Shorter Wings Research Articles

Juvenile hormone titer and morph-specific reproduction in the wing-polymorphic cricket, Gryllus firmus

Juvenile hormone titers and reproductive characteristics were measured in adult wing and flight-muscle morphs of the wing-polymorphic cricket, Gryllus firmus, during the first week of adulthood. This species has three morphs: one flight capable morph with fully-developed wings and fully-developed flight muscles [LW(F)], one flightless morph with fully-developed wings and histolyzed (non-functional) flight muscles [LW(H)], and another flightless morph with underdeveloped (short) wings and underdeveloped flight muscles (SW). Both flightless morphs [LW(H) and SW] had larger ovaries which contained a greater number of postvitellogenic eggs compared with the flight capable [LW(F)] morph. The juvenile hormone titer was significantly higher in SW compared with LW(F) females on days 3–7 of adulthood. On these days, the JH titer also was significantly higher in the other flightless morph, LW(H), compared with flight-capable [LW(F)] females as determined by one statistical test, but did not differ significantly by another test. The JH titer was positively correlated with ovarian mass or terminal oocyte length, but not with the number of post-vitellogenic eggs. This study is the first direct comparison of juvenile hormone titers in adult wing morphs of a wing-polymorphic insect. Results indicate that an elevated juvenile hormone titer may be at least partly responsible for one of the most distinctive features of wing-polymorphic species, the increased early fecundity of flightless females.

Breeding Biology of Barred Forest-Falcons (Micrastur ruficollis) in Northeastern Guatemala

Little is known about the reproductive biology of most Neotropical raptors (Thiollay 1985). One particularly little-known genus is Micrastur, the forestfalcons, which comprise a group of six species of small to medium-sized falconids that inhabit tropical forests from central Mexico to northern Argentina (Brown and Amadon 1968, del Hoyo et al. 1994). Forest-falcons are characterized by a long tail, short wings, and a slight facial ruff (Brown and Amadon 1968, del Hoyo et al. 1994), which appear to be adaptations to tropical forest environments. Here, we report new information on the breeding biology of the Barred Forest-Falcon (M. ruficollis) in a relatively undisturbed lowland tropical forest in Guatemala. Study area and methods.-We studied Barred ForestFalcons in Tikal National Park, northeastern Guatemala (17?13'N, 89?36'W), from 1988 to 1996. Vegetation in the 576-km2 park is semideciduous tropical forest with rolling hills ranging from 200 to 400 m elevation. Tikal has a pronounced wet and dry season. Rains usually start in May or early June and decrease by December. During our study, monthly precipitation ranged from 1 mm in March 1991 to 302 mm in September 1989. Mean annual rainfall was 1,309 mm from 1988 to 1995 (pers. obs.), and mean monthly temperatures ranged from 15?C in January to 35?C in May from 1989 to 1995. We searched the forest daily from March through July to document activity of potential breeding pairs. Forest-falcons are most active in the morning and evening, and we concentrated our searches to these hours, usually beginning between first light and 0900. We followed pairs by sight and sound until a nest was confirmed by behavior of the birds. When possible, we climbed nest trees to observe eggs or young in cavities, sometimes with the aid of a flashlight. Nest observations totaled more than 1,800 h, most of which occurred during the breeding seasons of 1989 through 1992, with incidental observations from 1993 to 1995 and for four weeks in 1996. For each nest, we determined laying date, clutch size, hatching success (by periodic checks of nest cav-

EFFECTS OF HATCHING DATE AND EGG SIZE ON GROWTH, RECRUITMENT, AND ADULT SIZE OF LESSER SCAUP

Abstract Evidence suggests that birds breeding early in the season or laying larger eggs are at a selective advantage because quality and survival of their offspring are higher. We tested whether wild Lesser Scaup (Aythya affinis) hatching early in the season or from larger eggs had enhanced growth as ducklings and larger size or higher probability of recruiting to the local breeding population in years after hatching. After correcting for age at capture, body mass, head length, and culmen of ducklings were inversely related to hatching date, but were unrelated to egg volume. As adults, late-hatched birds had shorter wing lengths (second-year birds only) and tended to have smaller head lengths (all after-hatch year birds) than early hatching birds. We suggest that later-hatching birds are smaller due to increased competition for food during brood rearing. Recruitment probability increased as natal egg volume increased and decreased among birds with later natal hatching dates. We speculate these results ar...

Colloidal CdTe/HgTe quantum dots with high photoluminescence quantum efficiency at room temperature

We have used an aqueous colloidal growth technique to form hybrid CdTe/HgTe quantum dots with a broad, strong fluorescence in the infrared (800–1200 nm). The quantum efficiency is high, around 44%, when pumped in the visible (488 nm), and the excited state lifetime is around 130 ns, making the material interesting as an optical amplifier medium. Using a pump-probe experiment, we have demonstrated weak optical amplification in a dilute aqueous suspension of CdTe/HgTe dots in the short wavelength wing of the emission spectrum at 808 nm.

Four characters in a trade-off: dissecting their phenotypic and genetic relations

Phenotypic characters may covary negatively because they are in a trade-off or positively because they contribute to a single function. Genetic correlations can be used to test the validity and generality of these functional relationships by indicating the level of genetic integration and checking the conditions under which they are expressed. Phenotypic correlations indicate that there is a widespread trade-off between flight capability and early fecundity in insects. Different wing morphs (long and short wing) are thought to have a suite of reproductive and flight capability traits. In a half-sib mating experiment, we estimated phenotypic relationships between two flight-capability-related characters (flight muscle condition, wing morph) and two components of early fecundity (number of eggs in the ovaries, number of eggs laid), as well as genetic correlations relating wing morph and both components of fecundity in the wing-dimorphic cricket, Gryllus firmus. The number of eggs in the ovaries and the number of eggs laid were negatively correlated phenotypically and genetically with wing length morph (i.e., long wings associated with low fecundity). Both fecundity characters differed between wing morphs, but only if flight muscle was present and not histolyzed. The phenotypic and genetic correlations between fecundity characters were not significant. This suggests that the phenotypic relationship between ovary development and eggs laid is complex, they are not genetically integrated, and they may evolve independently. However, both early fecundity characters are functionally and genetically integrated within the trade-off to a similar degree. Finally, the trade-off affects early fecundity of both wing morphs suggesting that the functional relationship depends on flight muscle size.

Feather mites, pectoral muscle condition, wing length and plumage coloration of passerines

I compared the feather mite (Acari, Proctophyllodidae) loads of moulting birds with features of the new plumage that they were growing. I examined 21 samples, each sample containing individuals of the same species, sex and age class (juvenile, yearling or adult). I used nine species: wren, Troglodytes troglodytes; dunnock, Prunella modularis; robin, Erithacus rubecula; blue tit, Parus caeruleus; great tit, P. major; chaffinch, Fringilla coelebs; greenfinch, Carduelis chloris; linnet, C. cannabina; and yellowhammer, Emberiza citrinella. As previously reported for the house finch, Carpodacus mexicanus, birds with more feather mites grew duller plumage and relatively shorter wings than less infested individuals of the same sex and age class. They also had lower protein reserves judged by the shape of their pectoral muscle. Mite load was usually a better predictor of coloration than pectoral muscle score, but the opposite was true for changes in wing length. In contrast to house finches, birds whose plumage was dull before moult had higher mite loads while moulting. Even if feather mites do not cause dull plumage or short wings, they appear to be a good indicator of birds in poor physiological condition.

Biometrics and post‐juvenile moult in the Goldcrest Regulus regulus

Goldcrests caught inland in Cleveland and on the Isle of May, Scotland had significantly shorter wings than migrant birds caught on the east coast of Cleveland, suggesting that continental birds had longer wings than those of the British population. Duration of post‐juvenile moult (and wing shape) was similar to that found in short distance migrant Sylvidae, which are closely related (Beaman 1994), but the extent of this moult was more in line with the longer distance migrant Sylvidae species and very dissimilar to resident birds in Britain. It is suggested that the reason for an abbreviated post‐juvenile moult is not time constraints after fledging but may be a cost effective method to conserve energy resources due to their small size. Body mass did not differ significantly at any site suggesting no undue loss or gain in mean weight. A non‐significant mean increase in body mass occurred during the mid post‐juvenile moult stage, coinciding with the time when most growing feathers were present.

Maximum Flight Performance of Hummingbirds: Capacities, Constraints, and Trade‐Offs

Flight performance trade‐offs and functional capacities of ruby‐throated hummingbirds (Archilochus colubris L.) were studied using an integrative approach. Performance limits were measured by noninvasively challenging birds with two strenuous forms of flight: hovering in low‐density gas mixtures (a lift assay for the capacity to generate vertical force) and fast forward flight in a wind tunnel (a thrust assay for the capacity to generate horizontal force). Functional capacities during hovering were measured by simultaneously collecting metabolic data using respirometry and information on wing‐beat kinematics for aerodynamic analysis. Intraspecific differences in flight capacity, presumably reflecting diverse selective forces because of sexual dimorphism, migration, and plumage renewal, were then compared. Birds with shorter wings (adult males) or with increased body weight displayed a reduced hovering capacity, although their maximum flight speed was unaffected by such morphological changes. Birds undergoing molt of their flight feathers exhibited a diminished performance during both hovering and forward flight. Hovering capacities in relation to variation in wing morphology and body mass were congruent with aerodynamic predictions, whereas performance capacities in fast forward flight differed from theoretical models. Kinematically, hovering hummingbirds operate within a narrow range of wing‐beat frequencies, and modulation of aerodynamic forces and mechanical power is achieved primarily through variation in wing‐stroke amplitude. Although differing in hovering performance, both sexes of nonmolt birds demonstrate similar mechanical and metabolic capacities, whereas molting inflicts high energetic costs. Relatively invariant physiological capacities may thus ultimately constrain the extent of intraspecific trade‐offs between morphology and performance, providing mechanistic insights into the multilevel functional design of the hummingbird flight system.

Colonization History of Atlantic Island Common Chaffinches (Fringilla coelebs) Revealed by Mitochondrial DNA

Common chaffinches (Fringilla coelebs) are thought to have colonized the Atlantic island archipelagoes (the Azores, Madeira, and the Canaries) from neighboring continental populations (Iberia and north Africa) within the last million years. However, colonization may have occurred separately from north Africa to the Canaries and from Iberia to the Azores (as would be predicted geographically) or in one wave from Iberia to the Azores and then to Madeira and the Canaries. These alternatives have different implications for the evolution of morphometric and plumage differentiation in island chaffinches. To determine the most likely colonization route, we estimated the phylogenetic relationships among island and continental subspecies of common chaffinch using sequences from four mtDNA genes (cytochromeb, ATPase 6, NADH 5, and the control region). The most strongly supported mtDNA phylogeny places the continental subspecies together as the sister group to a monophyletic clade containing the island subspecies. This is consistent with a single wave of colonization, and suggests that patterns of similarity among Atlantic island common chaffinches, such as blue pigmentation, short wings, and long tarsi, are due to common colonization history rather than to convergent evolution in a common island environment. However, spectral analysis of phylogenetic splits showed that although monophyly of island haplotypes is favored, there is also substantial support for their polyphyletic origin. We attribute the latter to the confounding effect of homoplasy at multistate sites and to the relatively rapid sequence of colonization events which provided insufficient time for the accumulation of strong phylogenetic signal. These problems are likely to be significant impediments in attempts to test hypotheses of phylogenetic histories of recently evolved populations and taxa.

Enhancement of short wing formation and ovarian growth in the genetically defined macropterous strain of the brown planthopper, Nilaparvata lugens

When JH II, III or methoprene was applied in the nymphal stages to two different strains of the brown planthopper which were selected to produce long (macropterous) or short (brachypterous) wing forms, no effect was observed on the molting profile or metamorphosis. Brachypterization of a majority of the presumptive macropters was, however, observed by application of these chemicals, although there was no effect on wing form in the presumptive brachypters. The results show that the sensitive periods for the brachypterization of the presumptive macropters falls between early antepenultimate instar and within 1 or 2 days of the penultimate instar, and that the chemicals were effective, in the following order of potency: methoprene>JH III>JH II. Ovarian growth was greatly enhanced in the presumptive macropters when JH III or methoprene was applied twice, within 12 h of the 3rd or 4th nymphal instar and 6 h before adult emergence. JH II on the other hand had no effect on ovarian growth when applied to the presumptive macropters at any of the nymphal stages. None of the chemicals had any effect on ovarian growth in the presumptive brachypters.

Capillarity and fiber types in locomotory muscles of wild common coots, Fulica atra.

Six locomotory muscles of wild common coots, Fulica atra, were analyzed histochemically. Capillarity and fiber-type distributions were correlated to the functional implications and physiological needs of each muscle. Leg muscles exhibit three unevenly distributed fiber types, a pattern that reflects the great variety of terrestrial and aquatic locomotory performances that coots are able to develop. Aerobic zones are presumably recruited during steady swimming and diving, while regions with anaerobic characteristics may be used for bursts of activity such as sprint swimming or during take off, when coots run along the water's surface. Fiber types and capillarization in wing muscles have a marked oxidative trend. High wing beat frequencies, short and broad wings, and the long distance migrations that these birds perform indicate that the presence of high numbers of oxidative fibers and the well developed capillary supply are needed for enhanced oxygen uptake. The pectoralis muscle, except in its deep part, has exclusively fast oxidative fibers with a very high staining intensity for succinate dehydrogenase assay as compared to the same fiber type of other muscles. Its predominant role in flapping flight justifies these characteristics that are typical of fibers with high aerobic metabolism. The deep part of the pectoralis muscle presents a low proportion of an unusual slow anaerobic fiber type. These fibers could play a role during feeding dives when the bird presses the air out of the feathers by tightening the wings against the body. A linear relationship between capillary and fiber densities in all coot muscles studied reflects an adjustment between fiber diameter and vascularization in order to obtain the oxygen for mitochondrial supply. This strategy seems a suitable way to cope with the rigid aerobic constraints that flying and diving impose upon the coot's physiology. J. Morphol. 237:147-164, 1998. © 1998 Wiley-Liss, Inc.

The role of wing length in the evolution of avian flightlessness

Flightlessness has evolved independently in at least 11 extant avian families. A number of hypotheses have been proposed to explain these transitions in individual families, including release from predation on oceanic islands, energetic costs of flight and use of forelimbs for activities other than flying. Few studies have sought to explore factors common to all families containing flightless species, which may explain the taxonomic distribution of flightlessness. In this study, we found that for all eight avian families which contain both flightless and flighted species, the flighted species have shorter wing lengths relative to body mass than their sister families. This result is not biased by taxon size. Models of avian aerodynamics predict that birds with relatively short wings pay a high energetic cost of flight. We suggest that these increased energetic costs of flying predispose these avian families to evolve flightless species. The various causes for the shortening of wings among flighted species of birds and the possibility of future transitions to flightlessness are discussed.

Blackcaps Sylvia atricapilla stopping over at the desert edge; inter‐ and intra‐sexual differences in spring and autumn migration

Spring and autumn Palaearctic‐African migration patterns of Blackcaps Sylvia atricapilla during stopover at Elat, Israel, showed that males appeared significantly earlier than females during spring but not during autumn migration, suggesting that in males there is a stronger drive to reaching breeding territories early. The difference in mean appearance dates between sexes in spring tended to be greatest in years when the males appeared earliest. Longer spread of passage (the dates between which the central 50% of individuals were captured) for each sex in spring was found in years with an early mean passage datebut was significant only for females. These observations suggest that the timing of Blackcap migration is governed not only by endogenous factors but also by exogenous factors, and when the environmental conditions are unfavourable, the differences in passage dates between sexes decrease and the passage lengths shorten. The early individuals (both males and females) that stopped over at Elat in spring were those with relatively small body size (as indicated by relatively short wings) and relatively large fat reserves and in good body condition (as indicated from fat score and body mass/wing‐length ratio). No differences in body size between early and late transients were detected during the autumn migration, but late birds of both sexes carried larger fat reserves. These phenomena may be explained either by leap‐frog migration or by differential fitness among wintering males and females or both, with only the fittest Blackcaps being capable of an early departure. These individuals probably face much less intensive intra‐ and interspecific competition with residents and other transients in stopover sites than do later transients.

Transient current collection and closure for a laboratory tether

The motion of tethered electrodes creates time‐varying plasma currents. A similar current system has been studied in a large laboratory plasma with a stationary, pulsed tether. It is shown that in the appropriate electron MHD regime, the transient current is transported in the whistler mode. The current exhibits helicity. The insulated tether induces electron Hall currents which provide the cross‐field current closure. The transient current increases with voltage and exhibits no saturation at the Langmuir limit due to electron heating. Superposition of delayed pulses emitted from displaced tether positions predicts that tethered satellite currents close along a short whistler wing rather than a long phantom loop.

A new winged seed from the Permian of China

Two specimens of a new type of winged seed, Semenalatum paucum Dilcher, Mei et Du, sp. nov., from the Huaibei Coal Field, Lower Shihhotse Formation of Early Permian age are described and discussed. It is suggested that this winged seed has coniferous affinities because there are sterile scales on one side of the seed, there is an inverted ovule, the seed is bilaterally symmetrical and the wings are formed from the outer integument of the seed coat. The seed has two lateral wings and a short central wing. The two lateral wings of the seed are oriented obliquely to the seed so it would have spun as it moved through the air reducing the settling time. The two specimens probably were transported from an upland flora into a Permian coal-forming swamp and are found in association with plants such as Lepidodendron, Lobatannularia, Gigantonoclea, Pecopteris and Caulopteris.

Juvenile wing shape, wing moult and weight in the family Sylviidae

A study of 56 species of Sylviidae occurring in the western Palaearctic showed a significantly less extensive post‐juvenile moult in those species which incur longer migrations to winter quarters than in species that migrate short distances. Species with the more extensive post‐juvenile moult also undertook their first full moult in summer compared with the less extensive post‐juvenile moult in species with a full moult in the winter. In 11 species, young birds had shorter wings and lower body mass than adults. These differences produced significantly lower wing loadings in young birds compared with adults. Those species undertaking a full moult in the winter had significantly more pointed wings than species with their full moult in the summer. I suggest that this difference is the result of winter‐moulting species evolving from the probably basic strategy of a full post‐breeding (summer) moult. Some species, such as the Barred Warbler Sylvia nisoria, may be in the process of changing the full‐moult season from summer to winter.

On ecology, life history and survival strategies of a wing‐dimorphic ground beetle (col.: Carabidae: Odacanthini: Colliuris) inhabiting central Amazonian inundation forests

The discovery of a lowland Amazonian wing‐dimorphic carabid species, Colliuris batesi Chaudoir, prompted a complete study of its biology and behaviour over a period of more than 4 years. Studies were made on development, fecundity, gonad development, life span and habitat shifts. Survival strategies and possible adaptations are examined with respect to seasonal flooding of their habitat. It is proposed that evolution of brachyptery in this species is rather recent in origin because macropterous specimens are widespread across the upper Amazon Basin, and because the only body change associated with short wings has been narrowing of the humeri.

REACTION NORMS OF MORPHOLOGICAL TRAITS IN DROSOPHILA: ADAPTIVE SHAPE CHANGES IN A STENOTHERM CIRCUMTROPICAL SPECIES?

Reaction norms of wing length, thorax length, and ovariole number were studied according to growth temperature in the circumtropical Drosophila ananassae, and compared to similar data from the cosmopolitan D. melanogaster. In the two species convex reaction norms were observed, but they were not parallel and sometimes exhibited intersections either at high (wing) or at low (thorax) temperature. On average, D. ananassae may be considered as a species with a bigger thorax but shorter wings than D. melanogaster. The shapes of reaction norms were analyzed and compared after quadratic polynomial adjustments. Significant differences were observed, in several cases between polynomial parameters, and in all cases between characteristic points that is, Maximum Value (MV) and Temperature of Maximum Value (TMV). The wing/thorax ratio may also be considered as a specific trait related to wing loading. Major differences were observed between the two species for the mean value and the shape of the response curves of this trait. The main observation of this work was however a shift of TMVs for wing and thorax length and ovariole number in D. ananassae toward higher temperatures. These variations in the reaction norms corresponded to a shift in the species thermal range, suggesting that temperature adaptation was accompanied by a modification of the shape of the response curves.

Phenotypic plasticity of wings in selection lines of Drosophila melanogaster

Plasticity in wing characters was investigated in lines selected for long and short wing length and for long and short thorax length in Drosophila melanogaster. Selection lines were reared at 20°C and at 25°C. All lines were raised across a temperature range from 17.5°C to 27.5°C after several generations of directional selection. We tested whether correlated responses in wing cell size and cell number and in plasticity occurred as a result of selection on wing size or thorax size. A difference in plasticity in the lines was observed at different selection temperatures. Selection at 25°C resulted only in a change in mean values, whereas selection at 20°C led to some correlated responses in plasticity. Different results might have been obtained if more replicates of the selection lines had been started from the same population. The results show that mean size at a temperature and plasticity across temperatures are at least partly determined by different genes.

Phenotypic plasticity of wings in selection lines of Drosophila melanogaster

Plasticity in wing characters was investigated in lines selected for long and short wing length and for long and short thorax length in Drosophila melanogaster. Selection lines were reared at 20°C and at 25°C. All lines were raised across a temperature range from 17.5°C to 27.5°C after several generations of directional selection. We tested whether correlated responses in wing cell size and cell number and in plasticity occurred as a result of selection on wing size or thorax size. A difference in plasticity in the lines was observed at different selection temperatures. Selection at 25°C resulted only in a change in mean values, whereas selection at 20°C led to some correlated responses in plasticity. Different results might have been obtained if more replicates of the selection lines had been started from the same population. The results show that mean size at a temperature and plasticity across temperatures are at least partly determined by different genes.