Egg clutch patterning in Lestes virens (Odonata,Lestidae) with evolutionary emphasis on endophytic oviposition in lestid dragonflies

Egg deposition within plants is one of the most widely distributed and ancient behaviors in Odonata. The resulting clutch consists of eggs placed in peculiar pattern that can be a characteristic for certain groups of Odonata. Despite their importance for paleontological and evolutionary research, data on egg‐clutch positioning are missing or insufficient for most species. Here, patterning of egg clutches in Lestes virens was measured and described in detail for the first time. The female usually produces a linear row of single eggs directed at an angle rightward or leftward to the longitudinal axis of plant substrate. Less often eggs are arranged in egg‐sets consisting of up to 4 eggs. Apparently, the female insect follows the rigid behavior stereotypes during oviposition and is unable to easily switch to the alternate stereotypical behavior of single egg deposition or production of multiegg sets. Based on a literature review and original data, egg clutch patterning of European Lestidae is overlaid on preexisting phylogenies. The resulting evolutionary scenario of egg‐clutch patterning can be considered in the framework of egg‐laying behavior in Lestidae.     

Effect of lamellae autotomy on survival and foraging success of the damselfly Lestes sponsa (Odonata: Lestidae)

Damselfly larvae can autotomize their caudal lamellae to escape predation. Costs of caudal lamellae autotomy were investigated by directly manipulating lamellae condition of Lestes sponsa in laboratory experiments. Larvae without lamellae had higher predation mortality in the presence of Notonecta. Both lamellae loss and larval density increased the probability of being cannibalized. The results suggest that the increased vulnerability after lamellae loss resulted from a reduced escape performance. Larvae were less mobile after lamellae loss or in the presence of a predator, but the decrease was no longer significant when both factors were combined. This indicates that larvae compensate for the increased predation risk with a fixed response. Both lamellae loss and predator presence reduced hunting success, but the decrease after lamellae loss was only significant in the absence of a predator. The fitness consequences of these effects for both the larval and adult stages are discussed. In general, the data strongly suggest that lamellae autotomy plays a role in population regulation of damselflies. Received: 1 April 1998 / Accepted: 28 August 1998     

Indirect Monitoring of Agonistic Encounters in Larvae of Lestes viridis (Odonata: Lestidae) Using Exuviae Lamellae Status

Differences in interference competition between larvae of the damselfly Lestes viridis (Vander Linden) were examined using caudal lamellae status of exuviae. Exuviae from a small temporary fishless pond near Antwerp (Belgium) where L.viridis was the only odonate present were studied. No lamellae loss during emergence was seen. Therefore, the lamellae status of the exuviae reflects the lamellae status of the final instar larvae. The deviations of the distribution of the number of missing lamellae per individual from a binomial distribution suggested that lamellae are not always lost separately or that some animals are more prone to agonistic encounters. I found no difference in agonistic encounters between sexes. In accordance with the hypothesis of Pierce et al. (1985) interference competition was higher in the lestid species inhabiting small, temporary fishless ponds than in the coenagrionid damselfly Ischnura posita inhabiting large permanent fish containing water bodies that was studied by Robinson et al. (1991).     

The Life Cycle of Lestes viridis (Odonata: Lestidae) in Two Seasonal Streams of the Sierra Morena Mountains (Southern Spain)

The life cycle of the zygopteran odonate Lestes viridis in two seasonal streams in the Sierra Morena Mountains is inferred from size-frequency analyses of handnet samples of larvae and records of presence and reproductive activity of adults during three consecutive years. The egg stage (duration 5–6 months) overwinters, larval development is brief (6–8 weeks) and adults undergo a protracted, prereproductive, summer diapause (up to 3 months) before mating and ovipositing in late September, about one week after the first appreciable fall of rain, but before surface water reappears in the streams after having been absent for about four months during the hot, dry summer. Comparison between this life cycle and those of more northerly populations reveals a latitude-correlated cline in phenology resembling that found in some other northern hemisphere odonates that, like L. viridis, maintain an obligatorily univoltine life cycle at different latitudes.     

Selective feeding by larval dytiscids (Coleoptera:Dytiscidae) and effects of fish predation on upper littoral zone macroinvertebrate communities of arctic lakes

Carbon and nitrogen stable isotopic data from the primary producers in mangrove ecosystems are needed to investigate trophic links and biogeochemical cycling. Compared with other mangrove species (e.g. Rhizophora mangle) very few measurements have been conducted on the white mangrove, Laguncularia racemosa. The carbon and nitrogen stable isotopic and elemental compositions of L. racemosa were analyzed and compared from Florida and Belize. ¹³C values of L. racemosa from Florida (mean = –26.4) were slightly higher than those from Twin Cays, Belize (mean = -27.4), which may be due to higher salinity in some parts of the Florida site. There was no difference between the ¹⁵N values from L. racemosa from these two sites (Florida mean = 0.6; Belize mean = 0.3), which are indicative of nitrogen derived from nitrogen fixation in a planktonic marine system. However, higher ¹⁵N values from L. racemosa at Man of War Cay in Belize (11.4 and 12.3), which is fertilized by roosting marine birds (14.0), illustrate that L. racemosa can sensitively reflect alternative nitrogen sources. Although the isotopic data could not distinguish between Avicennia germinans, R. mangle and L. racemosa in Belize the L. racemosa had considerably higher C/N ratios (46.5 – 116.1) compared with the Florida samples (42.2 – 76.0) or the other mangrove species. Unlike some previous findings from R. mangle, substrate characteristics (e.g. salinity, NH₄ ⁺, and H₂S) were not related to the isotopic or elemental composition of L. racemosa. ¹³C, ¹⁵N and C/N were analyzed for ecosystem components from L. racemosa habitats at Twin Cays, including other plants (e.g. R. mangle, A. germinans and seagrass), detritus, microbial mats and sediments. Results from mass-balance calculations show that mangrove detritus composes very little of the sediment, which is principally composed of microbial biomass (80 – 90%). Detritus at some sites is also influenced by sources other than that from L. racemosa, including seagrass leaves.     

Large net cage for captive breeding and behavioural studies of damselfly Lestes sponsa (Hansemann, 1823) (Odonata: Lestidae): submerged oviposition as a model behaviour

Odonata have a strong potential as model organisms for testing ecological and evolutionary hypotheses because of their short life history, relative ease and cost-effectiveness of care. Unfortunately, very few studies have examined how to create a semi-natural environment for odonates, limiting the biological validity of laboratory manipulation. To better study odonate life cycle and behaviour under controlled conditions, we designed a large net cage that imitated the natural terrestrial as well as aquatic habitat of the damselfly Lestes sponsa (Hansemann, 1823). This species is thought to be capable of submerged oviposition, an unusual behaviour in odonates. We compared multiple variables across natural conditions and the net cage. We demonstrated that between-year variability under natural conditions was generally greater than variability between natural and artificial environments. Overall, semi-natural conditions did not substantially change the L. sponsa life cycle (including the unique behaviour of submerged oviposition), suggesting that results from the net cage are likely generalisable to the field.     

Fish predation on epiphytic microcrustacea in Tivoli South Bay,a Hudson River tidal freshwater wetland

The littoral microcrustacean fauna of Tivoli South Bay was studied from July to September, 1989. The effects of fish predation on microcrustacean densities were tested in a short-term predator exclusion experiment. Fish were excluded from water chestnut (Trapa natans) plots in four screened exclosures. An equal number of open cages allowed foraging. Fish predation did not have a significant effect on densities of ostracods or other microcrustaceans. Ostracod densities increased in cages throughout the experimental period, whereas cladoceran and copepod densities decreased in both treatments. Gut contents analysis of banded killifish (Fundulus diaphanus) revealed that ostracods and other microcrustaceans were commonly ingested by larval, juvenile, and adult killifish utilizing T. natans as habitat. These results suggest that ostracods and other microcrustacean epifauna associated with T. natans may represent an important trophic link in the tidal freshwater wetlands of the Hudson River Estuary. Deceased     

Selective predation by four darter (Percidae) species on larval chironomids (Diptera) from a Mississippi stream

We determined seasonal foraging modes of four sympatric darter species, Etheostoma lynceum, E. stigmaeum, E. swaini and Percina nigrofasciata, from Beaverdam Creek, Mississippi (USA) at two scales of taxonomic resolution: (1) chironomid prey identified to family and (2) chironomid prey identified to genus/species. When chironomids were identified to family, high proportional similarity (PS) and low niche breadth (NB) values suggested the darters fed opportunistically on a relatively small number of available prey taxa. In contrast, when chironomids were identified to genus/species, concordant low PS and NB values suggested the darters fed like classic specialists, selecting a small number of prey taxa relative to prey availability in the resource base. The darters selected just one to four chironomid taxa from 52 available taxa across seasons. Our study shows that the scale of taxonomic resolution used to identify darter prey may influence the characterization of darter foraging modes.     

Selective predation favouring cryptic individuals of marine snails (Littorina)

Many gastropods have inherited conspicuous shell colour polymorphisms. A challenging question is, are colour frequencies under selection or is polymorphism owing to random evolutionary processes? The intertidal species Littorina saxatilis (a rock‐dweller) and L. obtusata (confined to macroalgae) both have genetically determined shell colour variation. In Iceland, Littorina obtusata are mostly cryptic on brown macroalgae by having brown or yellow shells (~95% of the snails), while Littorina saxatilis often appears conspicuous to the background of dark rocks owing to non‐cryptic colours (15–20%). This difference may be due to selective elimination of conspicuously coloured L. obtusata by visual predators, while L. saxatilis, largely living in another habitat, is not under a similarly intense colour selection. To test this hypothesis we increased the frequencies of conspicuous L. saxatilis in experimental populations (from <12 to 55%) and placed these in the seaweed zone, the main habitat of L. obtusata. Fifteen populations were released on isolated spots of seaweed and three of these were covered by net cages to exclude bird predators. One month later, yellow snails had increased in frequency within the patches, and to our surprise the result did not differ between bare and caged patches. This suggests selection favouring a colour that matches the background of fucoid seaweeds by visual predators able to enter the cages. Birds acted as important predators by picking 16% of the experimental snails in the uncaged spots, but were unable to enter the caged spots. However, the bird predation was non‐selective with respect to snail colour. For various reasons the most likely predators able to enter the cages were intertidal fish, these were thus responsible for the selection of non‐cryptic snails. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 76 , 137–144.     

Stream inflow and predation risk affect littoral habitat selection by benthic fish

1. We examined small, fishless headwater streams to determine whether transport of macroinvertebrates into the littoral zone of an oligotrophic lake augmented food availability for Cottus asper, an abundant predatory fish in our study system. We sampled fish and macroinvertebrates during the recruitment and growth season of 2 years, either monthly (2004) or bi‐monthly (2005), to observe whether stream inputs increased prey availability and whether variation in total macroinvertebrate biomass was tracked by fish. 2. Observations from eight headwater streams indicated that streams did not increase the total macroinvertebrate biomass in the shallow littoral zone at stream inflows, relative to adjacent plots without stream inputs (controls). The taxonomic composition of stream macroinvertebrates drifting toward the lake differed from that in the littoral lake benthos itself, although there was no evidence of any species change in the composition of the littoral benthos brought about by stream inputs. 3. Although streams made no measurable contribution to the biomass or taxonomic composition of the littoral macroinvertebrate benthos, there was substantial temporal variation in biomass among the eight sites for each of the (n = 7) sample periods during which observations were made. Variation in total biomass was primarily a function of bottom slope and benthic substrata in the lake habitats. Dominant taxonomic groups were Baetidae, Ephemerellidae (two genera), Leptophlebiidae, Chironomidae (three subfamilies) and Perlodidae, although we did not determine the specific substratum affinities of each taxon. 4. Mixed effects linear models identified a significant interaction between macroinvertebrate biomass and plot type (stream inflow vs. control) associated with fish abundance. Across the observed range of macroinvertebrate biomass, fish showed a significant preference for stream inflows, but more closely tracked food availability in the controls. For young‐of‐the‐year (YOY), a negative effect of temperature was also included in the model, and we observed lower temperatures at stream inflows. However, abundance of predatory adults affected habitat selection for YOY. Lake‐bottom slope also accounted for variation in abundance in both fish models. 5. Our results suggest that the effect of fishless headwater streams on downstream fish may not always be through direct delivery of food. In this study system, fish preferred stream inflow plots, but this preference interacted with macroinvertebrate biomass in a manner that was difficult to explain. For YOY, predation risk was related to the preference for stream inflows, although the specific factor that mitigates predation risk remains poorly understood.     

Selective predation by carp (Cyprinus carpio L.) on benthic molluscs in Skadar Lake, Yugoslavia

Analysis of predation by carp ( Cyprinus carpio L.) on mollusc species in Skadar Lake, Yugoslavia, indicated both generalized and specific features of a predator-prey interaction. Vertical distribution of molluscs in sediments seemed unrelated to predation rates by carp. Although size selective predation may occur, electivity indices appeared most related to shell shape and thickness. Of the three most abundant species, electivity was high for Valvata piscinalis but low for Pyrgula annulata and Dreissencia polymorpha. Valvata has a more readily crushed shell, a higher proportion of occupied shells and a greater percentage of organic content than Pyrgula. Although a potentially preferred prey item, Dreissencia probably escaped intensive predation by being attached to larger objects. Carp appeared to utilize a sequence of tactile and gustatory cues in the prey selection process.     

Selective predation on Utah prairie dogs

Predation always affects demography and population dynamics, but removal of certain types of individuals is especially consequential. Predators strike quickly and commonly avoid areas with human observers, however, and thereby make it difficult to document patterns of predation under natural conditions. At a colony of marked Utah prairie dogs (Cynomys parvidens), a high frequency of predation in 2005 provided an unusual opportunity to examine susceptibility of five types of individuals to predation by red foxes (Vulpes vulpes) and northern goshawks (Accipiter gentilis). Juveniles were more vulnerable than adults to predation by northern goshawks. Adults at the edge of the colony were more vulnerable than central adults to predation by both red foxes and northern goshawks. Recent immigrants, who were not yet familiar with the best routes for escape, were more likely than longtime residents to be captured by northern goshawks. Adult males, preoccupied with finding, impregnating, and guarding estrous females during the 17-day mating season, were easy targets for red foxes and northern goshawks. Pregnant females, who could not run quickly, were especially prone to predation by red foxes.     

Influences of slimy sculpin (Cottus cognatus) predation on the rocky littoral invertebrate community in an arctic lake

We tested the role of the slimy sculpin (Cottus cognatus), a benthic fish, in structuring the rocky littoral invertebrate community in Toolik Lake, Alaska. Comparisons of sculpin gut contents and prey community structure indicated that these fish forage selectively, eating proportionally more large and motile prey, and proportionally fewer small and sessile forms. Field experiments compared the effects of natural, reduced and elevated sculpin densities on benthic community structure. At natural levels of sculpin density, biomass of trichopteran larvae were reduced by more than 50%, and predatory chironomid larvae by 27%, in comparison to areas where sculpin were excluded. Tube-dwelling and small free living chironomid larvae were unaffected at normal sculpin densities. Under artificially high sculpin densities, there was some reduction of tube-dwelling chironomids, but the small free living ones remained unaffected. There appears to be a threshold length of about 3.5 mm, below which chironomid larvae are free form sculpin predation. Tube-dwelling chironomids may be longer than this threshold, but still avoid predation by having most of their body hidden in their tubes.     

Selective predation on zooplankton by pelagic Arctic charr, Salvelinus alpinus, in six subarctic lakes

Selective predation by planktivore fish appears to be an important regulatory factor of zooplankton communities, potentially causing large changes in species composition and size distributions within populations. In this study, prey preferences and size-selective predation on zooplankton by Arctic charr were examined in six subarctic lakes with Arctic charr as the dominant pelagic fish species. Most of the lakes had a zooplankton community dominated by copepods (Cyclops scutifer and Eudiaptomus graciloides), but the pelagic charr evidently selected cladoceran species (Bythotrephes longimanus, Daphnia sp. and Bosmina sp.), likely because the copepods have a higher mobility and evasiveness than the cladocerans. Furthermore, a strong size selection was also revealed for both Bosmina sp. and Daphnia sp., as individual prey from Arctic charr stomachs were exclusively larger than individuals sampled in the environment. Additionally, visibility due to size, morphology and pigmentation (egg-carrying females) was also a major factor for the selection of zooplankton prey. In conclusion, Arctic charr was found to be highly selective on zooplankton both in respect to species composition and individual size of Bosmina sp. and Daphnia sp.     

Central projections of ovipositor sense organs in the damselfly,Sympecma annulata (Zygoptera,Lestidae)

Central projections of sensilla on different parts of the endophytic ovipositor of the lestid damselfly Sympecma annulata are traced. Sensilla include apical hairs of the stylus (STh), hair rows on the ventral part of the valvula (Vh), and distal campaniform sensilla of upper (ULc) and lower (LLc) ovipositor leaves. Backfilling of afferent fibers, using anterograde cobalt fills, reveals the presence of contralaterally projecting fibers for all organs. The main fiber bundle of the LLc enters the terminal ganglion laterally via the genital nerve, but the fibers from ULc enter via the posterior nerve. Main fiber bundles of both leaves end in a lateral part of the ganglion called the lateral neuromere; they demonstrate that sensory information from the two leaves has the same target area. It is hypothesized that the independent pathways of nerves from upper and lower ovipositor leaves (ULc and LLc) may indicate the phylogenetic origin of these appendages from different abdominal segments—the lower leaf from the 8th and upper from 9th. The convergence of afferent fibers from the sensilla of the different ovipositor parts (median, anterior, and lateral processes) in common ganglionic centers may provide the anatomical basis to account for coordination of the movements of different ovipositor parts during oviposition. © 1994 Wiley-Liss, Inc.     

环斑猛猎蝽对猎物的选择捕食作用

研究了环斑猛猎蝽雌成虫对玉米螟和蚜虫混合种群的选择捕食作用。结果表明:当玉米螟2龄幼虫和3龄幼虫共存时,环斑猛猎蝽雌成虫对玉米螟在各猎物密度下均表现正喜好性,而对蚜虫在各猎物密度下均不表现喜好性。对玉米螟的转换效应因总猎物密度的不同而不同,即在低密度(60头·瓶-1)和中密度(90头·瓶-1)时无转换行为,在高密度(120头·瓶-1)时有负转换行为;对蚜虫在低密度(60头·瓶-1)和中密度(90头·瓶-1)时有负转换行为,在高密度(120头·瓶-1)时无转换行为。当2龄、3龄玉米螟幼虫和蚜虫3种猎物共存、总猎物密度为90头·瓶-1时,环斑猛猎蝽雌成虫对玉米螟3龄幼虫表现正喜好性并有正转换行为,对蚜虫则表现负喜好性和负转换行为。     

Selective predation on Cladocera by brown trout Salmo trutta L.

The size and species composition of zooplankton ingested by brown trout in Lough Sheelin was studied. Zooplankton and fish samples were taken simultaneously. The zooplankton samples consisted of Daphnia hyalina var. galeata , Copepoda and Bythotrephes longimanus in the proportion of 246: 10: 1. The entire stomach contents of the fish were examined with particular attention paid to the zooplankton component. The results indicated a high degree of selection for B. longimanus .     

Marine biodiversity of Costa Rica, the microcrustacea: Copepoda (Crustacea: Maxillopoda)

This report is part of a series that summarizes the species and localities of Costa Rican marine taxa. A review of the literature on copepods, both pelagic and benthic for the Pacific and Caribbean coast of Costa Rica, includes eighty species. Sixty seven pelagic species have been found, distributed between sixteen calanoid, one cyclopoid, three harparticoid and four poecilostomatoid families. Moreover, thirteen benthonic species distributed into six families, all harparticoids, are reported. Among the pelagic families, Pontellidae has six species, while Paracalanidae and Eucalanidae had five each. Other families, like Calanidae, Pseudodiaptomidae and Acartiidae had four species and most families only one. Forty five species are reported only for the Pacific coast, thirteen for the Caribbean coast, only nine species occurred in both coasts; being a direct consequence of the more intensive research effort in the Pacific. Pelagic copepod biodiversity reflects different oceanographic conditions in both coasts. Typical estuarine species were found in the lower region of the Gulf of Nicoya, while a mixture of estuarine and oceanic species were found in Golfo Dulce. Diversity in the Caribbean, specially at the Cahuita coral reef is lower in comparison with the copepod diversity found in other regions in the Caribbean sea. This may be due to the high sediment resuspension rate characteristic of the Cahuita coral reef, which could affect the reproduction of many holozooplankters, specially copepods. Although sixty seven pelagic copepod species appears to be in low numbers, in terms of specific biodiversity it is as high when compared to numbers found in other tropical areas. Thirteen species are reported in the literature, all harparticoids. Five species, three sub-species and one genera were new to science. Balacopsylla is reported for the first time from a neotropical regions, while the genus Karllangia, represented by two coexisting species in the Caribbean coast, belong to a few circumtropical-subtropical genera. The most diverse family was Tetragonicipitidae. This is the first effort to summarize the available information about the biodiversity of marine copepods for Costa Rica's coasts.     

Lake acidity,fish predation,and the distribution and abundance of some littoral insects

Densities of Corixidae (Hemiptera), larval Odonata, and large larval Trichoptera were estimated in the littoral zone of small lakes in an acid-stressed area near Sudbury, Ontario. Fish were present in some lakes and absent in others, and fishless lakes occurred across a wide range of pH. Corixidae were significantly more abundant in lakes without fish than in lakes with fish, and their numbers were not related to the pH of fishless lakes. Anisoptera (Odonata) larvae tended to be more numerous in benthic samples from fishless lakes than from lakes with fish, and their exuviae were significantly more abundant around fishless lakes. In most lakes, the assemblage was dominated by three species; Leucorrhinia glacialis, Libellula julia, and Cordulia shurtleffi. In lakes containing white sucker, Catostomus commersoni, Gomphus spp. were most numerous. In the most acid fishless lakes, L. julia was uncommon, and L. glacialis was extremely abundant. In fishless lakes, numbers of Anisoptera larvae and exuviae were negatively correlated with pH, though species richness was positively correlated with pH. Exuviae of Zygoptera (Odonata) were more abundant around fishless lakes, irrespective of pH. Larvae of Limnephilus (Trichoptera) were most abundant in non-acid fishless lakes, and absent at pH<5.2. Abundances of Banksiola (Trichoptera) were negatively correlated with the pH of fishless lakes.     

Selective predation on an introduced zooplankter ( Bythotrephes cederstroemi ) by lake herring ( Coregonus artedii ) in Harp Lake,Ontario

1. Bythotrephes cederstroemi (Crustacea: Onychopoda: Cercopagidae) invaded Harp Lake, Ontario in 1993, since when the zooplankton community has shifted from dominance of small-bodied to large-bodied species. During 1995 diets of adult lake herring (Coregonus artedii), Harp Lake’s primary planktivorous fish, were examined to determine the extent to which this conspicuous zooplankter has become integrated into the lake’s foodweb and whether fish condition has been affected in consequence. 2. Bythotrephes and Daphnia galeata mendotae were strongly preferred prey, whilst Holopedium gibberum and calanoid and cyclopoid copepods were negatively selected by lake herring. Predation on Bythotrephes and Holopedium was not size-selective, although D. galeata mendotae and calanoid copepods (Leptodiaptomus minutus and L. sicilis) consumed by herring were significantly larger than co-occurring conspecifics in the lake. 3. Caudal spines of Bythotrephes may form boluses in lake herring stomachs. However, the number of caudal spines in fish digestive tracts did not differ significantly from the number of Bythotrephes’ mandible pairs, indicating that the former were not differentially retained. 4. Lake herring weight-at-length relationships in lakes in Muskoka, Ontario, invaded by Bythotrephes did not differ from those in adjacent non-invaded lakes, indicating that Bythotrephes invasion of lakes apparently has not affected condition of lake herring.