The effect of DDT and rearing temperature on pecten spine number in larvae of the mosquito Aedes aegypti L.

Pecten spine number has been studied in larvae of Aedes aegypti exposed during development to low temperatures or to DDT at the fourth instar, both of which caused substantial mortality. But neither contingency caused stabilising selection for spine number, in contrast to what was observed in a previous study when larvae were exposed to scum on the surface of the rearing medium. — Two larval colour morphs, yellow and brown, did not differ in spine number.     

Spine number on the pecten and comb of fourth instar larvae of Aedes aegypti L. differences between two populations

Counts on four rows of spines, the two combs and the two pectens, in fourth instar larvae of the mosquito Aedes aegypti, have revealed consistent differences between two laboratory strains.Values of pecten spine number were normally distributed whereas the distribution of comb spines was bimodal. The sexes were identical in spine number. Left/right correlation (repeatability) was low for both sets of spines (comb, 0.13–0.22; pecten 0.37–0.45), implying a high stochastic component to variance within a single row. In one of two strains, a significant correlation was found between pecten and comb spine number Estimates of heritability for average pecten spine number (0.27–0.41) were obtained from selection data.Evidence is presented for stabilising selection for pecten spine number at the fourth larval instar under unfavourable rearing conditions. The intensity of selection has been estimated as 0.09–0.18.     

Specificity of predator-induced neck spine and alteration in life history traits in Daphnia pulex

It has been proposed that the predator-induced defensive neck spine in Daphnia pulex has a demographic cost. Our results show that this cost is not merely an allocation cost related to the formation and maintenance of the neck spine. In a life table experiment, we tested whether spine induction and life history traits in D. pulex are affected by different invertebrate predators: first and third instar Chaoborus, fourth instar Mochlonyx and two size classes of Notonecta and Dytiscus larvae. D. pulex showed sensitivity to the different predators. Predator-exposure affected one or more of the following life history traits of D. pulex: the timing of first reproduction, clutch size, and growth. In some cases, exposure to predators altered life history traits when neck spine induction did not occur. These shifts in life history traits occurring in the absence of spine induction may be caused by behavioral or physiological changes triggered by the predators.     

Complete larval development of the hermit crabs Clibanarius aequabilis and Clibanarius erythropus (Decapoda: Anomura: Diogenidae), under laboratory conditions, with a revision of the larval features of genus Clibanarius

The complete larval development (four zoeae and one megalopa) of Clibanarius aequabilis and C. erythropus, reared under laboratory conditions, is described and illustrated. The larval stages of the two northeastern Atlantic Clibanarius species cannot be easily differentiated. Their morphological characters are compared with those of other known Clibanarius larvae. The genus Clibanarius is very homogeneous with respect to larval characters. All Clibanarius zoeae display a broad and blunt rostrum, smooth abdominal segments and an antennal scale without a terminal spine. Beyond the second zoeal stage, the fourth telson process is present as a fused spine, and the uropods are biramous. In the fourth larval stage all species display a mandibular palp. The Clibanarius megalopa presents weakly developed or no ocular scales, symmetrical chelipeds, apically curved corneous dactylus in the second and third pereiopods, and 5–11 setae on the posterior margin of the telson. Apart from the number of zoeal stages, Clibanarius species may be separated, beyond the second zoeal stage, by the telson formula and the morphology of the fourth telson process.     

A new species of anglerfish (Lophiidae: <Emphasis Type="Italic">Lophiodes</Emphasis>) from the western Pacific

Lophiodes endoi sp. nov. is described from the western Pacific Ocean. Within the genus Lophiodes, the new species belongs in the L. mutilus group mainly defined by the absence of the fourth dorsal fin spine and differs from other species in the L. mutilus group in having a rounded esca with a paler tip, a third dorsal spine bearing a pair of black tendrils at two-thirds its length, 20–21 pectoral fin rays, a relatively short head, a relatively short illicium, a relatively short third dorsal spine, and a relatively long fifth dorsal spine, reaching the third soft dorsal fin ray when folded back. Comments on a similar species, L. bruchius, newly collected from the Kyushu–Palau Ridge, and notes on the distribution of congeneric species in the northwestern Pacific are provided.     

Palaumysis pilifera,a new species of cave-dwelling mysid (Crustacea: Mysidacea) from Okinawa,southwestern Japan,with an additional note on P. simonae Bacescu & Iliffe, 1986

A new species of Palaumysis, P. pilifera, the fourth species of the genus, is reported from two submarine caves of Okinawa, southwestern Japan. The new species closely resemble the two species previously reported from the Pacific by possessing a multi-segmented inner flagellum in the antennule, but it differs from them in having the terminal spine of the male fourth pleopod bearing rows of fine setules (or hairs) near midlength, as opposed to a naked spine in the latter two species. The present discovery extends the geographical limit of the genus further north to 26° N in the western North Pacific. Additional information on the colour pattern and ecological feature of P. simonae Bcescu & Iliffe, 1986, are provided on the basis of newly collected material from a submarine cave on Palau.     

Geographical variation in dormancy in a copepod: evidence from population crosses

Populations of the freshwater copepod Mesocyclops edax inhabiting Michigan lakes are dormant during winter, whereas populations inhabiting Florida lakes develop and reproduce continuously throughout the year. A Michigan and a Florida population were exposed to dormancy inducing conditions (low temperature and short photoperiod) in the laboratory and observed for indications of dormancy. All Michigan individuals and a small percentage of the Florida individuals entered dormancy as indicated by prolonged duration of the fourth copepodid instar and cessation of feeding. I suggest that in these population these observations represent diapause, rather than quiescence. The two populations were crossbred to examine the nature of inheritance of dormancy. The F₁ hybrids exhibited an incidence of diapause approximately intermediate between the Florida and Michigan parental stocks. The backcrosses of F₁ individuals to the Michigan and Florida stocks, respectively, exhibited a high and an intermediate incidence of diapause. Survival of the F₂ crosses was very low. The present study presents evidence of genetic differentiation between the Michigan and Florida populations of M. edax with respect to ability to diapause.     

Glucocorticoid-induced osteoporosis: a cross-sectional study.

We studied 70 patients (48 women and 22 men) with either rheumatic disease (n = 25) or lung disease (n = 45) who had been treated with glucocorticoids for at least 6 months (mean cumulative dose, 24.2 +/- 27.1 g of prednisone; mean current dose, 11.0 +/- 8.6 mg/d, mean duration of therapy, 8.1 years. We measured bone mineral density (BMD) of the hip (femoral neck) and spine (L2-L4) using dual-photon absorptiometry and BMD of the distal one third radius using single-photon absorptiometry. Compared with age-matched controls, the study population had decreased BMD of the spine (87.0%), hip (87.2%), and radius (90.6%). Current dose, cumulative dose, and duration of therapy were not correlated with BMD in the spine or hip in the total study population. The most significant correlations with low bone mass at the hip and spine were short height and low weight. There was a high incidence of hypercalciuria (30%) as compared with an age- and sex-matched control group (6.4%). Glucocorticoids are known to decrease vertebral and radial bone density. We conclude that glucocorticoids also decrease hip bone density as measured at the femoral neck. The high incidence of hypercalciuria may have implications for therapy of glucocorticoid-induced osteoporosis.     

The effect of prey morphology on the feeding behaviour and population growth of the predatory rotifer Asplanchna sieboldi: a case study using five species of Brachionus (Rotifera)

1. We investigated the numerical response, functional response and prey preference of Asplanchna sieboldi to five different prey brachionids. We also analysed the feeding behaviour of the predator in terms of encounters, attacks, capture and prey ingested per unit time. 2. The five prey species (Brachionus havanaensis, B. rubens, B. patulus, B. macracanthus and B. calyciflorus) differed in their body size and spine length. 3. The population growth rates of A. sieboldi ranged from 0.074 ± 0.03 to 0.431 ± 0.02 depending on prey type and density. There was a significant impact of the spine length rather than body size per se on the population growth rates of the predator. 4. The maximum number of prey consumed depended on both body size and spine length. In the functional response analyses, the plateau was reached at a prey density of 4–8 ind. mL^?1. 5. There was a significant impact of prey density on the prey preference of the predator.     

GENETIC VARIATION AND POLYMORPHISM IN THE INDUCIBLE SPINES OF A MARINE BRYOZOAN

Of particular value in understanding the evolution of genotypes with broad phenotypic ranges (phenotypic plasticity) are the few examples of organisms with adaptive plasticity, such as those that develop a defensive morphology in response to cues from predators. We know little about the heritability of inducible defensive characters or the range of phenotypes available for selection to act on in the field. Membranipora membranacea is a colonial marine bryozoan that produces spines within two days of exposure to waterborne predator extracts. Surveys done in 1993 and 1995 showed that the population at Friday Harbor Labs, Washington, was polymorphic for inducible spine type and was composed of a constitutively spined type that produced spines in the absence of a predator stimulus, an unspined phenotype that did not produce spines irrespective of a stimulus, and an inducibly spined phenotype that would produce spines if exposed to the appropriate cue. In 1995, the frequencies of these types were determined through a laboratory common-garden experiment; 178 colonies were cultured from metamorphosis through approximately 30 days and then exposed to the cue. The inducible type was the dominant, comprising 80.3% of the population. The constitutive type made up 6.2% of the population, and the remaining 13.4 % was the unspined type. The frequency of the three types was similar to a preliminary trial of the experiment run in 1993. Experiments also showed that the lengths of the spines of the inducible type varied continuously among genotypes. To assess causes of variation in the inducible spine response and its clonal heritability, 16 clones were subdivided and grown in a common environment and exposed to a single dosage of spine inducing substance (SIS). Spine length showed high clonal heritability. The range of colony responses from a single environment varied from relatively unresponsive to highly responsive colonies with a very low threshold of response. Norms of reaction were quantified for spine lengths of inducible genotypes originating from two field environments by testing them in a concentration series of SIS. Both spine length and spine type varied with concentration of inducer. Within a clone, colonies were more likely to produce membranous spines than corner spines at higher concentrations. At low concentrations, only straight spines were produced. This study showed that populations of M. membranacea at Friday Harbor are a mix of inducible, nonspined and constitutively spined individuals. Even the inducible individuals showed high heritable variation in the length of spine activated, suggesting that there is considerable scope for the evolution of this character. A norm-of-reaction experiment further showed that the type of spine produced, membranous or corner, varied with the concentration of the cue. Factors maintaining the polymorphism and the broad range of genotypes could include high costs of defending the spined types coupled with a shifting biotic regime.     

Effect of copper on stem melanosis and yield of wheat: Sources,rates and methods of application

Park wheat (Triticum aestivum cv. Park) is susceptible to stem melanosis when grown on Cu-deficient soils. Three field experiments were conducted to evaluate the effectiveness of various Cu sources, using different methods and rates of application for reducing the incidence of stem melanosis and increasing the grain yield of Park wheat on a Cu-deficient Black Chernozemic soil in central Alberta. A fourth experiment determined the residual effect of Cu over 4 years. In the first experiment, Park wheat had less disease and higher grain yield when Cu-chelate solution at 2 and 4 kg Cu ha⁻¹ or Cu-sulfate solution at 10 and 20 kg Cu ha⁻¹ was applied to the soil surface and incorporated to a depth of 8 cm or was applied at these rates as a foliar spray. The foliar application, however, was phytotoxic and delayed maturity by approximately two weeks. Sidebanding Cu (4 cm to the side and 4 cm below the seed row) was least effective. In the second experiment, Cu-sulfate solution incorporated into the soil was more effective than the soil incorporated granular Cu-sulfate in reducing disease incidence and increasing grain yield in the year of application. In the following year the granular Cu was as effective as solution Cu. The third experiment showed that Cu seed dressings did not have any effect on disease incidence or grain yield of Park wheat. In the fourth experiment, the residual effect of Cu-chelate was evident four years after application. The grain yield in the fourth year was about four times that of the control. Contribution No. 564     

Reduced maternal vitamin A status increases the incidence of normal aortic arch variants

While common in the general population, the developmental origins of “normal” anatomic variants of the aortic arch remain unknown. Aortic arch development begins with the establishment of the second heart field (SHF) that contributes to the pharyngeal arch arteries (PAAs). The PAAs remodel during subsequent development to form the mature aortic arch and arch vessels. Retinoic acid signaling involving the biologically active metabolite of vitamin A, plays a key role in multiple steps of this process. Recent work from our laboratory indicates that the E3 ubiquitin ligase Hectd1 is required for full activation of retinoic acid signaling during cardiac development. Furthermore, our study suggested that mild alterations in retinoic acid signaling combined with reduced gene dosage of Hectd1, results in a benign aortic arch variant where the transverse aortic arch is shortened between the brachiocephalic and left common carotid arteries. These abnormalities are preceded by hypoplasia of the fourth PAA. To further explore this interaction, we investigate whether reduced maternal dietary vitamin A intake can similarly influence aortic arch development. Our findings indicate that the incidence of hypoplastic fourth PAAs, as well as the incidence of shortened transverse arch are increased with reduced maternal vitamin A intake during pregnancy. These studies provide new insights as to the developmental origins of these benign aortic arch variants.     

Linear growth in spines from Acanthaster planci (L.) involving growth lines and periodic pigment bands

We report the first observations of a linear growth pattern in aboral spine ossicles of adult Acanthaster planci (L.). This is unlike the spine development of other echinoderms. Growth in aboral spine ossicles of A. planci is essentially by addition of stereom at the base and the spine's growth history is preserved along its length. There are numerous growth lines perpendicular to the long axis of the ossicle. These are clearly evident in longitudinal spine sections and apparently caused by frequent growth episodes. There are periodic pigment bands which are parallel to the growth lines and evident on the surface of the ossicle. Basal growth of the spine ossicle and the nature of the growth lines were confirmed by tetracycline staining. Size/frequency analyses of a population of A. planci from Davies Reef (GBR) found spine ossicle growth, but not body diameter growth, over the six month period between sampling dates. The additional pigment banding in spine ossicles of 4 individuals recaptured after 6 months suggests that pigment bands are laid down seasonally. If pigment band cyclicity is validated, it offers a simple method for ageing adults of A. planci in field populations.     

Effect of KK-42 on growth,development, molting,and metamorphosis of the european corn borer,Ostrinia nubilalis (Hübner)

KK-42 (1-benzyl-5-[(E)-2,6-dimethyl-1,5-heptadienyl]imidazole), administered by feeding, delayed the growth and development of nondiapause-bound and diapause-bound Ostrinia nubilalis larvae and increased the length of the instar. At doses of 80–240 ppm, 62–100% of nondiapause-bound fourth instars precociously pupated or remained as fourth instars, while 52–100% of diapause-bound fourth instars did not molt to the fifth instar. Injection of these nondiapause- and diapause-bound KK-42-fed fourth instars with ecdysone elicited a molt and resulted in the production of larval-pupal intermediates. When mature fourth instar controls were similarly injected, they molted into normal fifth instars. These results support the view that KK-42 delays/inhibits ecdysteroid production. Both eupyrene and apyrene spermiogenesis were prematurely initiated in nondiapause-bound fourth instars that were fed on medium containing 160 ppm KK-42. Fenoxycarb, a potent juvenile hormone mimic, rescued nondiapause-bound fourth instars from precocious pupation. All fenoxycarbtreated larvae either molted to the fifth instar or remained as fourth instars and eventually died. These results support the view that treatment with KK-42 inhibits JH production. When KK-42 treatment was begun in the third instar, a considerable number of nondiapause-bound and some diapause-bound third instars precociously molted to the fifth instar. There was a correlation between weight and the incidence of precocious molting in that third instars destined to skip the fourth instar attained a weight, as pharate fifth instars, of two to three times more than pharate fourth instar controls. Similarly, fourth instars that were destined to undergo precocious pupation attained a weight, as pharate pupae, that was approximately two times more than pharate fifth instar controls. More potent analogues of KK-42 may prove useful in controlling populations of 0. nubilalis by interfering with their growth, development, and metamorphosis. © 1995 Witey-Liss, Inc.

1 This article is a US Government work and, as such, is, in the public domain in the United States of America.

     

Callionymus omanensis,a new species of dragonet from Oman,north‐western Indian Ocean (Teleostei: Callionymidae)

A new species of deep‐living dragonet Callionymus omanensis from Oman is described on the basis of a single male specimen collected in a trawl from 500 m depth off the coast of Oman. The new species is characterized within the subgenus Bathycallionymus by having a small branchial opening; head short (3·9 in proportion to standard length); eye large (2·4 in proportion to head length); preopercular spine with a long, upcurved main tip, with a small antrorse barb and a larger antrorse spine, and with a strong antrorse spine laterally at the preopercular‐spine base, ventral margin smooth; first dorsal fin slightly higher than second dorsal fin (male); second dorsal fin distally straight; 17 pectoral fin rays; distal end of caudal fin slightly pointed, with two median unbranched rays bearing short filaments; first dorsal fin with basal black spot reaching from first to fourth membranes, third membrane with an ocellated distal black blotch; second dorsal fin with vertical dark grey bars; distal three‐fourths of anal fin black; upper half of caudal fin with oblique dark grey bars; pelvic fin dark grey, second ray basally with a black blotch. The new species is compared with similar species. Revised keys to callionymid species of the western Indian Ocean and the Red Sea, as well as species of the subgenus Bathycallionymus, are presented.     

Effects of an Ostracod (Cypris pubera) on the Rotifer Keratella tropica: Predation and Reduced Spine Development

This study investigates two different effects of an ostracod on a rotifer. The rotifer Keratella tropica and the ostracod Cypris pubera were cultured on the alga Cryptomonas erosa. Adult ostracods (2.2 mm body length) significantly reduced the population growth rate (r day^–1) of K. tropica from 0.42 to 0.13. Individuals of this size ingested live rotifers and produced fecal pellets with rotifer loricas. Smaller ostracods (both 0.59 and 1.61 mm body lengths) did not affect K. tropica 's population growth rate. Surprisingly, C. pubera significantly inhibited spine development in K. tropica. Rotifers cultured with juvenile, non‐predatory ostracods had similar lorica lengths but right and left posterior spines that were 10 and 30% shorter, respectively. The spine reduction induced by the ostracod kairomone is in striking contrast to the spine elongation induced in this rotifer by kairomones from copepods, cladocerans and Asplanchna. In shallow ecosystems, large ostracods that swim in the plankton may be important predators of rotifers. In addition, the presence of ostracods in plankton communities may be one of many factors affecting rotifer spine development. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The evolutionary history of Drosophila buzzatti. XXVI. Macrogeographic patterns of inversion polymorphism in New World populations

Inversion polymorphisms in the second and fourth chromosomes of the cactophilic Drosophila buzzatti in the native distribution range of the species are described. Over 5,000 flies from 26 localities were scored revealing interesting geographic structuring of arrangement frequencies. Multiple regression and partial correlation approaches showed that the frequencies of second and fourth chromosome arrangements vary clinically along latitudinal and altitudinal gradients and to a lesser extent with longitude. Although many non selective explanations can account for this pattern, its resemblance to the clinal pattern described in recently established Australian populations of Drosophila buzzatii, strongly suggests a selective explanation. Additionally, the correlated variation observed between the frequencies of arrangements 2St on the second chromosome and 4St on the fourth suggests a pattern of interchromosomal association, which, when considering the vast area surveyed, might be explained as the result of epistatic interactions. The analysis of population structure revealed a significant regional pattern, concordant with previously described phytogeographic regions. F-statistics showed that the patterns of variation were different not only between the second and fourth chromosomes, but also between second chromosome arrangements, suggesting that selective differentiation might have contributed to population structure. Since D. buzzatii breeds and feeds on the decaying tissues of diverse cactus species present in different phytogeographic regions, it is difficult to distinguish the underlying causes of the geographic patterns observed. However, inversion heterozygosity is not correlated with the diversity of potential cactus hosts. The evidence presented suggests that differential selection may be the main cause for the population structure. It is also possible to conclude that the inversion polymorphism of D. buzzatti is flexible rather than rigid.     

Within‐generation dynamics of leatherjackets (Tipula paludosa Meig.)

Larvae of Tipula paludosa (leatherjackets) are pests of grassland and cereals, and important prey items for a range of farmland birds. Their population dynamics from year to year have been the subject of study, but within‐generation dynamics have received much less attention. The duration and occurrence of instars and size of the population is important to both pest management and bird conservation. Leatherjackets were collected monthly from four grass fields over five generations (October to September). Count data were analysed for sources of variability and used to estimate the timing and duration of instars and population changes over a single generation. Instar durations were correlated with temperature. From the first to third instars, sample counts were strongly influenced by the location of the site and the generation. Fourth instar larvae showed a similar decline in numbers across all sites and generations. The duration and timing of first to third instars was more variable than that of the fourth instar, but there was limited evidence that this was influenced by temperature. Only the durations of the third and fourth instars were correlated. The population decline from April to September coincided with the onset of the fourth instar. Our results show that the factors influencing leatherjacket numbers change over the life cycle, but by the fourth instar, these are biotically driven. The predictability of its numerical decline indicates defined windows for crop damage and availability as prey. The stability of its timing suggests that day length may synchronize the annual cycle. Fixed timing of the fourth instar will have important consequences for the timing of crop damage and the conservation of farmland birds as climate changes.     

Two new soldierfishes (Beryciformes: Holocentridae:Myripristis) from Japan

Two species of the holocentrid fish genusMyripristis are described as new from Japan, both with a single pair of tooth patches outside the gape at tip of lower jaw, the third anal spine longer than the fourth, and 28–29 lateral-line scales:M. kochiensis from Kashiwa-jima, Kochi Prefecture, previously misidentified asM. murdjan, is distinct in having small scales in axil of pectoral fins, 32–36 gill rakers, interorbital space 4.45–5.1 in head, and lower jaw not strongly projecting when mouth closed;M. greenfieldi, from the Ryukyu Islands and Ogasawara Islands to Kochi Prefecture, previously misidentified asM. woodsi andM. randalli, is distinct in lacking scales in the pectoral axil, having 35–52 cteni on largest body scales, 43–47 gill rakers, and longest dorsal spine 2.0–2.25 in head.     

PATTERNS OF RUST INFECTION AS A FUNCTION OF HOST GENETIC DIVERSITY AND HOST DENSITY IN NATURAL POPULATIONS OF THE APOMICTIC CRUCIFER,ARABIS HOLBOELLII

It is often assumed that genetic diversity contributes to reduced disease incidence in natural plant populations. However, little is known about the genetic structure of natural populations affected by disease. Here I present data from three apomictic (asexual) populations of Arabis holboellii infected by the rusts Puccinia monoica and P. thlaspeos. An average of 300 host individuals per population were genotyped (using seven variable allozyme loci) and scored for disease presence. Arabis holboellii populations are genetically diverse; the number of clones detected per population ranged from 6 to 27. There was substantial variation in frequency of host clones within and among sites, and significant variation among clones in susceptibility to the different rusts. Contrary to predictions based on frequency-dependent selection theory there was not a consistent positive relationship between clone frequency and disease incidence within any of the populations (Spearman's r = -0.096, P > 0.5). In addition, clonally diverse populations did not necessarily have decreased disease incidence. The population with the lowest overall (both pathogens combined) disease incidence (7.5 ± 1.9%) had the smallest number of clones (6), the lowest spatial variability, and the highest Arabis density. By comparison, another population had 22 clones, high spatial variability, low Arabis density and significantly more disease overall (16.8 ± 2.7%). Although this study does not eliminate the possibility of frequency-dependent pathogen attack in these populations, the results suggest that it is likely to be weak or intermittent.