Reproduction, growth and circadian activity of the snail Bradybaena fruticum (O. F. Müller, 1774) (Gastropoda: Pulmonata: Bradybaenidae) in the laboratory

Selected life cycle parameters of the snail Bradybaena fruticum were studied in the laboratory. The initial material for the laboratory culture was taken from a population in South Western Poland; the snails were kept in Petri dishes and plastic containers. The temperature, humidity and lighting conditions were maintained at a constant level (day 18°C, night 12°C, rh 80%, light:dark 12:12). Circadian activity observations were conducted outside the climatic chamber. Eggs — calcified, slightly oval, of mean dimensions 2.67x2.56 mm — were laid singly or in batches of 6–62, as a result of both biparental and uniparental reproduction. Incubation took 27–76 days and hatching was asynchronous. Hatching success was lower among eggs produced by single parents compared to eggs produced by two parents (c.a. 56 and c.a. 88%, respectively). Growth included fast (2.25 to 5 whorls) and slow (1.9–2.25 and >5 whorls) phases as well as lip formation, and took 261 to 420 days. The first eggs/batches were laid c.a. one year later, and for uniparentally reproducing snails the period was even longer. The growth of snails kept singly was faster than in those kept in groups. Juvenile snails were much more active than adults in the spring, summer and autumn but the adults were more mobile in the winter. In all seasons, juveniles were more active at night than adults.     

Adaptations to the Arctic: low-temperature development and cold tolerance in the free-living stages of a parasitic nematode from Svalbard

For nematodes with a direct life cycle, transmission is highly dependent on temperature-related development and survival of the free-living stages. Therefore, in the Arctic, where the winter lasts from October to May, nematode transmission is expected to be focused in the short summer season, yet there is strong evidence that as well as focussing egg output during winter months, the nematode parasite, Marshallagia marshalli, infects Svalbard reindeer during the Arctic winter when temperatures are persistently below freezing. To investigate the potential for development and survival of eggs and infective third-stage larvae in winter and therefore the possibility of for winter transmission, we ran a series of low-temperature laboratory experiments. These provide five key insights into the transmission and survival of the free-living stages of M. marshalli: (1) eggs hatched at temperatures as low as 2 °C, but not below 0 °C, (2) eggs were viable and developed after being exposed to sub-zero temperatures for up to 28 months, (3) infective-stage larvae survived for up to 80 days at 5 °C, (4) infective-stage larvae could survive rapid exposure to temperatures below ?30 °C, and (5) desiccation resistance may be important for long-term larval survival at low temperatures. Together, these results indicate that eggs deposited during the winter are highly tolerant of prevailing environmental conditions and have the potential for rapid development with the onset of spring. It is therefore likely that the parasite remains in the egg stage in the faeces during the winter of deposition, hatch and develop into the infective larval stage in the summer, remaining viable on the tundra until the reindeer host returns to the winter feeding grounds the following winter.     

Seasonal Migration of Apolygus spinolae (Hemiptera: Miridae) between Grapevines and Herbaceous Plants

This study was conducted to verify the seasonal migration of Apolygus spinolae (Meyer-Dür) between grapevines and herbaceous plants. Overwintering eggs were hidden in the hair layer under grapevine bud scales. A. spinolae adults were captured on sticky traps in the grapevine yard from late spring to early summer, dwindled through the summer, and captured again in late fall. However, adults were observed from early summer in herbaceous plant fields. A. spinolae adults were abundant during the summer of July and August in the herbaceous field, and thereafter its density decreased through fall. A few or no A. spinolae was found on mesh-netted grapevines after the installation year of the mesh-net, which indicated that A. spinolae adults migrating to lay overwintering eggs during the autumn could not land at the grapevines because of the mesh-net. Damaged shoots by A. spinolae were concentrated near the edge of grapevine yards bordering the herbaceous plants. This distribution pattern of shoot damage was believed to be related to an oviposition behavior of A spinolae, reflecting that adults migrating from herbaceous plants lay eggs more frequently in grapevines adjacent to the summer host plants. Seasonal occurrence of A. spinolae in grapevine yards was suggested as follows: A. spinolae overwinter as eggs in dormant buds on grapevines and hatch in the spring. Nymphs feed on grapevines then develop to adults (spring population), and migrate to herbaceous plants. A. spimolae spends the summer on the herbaceous hosts (summer population). Then, adults migrate back to grapevines in late autumn and lay overwintering eggs.     

Studies on the epidemiology of Strongylus vulgaris infection of the horse.

Observations are reported on the size and age structure of Stronglyus vulgaris populations recovered from the anterior mesenteric artery and its main branches of horses slaughtered at regular intervals throughout a year. Marked seasonal variations were found in the mean monthly numbers of worms present. During spring/early summer the numbers were relatively low and a large proportion of the arteries had no worms in them at all. Thereafter, the arterial worm burdens quite rapidly increased and the highest levels were reached during the winter months. During summer, small, newly-arrived larvae were quite abundant but by the end of the year well-developed (fifth-stage and late fourth-stage) worms predominated. These observations support the view that S. vulgaris is in Britain an annual species completing its development mainly during the winter months of the year.     

Effects of seasonal variation on the biology and morphology of the dusky cotton bug,Oxcarenus laetus (Kirby)

The dusky cotton bug (Oxycarenus laetus, KIRBY) a pest of several crops. The effects of winter and summer on the biology and morphology was investigated. The sampled eggs of dusky cotton bug (DCB) were kept under controlled environment for biological and morphological investigations. In winter, the mating duration of DCB was observed longer significantly (74.2 days), egg development period (3.93 days), an egg laying period (3.6 days) and hatching period (6.66 days) noted longer in winter season. Interestingly, average number of hatched egg (16.8 days) observed significantly higher in summer and the percentage of the hatching of eggs (81.95%) were also observed higher in summer as compare to winter. Whereas, the longevity of all nymph stages in winter longer days as compare to summer nymph stages. Moreover, differences were also observed between male and female development days between winter and summer. In the winter, female DCB development was suggestively higher as compare to summer (24 days). Whereas, the developmental days were noted considerably more in winter for males as compare to summer (14.93 days). On other hand, for morphological parameters, no differences were observed between winter and summer population of DCB.     

Seasonal influence on the production of Schistosoma haematobium and S. mansoni cercariae in Rhodesia

Batches of Bulinus (Physopsis) globosus and Biomphalaria pfeifferi were exposed to Schistosoma haematobium and S. mansoni respectively each month for a 12-month period. The snails were kept out of doors in Salisbury (highveld) and indoors at Chiredzi (lowveld S. haematobium only) and examined weekly to determine the duration of prepatency, and the number of cercariae produced per infected snail. There was a strong seasonal influence in the highveld experiments which showed sporocyst dormancy in winter and the almost simultaneous maturation of infection in nine batches during early summer. In the lowveld the release of cercariae by infected B. globosus continued throughout the year although numbers fell off in winter. The prepatent period was prolonged in winter, but there was no evidence of sporocyst dormancy.     

Summer dormancy ensures univoltinism in the predatory bug Picromerus bidens

The seasonal cycle of Picromerus bidens L. (Heteroptera: Pentatomidae) is usually considered to be univoltine with an obligatory winter egg diapause. Seasonal adaptations of the species were studied in the laboratory and in field experiments. When reared under short-day photoperiodic conditions (L12:D12 and L14:D10), all females began to lay eggs synchronously soon after their emergence. However, in the females reared under long-day conditions (L18:D6 and L20:D4) and outdoors in June–July, oviposition was significantly delayed. This delay in reproduction induced by photoperiodic conditions and then spontaneously terminated was considered to be aestivation. Egg batches laid by females in the laboratory and in the field were kept at 25 °C for two months. From 30.8 to 93.8% of batches contained eggs which hatched without cold treatment between day 14 and 60 after oviposition. The proportion of eggs hatched was 17.7 to 20.9% in the short-day regimes, while it was significantly less (5.7 to 6.0%) under long-day conditions. It is concluded that in some eggs diapause is of low intensity and that if under natural conditions the first batches had been laid at the end of June, nymphs would have hatched at least from some eggs during the same season even without cold treatment. Such untimely hatching would have resulted in the death of nymphs and adults unprepared for overwintering. A photoperiodic response which induces aestivation in the early emerging adults in June–August may prevent early oviposition and occurrence of a second generation and thus maintains univoltinism in P. bidens.     

Rhipicephalus sanguineus: Observations on the parasitic stage on dogs in the Negev Desert of Israel

Sixteen dogs were studied for infestation with R. sanguineus in Kibbutz Ze'elim in the north-western part of the Negev Desert over a period of one year. The mean number of ticks per dog per month was 16.4. The majority of the ticks were adults: males (48.6%) and females (34.4%). The cars and abdomen of the dog were the predilection sites for the ticks. Male ticks were more abundant on the ears, whereas female ticks were more abundant on the ears and the abdomen. A strong correlation between tick numbers and the ambient temperatures was found. The mean percentage of dogs infested in the winter months was 16.6% and increased in the summer months to 34.4%. During winter, ticks were found more often on the ears and head of their hosts whereas in summer they were distributed mainly on the ears, headd and abdomen. The male: female ratio was higher in winter (2.3:1) than in summer (1.1:1).     

Demographic study of the reproductive potential of pear psylla, Cacopsylla pyri

Longevity and fecundity of pear psylla adults, Cacopsylla pyri (L.) (Homoptera: Psyllidae), were studied in Greece under field conditions, during 1991/92 and 1992/93. Net fecundity (mean fecundity of cohort) of the overwintered females (winter form) was low (24.1 and 43.4 eggs per female for 1991/92 and 1992/93 respectively) because only a small fraction of the females survive reproductive diapause. Surviving females, however, are capable of producing a relatively high number of eggs (135.0 and 151 9 eggs per female for the two seasons respectively). Net fecundity of summer form females was very high in spring (343.2 and 406.8 eggs per female for 1992 and 1993 respectively), relatively high in early autumn (130.4 and 192.5 eggs per female) and very low in summer (21.9 and 46.5 eggs per female). Male longevity was in all cases shorter than that of female. Longevity of both sexes of the summer form was higher in spring and autumn (for females it ranged from 22.3 to 28.4 days) than it was in summer (for females it ranged from 14.3 to 17.4 days).     

Fecundity and fertility of ladybird beetle Harmonia axyridis after prolonged cold storage

Some species of ladybird beetles (Coleoptera: Coccinellidae) mate both before and after overwintering. The purpose of the pre-diapause mating was studied in the alien invasive ladybird Harmonia axyridis (Pallas 1773). Our study demonstrates the persistence of high fecundity (daily oviposition rate of 21 eggs per fertilized female during the first month of reproduction) and fertility (85 % of eggs hatching) of females of H. axyridis after long storage (up to eight months) at low temperature (6 °C). The females were not mated after activation in spring and had to rely on the sperm supply maintained from the pre-winter period (58 % of females were fertilized). Unfertilized females also laid eggs but in low numbers (an average of 345 eggs by virgin females during an individual’s lifetime, 1,174 eggs by females fertilized before winter) and after a longer pre-oviposition period (2–5 weeks in comparison to 7–8 days for fertilized females). We show that the unfertilised eggs were not trophic eggs. The high sperm survival ability observed questions the need for the high levels of sexual activity generally observed in Coccinellidae. Fertilized females of H. axyridis may found large colonies after dispersal to new areas even without males, which contributes to the striking invasive ability of this species.     

The influence of food availability on population dynamics of a supralittoral isopod, Ligia dilatata brandt

Size frequency analysis of monthly samples of the isopod Ligia dilatata Brandt in the rocky supralittoral region on the west coast of the Cape Peninsula, South Africa, over a 20-month period shows that L. dilatata lives for 2 yr and that annual recruitment occurs from spring until autumn. Females start reproducing at 12 months but, unlike males, probably do not survive to breed twice. The brood period is 5–6 wk. Fecundity is described by the regression equation N = 1.9L – 3.7 (N =no. of eggs in brood pouch, L = length of females in mm). Growth is slow during summer but faster in winter when food is more plentiful. Two distinct phases of mortality are evident; a constant slow mortality for the first 9 months after recruitment, and a faster second phase culminating in the elimination of the cohort after a further 11 months. The in situ temperature range is only 6.2°C (mean: 14.6°C) due to the insulating effect of kelp debris and appears to be less important than food availability in influencing the regular annual cycles observed.     

Field and laboratory studies on the life-cycle, growth and feeding preference in the hairy snail Trochulus hispidus (L., 1758) (Gastropoda: Pulmonata: Hygromiidae)

For the first time the life cycle of the common land snail Trochulus hispidus was completely described in Central Europe (Poland). This is a semelparous species predominantly with an annual life cycle and the reproductive period lasting from April till October. The first young snails hatch in spring, grow rapidly in summer and reach ca. 4 whorls until winter. In spring of the next year they mature and reproduce. After that they die. There is hardly any growth from late autumn till early spring. The average proportional growth rate is ca. 0.3 whorl/month in the wild. The fastest growth is present in the youngest snails and then gradually decreases over the course of their age. Laboratory and field observations allowed for establishing the following life cycle parameters: eggs calcified, almost spherical, ca. 1.5 mm, laid in spring and summer in batches of between 1 and 47. Time to hatching is 6–24 days, hatching is asynchronous; newly-hatched snails have approximately 1.5 whorls. Analysis of food preferences revealed, that T. hispidus tends to restrict its diet during the life. Generally the youngest snails equally consumed leaves of all four tree species offered (Fraxinus excelsior, Acer pseudoplatanus, Tilia cordata and A. platanoides) whereas adults preferred F. excelsior over A. pseudoplatanus and A. platanoides.     

Microbiological characteristics of Crottin goat cheese made in different seasons

General profiles and effect of season on microbiological characteristics of Crottin goat's cheese were evaluated in different batches during storage. Microorganisms determined were: mesophilic, proteolytic, halotolerant, psychotrophs, coliforms, yeasts and Staphylococcus aureus. The presence of Escherichia coli, Salmonella spp., Yersinia enterocolitica and pH and moisture content were also analyzed. E. coli, Salmonella spp. and Y. enterocolitica were not detected in the Argentinian soft goat cheese. Cheese made during winter had significant differences in mesophilic, psychrotrophics, halotolerant microorganisms and yeast between batches. In fall cheese, there were significant differences to mesophilic, proteolytic and psychrotrophics. There were not significant differences to the microbial groups in summer cheese. The variability between batches in Crottin cheese occurred during cold months, which may be attributed to the coagulation process of the cheese at environmental temperature (without any control), creating a delay in the lactic flora activity in winter. The results showed a significant influence of the seasons in the microbial population evolution during storage, suggesting that the differences in each microbial group in different seasons could be caused by differences in the predominant strains of each group. Further studies are needed for the composition of the microorganisms, where goat's products have not specific hygienic and quality standards in Argentina.     

Spatial and temporal separation of littoral zone fishes of Lake Geneva (Switzerland-France)

The spatial (distance from the shore) and seasonal (summer-winter) distributions of the ichtyofauna in the littoral zone of Lake Geneva were studied between October 1991 and December 1992. Gill nets were set simultaneously at three different sites of a chosen littoral zone: shore, middle and far (50, 300 and 550 m from the shore, respectively).The results show that in summer more species and individuals are present in the littoral zone than in winter. Throughout the year, species richness is greater at the shore site than at the middle or far site. In summer, total abundance is greater at the far site, whereas there are more fish at the shore site during winter. Perch (juveniles and adults), roach and gudgeon (adults only), have maximum abundance during the summer, while lake trout, grayling and whitefish (adults) have maximum abundance during the winter. For five species (adults only) the site comparison shows spatial segregation of the habitats: greater numbers of perch are present at the far site while roach, tench, lake trout and grayling prefer the shore site.     

Phenology ofHippodamia undecimnotata (Col.: Coccinellidae) in Greece

Hippodamia (Semiadalia) undecimnotata (Coleoptera: Coccinellidae), collected from central Greece and reared in cages during 1993–1994 and in vials during 1994–1995 outdoors at Kifissia, Athens, completed 5 generations per year. In both cases, adults of the 1^st, 2^nd and 3^rd generations reproduced, completing their egg laying in the same year; 4^th and 5^th generation adults reproduced both in the year they emerged and the following year. In both cases, adults of the 1^st and 2^nd generations died before winter; in 1993, adults of the 3^rd generation died before winter, in 1994, they survived until April 1995. Adults of the 4^th and 5^th generations overwintered successfully. The greatest numbers of eggs were laid by females of the 1^st and 2^nd generations. Field observations and timed counts of specimens (30 minutes per location) made on the tops of Mounts Chlomo and Kitheron and on the neighboring plain of Kopais between 1991 and 1994 revealed that most adults arrived on the mountains between late June and early September and left between the end of March and beginning of May.H. undecimnotata were not found on the plain of Kopais during the winter. Overwintered adults arrived between the end of March and beginning of May; 1^st generation adults emerged in June. The presence of a few eggs, larvae, pupae and newly-emerged adults observed on the plain during August-September 1993 suggests that at least a portion of theH. undecimnotata population in central Greece completes 2 or more overlapping generations per year.     

The causes of seasonal changes in numbers of the yellow dung fly, Scathophaga stercoraria (Diptera: Scathophagidae)

ABSTRACT. 1. Counts of adult Scathophaga stercoraria (L.) on cow pats were made in Houghall, County Durham, in 1964 and 1965.
2. A spring peak of numbers was due to adults (overwintered mainly as pupae or larvae) maturing and going to dung to breed. Numbers then dropped, rising to one or more peaks in late June—early July. In 1964 there was then a summer drop in numbers until late September. In 1965 high numbers persisted in summer associated with cooler, wetter weather. Autumn peaks in both years persisted until severe frosts or snow.
3. Mature adults, developed from eggs laid during the spring peak, form the first generation when breeding in mid-late June. No clear generations can be identified after this, due to eggs being laid daily (females have successive gonotrophic cycles). Changes in adult numbers breeding reflects survival of eggs and newly-hatched larvae 5–6 weeks earlier, and lower survival rates of adults in mid-summer compared with spring and autumn.
4. Adult Scathophaga numbers in vegetation rose as numbers on dung dropped. Females dissected to count ovariole tunica dilatations showed that most flies in vegetation were immature, with some parous flies hunting insects to develop the next batch of eggs.
5. Females on dung were dissected and found to range from immature to seven-parous. Those gravid for the first time were grossly under-represented, possibly due to wider dispersal.
6. It is suggested that seasonal changes in this r-strategist cannot be explained simply in terms of generations nor by the occurrence of adult diapause.     

Temperature-dependent growth and life cycle of Deleatidium (Ephemeroptera: Leptophlebiidae) in two high-country streams in New Zealand

1. Measurements of larval growth rates were used to produce an empirical model for examining factors influencing patterns of size structure and emergence period for populations of the leptophlebiid mayfly Deleatidium ( lillii group) in two high-country streams (South Island, New Zealand). Growth rates were measured in situ by enclosing groups of larvae and natural stream substrata in growth chambers.
2. Multiple regression analysis showed that temperature explained most variation among growth rates in both streams. Growth rates were also significantly related to larval size, although the effect was minor compared with temperature. A significant relationship between larval biomass per chamber and growth rate was shown at only one site.
3. Growth models based on multiple regression equations ( R ² = 0.70–0.84) simulated the extended emergence period and complex size structure observed for populations of Deleatidium in the field. Larvae hatching from eggs deposited before mid-February (austral summer) probably emerge as adults before May (minimum cohort duration ≈ 3 months). Larvae hatching after mid-February probably do not emerge as adults until the following summer because of low growth rates during winter (maximum cohort duration ≈ 11 months).
4. On average, there are probably two generations of Deleatidium per year (bivoltine) at the study sites. The presence of numerous overlapping cohorts throughout summer, however, results in an extended emergence period and complex size structure.     

Temperature-dependent growth and life cycle of Deleatidium (Ephemeroptera: Leptophlebiidae) in two high-country streams in New Zealand

1. Measurements of larval growth rates were used to produce an empirical model for examining factors influencing patterns of size structure and emergence period for populations of the leptophlebiid mayfly Deleatidium ( lillii group) in two high-country streams (South Island, New Zealand). Growth rates were measured in situ by enclosing groups of larvae and natural stream substrata in growth chambers.
2. Multiple regression analysis showed that temperature explained most variation among growth rates in both streams. Growth rates were also significantly related to larval size, although the effect was minor compared with temperature. A significant relationship between larval biomass per chamber and growth rate was shown at only one site.
3. Growth models based on multiple regression equations ( R ² = 0.70–0.84) simulated the extended emergence period and complex size structure observed for populations of Deleatidium in the field. Larvae hatching from eggs deposited before mid-February (austral summer) probably emerge as adults before May (minimum cohort duration ≈ 3 months). Larvae hatching after mid-February probably do not emerge as adults until the following summer because of low growth rates during winter (maximum cohort duration ≈ 11 months).
4. On average, there are probably two generations of Deleatidium per year (bivoltine) at the study sites. The presence of numerous overlapping cohorts throughout summer, however, results in an extended emergence period and complex size structure.     

Vitamin D Status and Its Seasonal Variability in Healthy Young Adults in an Asian Indian Urban Population

ObjectiveTo assess the vitamin D status and its seasonal variability in healthy young adults in Chandigarh, a city in northern India.MethodsThe history was elicited and examination was performed pertaining to metabolic bone disease in 329 young adults (18 to 25 years of age) at the end of summer and 237 subjects from the same cohort at the end of winter. The calcium profile, 25-hydroxyvitamin D [25(OH)D], and intact parathyroid hormone were measured during both the seasons.ResultsAmong the young adults in this study cohort, 25(OH)D sufficiency (≥ 30 ng/mL) was found in 72.5% in summer and in 50.7% in winter. A significantly higher number of men were 25(OH)D sufficient in comparison with women in summer (P = .001). The mean (standard deviation) serum 25(OH)D levels were significantly higher at the end of summer—52.9 (33.7) ng/mL—in comparison with that at the end of winter—31.8 (21.1) ng/mL; P < .001. The intact parathyroid hormone levels were significantly lower in the 25(OH)D-sufficient group (P = .001) and began to increase at 25(OH)D levels below 25 ng/mL. The serum 25(OH)D levels correlated positively with the duration of exposure to sunlight during summer (r = 0.111; P = .05) and also the calcium intake during summer (r = 0.129; P = .03).ConclusionVitamin D sufficiency may be a reality with a combination of young skin, optimal and effective exposure to sunlight, and adequate calcium intake. (Endocr Pract. 2011;17:185-191)     

Invasive alien species under attack: natural enemies of Harmonia axyridis in the Netherlands

The aphid predator Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is an invasive alien species in Europe and North America with negative effects on non-target species (including a decline of native ladybird populations), as well as fruit production, and human health. It is, therefore, important to find out which natural enemies could be used to reduce their numbers. Knowledge of H. axyridis’ natural enemies is summarised and data collected from the Netherlands over the past ten years are presented. Beetles were sampled from winter aggregations and from spring through to autumn with illuminated screens at night. Natural enemies were not found in samples of H. axyridis from 2003–2007. From 2008 onward H. axyridis adults were infested by: Hesperomyces virescens Thaxt. fungi (summer and winter), Parasitylenchus bifurcatus Poinar and Steenberg nematodes (winter), Coccipolipus hippodamiae (McDaniel and Morrill) mites (winter), and Dinocampus coccinellae (Schrank) parasitoids (summer and winter). Our results indicate that these natural enemies are starting to use H. axyridis as a host, but are as yet not sufficiently abundant to control the population.