LIFE CYCLE OF THANASIMUS FORMZCARZUS (COLEOPTERA: CLERIDAE) IN SOUTHERN NORWAY*

Abstract Observations on the life cycle and bionomics of Thanasimus formicarius (L.) were made under natural conditions and in the laboratory. The studies provide information on mass flight, development periods of eggs, larvae, pupae and prepupae, and adult maturation stage based on monthly field investigations. The results of the research suggest that the overall life cycle of T. formicarius covers approximately two years and four months in southern Norway. During the first year of the life cycle, the clerid larvae overwinter in the pupal chambers at the bases of attacked spruce trees; adults emerge and mature sexually in the second year; and the mature adults overwinter inside the bark crevices of trunk and oviposit in the spring of the third year. The studies also expose that the clerid occurence coincides well with the bark beetle attacks occurring in spring and autumn in northern Norway.     

挪威南部地区蚁形郭公虫(Thanasimus formicarius)生活史(英文)

在自然和实验条件下,对蚁形郭公虫（Thanasimusformiyarius（L）生活史及有关生物学进行了研究。基于逐月野外调查结果,报道了蚁形郭公虫群飞期,以及该虫的卵、幼虫、蛹、预蛹和成虫等各发育阶段的历期。研究结果表明,蚁形郭公虫在挪威南部地区的生活史长达2年零4个月。在生活史的第1年里,该幼虫在受害的挪威云杉树基的蛹穴内越冬;成虫于次年羽化并逐步发育成熟。这些成虫将在树干裂缝中越冬,然后于第3年春产卵繁殖。研究揭示,在挪威南部地区,蚁形郭公虫的发生期与多种小蠹虫的危害期吻合。     

Phytoplankton as a stimulus for spawning in three marine invertebrates

A distinct annual reproductive cycle with spring spawning was observed in Strongylocentrotus droebachiensis Müller, Tonicella lineata Wood and Tonicella insignis Reeve. This study gives evidence that the cue for spawning in these species is the spring phytoplankton bloom. In 1973 spawning occurred abruptly in early April at the time of the spring phytoplankton outburst, but in 1974 spawning was less abrupt corresponding to the slow development of the phytoplankton bloom in that year. Animals were collected prior to spawning and maintained in the laboratory under various temperature and light regimes: at 5 ° and 14 °C in darkness, and at 5 ° and 14 °C in light conditions similar to those in the field. These animals did not spawn when spawning occurred in the field, but animals returned to the field from the laboratory did spawn. In the laboratory a large proportion of animals spawned when they were exposed to phytoplankton collected with a 50μm mesh net. The results suggest that some substance bound to or released by phytoplankton stimulates spawning. For species with planktotrophic larvae the synchronization of spawning with the phytoplankton bloom increases the probability of favourable food and temperature conditions for the development of the larvae and juveniles.     

Seasonal growth,density, reproductive phenology and agar quality of Gracilaria sordida (Gracilariales,Rhodophyta) at Mokomoko Inlet,New Zealand

Growth of mesh-enclosed Gracilaria sordida plants was determined monthly for one year at the Mokomoko mudflat, South Island, New Zealand. Growth of plants with permanent water cover was correlated with water temperature and was most rapid during summer months. Plants exposed at low tide grew only during early spring and late autumn. Bimonthly quadrat sampling of a mudflat population showed that all stages of the life cycle were present throughout the year. Spermatangial plant length and biomass were greatest in early spring; cystocarpic and tetrasporic plants were greatest in midsummer. Sterile plants were most numerous in the late summer. Agar yield showed little variation either seasonally or between different stages of the life cycle. Agar gel strengths for all life cycle stages were greatest at the time of peak plant size and abundance. Gels from spermatangial plants generally were weaker than those from other stages.     

An indoor mesocosm system to study the effect of climate change on the late winter and spring succession of Baltic Sea phyto- and zooplankton

An indoor mesocosm system was set up to study the response of phytoplankton and zooplankton spring succession to winter and spring warming of sea surface temperatures. The experimental temperature regimes consisted of the decadal average of the Kiel Bight, Baltic Sea, and three elevated regimes with 2°C, 4°C, and 6°C temperature difference from that at baseline. While the peak of the phytoplankton spring bloom was accelerated only weakly by increasing temperatures (1.4 days per degree Celsius), the subsequent biomass minimum of phytoplankton was accelerated more strongly (4.25 days per degree Celsius). Phytoplankton size structure showed a pronounced response to warming, with large phytoplankton being more dominant in the cooler mesocosms. The first seasonal ciliate peak was accelerated by 2.1 days per degree Celsius and the second one by 2.0 days per degree Celsius. The over-wintering copepod populations declined faster in the warmer mesocosm, and the appearance of nauplii was strongly accelerated by temperature (9.2 days per degree Celsius). The strong difference between the acceleration of the phytoplankton peak and the acceleration of the nauplii could be one of the “Achilles heels” of pelagic systems subject to climate change, because nauplii are the most starvation-sensitive life cycle stage of copepods and the most important food item of first-feeding fish larvae. Priority programme of the German Research Foundation—contribution 3.     

Voltinism and diapause in the spruce web-spinning sawflyCephalcia arvensis

Cephalcia arvensis Panzer (Hym., Pamphiliidae) spends most of the life cycle as a prepupa inside an earth-walled chamber in the soil of spruce (Picea abies Karst.) forests. There are two types of prepupae in diapause in the soil, the eonymph and the pronymph. Prolonged diapause as an eonymph occurs in prepupae just after soil penetration at temperatures below 12°C. Eonymphs change into pronymphs during the following summer and the life cycle lasts for two years. Mature larvae that enter the soil at temperatures above 12°C change immediately into pronymphs and these individuals will emerge during the next spring. Other factors such as photoperiod do not appear to be correlated with prolonged diapause. The depth reached by the mature larvae in the soil is proportional to their size and inversely proportional to the soil temperature. Consequently, voltinism depends on both the conditions affecting development of the larvae in the crowns and the temperature at different soil depths.     

Influence of low temperature on pupation induction in Costelytra zealandica (Coleoptera: Scarabaeidae)

Costelytra zealandica (White) lives within the soil throughout its life cycle, except for brief, crepuscular excursions to the surface by the adults to mate and feed. Larvae collected more than 18 weeks before 50% field pupation did not pupate unless they were artificially chilled. Such chilling had no significant effect on the percentage pupation of larvae collected after this time; it is assumed that these larvae had received sufficient chilling from their environment to induce pupation. Larger larvae were more likely to pupate than smaller larvae during the period 13–7 weeks before 50% field pupation. It is postulated that larvae remain quiescent until the soil temperature increases in the spring, and pupate only then. Such a process would explain how the adults of a population emerge at about the same time.     

Seasonal variations in abundance, development and vertical distribution of Calanus finmarchicus, C. hyperboreus and C. glacialis in the East Icelandic Current

The seasonal variation in abundance and development of Calanusfinmarchicus, Calanus hyperboreus and Calanus glacialis in relationto hydrography and chlorophyll (Chl) a was studied in the Arcticwaters of the East Icelandic Current to the north-east of Icelandfrom March 1995 to February 1996. The sampling was carried outat approximately monthly intervals on a transect of five stationsextending from 67°00'N, 13°55'W to 68°00'N, 12°40'W.In April, May and June, vertical distribution was also investigated.Spring warming of the surface waters began in May, with maximumtemperatures recorded in August (~5°C, mean for uppermost50 m). Below 75 m, temperature remained at <0°C throughoutthe year. The spring bloom of phytoplankton started in earlyMay and the highest Chl a concentrations were measured duringlate May to early June (~1 mg Chl a m^-3). Calanus finmarchicusdominated in terms of numbers (~75%), while C. hyperboreus dominatedbiomass (~76%). Calanus glacialis occurred only in low numbers(~1%) and was only a small portion of biomass (~0.7%). The abundanceof all species was low during the winter and peaked once duringsummer: C. finmarchicus in July (~16 000 ind. m^-2) and C. glacialisand C. hyperboreus in June (~370 and ~7700 ind. m^-2, respectively).The biomass of C. finmarchicus had two maxima, in April (~1.9g m^-2) and July (~1.5 g m^-2), while C. hyperboreus peaked inJune (~12.3 g m^-2). Calanus finmarchicus was estimated to spawnin early May at about the start of the spring bloom, while C.hyperboreus spawned prior to the spring bloom, in late Februaryto early March. On the basis of copepod stage distribution,C. finmarchicus was considered to have a 1-year life cycle andC. hyperboreus at least a 2-year life cycle.     

Enhancing conservation of the Tasmanian glow-worm, <Emphasis Type="Italic">Arachnocampa tasmaniensis</Emphasis> Ferguson (Diptera: Keroplatidae) by monitoring seasonal changes in light displays and life stages

The light displays by the Tasmanian Glow-worm, Arachnocampa tasmaniensis Ferguson (Diptera: Keroplatidae), in Exit and Mystery Creek caves in southeast Tasmania, Australia have been recognised as a world heritage value under the criterion relating to outstanding natural phenomena. To conserve and manage these populations, particularly in response to potential tourism development, a better understanding of their ecology is needed. Aspects of the life cycle of A. tasmaniensis were monitored over 24 months. A strong seasonal pattern was found, with pupae and adults most common in spring and summer. The increase in numbers of pupae and adults coincided with an increase in the number of prey caught in silk threads produced by the larvae. Larvae were present throughout the year but the number glowing varied both seasonally and spatially. In Mystery Creek Cave, the number of larvae glowing was generally highest during summer and autumn and lowest in winter and early spring. In Exit Cave, there was no consistent seasonal pattern in the number of larvae glowing among sites, and overall there was less variation between monthly counts than at Mystery Creek Cave. This difference in seasonal patterns between the two caves may be due to a difference in climate, with Mystery Creek Cave possibly experiencing a greater drying out of the cave air in winter than Exit Cave.     

Notes on the life-history of the rabbit flea Caenopsylla laptevi ibera Beaucournu & Marquez, 1987 (Siphonaptera: Ceratophyllidae) in eastern Spain

The rabbit flea Caenopsylla laptevi ibera occurs in arid environments of central and eastern Spain. Although the fleas breed during the coolest, most humid part of the year, the larvae survive and grow in sand at only 50-60% relative humidity. At 22 degrees C and 80% relative humidity eggs hatch in six days and the cocoon stage is reached 10-11 days after hatching. Female fleas emerge from pupation at about 17 days after cocoon spinning; males emerge a little later at a mean of 20 days. Adult fleas are mainly found on the host Oryctolagus cuniculus. Measurements of burrow microclimate confirmed that in south-eastern Spain burrow humidity was adequate for the development of C. I. ibera larvae over most of the year. However, breeding may be restricted for at least part of the year, as the larvae of C. I. ibera apparently cannot complete development at 25 degrees C or above. In the laboratory, fleas can enter a prolonged quiescent period while in the cocoon. This is possibly a facultative, pre-pupal diapause and the likely mechanism that accounts for the disappearance of adult fleas from the field by spring and their reappearance each autumn.     

Growth and survival rate of the larvae ofHynobius nebulosus Tokyoensis Tago (Amphibia,Hynobiidae)

Growth and population density of the larvae, Hynobius nebulosus tokyoensisTago , were estimated in a small pond within the study site settled in Habu village of Hinodemachi, a suburb of Tokyo City, during the period from 1975 to 1980. The mortality factors which influenced the survival rate of larvae were also evaluated from the ecological point of view. Laboratory experiments on the growth of larvae and predation by newts were conducted in pararell with the field survey. The results showed that growth rate of larvae under the natural condition was very slow, as compared with that under the laboratory condition with sufficient food supply, and mean body size at metamorphosis was negatively correlated with the density at that time. This suggested that food resources were in short supply in the pond, and there occurred a severe intraspecific competition for food among larvae. The mortality rate of larvae was so high, 80–99% in each year, and the density of larvae survived until metamorphosis varied so greatly from year to year that the larval stage was the most important stage throughout the life cycle to the maintenance of a population for this salamander. The most important factors which contributed to this high mortality were the predation by the newt, Triturus pyrrhogaster pyrrhogasterBoie , and cannibalism. From the laboratory experiment, it was found that predators could attack only small larvae successfully, and successful attack rate decreased sharply as larvae grew larger. This relationship resulted in the characteristic L-shaped pattern of survivorship curve of larvae; that is, heavy mortality just after hatching period.     

The phytoplankton community of a eutrophic reservoir

The dynamics of the phytoplankton community of a eutrophic reservoir are described for a two year period. Fifty-eight species were recorded, 25 of them common. Bacillariophyta dominated during the winter and early spring and Chlorophyta during late spring, to be replaced by a bloom of Cyanophyta. The mean and peak biomass of phytoplankton was 8.6 mg 1^–1 and 40.8 mg 1^–1 in 1981, and 8.3 mg 1^–1 and 37.6 mg 1^–1 in 1982. Temperature accounted for 67.3% and pH for 8% of the variation in total phytoplankton biomass over the two year period, using a multiple regression technique.Both horizontal and vertical patchiness, measured as an index of mean crowding, were recorded in the reservoir. Horizontal aggregations were associated with spring blooms of Chlorophyta and summer blooms of Cyanophyta, while vertical aggregations were most marked during the summer bloom of Cyanophyta. Concentrations of phytoplankton were influenced by wind, the prevailing southwesterly wind accumulating algae in the northeasterly arm of the reservoir during much of the year.     

Abundance and distribution of early life stages of krill around Iceland during spring

Abundance, distribution and development of early life stages of krill (eggs, nauplii, calyptopes and furciliae) around Iceland were studied during the latter half of May 2013. Multivariate analyses were used to examine the relationships between water mass characteristics and phytoplankton spring bloom dynamics and distribution of krill. The results show that krill eggs, nauplii and calyptopes were most abundant over the shelf edges off the southwest and east coasts, while furciliae were most abundant on the shelf off the southwest coast. Meganyctiphanes norvegica and Thysanoessa longicaudata larvae were found mainly in the southwest, while T. inermis larvae were found in highest numbers on the east coast. Redundancy analysis showed that phytoplankton biomass, temperature and bottom depth explained 41% of the distribution pattern of early ontogenetic krill stages. In areas where krill eggs and larvae were most abundant (off the southwest coast), the phytoplankton spring bloom was in an advanced state, and the phytoplankton biomass and temperature were particularly high.     

Life History of a Population of Protonemura intricata (Ris, 1902) (Insecta,Plecoptera) in a Constant Temperature Stream in Central Europe

The nymphal biology (life cycle, secondary production and feeding) of a population of Protonemura intricata was studied in a calcareous stream with almost constant temperature (7–8 °C) through the year at Prosiek valley (Chočské Vrchy Mts., West Carpathians, Slovakia). The results were compared with those previously known for this species in other areas. According to our data, the species has a complicated life cycle consisting of two cohorts with different duration (probably a cohort splitting). This life cycle seems to be uncommon among the Plecoptera, which usually has simple univoltine or semivoltine life cycles, and could be probably attributed to the constant temperature regime similar to that of tropical environments. One factor, the photoperiod length, was positively correlated with monthly growth rates. The nymphal growth varied throughout the year, but the highest growth was in late spring and summer, and the lowest was in winter. The annual secondary production was very high (909.4 mg · m^–2) despite not being the most frequent taxon in the stream. The highest monthly production values were observed in the autumnal‐winter period (November–December) due to massive hatching of nymphs. The lowest production values were observed in late summer and early autumn. Analyses of gut contents showed that this species behaves mainly as gatherer‐collector, but also as shredder and, occasionally, as scraper. Changes in the gut content composition were detected in relation to the size. Comparing our results with those of the literature, it can be inferred that different populations of P. intricata can show notable differences in their life history when inhabiting places with different thermal conditions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spatial and seasonal changes of dissolved and particulate organic C in the North Sea

Sampling of the central region of the North Sea was carried out to study the spatial and seasonal changes of dissolved and particulate organic C (DOC and POC, respectively). The surface waters were collected during four cruises over a year (Autumn 2004–Summer 2005). DOC and POC concentrations were measured using high temperature catalytic oxidation methods. The surface water concentrations of DOC and POC were spatially and temporally variable. There were significantly different concentrations of DOC and POC between the inshore and offshore waters in winter and summer only, with no clear trend in autumn and spring. Highest mean concentrations of DOC were measured in spring with lower and similar mean concentrations for other seasons. POC showed a clear seasonal cycle throughout the year with highest surface mean concentrations found in autumn and spring, but lowest in winter and summer. The DOC distributions during autumn and spring were strongly correlated with chlorophyll suggesting extracellular release from phytoplankton was an important DOC source during these two seasons. The lower concentrations of DOC in summer were probably due to the heterotrophic uptake of labile DOC. The seasonal changes in the C:N molar ratios of surface DOM (dissolved organic matter) resulted in higher mean C:N molar ratios in spring and lower ratios in winter. These high ratios may indicate nutrient limitation of heterotrophic uptake immediately after the spring bloom. There is limited data available for DOC cycling in these productive shelf seas and these results show that DOC is a major component of the C cycle with partial decoupling of the DOC and DON cycling in the central North Sea during the spring bloom. Handling editor: Luigi Naselli-Flores     

Production and Ecology of Benthic Chironomid Larvae (Diptera) in Lake Hayes,New Zealand,a Warm-monomictic Eutrophic Lake

The distribution and abundance of larval chironomids in Lake Hayes were studied from December 1973 to March 1975. The mean annual production of the two dominant species, Chironomus zealandicus and Chironomus sp. a, was 29.2 g m⁻² dry weight which is approximately 4.3 % of the average annual phytoplankton production in the lake. A high annual P/B ratio of 18.5 is consistent with the multivoltine life cycle of C. zealandicus. Larval chironomid production in the second summer when Anabaena blooms were absent was only one quarter of that in the first summer and is consistent with the hypothesis that the production of benthic chironomids in Lake Hayes is closely linked to that of the phytoplankton through the sedimentation of autochthonous organic matter.     

Water temperature behaviour in the River Danube during the twentieth century

Monthly mean water temperatures in the River Danube at Linz, Austria during the period 1901–1990 have been investigated in relation to equivalent information on air temperature and river discharge. Statistical analysis revealed a significant increase in monthly mean water temperatures of 0.8 °C and showed strongest rises in mean values for autumn and early winter months. No statistically significant trends were evident for air temperature or river discharge, and rising water temperatures are likely to reflect increasing human modification of the river system. A strong overall correlation between monthly mean water and air temperatures at Linz was made up of a series of more scattered and less steep water/air temperature relationships for individual months, while the influence of snowmelt runoff depressed average water temperatures in the spring and early summer period by 1.5 °C. Multiple regression relationships developed for individual months from data on air temperature, river discharge and time trend during the study period were able to predict monthly mean water temperatures in 1991 and 1992 with a root mean square error of 0.5 °C. These regression equations, when combined with scenarios of future changes in air temperature and river flow as a consequence of global warming, suggest that only modest rises in monthly mean water temperature will be experienced in the River Danube by the end of the present century, but that increases of > 1 °C for all months, and > 2 °C for the autumn period of low flows, can be anticipated by the year 2030.     

Life cycle and population dynamic of Armadillidium pelagicum Arcangeli, 1955 (Isopoda, Oniscidea) at Aouina

Armadillidium pelagicum Arcangeli, 1955 is a terrestrial isopod endemic to the circum-Sicilian islands and the North of Tunisia. The life cycle and the population structure of this species were studied on a natural population at Aouina, in the surroundings of Tunis, over 16 months from, January 2000 to April 2001, by monthly or semi-monthly samplings. The ovigerous females were present from March/April to the end of August and absent from September to February/March. These observations indicate that A. pelagicum at Aouina has a seasonal reproduction, followed by a sexual rest. The recruitment period is spread from April/May to mid-September. The fecundity, estimated by the number of eggs in the marsupium of ovigerous females, exhibited a great variability, which is related to the weight of these females. The sex ratio underwent fluctuations throughout the sampling period. It was female-biased in most samplings. Mass frequency distribution was analysed and nine cohorts were identified during the sampling period. The field growth rates are high in the first life phase, decrease during winter and increase during spring. The characteristics of the life cycle of A. pelagicum at Aouina may be summarized as follows: (i) Semi-annual species, since females appear to produce up to five broods per year, (ii) iteroparous females, since females seem to reproduce twice or more in life; (iii) bivoltine life cycle, since the population produces two generations per year; (iv) variability of cohorts' life span.     

Temperature is the key factor explaining interannual variability of Daphnia development in spring: a modelling study

Plankton succession during spring/early summer in temperate lakes is characterised by a highly predictable pattern: a phytoplankton bloom is grazed down by zooplankton (Daphnia) inducing a clear-water phase. This sequence of events is commonly understood as a cycle of consumer-resource dynamics, i.e. zooplankton growth is driven by food availability. Here we suggest, using a modelling study based on a size-structured Daphnia population model, that temperature and not food is the dominant factor driving interannual variability of Daphnia population dynamics during spring. Simply forcing this model with a seasonal temperature regime typical for temperate lakes is sufficient for generating the distinctive seasonal trajectory of Daphnia abundances observed in meso-eutrophic temperate lakes. According to a scenario analysis, a forward shift of the vernal temperature increase by 60 days will advance the timing of the Daphnia maximum on average by 54 days, while a forward shift in the start of the spring bloom by 60 days will advance the Daphnia maximum only by less than a third (17 days). Hence, the timing of temperature increase was more important for the timing of Daphnia development than the timing of the onset of algal growth. The effect of temperature is also large compared to the effect of applying different Daphnia mortality rates (0.055 or 0.1 day(-1), 38 days), an almost tenfold variation in phytoplankton carrying capacity (25 days) and a tenfold variation in Daphnia overwintering abundance (3 days). However, the standing stock of Daphnia at its peak was almost exclusively controlled by the phytoplankton carrying capacity of the habitat and seems to be essentially independent of temperature. Hence, whereas food availability determines the standing stock of Daphnia at its spring maximum, temperature appears to be the most important factor driving the timing of the Daphnia maximum and the clear-water phase in spring.     

The effect of nutrient addition on the phytoplankton community of an oligotrophic lake

This investigation was performed during a 5-yr period (1974–1978) in the oligotrophic Lake Langvatn, Central Norway. In 1975 and 1976 the lake was enriched with a commercial fertilizer, In 1975 increase in phytoplankton biomass was first recorded more than three weeks after the fertilization started, despite a near fivefold increase in the primary production after fertilizer application. The mean seasonal biomass increased from c. 3500 mg wet weight m⁻² in 1974 to 4400 mg in 1975. In 1976 the biomass increased to near 9600 mg ⁻² and the seasonal primary production to 49.0 g C m⁻² (22.2 g C in 1975), despite a reduction in the nutrients added. Chrysophytes constituted the largest share of the seasonal algal biomass in all years, but in fertilization periods cryptophytes dominated in 1975 and diatoms, chlorophytes and cryptophytes in 1976. The highest biomass turnover rate was recorded during a period of cryptophyte dominance. The different biomass and production development in the fertilization years may be explained by a change in the consumer level.