Microsatellite loci for the mayfly Baetis rhodani (Baetidae,Ephemeroptera)

The first microsatellite primers are described for the mayfly family Baetidae (order Ephemeroptera). Seven polymorphic loci were isolated and characterized for the species Baetis rhodani from two enriched genomic libraries. A total of 183 individuals were genotyped using these loci. Allelic diversity was high for all loci, and observed heterozygosities ranged between 0.382 and 0.772. A heterozygote deficiency was detected in some loci, suggesting the presence of ‘null’ alleles.     

Evolution and island endemism of morphologically cryptic Baetis and Cloeon species (Ephemeroptera,Baetidae) on the Canary Islands and Madeira

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Molecular systematics and phylogeography of the cryptic species complex Baetis rhodani (Ephemeroptera, Baetidae)

Genetic studies have highlighted cryptic diversity in many well-known taxa including aquatic insects, with the general implication that there are more species than are currently recognised. Baetis rhodani Pictet are among the most widespread, abundant and ecologically important of all European mayflies (Ephemeroptera), and used widely as biological indicators of stream quality. Traditional taxonomy and systematics have never fully resolved differences among suspected cryptic species in the B. rhodani complex because morphological characters alone do not allow reliable distinction. This is particularly true among larvae, the life-stage used most widely in monitoring. Here, we assess the molecular diversity of this complex in one of the largest such studies of cryptic species in the order Ephemeroptera to date. Phylogenies were constructed using data from the mitochondrial cytochrome oxidase subunit I (COI) gene. Two monophyletic groups were recovered consisting of one major haplogroup and a second clade of 6 smaller but distinct haplogroups. Haplogroup divergence ranged from 0.2-3% (within) to 8-19% (among) with the latter values surpassing maxima typically reported for other insects, and provides strong evidence for cryptic species in the B. rhodani complex. The taxonomic status of these seven haplogroups remains undefined. Their distributions across Western Europe reveal no obvious geographic pattern, suggesting widespread diffusion of genetic lineages since the last glacial maximum. The implications of these findings are far-reaching given the ecological and bioindicator significance of what now appears to be several taxa.     

Genetic structure in a montane mayfly Baetis bicaudatus (Ephemeroptera: Baetidae), from the Rocky Mountains, Colorado

1. Populations of a number of sub‐tropical stream insect species have been found to show unexpected patterns of genetic variation, with more differences between samples from the same stream than between whole streams or between subcatchments. Many samples also showed deviations from Hardy–Weinberg proportions. It has been proposed that these patterns result from limited numbers of matings contributing to a given stream reach, because adults emerge throughout the year, and low levels of larval drift between reaches. These patterns may be less likely in a northern hemisphere montane species with synchronous emergence of adults and high levels of drift. We tested the hypothesis that patterns of genetic variation in a montane mayfly from the Rocky Mountains, Colorado, would reflect a pattern of ‘isolation by distance’ with samples from the same creek being more similar than samples from different creeks and that deviations from Hardy–Weinberg proportions would be minimal. 2. Based on allozyme variation, the hypothesis of minimal deviations from Hardy–Weinberg proportions was not supported and there was no evidence of isolation by distance. Nevertheless the levels of differentiation among samples from within the same stream were less than those reported for most subtropical species. 3. Results from analysis of a fragment of the cytochrome oxidase gene (subunit 1) revealed contrasting patterns. The levels of genetic differentiation were an order of magnitude higher between streams than among samples within streams. In addition, although there was no significant isolation by distance effect overall, a nested clade analysis provided evidence for restricted gene flow with isolation by distance for some clades. 4. We suggest that these contrasting results may reflect the differences in male and female dispersal patterns. While differentiation at nuclear gene markers (allozymes) give information about both male and female dispersal, mitochondrial DNA markers reflect only female dispersal. We suggest that in this species, female dispersal may be more restricted, perhaps mostly along stream channels, whereas male dispersal is more widespread. An alternative explanation for the different results is the different evolutionary rates of the mitochondrial and nuclear markers.     

Ultrastructure of the antennal sensilla of the mayfly Baetis rhodani (Pictet) (Ephemeroptera : Baetidae)

The distribution and fine morphology of antennal sensilla of nymphal and adult mayfly, Baetis rhodani (Ephemeroptera : Baetidae), were examined. In the nymph, various kinds of sensilla (chaetica, basiconica, coeloconica and cuticular pits) are differently arranged on the antennal segments, whereas sensilla campaniformia delimit the distal border of the pedicel. A peculiar kind of sensillum basiconicum, named flat-tipped sensillum, is present along the entire antenna, even though in the flagellum it has a regular arrangement between the cuticular lobes that delimit the distal border of each article. In the subimago the scape and pedicel are profusely covered with microtrichia and scattered sensilla trichodea, whereas the flagellum shows cuticular ribs. Sensilla coeloconica are present along the ventral side of the flagellum. In the imago, the antenna is completely decorated with scales among which sensilla trichodea and sensilla coeloconica occasionally occur. As in the nymph, adult mayflies have a ring of sensilla campaniformia along the distal border of the pedicel. When compared with nymphal antennae, those of adults have fewer types of sensilla, presumably in relation to the short, non-feeding terrestrial life.     

Life cycle and secondary production of two species of Campsurus (Ephemeroptera,Polymitarcyidae) in reservoirs of southeastern Brazil

The aim of this paper was to study the life cycle, the annual secondary production, and the spatial and temporal variation of the species Campsurus truncatus and C. violaceus in two reservoirs in Minas Gerais, Brazil. Campsurus truncatus was recorded in 11 months and had a multivoltine lifecycle with a secondary production of 4.61 g.m^?2.year^?1. Campsurus violaceus was collected in eight months and had a bivoltine lifecycle with a secondary productivity of 1.96 g.m^?2.year^?1.     

Cryptic diversity and multiple origins of the widespread mayfly species group Baetis rhodani (Ephemeroptera: Baetidae) on northwestern Mediterranean islands

How the often highly endemic biodiversity of islands originated has been debated for decades, and it remains a fervid research ground. Here, using mitochondrial and nuclear gene sequence analyses, we investigate the diversity, phylogenetic relationships, and evolutionary history of the mayfly Baetis gr. rhodani on the three largest northwestern Mediterranean islands (Sardinia, Corsica, Elba). We identify three distinct, largely co‐distributed, and deeply differentiated lineages, with divergences tentatively dated back to the Eocene–Oligocene transition. Bayesian population structure analyses reveal a lack of gene exchange between them, even at sites where they are syntopic, indicating that these lineages belong to three putative species. Their phylogenetic relationships with continental relatives, together with the dating estimates, support a role for three processes contributing to this diversity: (1) vicariance, primed by microplate disjunction and oceanic transgression; (2) dispersal from the continent; and (3) speciation within the island group. Thus, our results do not point toward a prevailing role for any of the previously invoked processes. Rather, they suggest that a variety of processes equally contributed to shape the diverse and endemic biota of this group of islands.     

Sperm ultrastructure of an oviparous and an ovoviviparous onychophoran species (Peripatopsidae) with some phylogenetic considerations

The spermatozoa of the Australian oviparous Ooperipatellus insignis and the South African ovoviviparous Opisthopatus cinctipes (both: Onychophora, Peripatopsidae) were studied and compared with the spermatozoal patterns already described in the taxon. The spermatozoa of both species conform with the general plan described for the Onychophora: they are filiform cells formed, in sequence, by an elongated, fully condensed nucleus capped by an acrosome and surrounded by several spiral ridges; by a mitochondrial midpiece characteristically interpolated between the nucleus and a characteristic flagellum. Major differences between the spermatozoa of both species concern their acrosome organization. The correlation between the acrosomal pattern and the size and structure of the ovarial eggs (oocytes) in onychophorans has been investigated. A parsimony analysis was performed on 21 spermatozoal characters of the species considered. Its results are congruent with those of the traditional systematics. A new set of autapomorphies characterising onychophoran sperm is suggested and some of the spermatological homologies proposed between Onychophora and Euclitellata spermatozoa are critically discussed. Our analysis suggests that spermatozoal characters are good phylogenetic markers among onychophorans, also at low taxonomic level.     

Mortality of the terrestrial adult and aquatic nymphal life stages of Baetis vernus and Baetis rhodani in the Breitenbach, Germany (Insecta: Ephemeroptera)

1. The mortality of Baetis vernus Curtis and Baetis rhodani Pictet during the terrestrial-aerial and aquatic life stages was studied at the Breitenbach near Schlitz, Hesse, Germany. The number of females emerging from the stream was recorded with emergence traps. To estimate mortality of females of both species during terrestrial life, numbers of emerging females were compared with numbers of females returning to the stream for oviposition, as shown by numbers of egg masses found in the stream. 2. Mortality of female B. vernus during their terrestrial life stage was 98.8%. It was 91.2 and 96.6%, respectively, during the first and second generations of B. rhodani. 3. To estimate the mortality of both sexes of B. rhodani during the aquatic life stage, the number of eggs laid by the first generation was compared with the number of adults emerging during the second generation. 4. Mortality during the aquatic phase (both sexes combined) of B. rhodani was 91.1%. 5. Mortality during the terrestrial life stages was at least as high, if not higher than during the aquatic stages. Evidently, there is a considerable export of organic material into the terrestrial environment around the stream. Mortality during terrestrial life may be an important regulator of population size.     

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.     

Discovery of an alien species of mayfly in South America (Ephemeroptera)

Despite its wide, almost worldwide distribution, the mayfly genus Cloeon Leach, 1815 (Ephemeroptera: Baetidae) is restricted in the Western hemisphere to North America, where a single species is reported. In the Neotropics, except for some species wrongly attributed to the genus in the past, there are no records of Cloeon. Recently, however, specimens of true Cloeon were collected along the coast of Espírito Santo, Southeastern Brazil. In order to verify the hypothesis that this species was recently introduced to Brazil, our aim was to identify the species based on morphological and molecular characters and to confirm the presence of true representatives of the genus in the Neotropics. Our results revealed that the specimens found in Brazil belong to the Afrotropical species C. smaeleni Lestage, 1924. The identity of the species, its distribution, along with its previous absence in regularly sampled sites, is a clear sign that the specimens of C. smaeleni found in Espírito Santo are introduced, well established, and that the colonization took place very recently.     

Predation on mayfly nymph, Baetis rhodani, by native and introduced Gammarus: direct effects and the facilitation of predation by salmonids

1. In a series of laboratory experiments, we assessed the predatory nature of the native Irish amphipod, Gammarus duebeni celticus , and the introduced G. pulex , towards the mayfly nymph Baetis rhodani . We also investigated alterations in microhabitat use and drift behaviour of B . rhodani in the presence of Gammarus , and indirect predatory interactions with juvenile Atlantic salmon, Salmo salar .
2. In trials with single predators and prey, B. rhodani survival was significantly lower when Gammarus were free to interact with nymphs as than when Gammarus were isolated from them. The invader G. pulex reduced the survival of B. rhodani more rapidly than did the native G. d. celticus . Both Gammarus spp. were active predators.
3. In `patch' experiments, B. rhodani survival was significantly lower both when G. pulex and G. d. celticus were present, although the effect of the two Gammarus species did not differ. Again, active predation of nymphs by Gammarus was observed. Significantly more nymphs occurred on the top and sides of a tile, and per capita drifts were significantly higher, when Gammarus were present. Baetis rhodani per capita drift was also significantly higher in the presence of the introduced G. pulex than with the native G. d. celticus .
4.  Gammarus facilitated predation by salmon parr of B. rhodani by significantly increasing fish–nymph encounters on exposed gravel and in the drift. There were no differential effects of the two Gammarus spp. on fish – B . rhodani encounters or consumption.
5. We conclude that Gammarus as a predator can have lethal, nonlethal, direct and indirect effects in freshwaters. We stress the need for recognition of this predatory role when assigning Gammarus spp. to a `Functional Feeding Group'.     

The effect of rock size upon the distribution of species of Orthocladiinae (Chironomidae: Diptera) and Baetis intercalaris McDunnough (Baetidae: Ephemeroptera)

Abstract. 1. Three experimental stream bed sections were established in areas of similar depth and current velocity to examine the effect of rock size upon the distribution of Baetis intercalaris and Orthocladiinae. Each section was composed of one rock size with the diameters (mm) of the three rock classes being 30–70, 90–140 and 160–190.
2. Colonization was measured at 2 week intervals over an 8 week period, and these data were used to calculated abundance or the number of individuals per unit area of stream bed and density or the number of individuals per unit area of rock surface.
3. Statistical analyses reveal that rock size was of secondary importance in determining Orthocladiinae abundance and density among the experimental bed sections. Rock size differences had a more pronounced effect upon B. intercalaris since on every sampling date both abundance and density increased with rock size.
4. Rock size differences appeared to have little effect on the response of Orthocladiinae to silt deposition, whereas the reverse was true for B.intercalaris.     

Egg development of Plecoptera,Ephemeroptera and Odonata along latitudinal gradients

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Effects of aluminum,calcium and low pH on egg hatching and nymphal survival of Cloeon triangulifer McDunnough (Ephemeroptera: Baetidae)

Laboratory experiments were conducted to assess the effects of aluminum, calcium and low pH on egg hatching and nymphal survival of the mayfly Cloeon triangulifer. Percent successful hatch (living nymphs breaking free of the chorion) decreased and percent partial hatch (nymphs dying attached to the chorion) increased with increasing acidity (pH 7.5–3.0). Most hatches occurring below pH 5.0 were partial hatches. Decreased time of exposure to acidic waters increased percent successful hatch and decreased percent partial hatch. Time to first hatch was not affected by pH. Eggs were incubated in acidic waters (pH 4.0 and 5.5) with additions of calcium (10 and 100 mg l^–1) and aluminum (100 and 500 g l^–1). Aluminum decreased percent successful hatch and increased percent partial hatch and calcium increased both percent successful hatch and percent partial hatch. Time to first hatch was increased by both aluminum and calcium. The 96 h LC50 for small nymphs was pH 4.75. Addition of aluminum (100 and 500 µg l^–1) to acidic waters (pH 4.0 and 5.0) reduced nymphal mortality by 8–22%. Toxic effects of low pH on egg hatching and early nymphs may contribute to the absence of mayflies from acidified habitats.Contribution No. 1469 of the Maine Agricultural Experiment Station, University of Maine, Orono, Maine 04469 USA.Contribution No. 1469 of the Maine Agricultural Experiment Station, University of Maine, Orono, Maine 04469 USA.     

New species of Nanomis Lugo-Ortiz and McCafferty, 1999 (Ephemeroptera: Baetidae) from Venezuela

As the first taxonomic and faunistic report of Nanomis Lugo-Ortiz and McCafferty, 1999 for Venezuela, we describe a new species, N. rasmusseni sp. n., based on material from Andean streams. Comparisons of the nymphal and imaginal stages of N. rasmusseni with those of N. galera Lugo-Ortiz and McCafferty, 1999 – the only species currently known for this genus – are done in detail. Further, additional morphological characters are discussed to delineate the genus from the other baetid genera. Likewise, ecological data and distribution of N. rasmusseni in the Andean highlands of Venezuela are provided, which improves knowledge of the richness and distribution of the genus in South America.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:C9DF3936-101F-4240-B067-AC5DF394C805     

The rowing-to-flapping transition: ontogenetic changes in gill-plate kinematics in the nymphal mayfly Centroptilum triangulifer (Ephemeroptera, Baetidae)

Comparative studies encompassing a wide range of aquatic animals have shown that rowing is exclusively used at low Reynolds numbers ( Re  < 1), whereas flapping is predominantly used at Re  > 100, although few studies have been undertaken to document the transition in individual species that traverse the intermediate Re regime using a single set of appendages. Thus, it is not generally known whether a gradual increase in Re within a system results in a gradual or sudden shift between rowing and flapping. In the present study, we document ventilatory kinematics of a nymphal mayfly Centroptilum triangulifer that develops using a serial array of seven pairs of abdominal gill plates and operates at Reynolds numbers in the range 2–22 during ontogeny. We found that some kinematic variables (stroke frequency and metachronal phase lag) did not change during ontogeny but that others changed substantially. Specifically, gill kinematics in small instars used strokes with large pitch and stroke-plane deviations, whereas larger instars used strokes with minimal pitch and minimal stroke-plane deviation. Gills in larger instars also acquired an intrinsic hinge that allowed passive asymmetric movement between half strokes. Net flow in small animals was directed ventrally and essentially parallel to the stroke plane (i.e. rowing), whereas net flow in large animals was directed dorsally and essentially transverse to the stroke plane (i.e. flapping). The change in whole-gill kinematics from rowing to flapping occurred across a narrow Re range (3–8), which suggests a possible hydrodynamic demarcation between rowing and flapping.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 540–555.