KT attended females more than castrated males given T implants or implants containing no hormone, but not more than sham-operated males. Circling was eliminated by castration but restored by implantation with T or 11-KT to values exhibited by sham-operated males. This is one of the few demonstrations that KT can regulate courtship behavior in a non-territorial and economically important fish species.     

Courtship inDrosophila sechellia: Its structure,functional aspects,and relationship to those of other members of theDrosophila melanogaster species subgroup

The courtship behavior of Drosophila sechelliais described. Male wing displays are mainly vibration and scissoring, with low levels of rowing. As courtship proceeds the proportion of courtship spent in male wing vibration and licking increases, whereas female movement decreases. The male courtship song of sechelliacontains pulse song but no sine song. This species also shows a distinctive copulation song associated with mounting and copulation. The main cuticular hydrocarbon in females is 7,11-heptacosadiene. The number of copulations increased when flies were placed in the presence of food. Visual and acoustic stimuli appear to be important for mating. A multidimensional comparison was used to compare members of the melanogaster species subgroup, based upon courtship behavior, song characteristics, and cuticular hydrocarbons. A multidimensional comparison of courtship sequences in sechellia, melanogaster, simulans,and mauritianashowed differences in variability between the two island species as compared to the two cosmopolitan species. The courtship song of D. orenais described: it shows both sine and pulse song; there is also a copulation song in this species.     

A mariner-like element with a 5' lesion in Drosophila simulans

The unstable white-S2 (wS2) allele of the white gene occurred spontaneously in the S2 strain of Drosophila simulans. This mutation was caused by insertion of the submariner element, a mariner-like element with an abnormal tandem duplication of the 5' inverted terminal repeat (ITR). Although it has an incomplete ITR, submariner excises efficiently. The rate of somatic reversion, estimated by the number of eye-color mosaic flies, was 79.9%, and the reversion frequency in the germline was 0.6%. The change to the 5' ITR contributes to make this transposon precise excision.     

Estimation of relative reproductive expenditure in the courtship-role-reversed bean weevil, Bruchidius dorsalis (Fahraeus)

It is often difficult to measure the parental expenditure on reproduction by both sexes, because even in species where both sexes invest only nutrient to produce eggs, the nutrition invested by the male is inevitably mixed with that from the female in the body of the female. In this paper, I propose a regression-analysis-based method to estimate the relative amount of investment by both sexes separately, which I have applied to the bean weevil Bruchidius dorsalis (Fahraeus: Bruchidae; Coleoptera), which shows role-reversal in its courtship behavior. The results indicated that lifetime maternal expenditure (the estimated intercept) was fivefold higher than paternal expenditure in a single copulation (the estimated coefficient). Although the number of copulations by wild males was not measured in this study, it is unlikely that they copulate fewer than six times during their lifetime, judging from their longevity and the frequency of copulation in the laboratory. In the experiment, males were divided into two different feeding regimes to test whether their nutritional condition affected their paternal expenditure, but no significant effect was detected.     

Basal relationships in the Drosophila melanogaster species group

The Drosophila melanogaster species group is a popular model for evolutionary studies due to its morphological and ecological diversity and its inclusion of the model species D. melanogaster. However, phylogenetic relationships among major lineages within this species group remain controversial. In this report, the phylogeny of 10 species representing each of the well-supported monophyletic clades in the melanogaster group was studied using the sequences of 14 loci that together comprise 9493 nucleotide positions. Combined Bayesian analysis using gene-specific substitution models produced a 100% credible set of two trees. In the strict consensus of these trees, the ananassae subgroup branches first in the melanogaster species group, followed by the montium subgroup. The remaining lineages form a monophyletic clade in which D. ficusphila and D. elegans branch first, followed by D. biarmipes, D. eugracilis, and the melanogaster subgroup. This strongly supported phylogeny resolves most basal relationships in the melanogaster species group, and provides a framework that can be extended in the future to encompass more species.     

A novel eye morphology induced by a P element in somatic tissue of Drosophila melanogaster.

Summary We found a specific eye morphology designated as Square, which is induced when some Drosophila melanogaster strains harboring P elements are crossed with the 2–3 strain carrying a modified P element, P[ry ⁺, 2–3], which produces transposase in somatic tissue. This phenotype was dominant and also induced in the reciprocal crosses. Square was induced when the 2–3 strain was crossed with Q and M strains such as the sn^w (M) strain carrying three small P elements but not with P strains. Inheritance of Square was also tested and its phenotype was not transmitted to the next generation. These results suggest that Square is caused by the transposition of P elements in somatic cells.     

A rapid decrease in number of the complete <Emphasis Type="Italic">ninja</Emphasis> element and concomitant increase of the defective element in a strain of <Emphasis Type="Italic">Drosophila simulans</Emphasis>

The ninja element, originally isolated from an unstable white mutant strain white-milky (w^mky) of Drosophila simulans, is a member of the retrotransposon family with long terminal repeats (LTRs). We show that ninja is present in high copy numbers in the w^mky-derivative sublines white-chocolate (w^cho) and white-persimmon1 (w^psm1), in a low copy number in another derivative subline white-milky 3 (w^mky3), and in only a few copies in a wild type strain. We have cloned the ninja elements from these sublines and examined their structures. Most of the elements cloned (38 out of 41 independent clones) from w^cho were full length. In contrast, only 9 of 23 independent clones from w^mky3 were full length. We hypothesize that ninja elements were integrated and lost frequently in the w^mky strain and its derivative genomes, and that a rapid decrease in numbers of the ninja element was caused not by an increased rate of loss but by a reduction of integration of full length ninja elements in w^mky3. Each defective element had a unique deletion and/or an insertion except for the three from w^mky3, which had exactly the same 81-bp deletion in each of the 5 and 3 LTRs. The 5 and 3 ends of the deletion appeared to represent sequences similar to those of Drosophila consensus splicing sites. Ectopic splicing may have produced these defective ninja elements.     

In Situ Hybridisation Analysis of the X-Linked Genes in the Species of the Virilis Group of Drosophila

When estimating the level of DNA sequence variation within and between populations or when planning QTL analysis, it is essential to know the location of the genes under study. In the present work, five X chromosomal genes, earlier localised in Drosophila virilis and D. littoralis, were mapped by in situ hybridisation on the larval polytene chromosomes of four other virilis group species, D. a. americana, D. flavomontana, D. lacicola and D. montana. Conjugation of X chromosomes of the most interesting species pairs was studied in interspecific hybrids. Three of the marker genes were used as RFLP markers to examine the occurrence of recombination in D. flavomontana and D. montana hybrid females. The gene arrangement of all species studied, appeared to be different at the proximal end of the X chromosome, which prevented normal conjugation along the most part of the X chromosome. The data illustrating the locations of five X chromosomal marker genes are presented for D. a. americana, D. flavomontana, D. lacicola and D. montana.     

Molecular phylogeny of the subgenus Drosophila (Diptera, Drosophilidae) with an emphasis on Neotropical species and groups: a nuclear versus mitochondrial gene approach

The genus Drosophila has played an essential role in many biological studies during the last 100 years but much controversy and many incompletely addressed issues still remain to be elucidated regarding the phylogeny of this genus. Because information on the Neotropical species contained in the subgenus Drosophila is particularly incomplete, with this taxonomic group being underrepresented in many studies, we designed a study to answer some evolutionary questions related to these species. We subjected at least 41 Drosophilidae taxa to a phylogenetic analysis using a 516-base pair (bp) fragment of the alpha-methyldopa (Amd) nuclear gene and a 672 bp fragment of the mitochondrial cytochrome oxidase subunit II (COII) gene both individually and in combination. We found that the subgenus Drosophila is paraphyletic and subdivided into two main clusters: the first containing species traditionally placed in the virilis-repleta radiation and the second assembling species of the immigrans-Hirtodrosophila radiation. Inside the first of these clusters we could detect the monophyly of both the flavopilosa (the sister-clade of the annulimana group) and the mesophragmatica (closely related to the repleta group) species groups. Concerning the immigrans-Hirtodrosophila lineage, Zaprionus, Liodrosophila, Samoaia, and Hirtodrosophila were the early offshoots, followed by the immigrans, quinaria, testacea, and funebris species groups. The tripunctata radiation appears to be a derived clade, composed of a paraphyletic tripunctata group, intimately interposed with members of the cardini, guarani, and guaramunu species groups. Overall, the COII gene yielded a poor phylogenetic performance when compared to the Amd gene, the evolutionary hypothesis of which agreed with the total evidence tree. This phenomenon can be explained by the fast saturation of transitional substitutions in COII, due to strong biases in both base composition and substitution patterns, as also by its great among-site rate variation heterogeneity.     

Interspecific divergence, intrachromosomal recombination, and phylogenetic utility of Y-chromosomal genes in Drosophila

Reconstruction of phylogenetic relationships among recently diverged species is complicated by three general problems: segregation of polymorphisms that pre-date species divergence, gene flow during and after speciation, and intra-locus recombination. In light of these difficulties, the Y chromosome offers several important advantages over other genomic regions as a source of phylogenetic information. These advantages include the absence of recombination, rapid coalescence, and reduced opportunity for interspecific introgression due to hybrid male sterility. In this report, we test the phylogenetic utility of Y-chromosomal sequences in two groups of closely related and partially inter-fertile Drosophila species. In the D. bipectinata species complex, Y-chromosomal loci unambiguously recover the phylogeny most consistent with previous multi-locus analysis and with reproductive relationships, and show no evidence of either post-speciation gene flow or persisting ancestral polymorphisms. In the D. simulans species complex, the situation is complicated by the duplication of at least one Y-linked gene region, followed by intrachromosomal recombination between the duplicate genes that scrambles their genealogy. We suggest that Y-chromosomal sequences are a useful tool for resolving phylogenetic relationships among recently diverged species, especially in male-heterogametic organisms that conform to Haldane's rule. However, duplication of Y-linked genes may not be uncommon, and special care should be taken to distinguish between orthologous and paralogous sequences.     

A Genomic Comparison of Faster-Sex, Faster-X, and Faster-Male Evolution Between Drosophila melanogaster and Drosophila pseudoobscura

A genomic comparison of Drosophila melanogaster and Drosophila pseudoobscura provides a unique opportunity to investigate factors involved in sequence divergence. The chromosomal arrangements of these species include an autosomal segment in D. melanogaster which is homologous to part of the X chromosome in D. pseudoobscura. Using orthologues to calculate rates of nonsynonymous (d_N) substitutions, we found genes on the X chromosome to be significantly more diverged than those on the autosomes, but it is not true for segment 3L-XR which is autosomal in D. melanogaster (3L) and X-linked in D. pseudoobscura (XR). We also found that the median d_N values for genes having reproductive functions in either the male, the female, or both sexes are higher than those for sequences without reproductive function and even higher for sequences involved in male-specific function. These estimates of divergence for male sex-related sequences are most likely underestimates, as the very rapidly evolving reproductive genes would tend to lose homology sooner and thus not be included in the comparison of orthologues. We also noticed a high proportion of male reproductive genes among the othologous genes with the highest rates of d_N. Reproductive genes with and without an orthologue in D. pseudoobscura were compared among D. melanogaster, D. simulans, and D. yakuba and it was found that there were in fact higher rates of divergence in the group without a D. pseudoobscura orthologue. These results, from widely separated taxa, bolster the thesis that sexual system genes experience accelerated rates of change in comparison to nonsexual genes in evolution and speciation. [Reviewing Editor: Dr. Willie J. Swanson]     

Plasticity in courtship and sneaking behaviors depending on tail length in the male guppy, <Emphasis Type="Italic">Poecilia reticulata</Emphasis>

Male guppies Poecilia reticulata exhibit two types of mating behavior, i.e., courtship displays for cooperative copulation and sneaking attempts for forced copulation. The frequencies of the two male mating behaviors are influenced by tail length. Males possessing long tails exhibit courtship displays less frequently and sneaking attempts more frequently than those possessing short tails, even though they have similar total lengths. To examine whether these male behavioral tendencies depending on tail length are genetically controlled or are determined by tail length per se, tail length manipulation was conducted. The tail lengths of males that had previously possessed longer tails were surgically shortened to a greater degree than those of their counterparts that had previously possessed shorter tails. Although the frequencies of the mating behaviors exhibited by the latter males did not apparently change, the former males clearly increased the frequency of courtship displays and decreased that of sneaking attempts following tail shortening. These results indicate that males adjust the frequencies of the two mating behaviors according to their tail length. Since females avoid cooperative mating with males possessing long tails, the change in mating behavioral patterns by males depending on their tail length may increase their mating opportunities.     

Construction of pFRT,a Convenient Drosophila Transformation Vector with Functional FRT Sites

P-element transformation vector pCaSpeR3 was modified to obtain pFRT. The new vector contains two tandem FRT sites flanked by several unique restriction sites and separated by a polylinker harboring five convenient restriction sites, and allows easy cloning of DNA fragments between or close to the FRT sites. FLP-mediated excision of DNA sequences cloned between the FRT sites was demonstrated in vivo. The vector was proposed for molecular genetic studies of the position effect variegation, structural and molecular organization of Drosophila polytene chromosomes, etc.     

The foraging locus: behavioral tests for normal muscle movement in rover and sitter Drosophila melanogaster larvae

We used Drosophila melanogaster larvae with different alleles at the foraging (for) locus in a variety of behavioral tests to evaluate normal muscle usage of rover and sitter phenotypes. The results show that sitter and lethal sitter alleles of for do not affect larval behavior through a mutation which affects larval muscle usage. In general the behavior of rovers and sitters differed on food but not on non-nutritive substrates. Rovers and sitters moved equally well on non-nutritive substrates, and measures such as the time to roll over and length of forward stride showed no significant strain differences. Larvae with different alleles at for did not differ in body length. Rovers took more strides, not longer ones, than sitters while on foraging substrates. We conclude that differences in larval locomotion during foraging found in larvae with different alleles at for can not be explained on the basis of muscle usage alone. It is more likely that for affects larval ability to perceive or respond to the foraging environment.     

The transmembrane protein,Tincar, is involved in the development of the compound eye in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

We previously cloned and characterized the Drosophila gene, tincar (tinc), which encodes a novel protein with eight putative transmembrane domains. Here, we have studied the expression pattern and functions of tinc during developmental processes. tinc mRNA is expressed in the central and peripheral nervous systems, and midgut during embryogenesis. In the third-instar larval eye disc, tinc mRNA is strongly expressed in all the differentiating ommatidial cells within and in the vicinity of the morphogenetic furrow. Loss-of-function analysis using the RNA-interference method revealed severe defects of eye morphogenesis during the late developmental stages. Our results suggested that tinc may have an indispensable role in the normal differentiation of ommatidial cells.Edited by C. Desplan     

Cactophilic Drosophila in South America: A Model for Evolutionary Studies

The Drosophila buzzatii cluster is composed of seven cactophilic species and their known geographical distribution encompasses the open vegetation diagonal, which includes the morphoclimatic Domains of the Caatinga, Chaco and Cerrado, which are situated between the Amazon and the Atlantic forests. Besides these areas, these cactophilic species are also found in a narrow strip along the Atlantic coast from northeastern Brazil to the southern tip of the country. The hypothesis of vicariant events, defining the core areas of each species, is proposed to explain the historical diversification for the cluster. The intraspecific analysis for the cluster shows a population structure with gene flow restricted by distance, range expansion with secondary contact resulting in introgression and simpatry, especially in the limits of the species distribution, polytypic populations and assortative mating in inter population experiments. There is a variation related to these events that depends on the species and geographic origin of the population analyzed. These events are, hypothetically, described as the results of expansion and retraction of the population ranges, as a consequence of their association with cacti, which theoretically follow the expansion and retraction of dry areas during the paleoclimatic oscillations in South America, as that promoted by the glacial cycles of the Quaternary. The Drosophila buzzatii cluster is divided into two groups. The first one is composed of D. buzzatii, a species that has a broad geographic distribution and no significant differentiation between its populations. The second is the Drosophila serido sibling set, which encompasses the others species and is characterized by a significant potential for differentiation.     

Courtship song, male agonistic encounters, and female mate choice in the house cricket,Acheta domesticus (Orthoptera: Gryllidae)

Whether female crickets choose among males based on characteristics of the courtship song is uncertain, but in many species, males not producing courtship song do not mate. In the house cricket,Acheta domesticus, we examined whether a female chose or rejected a male based on his size, latency to chirp, latency to produce courtship song, or rate of the high-frequency pulse of courtship song (“court rate”). We confirmed that females mated only with males that produced courtship song, but we found no evidence that the other factors we measured affected a female’s decision to mate. In addition, we investigated whether the outcome of male agonistic encounters affected the subsequent production of courtship song. In one experiment, we observed courtship and mating behavior when a single female was placed with a pair of males following a 10-min interaction period between the two males. Winners of male agonistic encounters had higher mating success. However, winners and losers of agonistic encounters were not different in their likelihood or latency to produce courtship song or in the number of times they were disrupted by the other male in the pair. In a second experiment, we allowed two males to interact for a 10-min period, but following this interaction period, we placed a female with each male separately and observed courtship and mating behavior. The mating success of winners and losers was not different under these circumstances, and we found no differences between winners and losers in any subsequent courtship or mating behavior examined. We conclude that winning agonistic encounters influences a male’s mating success in ways other than his production of courtship song and this effect is lost when winning and losing males are separated and each is given an opportunity to mate.