Coevolution of male and female genital morphology in waterfowl

Most birds have simple genitalia; males lack external genitalia and females have simple vaginas. However, male waterfowl have a phallus whose length (1.5->40 cm) and morphological elaborations vary among species and are positively correlated with the frequency of forced extra-pair copulations among waterfowl species. Here we report morphological complexity in female genital morphology in waterfowl and describe variation vaginal morphology that is unprecedented in birds. This variation comprises two anatomical novelties: (i) dead end sacs, and (ii) clockwise coils. These vaginal structures appear to function to exclude the intromission of the counter-clockwise spiralling male phallus without female cooperation. A phylogenetically controlled comparative analysis of 16 waterfowl species shows that the degree of vaginal elaboration is positively correlated with phallus length, demonstrating that female morphological complexity has co-evolved with male phallus length. Intersexual selection is most likely responsible for the observed coevolution, although identifying the specific mechanism is difficult. Our results suggest that females have evolved a cryptic anatomical mechanism of choice in response to forced extra-pair copulations.     

Leptidea sinapis (Wood White butterfly) egg-laying habitat and adult dispersal studies in Herefordshire

The Wood White butterfly Leptidea sinapis, a UK BAP Priority species, is present in a number of Forestry Commission woodlands in the West Midlands and these constitute an important part of the national resource of this butterfly. A joint SITA Trust funded project between the Forestry Commission and Butterfly Conservation (linking with the National Wood White Conservation Project) is researching the use of habitat by Leptidea sinapis within these sites with regard to targeting conservation management. Two aspects of this research are presented: the results of a mark-recapture study and an analysis of egg-laying habitat. Mark-recapture results show considerable movement between areas of concentrations of adults and between egg-laying areas, with males moving further and faster than females. Movements do occur across potential habitat barriers. Egg locations were found by following females and by searching for eggs. The habitat used for egg-laying is extremely variable even within a site. A number of foodplants species are used and habitat ranges from low height foodplants within bare ground to a foodplant height of over 1 m within thick vegetation and scrub. These results are being integrated into an ongoing project to restore Leptidea sinapis habitat within managed Forestry Commission woodlands.     

The nesting biology of the bee, Osmia dimidiata Morawitz, 1870 (Hymenoptera, Megachilidae) in the Crimea

The structure and composition of Osmia dimidiata nests were studied based on the material of 133 nests obtained from trap-nests in five localities of the Crimea. The nests contained from 1 to 9 cells (on average, 2.2), separated with partitions made of masticated leaves. Most of the cells had a massive hemispherical bottom and a thin flat cover. The final plug had a structure similar to the cell bottom. The cells occurred singly in the nest cavity or were arranged in rows of 2 or 3 cells separated by galleries. The diameter of the occupied cavities was positively correlated with the fraction of the females in the progeny and with the mass of the cocoons, but negatively correlated with the cell length. The cells with females were 1.5 times as long as those with males. The cocoons with females were twice as heavy as those with males. The peculiar characters of the nest structure of O. dimidiata may mean that the typical nesting substrates of this species are abandoned cells of other bee and wasp species. The characteristic mechanism of estimating the mass of the pollen loaf stored in the cells and determining the brood sex ratio has evolved in the O. dimidiata due to its tenantry. This mechanism is based on two constants: the sex-linked cell length and the fixed distance between the pollen loaf and the cell cover. When choosing the nesting cavities, the female prefers broader and longer tubes for cells with females and narrower and shorter ones for cells with males. The overall sex ratio of the progeny was male-biased (1 ♀: 2.5 ♂) and depended on the food supply abundance. The adults of O. dimidiata fly in the Crimea from the last decade of May until the end of July. Hibernation occurs at the adult stage in the cocoons. Females collect pollen from flowers of Asteraceae or, rarely, Fabaceae. The nests may be destroyed by Melittobia acasta, Monodontomerus aereus, M. obscurus, Sapyga quinquepunctata, Stelis phaeoptera, and Trichodes apiarius; 21% of the progeny died from these enemies, and 22%, due to other factors. The previously proposed synonymy of Pseudosmia taurica Radoszkowski, 1874 (nec Osmia taurica Radoszkowski, 1887) and O. dimidiata is rejected.     

Comparative morphology of the male genitalia of Aphididae (Insecta,Hemiptera): part 1

The present study provides new data concerning the morphology of the male genitalia of Aphididae and unifies their nomenclature. The structure of the male genitalia of 31 species from 26 genera of Aphididae was studied with light and scanning electron microscopy. In the studied species, the genitalia of males consist of a phallus composed of the sclerotized basal part with its articulation and a membranous apical part—an aedeagus. Laterally of the phallus, there is a pair of setose parameres. The shape of the aedeagus, the shape and length of the sclerotized basal part and its articulation as well as the variability of parameres in their form and the number of setae are recognized as important systematic signs of the genitalia. These characters are considered in conjunction with the phylogenetic relationships among the studied taxa.     

Dermacentor variabilis and Dermacentor andersoni: Genital sex pheromones

There is evidence for the existence of a previously undescribed sex pheromone (or pheromones) in the ticks Dermacentor variabilis and D. andersoni. In addition to 2,6-dichlorophenol, which attracts mate-seeking males, a pheromone released on the cuticle of the female genital area enables the sexually excited male to locate the gonopore. The compound (or compounds) appears to act as a contact pheromone; male copulation responses are greatly reduced when the female genital surface is washed with solvents, especially hexane. It is also a potent excitant; males will puncture or dislodge barriers placed over the gonopore to copulate. However, the response is eliminated if the genital area is washed (hexane or acetone) prior to sealing the gonopore, suggesting the reproductive system as the source of the pheromone. A species specific copulation-eliciting pheromone appears necessary to excite the male to form and implant its spermatophore in the vulva of a conspecific female. Males encountering trans-specific females probe their gonopores, but mating attempts are almost always aborted within 5–10 min. The copulation-eliciting pheromone may be the same, or similar, to that used to locate the gonopore. Physical differences in the shape of the female gonopore in the two species, although slight, may contribute to the male's ability to identify conspecific females. Using this pheromone-guided process of attraction and identification, females present in mixed species populations will almost always be distinguished and inseminated by conspecific mate-seeking males.     

Evaluation of Morphological Variability in Meloidogyne arenaria

Seven populations, representing cytological race A (triploid, 3n = 51-56) and the two host races (infective and noninfective on peanut) of Meloidogyne arenaria were studied with light microscopy (LM) and scanning electron microscopy (SEM). Characteristics of root-knot nematodes, recently recommended as useful taxonomic traits, were reexamined among these populations, and their variability both within and between populations was ascertained. We found that stylet morphology of females and head and stylet morphologies of males and second-stage juveniles were the most reliable characters for identification. The two host races of M. arenaria could not be distinguished morphologically. Two of the populations could be separated consistently from the remainder but were not sufficiently divergent to be considered new species. These two variant populations were similar; neither produced males in culture, and they differed from the typical populations in female perineal patterns (LM) as well as in cephalic structure (SEM) and tail shape (LM) of second-stage juveniles. In morphometric studies, most characters of the variant populations differed significantly from those of the typical M. arenaria.     

Niche separation in space and time between two sympatric sister species—a case of ecological pleiotropy

We investigate the niche separation in space and time between the Palearctic sister species Leptidea sinapis and L. reali (Lepidoptera, Pieridae) in central Sweden. Using field sampling, we show that L. reali is a habitat specialist confined to meadows, whereas L. sinapis is a habitat generalist also inhabiting forests. This difference in habitat utilization was corroborated by experimental release of laboratory-reared L. sinapis and L. reali in two adjacent forest and meadow habitats during their natural flight period; virtually all recaptured L. reali that were released in the forest were later caught in the meadow, whereas L. sinapis shifted equally often from meadow to forest as in the opposite direction. In the field, both species fly in May–June, but L. reali appears on average a week earlier in spring and has a substantial second generation in July, whereas L. sinapis is practically univoltine. When overwintered pupae were incubated under identical conditions in the laboratory, females did, however, not differ in phenology, and L. sinapis males actually emerged earlier than L. reali males. When larvae were reared at 23°C on the host plant Lotus corniculatus at a range of daylengths, both species produced a substantial proportion of directly developing individuals at an 18.5 h daylength or longer. When reared at 23°C and a 22 h daylength, L. reali showed an overall higher propensity to develop directly than L. sinapis on plant species originating from both the meadow and the forest habitat. Both Leptidea species showed a lower propensity to enter direct development on forest associated plants than on meadow associated plants. Hence, we suggest that the difference in phenology and voltinism between L. sinapis and L. reali is largely the result of environmentally implemented ecological pleiotropic effects caused by the between-species difference in habitat preference.     

A key to Palaearctic dragonflies of the genus <Emphasis Type="Italic">Aeschna</Emphasis> Fabricius, 1775 (Odonata,Aeschnidae)

Keys to 10 Palaearctic species of the dragonfly genus Aeschna are given. For adults of the two morphologically similar species Ae. juncea (Linnaeus, 1758) and Ae. subarctica Walker, 1908, new distinguishing characters are given. These are the shape of the genital plate and position of the anal appendages relative to the horizontal plane of the female body, and the shape of the processes of the anterior hooks of the male genitalia. Additionally, keys to the larvae based on characters of larvae reared in the laboratory are given. These keys allow species-level identification for early and middle larval instars.     

Neosteinernema longicurvicauda n. gen., n. sp. (Rhabditida: Steinernematidae), a Parasite of the Termite Reticuldermes flavipes (Koller)

A nematode isolated from the termite Reticulitermes flavipes (Koller) was identified and described as a new genus and species, Neosteinernema longicurvicauda. Primary distinguishing characters, by contrast to members of the genus Steinernema, were females having prominent phasmids, a curved tail longer than the body width at the anus, a spiral shape in juvenile-bearing females, and juveniles becoming infective-stage juveniles before emerging from the female; males having prominent phasmids, a digitate tail tip, a characteristic shape of the spicules (foot-shaped with a hump on the dorsal side), and 13-14 pairs of genital papillae, with eight pairs preanal; and infective juveniles having prominent phasmids and a filiform curved tail as long as the esophagus. Adult nematodes are found outside the termite cadaver. Diagnosis of the family Steinernematidae was emended to accommodate the new species.     

Morphological Variation in Pratylenchus penetrans

Variability of morphological characters used to separate Pratylenchus penetrans from other species of the genus was studied in a population originating from a single gravid female. Pronounced heteromorphism was observed and characterized. About 30% of females had a crenate-tail terminus. Several shapes of stylet knobs were characterized; 50% of them were anteriorly flattened to indented. The outer margin of the cephalic framework extended into the body from one-half to two annules. The shape of the spermatheca varied from round to oval. A fifth lateral line was observed in many specimens. Environmental factors, and particularly the host plant, influenced such morphometric characters as body length, width, esophagus length, stylet length, V value, a and b'' ratios, as well as qualitative characters such as tail terminus, growth of ovary, and shape of median bulb. Nematodes reared on pea and cabbage had a higher percentage of females with a crenate-tail terminus than those from tomato, rye, beet, and alfalfa callus culture. Nematodes from peas were longer and wider; they often had gonads that extended to esophagi, but they had shorter esophagi amt stylets than those from callus culture. Populations from different geographical locations also exhibited variahility in morphological characters, as did the Cornell population. The validity of many characters used in species identification is discussed, and the possibility that other related Pratylenchus species are conspecific with P. penetrans is suggested.     

Redescription of Nyssomyia intermedia (Lutz & Neiva, 1912) and Nyssomyia neivai (Pinto, 1926) (Diptera: Psychodidae)

The phlebotomine sand flies Nyssomyia intermedia and Nyssomyia neivai are the probable vectors of American tegumentary leishmaniasis in the Southern and Southeastern regions of Brazil. These species form a complex, being difficult to separate between either females or males of the two members based on recognized morphological characteristics. Both N. intermedia and N. neivai are redescribed here in the search for characters that facilitate their correct identification. It was possible to differentiate females by means of spermathecal characteristics. Males could be separated with confidence by the tips of the genital filaments, which have the form of a deep spoon, the angle of the concavity being well accentuated in N. intermedia and much shallower in N. neivai.     

Observations on a Xiphinema insigne Population with Several Males from Hangzhou,China

A population of Xiphinema insigne with several males was found on the campus of Zhejiang University, Hangzhou, China, in November 1998 in the rhizosphere of Yulan Magnolia. Morphometrics of nine males and 25 females of this population are given herein. No sperm were found in the genital tracts of 118 females that were examined. This agrees with all other observations reported for this species except for the synonym of X. insigne, X. neodimorphicaudatum, in which males are as common as females and the females genital tracts contain numerous sperm. In the males of this study population, sperm were observed only in the seminal vesicles at the distal end of the testes before their juncture with the vas deferens. The population did not fit within either of the two forms of the species. This and other populations have filled in the gaps between the two forms, making the morphometrics for all reported populations a continuum.     

Chaerilus pseudoconchiformus sp. n. and an updated key of the chaerilid scorpions from China (Scorpiones,Chaerilidae)

A new species, Chaerilus pseudoconchiformus sp. n., is described from Xizang, China. The present new species is distinguished from its congeners by a body length of 32−40 mm, carapace with the anterior margin straight, chela with length/width ratio average of 3.3 in males (3.2−3.4, two adults), and 2.5 in females (2.3−2.6, nine adults), eight or nine (eight usually) rows of denticles on fixed and movable fingers of pedipalp chelae, five pectinal teeth in males and three or four in females. To date, the chaerilid species fauna of China consists of nine species. An updated identification key to Chaerilus from China is presented.     

Females prefer to associate with males with longer intromittent organs in mosquitofish

Sexual selection is a major force behind the rapid evolution of male genital morphology among species. Most within-species studies have focused on sexual selection on male genital traits owing to events during or after copulation that increase a male''s share of paternity. Very little attention has been given to whether genitalia are visual signals that cause males to vary in their attractiveness to females and are therefore under pre-copulatory sexual selection. Here we show that, on average, female eastern mosquitofish Gambusia holbrooki spent more time in association with males who received only a slight reduction in the length of the intromittent organ (‘gonopodium’) than males that received a greater reduction. This preference was, however, only expressed when females chose between two large males; for small males, there was no effect of genital size on female association time.     

Reproductive and brood cycles of Artemia persimilis Piccinelli & Prosdocimi from Colorada Chica Lake (Province of La Pampa,República Argentina), under laboratory conditions

The brood cycle in anostracans results from the overlapping of two successive reproductive cycles in the genital tract of females. While a clutch of oocytes begins to mature at the ovaries (ovarian period), the nauplii, cysts or unfertilised products of a previous clutch are developing in the ovisac or being released to the medium (oviduct-ovisac period). Models are proposed for the sequence of stages and their duration in a complete brood cycle under two treatments, i.e., females with males (1:1 ratio), and isolated virginal females of Artemia persimilis in laboratory conditions. The whole brood cycle in both treatments took 6 days, however, they differed in the duration of some stages. The differences are discussed and observations on amplexus are added.     

Morphometric and molecular identification of the female castes of Bombus ignitus and B. ardens (Apidae: Hymenoptera)

Among Korean bumblebees, Bombus ignitus and B. ardens are relatively abundant and important for pollination of wildflowers and agricultural crops. Although the males are easily distinguishable phenotypically, the female castes are difficult to identify from each other. Here we evaluated the value of some morphometric characters in species identification. Also, we developed a polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) to discriminate these similar species. In spite of statistically significant differences of some morphological characters between two species, overlapping quantitative traits hindered accurate identification of the species. However, using 435 bp of COI gene and AluI, BspHI and Earl restriction enzymes allowed molecular identifications of these two species with unique profiles from the digestion by these restriction enzymes. This method can also be applied for older specimens with some morphological characters damaged. We also developed species-specific primers for fast and cost-effective identification of these species.     

Mating system and sex allocation in the gregarious parasitoid Cotesia glomerata

The gregarious parasitoid Cotesia glomerata (L.) is often presumed to possess the characteristic attributes of a species that manifests local mate competition (LMC), as it commonly produces female-biased broods. However, our field surveys of sex ratio and laboratory observations of adult behaviour showed that this species is subject to partial local mate competition caused by natal dispersal. On average, 30% of males left their natal patch before mating, with the proportion of dispersing males increasing with an increase in the patch's sex ratio (i.e. proportion of males). Over 50% of females left their natal patch before mating, and only 27.5% of females mated with males emerging from the same natal patch. Although females showed no preference between males that were and were not their siblings, broods from females that mated with siblings had a significantly higher mean brood sex ratio (0.56) than broods from females that mated with nonsiblings (0.39). Furthermore, brood sex ratios increased as inbreeding was intensified over four generations. A field population of this wasp had a mean brood sex ratio of 0.35 over 3 years, which conformed well to the evolutionarily stable strategy sex ratio (r=0.34) predicted by Taylor's partial sibmating model for haplodiploid species. These results suggest that the sex allocation strategy of C. glomerata is based on both partial local mate competition in males and inbreeding avoidance in females. In turn, this mating system plays a role in the evolution of natal dispersal behaviour in this species.Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.      

Leptosomatides brevicaudatus n. sp. and a Redescription of Leptosomatides marinae Platonova, 1967 (Enoplida: Leptosomatidae)

The free-living marine nematodes Leptosomatides brevicaudatus n. sp. and L. marinae were described and redescribed, respectively, from material collected in the northwest Pacific. Leptosomatides brevicaudatus n. sp. from Simushir Island differs from L. marinae in the ratio c8 (body length divided by tail length measured on the chord) and the length of the spicules. Leptosomatides marinae is redescribed from light microscopy (LM) observations of the type specimens and LM and scanning electron microscopy (SEM) observations of specimens from Hokkaido, Japan. It appears to be impossible to distinguish among some species of Leptosomatides because they are either insufficiently described or known only from females. Secondary sexual characters of males are essential for purposes of identification.