Prosimulium Fuscum Research Articles

Feeding variability among individual aquatic predators in experimental channels

Experiments were conducted in experimental channels to study feeding variability through time and between conspecific individuals of four species of lotic predators. Large and small Rhyacophila dorsalis (Trichoptera: Rhyacophilidae) were given black fly larvae, mainly Simulium ornatum (Diptera: Simuliidae) of two size classes during laboratory feeding trials lasting up to 5 days. Acroneuria lycorias (Plecoptera: Perlidae) were also given black fly larvae (Prosimulium fuscum, S. venustum) during 11-day laboratory feeding trials. Paragnetina media (Perlidae) and Isoperla signata (Plecoptera: Perlodidae), were supplied with a mixed prey assemblage of black fly larvae and mayfly nymphs, Baetis flavistriga (Ephemeroptera: Baetidae), and Epeorus vitrea (Heptageniidae), for 9 days in field experiments. There was significant variability in the consumption of prey among individuals of R. dorsalis, this being true for both large and small predators. Significant among-predator and day-to-day feeding variability also occured with A. lycorias, P. media, and I. signata. Our experiments showed that there are significant differences in prey consumption among individual predators within a given species, and these differences need to be considered when planning, and interpreting, future studies on predator – prey interactions, particularly those conducted in experimental streams.

Comparison of mitochondrial DNA sequences of seven morphospecies of black flies (Diptera: Simuliidae)

Universal primers constructed from the 16S ribosomal RNA gene in the Drosophila yakuba mitochondrial genome were successfully used to amplify, via the polymerase chain reaction, the homologous region of mitochondrial DNA from seven black fly morphospecies. Amplification was achieved from single larval salivary glands and from single adults preserved in Carnoy's fixative (ethanol - acetic acid, 3:1), allowing DNA sequences and polytene chromosome banding pattern data to be gathered from the same individuals. Nucleotide sequences of the amplified DNA segment (347 base pairs) were obtained from all the species examined. As in Drosophila, the nucleotide base composition of the sequenced segment from black flies had a high adenine (A) and thymine (T) content (A + T on average comprised 77% of all nucleotides.). Nucleotide differences among the seven species were observed at 59 positions (55 nucleotide substitutions and 4 deletions). There were more transversion differences than transition differences both among and within genera; the proportion of transversions was higher between genera than within genera. Most transversion differences were A----T type, comprising 79% of all transversion differences and 50% of all sequence differences. Phylogenetic inference based strictly on transversion differences confirmed traditional generic and tribal groupings, i.e., Prosimulium fuscum (Syme & Davies) is close to Prosimulium magnum (Dyar & Shannon); Simulium decorum (Walker), Simulium venustum s.l. (Say), and Simulium vittatum s.l. (Zetterstedt) are close to each other; Stegopterna mutata (Malloch) and Cnephia dacotensis (Dyar & Shannon), which belong to the tribe Cnephiini, are grouped together.

The digestive enzymes of larvae of the black fly, Prosimulium fuscum (Diptera, Simuliidae)

1. 1. The digestive system of larvae of the black fly, Prosimulium fuscum, resembles those of other aquatic dipteran detritivores, such as mosquito and crane fly larvae. 2. 2. Midgut proteolytic activity is very high, due to the presence of high levels of alkaline proteinases. 3. 3. The only polysaccharides toward which significant enzymatic activity is evident in midgut extracts are α-1,4- and β-1,3-glucans. 4. 4. There is negligible activity toward cellulose, carboxymethylcellulose, xylan, locust bean gum, pectin, chitin, Micrococcus lysodeikticus cells, and phenolphthalein mono-β-glucuronate. 5. 5. The larvae are better adapted to exploit the polysaccharides of fungi and algae than those of vascular plants.

POPULATION STRUCTURE IN BLACK FLIES: ALLOZYMIC AND MORPHOLOGICAL ESTIMATES FOR PROSIMULIUM MIXTUM AND P. FUSCUM (DIPTERA: SIMULIIDAE).

Two aspects of the biology of black flies make the family Simuliidae an evolutionarily interesting group. First, every morphospecies that has been examined cytogenetically has proven to be divisible into multiple chromosomally distinct sibling species (Rothfels, 1979). Second, widespread cytospecies of a sibling species complex are usually broadly sympatric, and narrowly endemic species are embedded entirely within the ranges of the common species. In virtually all cases, the most closely related species pairs within a complex are found sympatrically (Rothfels, 1979, pers. comm.). Species within complexes show very small amounts of genetic divergence at the morphological, karyotypic and allozymic levels (Rothfels, 1979; Crosskey, 1981; Snyder, 1981, 1982; Snyder and Linton, 1983). Taken together, the data on distributions and genetic differentiation suggest that speciation in black flies does not occur through adaptive, allopatric divergence. Understanding the aspects of the genetic organization and biology of black flies that facilitate the apparently ready speciation that occurs in the family will require many diverse studies. One aspect of the genetic organization of a species that is often cited to play a key role in determining speciation ability is population structure (Wright, 1940, 1955; Carson, 1975; Templeton, 1980). The population structure of a species (that is, the distribution of genetic variation within and among its populations) can be readily analyzed. This study is an investigation of the population structure of two closely related species of black flies, Prosimulium mixtum and P. fuscum, using allozymic and morphological variability. Prosimulium mixtum and P. fuscum are the most widely distributed and abundant members of the P. mixtum species complex. These species are sympatric over most of northeastern North America (Peterson, 1970). Five additional members of the species complex are narrowly endemic or widespread but uncommon within this range (Rothfels and Freeman, 1977; K. Rothfels, pers. comm.). Prosimulium mixtum and P. fuscum are the most divergent members of the complex, differing by three fixed autosomal inversions and possessing unique sex chromosome arrangements (Rothfels and Freeman, 1977). These species also possess unique complements of electromorphs at the 6-Pgd locus (Snyder and Linton, 1983) and differ by minor morphological features (Peterson, 1970; Snyder and Linton, 1983). Prosimulium mixtum and P. fuscum have undergone some ecological and life history divergence. While they often occur together in the same stream, they are usually asynchronous (Snyder, unpubl.; K. Rothfels, pers. comm.) and some streams of an area may contain only one species. Prosimulium fuscum females are autogenous (may complete the first ovarian cycle without a blood meal) while P. mixtum females are anautogenous (require a blood meal) (Davies, 1961). Rothfels (1981a) hypothesized that the anautogeny of P. mixtum leads to dispersal among populations and results in a more cohesive gene pool with less population differentiation than is encountered in P.fuscum. This is consistent with

Larval distribution and succession of outlet-breeding blackflies (Diptera: Simuliidae) in New Hampshire

Thirteen described species of outlet-breeding simuliids and five isomorphic sibling species of the Simulium venustum/verecundum complexes were collected in 1978 and 1979. Prosimulium fuscum, P. mixtum, Simulium aestivum, S. aureum, S. decorum; S. tuberosum, S. venustum (CC) and S. vernum were the most widely distributed species while S. aureum, S. decorum and S. venustum (CC) were the most abundant. Simulium decorum, S. tuberosum and S. venustum (AC(gB) and CC) were present at the same sites during both years while the remaining species varied in their occurrence at a specific site between the two years. Succession of Simulium spp. in late winter and spring was similar to that reported from other areas of northern North America. Most Simulium spp. studied were multivoltine while S. corbis, S. croxtoni and S. venustum (A/C) were univoltine. Simulium decorum had single or multiple generations, depending on the site. Larvae of S. venustum (A/C) and most species of the subgenus Eusimulium attached to trailing vegetation, while S. corbis, S. decorum, and S. tuberosum attached more frequently to submerged rocks and sticks. Prosimulium fontanum, S. gouldingi, S. venustum (CC and AC(gB)), and S. verecundum (A/C and ACD) did not demonstrate preference for a particular substrate. Reduction in stream flow affected the number of cohorts of S. aestivum and S. aureum and the number of generations per year of S. aureum and S. vernum.

Succession saisonnière, émergence, voltinisme et répartition de mouches noires des Laurentides (Diptera; Simuliidae)

A study of the distribution and the emergence of blackflies in 33 stations in streams at the Saint Hippolyte Biology Station gives the following dynamic picture: (1) The main emergence starts in May with the appearance of the univoltine species that have grown through the winter, followed by the first generation of spring-growing or summer-growing polyvoltine species. The predominance of the eurytopic univoltine species, mainly Prosimulium fuscum and Cnephia mutata, explains the presence of blackflies in nearly all the stations. (2) In July the second generation of the polyvoltine species appears, Simulium decorum, S. vittatum, S. aureum, S. verecundum, S. croxtoni, and S. vernum; these species lend to be more stenotopic, which restricts emergence mainly to stations near lake outlets; the other stations harbour only small populations of S. tuberosum. (3) The same distribution is evident in late August and early September when the third generation of the polyvoltine species matures, particularly S. tuberosum, S. aureum, and S. verecundum. A wet and cool summer tends to favour the development of large populations of blackflies.

The larval instars and population dynamics of five species of black flies (Diptera: Simuliidae) and their responses to selected environmental factors

The larval instars of four species of black flies were determined. Prosimulium fuscum Syme and Davies and Prosimulium mixtum Syme and Davies had seven instars; however, larvae of these Prosimulium spp. passed through only six instars when development occurred at warmer temperatures. Simulium vittatum Zetterstedt and Stegopterna mutata (Malloch) had seven and six larval instars, respectively. The instars of Cnephia dacotensis (Dyar and Shannon) could not be positively segregated.Stream temperature was the most important physical factor regulating larval black fly population dynamics, determining hatching time and developmental rates. Prosimulium mixtum/fuscum larvae required 240 D °C (day-degrees) above 0 °C for maturation, while St. mutata and C. dacotensis needed 250–275 and 475 D °C, respectively. Stream discharge also influenced the annual dynamics of simuliid populations, as spring floods produced second cohorts of some univoltine species which normally have one cohort of overwintering larvae per generation. Changes in discharge also affected estimates of larval densities by influencing the number of larvae colonizing artificial substrates.

Studies on Pythiopsis cymosa from Newfoundland

An isolate of Pythiopsis cymosa de Bary was obtained from a pupa of the blackfly Prosimulium fuscum (Syme & Davies). The optimum temperature for growth of the isolate was 17°C. The isolate was highly aerobic and grew best at pH 6·9 on a medium containing 4 g of casamino acids per litre. Glucose utilization was first detected at the end of the lag phase, and 79% of the total glucose supplied was utilized during the 24 h period following the end of the lag phase. Ninhydrin-positive substances supplied by casamino acids were utilized except cysteic acid and urea. Compounds released by the fungus into the medium were: γ -aminobutyric acid, citrulline, α -aminoadipic acid, carnosine, α -amino- n -butyric acid, β -alanine and glutamine or asparagine (or both). The morphology of the isolate is described. An attempt to infect a mixed blackfly larval population in the laboratory by using fungal cysts failed.

Collecting and rearing black flies.

This paper, based on a study carried out at the Seney National Wildlife Refuge, Seney, Michigan, and the Patuxent Wildlife Research Center, Laurel, Maryland, describes methods and techniques for collecting, storing, and rearing 8 species of Simuliidae. Included in the study were Cnephia dacotensis (Dyar & Shannon), C. mutata (Malloch), Prosimulium fuscum Syme & Davies, Simulium aureum Fries, S. decorum (Walker), S. venustum Say, S. verecundum Stone & Jamnback, and S. vittattum Zetterstedt. Simuliid eggs collected from a variety of habitats, packed with wet materials in plastic bags and held at 4°C, have remained viable, thus far, up to 424 days. Eggs held at 0° to −70°C failed to hatch when placed in rearing aquariums. Air-dried eggs held at 4°C for 339–535 days failed to hatch after being held in aquariums for 166 days. Immature stages of black flies were successfully reared in 1¼-gallon Pyrex jars and 15-gallon plexiglas aquariums in which the water was agitated by compressed air and aquarium pumps. Water velocities of 0.250–0.542 feet per second were obtained in streams of air bubbles created by use of air stones. Of 21 larval diets used, one consisting of Purina Dog Chow (60-mesh or finer), brain-heart infusion broth, and brewer's yeast powder, and a second consisting of Wayne's dog chow (60-mesh or finer) and brain-heart infusion broth without brewer's yeast powder, were most satisfactory. Larvae were fed 1 gram of diet per 1¼- gallon aquarium and 2 grams per 15-gallon aquarium biweekly. In most of the 225 cultures of S. aureum, S. decorum, S. verecundum, S. venustum, and S. Vittatum it took from 1 to 5 days for the development of eggs to larvae (165 cultures, 73%) and the same number of days for the development of pupae to adults (172 cultures, 76%). Development time for larvae to pupae was fairly closely divided between 11–15 days (63 cultures, 28%) and 16–20 days (53 cultures, 23.6%). The entire period for development from egg to adult after placement of eggs in rearing aquariums was from 21 to 25 days for 26.7% of the cultures.

Occurrence and nature of invertase activity in adult black-flies (Simuliidae)

In vitro invertase activity was shown from two black-fly species, Prosimulium fuscum and Simulium venustum. Invertase activity was confined mainly, if not entirely, to the midgut, sucrose-fed females of the two species having similar levels of the enzyme activity. No invertase activity was found in the salivary glands or the crop. The pH optimum for invertase activity in S. venustum was 6·2. No increase in invertase activity occurred when water-fed S. venustum males were fed sucrose, and the small increase in the females was statistically insignificant. However, after feeding on human blood, the females showed a sharp increase in invertase activity, which then remained at an almost constant level for at least 48 hr. In sucrose-fed adults of both species, homogenates of midguts or of whole bodies of males and females showed oligosacharide synthesis when high concentrations of substrate and homogenates were used.

MS-222 Sandoz as an anesthetic for black fly larvae (Diptera: Simuliidae).

Tests were conducted to determine if MS-222 Sandoz, a widely employed anesthetic for cold-blooded animals, could be used on black fly larvae (Diptera: Simuliidae). Preliminary studies, using Simulium vittatum, S. pictipes, and Prosimulium fuscum indicated that a concentration of about 1:2000 MS-222 Sandoz to water quickly quieted the larvae with sufficiently low larval mortality after 24 and 48 hours.

Three New Ontario Black Flies of the Genus Prosimulium (Diptera: Simuliidae): Part II. Ecological Observations and Experiments

In an earlier paper (Syme and Davies, 1958), three new species in the hirtipes-complex (Prosimulium fuscum Syme and Davies, P. mixtum Syme and Davies and P. fontanum Syme and Davies) were described, compared with related species in other parts of the world, and their known distribution in northeastern North America indicated. In this paper are presented observations on the manner and dates of oviposition, on incubation, on the larval feeding, on the rate of larval growth during the fall and winter in a spring-fed stream, and on differences in habitat and seasonal emergence of the three new species.