Spatial and temporal variation in the diet of a predaceous stonefly (Plecoptera: Perlodidae)

SUMMARY. 1. Spatial and temporal variation in the diet of the univoltine predatory stonefly, Kogotus nonus , was studied over 3 years in a small Alberta stream to determine whether the relative abundance of prey types in the diet of Kogotus reflected relative prey densities in the stream and whether the variation in absolute feeding rate was related to either prey or predator density.
2. The seasonal shift from sole utilization of Orthocladiinae to inclusion of Baetis in the diet could not be attributed to seasonal changes in prey density, but was probably related to predator size and ability to handle very active prey. Most of the spatial variation in diet could be related to differences in background prey densities, but very high densities of Baetis caused the predator to specialize on this prey.
3. Feeding rate on Baetis . as assessed by per capita gut contents, showed a seasonal shift from a positive correlation with Baetis density in winter to a negative relationship with predator density in spring. This suggested that feeding by small Kogotus is a function of prey density. while feeding by later instars is influenced by between predator interactions such as interference.     

The Ecology of Baetis muticus and Baetis rhodani (Insecta,Ephemeroptera), with Special Emphasis on Acid Water Backgrounds

The two mayflies (Insecta, Ephemeroptera) Baetis muticus and Baetis rhodani are absent from the acid water (pH 4.8–5.2) streams of the Upper Duddon drainage basin. Field observations and laboratory experiments were used in an attempt to explain this absence. Baetis muticus could not tolerate acid water; in addition it was deduced that available foods in the Upper Duddon streams would not sustain it there, even if the water could be tolerated. Baetis muticus feeds by browsing on decaying, allochthonous leaves, implying an input of micro-organisms, especially fungi, to the diet. Well-decayed, allochthonous leaves do not occur in the acid water, Upper Duddon streams. Baetis rhodani proved to be acid water tolerant, but only if the background waters had high ionic loadings. Since Upper Duddon waters have only low ionic loadings, Baetis rhodani is apparently excluded from them on this account. The evidence was that if the Upper Duddon waters were chemically suitable, then Baetis rhodani could survive in them, because a suitable food, the alga Hormidium subtile is present.     

Biometric studies of some stoneflies and a mayfly (Plecoptera and Ephemeroptera)

Aspects of the nymphal/adult developmental change were investigated in biometric studies of several species of Plecoptera: Nemouridae near Schlitz, Hesse, Germany. Preliminary information on the mayfly, Baetis vernus Curtis, is also provided. Nemourid nymphs pass through 3 wing bearing stages before reaching adulthood. Instars can be identified by their characteristic shapes, as expressed by the wing length/head width (WL/HW) ratio. Size does not allow instar discrimination, mainly due to sexual size differences. HW is ca 10% larger in last instar female than in male nemourid nymphs; exuviae shed at the moult to adult represent about 14% of nymphal ash free dry weight (AFDW). Biomass lost with exuviae during the many larval moults should be accounted for in estimates of production. Freshly emerged nemourid females are about 6% larger and 30% heavier than males. The HW/AFDW relationship is the same in both sexes. Through terrestrial feeding during adult life, males double their weight on average. Mature females are up to three times heavier than freshly emerged ones. They invest about 30% of their final AFDW in reproduction.Shape of last instar nymphal Baetis was expressed as the ratio wing length/mesonotum length. It is size-dependent, a characteristic, instar-specific shape may not occur in this mayfly. Nymphal and subimaginal exuviae together represent about 14% of last instar nymphal dry weight. Females of Baetis are about 55% heavier than males. Unlike in Plecoptera, the size/weight (ML/AFDW) relationship differs between sexes.     

Hunting behaviour of the perlid stonefly nymph Dinocras cephalotes (Plecoptera) under different light conditions

The hunting behaviour of Dinocras cephalotes nymphs was studied during two different light intensities, darkness and twilight (0·1 cd m^?2). Nymphs of the mayfly Baetis rhodani were provided as food. In darkness the predator moved slowly without stopping, encountering the prey with the antennae and the hair fringes on the tibiae. Little time was spent in a shelter. There was little tendency to pursue the prey after a missed first attack and the pursuing distance was short. In twilight the speed of the predator was higher and the movement was interrupted by long periods of rest. The number of successful attacks was higher and more attacks were initiated when the predator was immobile. Time of activity outside the shelter was short. There was a greater tendency to pursue the prey after a missed first attack and the pursuing distance was longer compared with that in darkness. There are two main advantages of changing strategy from ‘searcher’ in darkness to ‘ambusher’ in the light: to avoid being detected by predators hunting by vision and to avoid being detected by potential prey species relying on visual cues for the detection of predators. The optical design of the eye revealed that only those parts of the eye directed upwards and backwards were optimized to the light conditions at which the predator preferred to be active, suggesting that the main function of these areas is to detect predators, though an additional gain in detecting prey could also be seen.     

Life history and larval feeding of some species of Ephemeroptera and Plecoptera (Insecta) in the Sierra Nevada (Southern Iberian Peninsula)

We monitored two high mountain streams from the Sierra Nevada (Southern Spain) monthly throughout an annual cycle, measuring and analyzing physical and chemical parameters. Temperature was hourly registered. We studied life cycles and larval feeding of four mayfly species [Serratella ignita (Poda, 1761), Serratella spinosa nevadensis (Alba-Tercedor, 1981), Alainites muticus (Linnaeus, 1758), and Baetis alpinus Pictet, 1843] and two stonefly species [Amphinemura triangularis (Ris, 1902) and Capnioneura mitis Despax, 1932]. Some species changed their strategies (growth rate, life cycle duration, and/or voltinism) in accordance with different conditions (depending on the altitude and temperature). The gut content data showed that species fed mainly on detritus (as collector-gatherers or as shredders), except B. alpinus that behaved as a scraper in one of the streams. Differences in the larval diet of the same species in different streams, and even through its life, support the idea of not using general models to extrapolate the function of a species from a higher taxonomical level. Handling editor: D. Dudgeon     

The status of the Mayfly species described by O. A. Tshernova from the Amur basin in the genus Baetis leach (Ephemeroptera, Baetidae)

Type specimens of Baetis obtusiceps, B. obscuriventris, B. diversicolor and B. mongolicus have been reexamined; lectotypes of B. obtusiceps, B. obscuriventris and B. mongolicus are designated. The following new synonymy is suggested: Baetis vernus Curtis, 1834 = B. obtusiceps Tshernova, 1952, syn. n.; Baetis fuscatus (Linnaeus, 1761) = B. diversicolor Tshernova, 1952, syn. n.; Labiobaetis tricolor (Tshernova, 1928) = Baetis obscuriventris Tshernova, 1952; = B. mongolicus Tshernova, 1952, syn. n.     

Size-dependent flight initiation by a lotic mayfly in response to a predatory fish

1. Laboratory experiments were performed to determine whether flight initiation by lotic mayfly larvae of Baetis tricaudatus exposed to the longnose dace ( Rhinichthys cataractae ) is affected by an individual's size and its physiological state.
2. We used a three factorial ANOVA design to test whether flight initiation distances (FIDs) were affected by Baetis size (small, large), starvation level (low, high), and the length of a predator-free foraging period (short, long).
3. FIDs were significantly affected by the interaction between Baetis size and starvation level, and the main level effects of starvation and Baetis size. FIDs of small larvae were unaffected by starvation level and the length of the predator-free feeding period, whereas starvation reduced FIDs of large larvae 2-fold.
4. Subsequent experiments showed that size-dependent differences in FIDs could not be attributed to size-specific differences in the economics of rates of food intake or gut evacuation. For both small and large larvae, food intake rates declined with increasing time spent foraging and both small and large larvae consumed the majority (70–75%) of food within the first 3 h of the 12-h feeding period. Similarly, gut evacuation declined with increasing starvation time and rates of evacuation did not differ between small and large larvae. These data suggest that size-dependent differences in flight initiation by Baetis larvae do not involve the energetics of food intake or processing.     

城市食物-能源-水关联关系:概念框架与研究展望

食物、能源和水(Food, Energy and Water, FEW)是人类生存与发展不可或缺的基础性资源,且三者之间存在密切的关联关系(Nexus),即其中任何一项资源的生产与供给均依赖于另外两项资源。FEW关联关系作为应对全球人口增长、资源短缺和生态环境恶化等问题的系统性管理理念,已引起国际学术界与实践管理领域的广泛关注。然而,目前对FEW关联关系仍然缺乏统一和清晰的界定,现有研究大多是基于不同角度理解与量化"关联关系"。城市作为全球资源消费的主阵地,其FEW关联关系更为复杂,亟待建立针对城市生态系统的概念框架。对FEW关联关系的发展历程、概念表述以及研究方法等方面进行全面回顾和系统分析。在此基础上,从"资源依存"、"资源供给"和"系统集成"等3个视角构建了城市FEW关联关系的概念框架,并进一步阐述FEW关联关系未来研究的重点方向——"系统性表征"、"时空演化"与"协同管理",为城市优化资源配置,实现集成管理提供一种新思路和定量化的参考依据。     

Size-dependent flight initiation by a lotic mayfly in response to a predatory fish

1. Laboratory experiments were performed to determine whether flight initiation by lotic mayfly larvae of Baetis tricaudatus exposed to the longnose dace ( Rhinichthys cataractae ) is affected by an individual's size and its physiological state.
2. We used a three factorial ANOVA design to test whether flight initiation distances (FIDs) were affected by Baetis size (small, large), starvation level (low, high), and the length of a predator-free foraging period (short, long).
3. FIDs were significantly affected by the interaction between Baetis size and starvation level, and the main level effects of starvation and Baetis size. FIDs of small larvae were unaffected by starvation level and the length of the predator-free feeding period, whereas starvation reduced FIDs of large larvae 2-fold.
4. Subsequent experiments showed that size-dependent differences in FIDs could not be attributed to size-specific differences in the economics of rates of food intake or gut evacuation. For both small and large larvae, food intake rates declined with increasing time spent foraging and both small and large larvae consumed the majority (70–75%) of food within the first 3 h of the 12-h feeding period. Similarly, gut evacuation declined with increasing starvation time and rates of evacuation did not differ between small and large larvae. These data suggest that size-dependent differences in flight initiation by Baetis larvae do not involve the energetics of food intake or processing.     

Emergent body size of mayfly survivors

1. Employing field-deployed mesocosms, we examined the effects of 12-h pulse and 20-day press (continuous) exposures of the common agricultural insecticide, imidacloprid, on nymph abundance, emergence patterns and adult body size of Epeorus spp. (Heptageniidae) and Baetis spp. (Baetidae).
2. In press exposures, reduced nymph density was driven by reduced survivorship; in pulse exposures, reduced nymph density may reflect increased emergence because of stress.
3. Once exposed to imidacloprid, Epeorus and Baetis mayflies developed less and emerged smaller than their control counterparts. Concentrations as low as 0.1  μ g L⁻¹ (12-h pulse) reduced head length in Baetis and thorax length in Epeorus .
4. In all of the Baetis and Epeorus examined, effects were only found in males. Male survivorship and body size can affect population dynamics. Sublethal doses of this widely applied agricultural insecticide have the potential to reduce reproductive success of mayfly populations.     

Life histories, microdistribution and drift of two mayfly (Ephemeroptera) species in the Pembina River, Alberta, Canada

Ephemerella inermis Eaton is a univoltine species that emerges in July. Eggs hatch in August and larvae grow rapidly in autumn and spring, but not during winter. Baetis tricaudatus Dodds produces three cohorts per year. Emergence periods occur in early June, July and early September. Only one cohort overwinters as larvae.
Microdistribution of both species is controlled largely by the discharge pattern of the river. During 1978, a year of frequent floods, animals were equally distributed among slow and fast water portions of the river. Nocturnal drift densities of both species were much greater in slow than in fast water areas. During 1979, a year of relatively stable flow, benthic larval densities were significantly greater in fast water than in slow water.
Early instar E. inermis larvae are most abundant in nearshore areas, but move to deeper water in late autumn. Baetis tricaudatus larvae are seldom numerous in near-shore areas.
Densities of both species were positively associated with concentrations of detritus and of other invertebrates, but only when relationships were considered in areas of similar current velocity independently of season.     

MtDNA COI barcodes reveal cryptic diversity in the Baetis vernus group (Ephemeroptera, Baetidae)

Partial mitochondrial COI sequences (barcoding fragment) were explored for the understanding of the species boundaries of Baetis vernus group taxa (Ephemeroptera, Baetidae) in northern Europe. We sampled all species of this group occurring in Finland, but focused on taxa for which morphological and taxonomical confusion have been most apparent. The sequence matrix comprised 627 nucleotides for 96 specimens, and was analysed using parsimony. Results provided strong evidence that Baetis macani Kimmins and B. vernus Curtis comprise morphologically cryptic but molecularly distinct taxa, as intraspecific uncorrected divergences within haplogroups ranged between 0.3% and 1.4% and interspecific divergences were from 13.1% to 16.5%. These interesting findings prompt for further taxonomic studies of B. vernus taxa using more extensive specimen sampling from the known distributional areas in the Palaearctic/Holarctic region for better understanding of haplotype distributions. We stress the importance of integration of morphological and molecular data, and the necessity to employ additional nuclear DNA sequence data.     

The effects of prey profitability and habitat complexity on the foraging success and growth of stonefly (Plecoptera) nymphs

• 1 The feeding behaviour of nymphs of the perlid stonefly Dinocras cephalotes when presented with two different mayfly prey types on different substrates was examined in the laboratory.
• 2 Most of the evidence suggested that Dinocras cephalotes did not choose between Baetis rhodani and Rhithrogena semicolomta as, under identical circumstances: (i) the survival of both prey types was the same; (ii) the predator's overall searching behaviour was similar in the presence of either mayfly, although B. rhodani was pursued more, especially on complex substrates; (iii) the number of attacks on both prey types was the same; and (iv) the intake of dry weight prey biomass over 24 h remained the same, irrespective of prey species.
• 3 The predation efficiency (no. of prey captured/no, of encounters) of D. cephalotes decreased with increasing substrate complexity—but only with R. semicolorata as prey, and also when more than one stonefly was present—but only when B. rhodani was the prey. Predator efficiency was greater at low densities of R. semicolorata but highest at a medium density of B. rhodani.
• 4 Increase in the body weight of D. cephalotes was greater when nymphs were fed a monospecific diet of R. semicolorata compared with one of B. rhodani. This was despite the findings that: (i) nymphs of B. rhodani contained 31.3% more protein (per mg dry body weight) than nymphs of R. semicolorata, whereas the latter contained 81.0% more chitin; and (ii) nymphs of R. semicolorata took 2.7 times as long to consume and almost twice as long to pass through the predator's gut. The longer gut passage time may have allowed a greater assimilation efficiency which may have led to the observed better growth.
• 5 Dinocras cephalotes is thought to feed opportunistically, with a certain daily food biomass intake as its primary need rather than any specific prey preference. Foraging decisions, or opportunities, affect the fitness of individual nymphs and this may be reflected in the wide size range of contemporary nymphs found in field populations. Variation in foraging efficiency by predators and evasion success by prey, across substrate types, is thought to contribute to the well-known microdistribution patterns of species observed in lotic communities.

     

Drift dispersal of mayfly nymphs in the presence of chemical and visual cues from diurnal drift- and nocturnal benthic-foraging fishes

1. The drift of Baetis thermicus nymphs in the presence of chemical, visual and hydrodynamic cues, considered individually and in combination, produced by different predatory fishes was examined experimentally in laboratory streams. Masu salmon ( Oncorhynchus masou ) and freshwater sculpin ( Cottus nozawae ) are typical drift- and benthic-foraging fishes, respectively.
2. Observations of fish swimming in the streams revealed differing diel periodicity between the species; sculpin were nocturnal foragers and salmon diurnal.
3. The drift rate of Baetis by night increased in the presence of chemical cues from sculpin, with other cues having no interactive effects. In contrast, the drift rate increased primarily in the presence of both chemical and, particularly, visual cues from salmon, although no additional effects were found for any non-visual cues. Visual cues could enable Baetis to assess precisely the predation risk from foraging salmon by day, whereas Baetis could not use visual cues to detect sculpin either at night, because of the low light intensity, or during the day, because of the low activity of sculpin at that time.
4. In natural streams, which are often inhabited by several predatory fish employing different modes of foraging, invertebrates may be able to precisely assess the risk and effectively to avoid predators by using cues unique to each.     

A possible explanation of emergence patterns of Baetis vernus curtis (Ins.: Ephemeroptera) on the breitenbach — schlitz studies on productivity,Nr. 22—

Baetis vermis, a major contributor to the biomass of the Breitenbach, shows a remarkable degree of fluctuation in its emergence, which — in the years under observation (1969–1975)—ranges from univoltine to trimodal patterns. It is postulated, that warm overwintering temperatures produce unimodal emergence whereas cold winter temperatures (esp. periods with less than 5° C) produce bimodal or trimodal emergence. The relations between egg-hatching, larval growth and temperature are discussed.     

Redundancy among three herbivorous insects across an experimental current velocity gradient

We conducted streamside experiments to determine if the ability of herbivorous insects to remove algal periphyton varies with local current velocity. We used two mayfly species (Baetis bicaudatusand Drunella grandis) and one caddisfly species (Glossosoma verdona), which differ from one another in body morphology and mobility. Periphyton was grown for 30 days on ceramic tiles in constant velocity to create similar initial forage conditions for grazers. Tiles were transferred to three velocity regimes characteristic of the natural streambed: slow (3-5 cm s(-1)), medium (15-20 cm s(-1)) and fast (32-41 cm s(-1)). Four grazer treatments (Baetis, Drunella, and Glossosoma alone, and all species combined) were repeated for each velocity treatment to isolate the effect of local current on grazer ability to crop periphyton. Grazers differed in their abilities to remove periphyton across current treatments. Glossosoma removed significantly (P<0.05) more periphyton at fast versus either slow or medium velocities; Baetis showed a similar (but non-significant) trend; and, Drunella always removed about 75% of periphyton, irrespective of current. At fast current, periphyton removal was equivalent among the species. At medium current, Drunella removed significantly more than both Baetis and Glossosoma, whereas at slow current, Drunella removed more than Baetis, which removed more than Glossosoma. Periphyton removal under the combined three-grazer treatment was similar qualitatively to the combined effects of individual grazers. More periphyton tended to be removed as current increased, with the fast versus slow contrast showing marginal significance (P=0.10). Under all current regimes, the quantity of periphyton removed did not differ from the null model expectation of simple additive effects among individual grazers (i.e., no facilitation or inhibition). These experiments show that for some species, herbivory varies with current, which suggests that the herbivore "function" of cropping periphyton may vary with the environmental context of local current. Under some local velocities, however, different herbivore species "function" similarly and are potentially redundant with respect to periphytic removal. In naturally heterogeneous streams characterized by sharp gradients in local current velocity, we expect current-dependent species interactions to be common and at least partially contribute to intra-guild co-existence of species.     

Nested species subsets, gaps, and discrepancy

Chemical cues from fish can alter the behaviour of stream invertebrates in experimental tanks but their effect in natural streams has received little attention. By adding brook trout (Salvelinus fontinalis) odour to a trout stream in the Rocky Mountains of Colorado, USA, we tested whether changes in the concentration of chemical cues from visually feeding predatory fish would alter the drift of mayfly nymphs (Ephemeroptera). Stream water was piped from stream-side tanks with (odour) and without (control) three brook trout to two locations in the stream 3.5 m upstream of drift nets at six replicate sites. Five-minute drift samples were collected downstream from odour and control pipes before, during and after the release of water from the tanks into the stream during both the day and night. Almost all drift occurred at night and consisted predominantly of Baetis bicaudatus nymphs. The odour manipulation had no measurable effect on Baetis drift during the day but statistical power was low. During the night, however, the drift of large (>0.65 mm head capsule width, HCW) Baetis nymphs decreased significantly during the odour addition compared to control drift. In contrast, the drift of small nymphs (≤0.65 mm HCW) increased both during and after the odour addition in comparison to control drift. Since the stream contains brook trout (0.04–0.18 m⁻²), and water from the stream (presumably containing fish odour) altered the behaviour of fishless-stream Baetis nymphs in another experiment, we conclude that the changes in Baetis drift density were a response to an increase in the concentration of fish odour in the stream. Furthermore, we were able to detect the effect within 5 min. of odour addition, indicating that mayfly behavioural response to trout odour was rapid. These results suggest that mayflies can distinguish different concentrations of trout odour in natural streams and that the response is size-specific, according to the relative risk of predation of large and small Baetis. Received: 12 May 1998 / Accepted: 23 October 1998     

The life cycles of three species of Ephemeroptera in two streams in Poland

Nymphs of Rhithrogena iridina, Baetis alpinusand Baetis melanonyx were collected in theWoosatka and Terebowiec streams; Bieszczady NationalPark, southeastern Poland. The streams have differentenvironmental conditions. The life cycles of Rhithrogena iridina in the Woosatka and theTerebowiec streams were of the univoltine winter type.In the Woosatka (Station 1) this species had aunivoltine life cycle with one cohort. In theTerebowiec (Station 2), R. iridina had aunivoltine life cycle with two cohorts – winter andsummer. The development of Baetis alpinus tookvarious courses depending on environmental conditions.At the lower station (Woosatka), where watertemperature reached higher values and the stream bedis less shady, the species had a winter-summer cyclewith two generations a year. At the higher station,(Terebowiec) it likely had a winter cycle with one ortwo generations. Baetis melanonyx had summercycles with one generation at both stations.     

Drumming signals within the family Taeniopterygidae (Plecoptera)

Drumming signals of the 11 species of Palaearctic Taeniopterygidae are described for the first time based on the study of populations from nine different European countries from Spain to Russia. In this way, a contribution is made to our knowledge of the constancy respectively the divergence of signals typical for the species distributed over a very wide area. Communication patterns of the family under varying temperatures were analysed. The dependence on temperature indicates that the adults of this family are cold stenothermic insects. Within the genus Brachyptera (Newport, 1851), the call signal of males is significantly different from their response signal (duration and drumming frequency). The marked modulation of the drumming frequency, e.g., of B. risi (Morton, 1896) and B. seticornis (Klapálek, 1902) is reached by a modulation of the amplitude of abdominal movements. Based on the study of the drumming signals, Taeniopteryx auberti (Kis and Sowa, 1964) is proposed as a subspecies of T. hubaulti (Aubert, 1946). Actual intensity of the drumming signals of T. auberti was measured. Taeniopteryx hubaulti is recorded for the first time outside the Alps.