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.     

Growth Response of Three Vegetables to Smooth- and Crenate-Tailed Females of Three Species of Pratylenchus

The effect of morphological variants of females of Pratylenchus penetrans, P. neglectus, and P. crenatus on the growth of three vegetables was studied. Variants were characterized by having either a smooth or crenate tail terminus. Pea was inoculated with variants of P. penetrans, one female per seedling, and grown at light intensities ranging from 1,350 to 21,600 lux in a series of five experiments. Only crenate-tailed females of P. penetrans suppressed the growth of pea and only when pea was grown at 3,900 lux. Radish was inoculated with morphological variants of P. penetrans, P. neglectus, and P. crenatus, four females per seedling, and grown at 3,900 lux in two experiments. Again, truly creuate-tailed females of P. penetrans inhibited growth. The two variants of P. penetrans had a similar infectivity, greater than that of the other two species of Pratylenchus. Only crenate-tailed P. penetrans reproduced on radish. Onion was inoculated with variants of P. penetrans and P. crenatus, four females per seedling, and grown at 14 C at 12,900 lux. Again, only crenate-tailed P. penetrans inhibited growth. The variants of P. penetrans had a similar infectivity, greater than that of P. crenatus. Neither species reproduced on onion at low temperatures.     

Morphological Observations of Pratylenchus penetrans from Celery and Strawberry in Southern Ontario

Pratylenchus penetrans was obtained from Premier strawberry in Norfolk County and the Niagara Peninsula and from celery in the latter area. Host affected the dimensions of P. penetrans to a greater extent than geographical area in Ontario. Adults of P. penetrans from southern Ontario tended to be smaller than those reported elsewhere. The presence of three lip annules was consistent in the seven populations studied, although in some specimens one of the annules did not entirely encompass the head. Crenations around the tail tip of females of P. penetrans was common in the populations studied. Not all of the morphological characters were proportional in size to length of the females of P. penetrans.     

Effects of Fluctuating Temperatures and Different Host Plants on Development of Pasteuria penetrans in Meloidogyne javanica

Greenhouse and growth room experiments were conducted to investigate the effect of host plant in relation to different nematode inoculum levels, and temperature fluctuations on the development of Pasteuria penetrans. Host plant affected the development of P. penetrans indirectly through its effect on nematode development. Endospores collected from Meloidogyne javanica females reared on different hosts did not show any differences in subsequent attachment and infectivity. The numbers of endospores produced per infected female were reduced with increasing numbers of females parasitizing okra and tomato roots. Fluctuating temperatures retarded the development of P. penetrans. The life cycle of the parasite was completed faster at approximately constant temperatures close to 30 °C than when the temperature fluctuated away from 30 °C. The temperature of irrigation water did not affect the duration of life cycle of P. penetrans.     

Reproductive correlates of plumage coloration of female Mountain Bluebirds

Many studies have shown that the plumage coloration of male birds can act as an honest signal of quality, indicating benefits that a female could gain from pairing with a specific male. In some species, females also display ornamental plumage, but less is known about the function and potential adaptive significance of female coloration because most research has focused on male coloration. Male Mountain Bluebirds (Sialia currucoides) display full body, ultraviolet (UV)‐blue plumage, whereas female plumage is more subdued, with blue color focused on the rump, wing, and tail. During the 2011 and 2012 breeding seasons (May–July) near Kamloops, BC, Canada, we examined coloration of the rump and tail of female Mountain Bluebirds to determine if their plumage could act as an indicator of direct reproductive benefits (e.g., enhanced parental care or reproductive success) to potential mates. We found no relationship between female plumage coloration and either provisioning rate or fledging success. However, female coloration varied with age, with after‐second‐year (ASY) females having brighter, more UV‐blue tail feathers than second‐year (SY) females. In addition, ASY females with brighter, more UV‐blue tails had larger clutches. We also observed positive assortative mating by tarsus length. Because previous work with other species suggests that female body size may be a good predictor of breeding success, males could potentially benefit from pairing with larger females. However, reproductive success did not vary with female size in our study. Although our evidence that structural plumage coloration of female Mountain Bluebirds is a signal of direct reproductive benefits for males (e.g., higher reproductive success) is limited, our results (i.e., ASY females with brighter tails than SY females, and ASY females with brighter tails having larger clutches) do suggest the potential for sexual selection to act on female coloration.     

Subtle,pervasive genetic correlation between the sexes in the evolution of dimorphic hummingbird tail ornaments*

Male hummingbirds have repeatedly evolved sexually dimorphic tails that they use as ornaments during courtship. We examine how male ornament evolution is reflected in female morphology. Lande's two-step model of the evolution of dimorphism predicts that γ (the genetic correlation between the sexes) causes trait elaboration to first evolve quickly in both sexes, then dimorphism evolves more slowly. On the hummingbird phylogeny, tail length does not fit this two-step model; although hummingbirds repeatedly evolved ornamental, elongated tails, dimorphism evolves on the same phylogenetic branch as elongation, implying that γ quickly evolves to be low over phylogenetic timescales. Male “bee” hummingbirds have evolved diverse rectrix shapes that they use to produce sound. Female morphologies exhibit subtle, pervasive correlations with male morphology. No female-adaptive hypotheses explain these correlations, since females do not also make sounds with their tail. Subtle shape similarity has arisen through the genetic correlation with males, and is subject to intralocus sexual conflict. Intralocus sexual conflict may produce increased phenotypic variation of female ornaments. Other evolutionary constraints on tail morphology include a developmental correlation between neighboring tail-feathers, biasing tail elaboration to occur most often at the ends of the feather tract (rectrix 5 or 1) and not the middle.     

Flight costs of long,sexually selected tails in hummingbirds

The elongated tails adorning many male birds have traditionally been thought to degrade flight performance by increasing body drag. However, aerodynamic interactions between the body and tail can be substantial in some contexts, and a short tail may actually reduce rather than increase overall drag. To test how tail length affects flight performance, we manipulated the tails of Anna''s hummingbirds (Calypte anna) by increasing their length with the greatly elongated tail streamers of the red-billed streamertail (Trochilus polytmus) and reducing their length by removing first the rectrices and then the entire tail (i.e. all rectrices and tail covert feathers). Flight performance was measured in a wind tunnel by measuring (i) the maximum forward speed at which the birds could fly and (ii) the metabolic cost of flight while flying at airspeeds from 0 to 14 m s⁻¹. We found a significant interaction effect between tail treatment and airspeed: an elongated tail increased the metabolic cost of flight by up to 11 per cent, and this effect was strongest at higher flight speeds. Maximum flight speed was concomitantly reduced by 3.4 per cent. Also, removing the entire tail decreased maximum flight speed by 2 per cent, suggesting beneficial aerodynamic effects for tails of normal length. The effects of elongation are thus subtle and airspeed-specific, suggesting that diversity in avian tail morphology is associated with only modest flight costs.     

Temperature-Dependent Development of Pasteuria penetrans in Meloidogyne arenaria

Pasteuria penetrans is a promising biological control agent of plant-parasitic nematodes. This study was conducted to determine effects of temperature on the bacterium''s development in Meloidogyne arenaria. Developmental stages of P. penetrans were viewed with a compound microscope and verified with scanning electron microscopy within each nematode at 100 accumulated degree-day intervals by tracking accumulated degree-days at three temperatures (21, 28, and 35 °C). Five predominant developmental stages of P. penetrans were identified with light microscopy: endospore germination, vegetative growth, differentiation, sporulation, and maturation. Mature endospores were detected at 28, 35, and >90 calendar days at 35, 28, and 21 °C, respectively. The number of accumulated degree-days required for P. penetrans to reach a specific developmental stage was different for each temperature. Differences were observed in the development of P. penetrans at 21, 28, and 35 °C based on regression values fitted for data from 100 to 600 accumulated degree-days. A linear response was observed between 100 to 600 accumulated degree-days; however, after 600 accumulated degree-days the rate of development of P. penetrans leveled off at 21 and 28 °C, whereas at 35 °C the rate decreased. Results suggest that accumulated degree-days may be useful only in predicting early-developmental stages of P. penetrans.     

Effect of Temperature on Attachment,Development, and Interactions of Pasteuria penetrans on Meloidogyne incognita

The effect of temperature (10, 20, 25, 30, and 35 C) on attachment and development of Pasteuria penetrans on Meloidogyne arenaria race 1 was elevated in growth chambers. The greatest attachment rate of endospores of P. penetrans occurred on second-stage juveniles at 30 C. The bacterium developed more quickly within its host at 30 and 35 C than at 25 C or below. The development of the bacterium within the nematode female was divided into nine recognizable life stages, which ranged from early vegetative thalli to mature sporangia. Mature sporangium was the predominant life stage observed after 35, 40, 81, and 116 days at 35, 30, 25, and 20 C, respectively. The body width and length of M. arenaria females infected with P. penetrans were smaller initially than the same dimensions in uninfected females, but became considerably larger over time at 25, 30, and 35 C. This isolate of P. penetrans also parasitized and completed its life cycle in males of M. arenaria.     

Female Cape sugarbirds (Promerops cafer) modify egg investment both for extra‐pair mates and for male tail length

The differential allocation hypothesis predicts that females should invest more in reproduction when paired with attractive males. We measured egg volume in Cape sugarbirds (Promerops cafer), a sexually dimorphic passerine, in relation to paternity of the offspring and in response to an experimental tail length treatment. We manipulated tail length, after pair formation, but before egg laying: males had their tails either shortened or left unmanipulated. Our manipulation was designed to affect female allocation in a particular breeding attempt rather than long‐term mate choice: males with shortened tails would appear to be signalling at a lower level than they should given their quality. We found that egg volume was smaller in the nests of males with experimentally shortened tails but larger when the offspring were the result of extra‐pair matings. Both these findings are consistent with the differential allocation hypothesis. We suggest that tail length may be used by females as a cue for mate quality, eliciting reduced female investment when breeding with social mates; and with males with shortened tails.     

Interaction of Meloidogyne naasi,Pratylenchus penetrans,and Tylenchorhynchus agri on Creeping Beentgrass

The pathogenicity and interactions of Meloidogyne naasi, Pratylenchus penetrans, and Tylenchorhynchus agri on ''Toronto C-15'' creeping bentgrass, Agrostis palustris, was studied in a long-term greenhouse experiment. Based on dry weights of roots and clippings, M. naasi alone and in all combinations with P. penetrans and T. agri was highly pathogenic to creeping bentgrass. P. penetrans and T. agri alone and in combination inhibited root growth but adversely affected top growth only when the two were co-inoculated. In combination, the effects of each species on top growth were additive, with M. naasi the dominant pathogen. Creeping bentgrass was an excellent host for M. naasi and T. agri, but a poor host for P. penetrans. T. agri inhibited population increase of M. naasi, indicating nematode-nematode competition, but neither T. agr/ nor P. penetrans was affected by any of the combinations.     

Experimental manipulation of tail length in female barn swallows (Hirundo rustica) affects their future reproductive success

Previous studies have shown no significant effect of experimentaltail length manipulation in female barn swallows (Hirundo rustica)at the beginning of a breeding season on reproductive successor behavior during that breeding season. In the present study,we investigate if tail length manipulation had any effect onreproductive performance the following year, the so-called long-termeffect, in contrast to the short-term effects already studied.We found that females with experimentally elongated externaltail feathers at the beginning of a breeding season producedless offspring during the breeding season the following yearthan did females with shortened or unmanipulated tails. Theseresults suggest that tail elongation caused flight deficienciesthat deteriorated the condition of females and eventually reducedreproductive success. The finding of long-term effects but nosignificant short-term effects for female tail elongation suggeststhat female barn swallows have the ability to adjust immediateparental investment. Detrimental effects of long tails in femalesin terms of decreased reproductive success might explain whyfemale tails are not as long as those of males. Finally, femalesmated to long-tailed (sexually attractive) males decreased theirreproductive success the following year more than did femalesmated to short-tailed males, possibly owing to differentialparental effort causing a deterioration of their condition.     

Extraction and Purification of Pasteuria spp. Endospores

Pasteuria penetrans is an endospore-forming bacterial parasite of root-knot nematodes that has potential as a biological control agent. Biochemical investigations of P. penetrans are limited because of difficulty in obtaining large quantities of endospores free of plant debris and contaminating microorganisms. Our objective was to develop a technique for extraction and purification of P. penetrans endospores from root-knot nematodes. Tomato roots infected with Meloidogyne arenaria that was parasitized by P. penetrans were digested with cytolase. The nematode females along with plant debris were washed with a jet stream of water onto an 800-µm-pore sieve nested on a 250-µm-pore sieve. The materials retained on the 250-µm-pore sieve were centrifuged through a 20% sucrose solution. The resulting loose pellet fraction was collected on a 250-µm-pore sieve and then centrifuged through a 47% sucrose solution. Endospore-filled females were handpicked from the 47% sucrose pellicle fraction. Endospores were released by grinding the females with a glass tissue grinder. The endospores were then filtered through a nylon filter with 8-µm openings, collected by centrifugation, and subjected to buoyant density centrifugation in different media. Further purification by buoyant density centrifugation in a linear gradient of sodium diatrizoate resulted in a preparation of endospores free of debris. This additional step may be desirable for the further characterization of components unique to the endospores.     

Partial tail loss has no severe effects on energy stores and locomotor performance in a lacertid lizard, <Emphasis Type="Italic">Takydromus septentrionalis</Emphasis>

Many species of lizards use caudal autotomy as a defense strategy to avoid predation, but tail loss entails costs. These topics were studied experimentally in the northern grass lizard, Takydromus septentrionalis. We measured lipids in the three-tail segments removed from each of the 20 experimental lizards (adult females) initially having intact tails to evaluate the effect of tail loss on energy stores; we obtained data on locomotor performance (sprint speed, the maximal length traveled without stopping and the number of stops in the racetrack) for these lizards before and after the tail-removing treatments to evaluate the effect of tail loss on locomotor performance. An independent sample of 20 adult females that retained intact tails was measured for locomotor performance to serve as controls for successive measurements taken for the experimental lizards. The lipids stored in the removed tail was positively correlated with tailbase width when holding the tail length constant, indicating that thicker tails contained more lipids than did thinner tails of the same overall length. Most of the lipids stored in the tail were concentrated in the proximal portion of the tail. Locomotor performance was almost unaffected by tail loss until at least more than 71% of the tail (in length) was lost. Our data show that partial tail loss due to predatory encounters or other factors may not severely affect energy stores and locomotor performance in T. septentrionalis.     

Pathogenicity of Pratylenchus penetrans,Heterodera glycines,and Meloidogyne incognita on Soybean Genotypes

The pathogenicity of Heterodera glycines, Meloidogyne incognita, and Pratylenchus penetrans on H. glycines-resistant ''Bryan,'' tolerant-susceptible ''G88-20092,'' and intolerant-susceptible ''Tracy M'' soybean cultivars was tested using plants grown in 800 cm³ of soil in 15-cm-diam. clay pots in three greenhouse experiments. Plants were inoculated with 0, 1,000, 3,000, or 9,000 H. glycines race 3 or M. incognita eggs, or vermiform stages of P. penetrans/pot. Forty days after inoculation, nmnbers of all three nematodes, except H. glycines on Bryan, generally increased with increasing inoculum levels in Experiment I. Heterodera glycines and M. incognita significantly decreased growth only of Tracy M. At 45 and 57 days after inoculation with 6,000 individuals/pot in experiments II and III, respectively, significantly more P. penetrans and M. incognita than H. glycines were found on Bryan. However, H. glycines and M. incognita population densities were greater than P. penetrans on G88-20092 and Tracy M. Growth of Tracy M infected by H. glycines and M. incognita and growth of G88-20092 infected by M. incognita decreased in Experiment III. Pratylenchus penetrans did not affect plant growth. Reduction in plant growth differed according to the particular nematode species and cultivar, indicating that nematodes other than the species for which resistance is targeted can have different effects on cultivars of the same crop species.     

Description of Dolichodorus cobbi n. sp. (Nematoda: Dolichodoridae) with Description of Dolichodorus cobbi n. sp. (Nematoda: Dolichodoridae) with Morphometrics and Lectotype Designation of D. heterocephalus Cobb, 1914

Dolichodorus cobbi n. sp. is described and illustrated from soil around roots of "woods" on the Stanley Farm, Scott County, Arkansas. This species is distinguishable from others of the genus by its short tail projection. It is most closely related to D. marylandicus but differs in having a short tail projection, longer stylet, greater body length, larger c value, and also in position of excretory pore. A limited number of Cobb''s original specimens and drawings of D. heterocephalus were examined. A lectotype and paralectotype were designated to establish the taxonomic base for the genus. Cobb''s original modified labeled drawing of D. heterocephalus is also included. Morphometric data on D. heterocephalus from the type locality and several other populations are given. Some variations in female tail shape, body length, and stylet length were noted.     

Effect of Single and Interplantings on Pathogenicity of Pratyenchus penetrans and P. neglectus to Alfalfa and Crested Wheatgrass

Alfalfa is a host of Pratylenchus penetrans and P. neglectus, whereas crested wheatgrass is a host of P. neglectus but not of P. penetrans. In a 120-day greenhouse experiment at 24 ñ 3 C, P. neglectus inhibited the growth of ''Lahontan'' alfalfa and ''Fairway'' crested wheatgrass. There were no differences in persistence and plant growth of alfalfa and crested wheatgrass, or reproduction of P. neglectus, in single plantings of alfalfa (AO) or crested wheatgrass (CWO), or in interplanted alfalfa and crested wheatgrass (ACW) treatments. On alfalfa, P. penetrans inhibited growth and reproduced more than did P. neglectus. Inhibition of plant growth and reproduction of P. penetrans was greater on alfalfa in AO than in ACW treatments. Pratylenchus penetrans did not reproduce on crested wheatgrass, but inhibited growth of crested wheatgrass in interplanted treatments and was avirulent in single planted treatments. Results were similar in a controlled growth chamber experiment at 15, 20, 25, and 30 C. Both nematode species inhibited alfalfa growth at all temperatures, and P. penetrans was more virulent than was P. neglectus to alfalfa at all temperatures and treatments. Plant growth inhibition and reproduction of P. penetrans on alfalfa in single and interplanted treatments were similar at 15-20 C, but were greater in single than in interplanted treatments at 25-30 C. Pratylenchus penetrans was avirulent to crested wheatgrass in the single planted treatments at all temperatures, but inhibited growth of crested wheatgrass in interplanted treatments at 20-30 C. Plant growth and reproduction of P. neglectus on crested wheatgrass was similar in single and interplanted treatments at 20-30 C and 15-30 C, respectively.     

Infection of Seedlings of Alfalfa and Red Clover by Concomitant Populations of Meloidogyne incognita and Pratylenchus penetrans

Invasion of 2-day-old seedlings of ''Buffalo'' alfalfa and ''Kenland'' red clover by larvae of M. incognita and adults of P. penetrans, during 1-3 day periods of incubation at 24 C, was investigated in 50-mm petri dishes on 1% agar. Penetration by both nematodes increased arithmetically with increased numbers in inocula. P. penetrans invaded alfalfa more readily than red cover, but M. incognita invaded red clover more readily than alfalfa. Both nematodes inhibited root-elongation of alfalfa more than that of red clover. In combinations of 10 and 50 of both nematodes, invasion of both plants by both nematodes was the same as for each nematode alone. Penetration by M. incognita into alfalfa, but not into red clover, was significantly reduced when combinations of 50 M. incognita and 200 P. penetrans were inoculated simultaneously. In the presence of large numbers of entrant P. penetrans in both plants, penetration by M. incognita was highly significantly reduced. Penetration by P. penetrans was unaffected in the reciprocal situations.     

The function of long tails in female barn swallows (Hirundo rustica): an experimental study

The outermost tail feathers in male barn swallows (Hirundo rustica)are the target of a strong directional female mate preference.The tail ornament is also expressed in females, since femaleshave considerably longer tails than juveniles, either due to(1) a strong genetic correlation between the characters in thetwo sexes, or (2) direct sexual selection on females. To discriminatebetween these two hypotheses, we manipulated the length of theoutermost tail feathers in female barn swallows shortly afterarrival by either shortening or elongating the outermost tailfeathers, or maintaining their length among control individuals.Start of laying of the first clutch, reproductive performance,or provisioning of offspring did not show any significant differencesamong treatments. Original female tail length before manipulationwas unrelated to reproductive performance, while male tail lengthexplained some variation in the number of clutches and, to someextent, the total number of eggs laid per year. Females withlonger tails arrived earlier at the breeding grounds. Manipulatedfemale tail length was positively correlated to the tail lengthof their mates. Our results support the correlated responsehypothesis but do not support the sexual selection explanationfor the existence of exaggerated tail feathers in female barnswallows.