Anthropophilic blackflies (Diptera: Simuliidae) and onchocerciasis transmission in southwest Ethiopia

Abstract. From May 1984 to May 1985, the transmission of onchocerciasis by blackflies (Dipteria: Simuliidae) was studied around Gilgel Ghibe and Gojeb rivers in southwest Ethiopia. The predominant anthropophilic species of Simulium at both localities were S.(Edwardsellum) damnosum sensu law and S.(Lewisellum) ethiopiense. Some S.(Anasolen) dentulosum also landed on human bait at Gilgel Ghibe river.
Dissections of S. damnosum from Gilgel Ghibe and Gojeb revealed mean parous rates of 92% (n = 18,291) and 84% (n = 9530), respectively. S. ethiopiense from Gilgel Ghibe and Gojeb showed mean parous rates of 53% (n = 322) and 93% (n = 14), respectively. Of the parous S. damnosum , 1.3% at Gilgel Ghibe and 0.5% at Gojeb harboured infective third-stage larvae (L3) of Onchocerca volvulus (or morphologically indistinguishable from it). Unknown filariae of animal origin, indicative of zoophily, were found in 0.3% and 0.7% of Simulium damnosum complex females from Gilgel Ghibe and Gojeb, respectively. S. ethiopiense harboured developing (L,) larvae only, with 7.7% infection rate in both localities. In contrast, S. dentulosum did not harbour any filaria larvae. The annual infective biting rate (AIBR) and transmission potential (ATP) of the S. damnosum complex at Gilgel Ghibe river were 858 and 5478, respectively. The AIBR and ATP of S. damnosum s.I. at Gojeb river were 519.5 and 1963, respectively. These results emphasize the predominant role of the S. damnosum complex in the transmission of O. volvulus in southwest Ethiopia     

Effect of weather conditions on the flight activity of Nigerian blackflies (Diptera: Simuliidae)

Abstract. A vehicle-mounted net was used to make hourly catches of blackflies at 700–1000 m altitude in the River Assob valley, central Nigeria, on 20 days during the dry season. Pearson Correlation Matrix analysis of the collection data and meteorology showed that the main factors affecting flight activity of each of the four most abundant blackfly species were primarily light intensity and secondly wind velocity, whereas relative humidity was the least important factor. Right activity showed a negative linear regression against wind, with some activity occurring in wind speeds up to 15 km/h. Distance-weighted least-squares (DWLS) regressions showed little correlation of temperature with activity for Simulium hargreavesi and S.adersi , but S.squamosum and S.vorax had small peaks at 28C and 31C, respectively. DWLS regression against light intensity showed an activity peak at 6000 lux, except in Simulium adersi.     

Light and Electron Microscope Observations On Presporogonic and Sporogonic Stages of Sphaerospora Epinepheli (Myxosporea) In Grouper (Epinephelus Malabaricus)

ABSTRACT. Presporogonic (blood) stages of Sphaerospora epinepheli Supamattaya, Fischer-Scherl. Hoffmann, Boonyaratpalin, 1990 were observed in the circulating blood, sinus of kidney, glomerurar capillaries and liver arteries of grouper Epinephelus malabaricus. the earliest detectable stage was a primary cell with one secondary cell. After cell divisions, nine to 16 secondary cells were found in one primary cell. Ultrastructural examination revealed electron-dense bodies (118-145 nm) in the cytoplasm of primary cells. Sporogonic stages and spores were located in Bowman's space and in kidney tubule lumens. Electron micrographs revealed a similar pattern of spore development as described from other Sphaerospora spp. Kidneys infected with S. epinepheli showed highly vacuolated tubular epithelial cells and severely affected renal corpuscles.     

Embryonic development of the European smelt Osmerus eperlanus eperlanus (L.) (Neva population)

The embryonic development of the European smelt Osmerus eperlanus eperlanus has been described. The whole period of the development has been subdivided into 6 subperiods. More than 80 stages may be described for all of these periods. The development of the European smelt embryo was studied in the 5 different regimes of a constant temperature in the range 9.5–18.3°C. The duration of different stages under different temperature regimes was expressed in the relative units of τ₀ (the time of a single cleavage) and τ_s (the time of formation of a single pair of somites). It was established that the τ_s value had proportionally changed by embryogenesis. Due to this fact, the duration of the stages was expressed only as τ_s. The dependency of the speed of the European smelt embryogenesis on temperature has been shown. This dependence was expressed using the standard interval τ_s and described using the equation log τ_s(t) = 3.22665?0.13876t + 0.00297t ², where t is the temperature.     

In vitro haemagglutination and attenuation of microfilarial motility by haemolymph from individual blackflies (Simulium ornatum) infected with Onchocerca lienalis

Two in vitro tests were used to investigate the effect of Onchocerca lienalis Stiles infection on the haemolymph of Simulium ornatum Meigen. The first of these examined the effect of infected haemolymph on the motility of fresh O. lienalis or Brugia pahangi Buckley & Edeson microfilariae. Incubation of haemolymph from individual flies with fresh microfilariae was performed in the wells of Terasaki micro-tissue culture plates. Motility of both species of parasite was found to be significantly attenuated when compared to worms incubated in control haemolymph groups. The second assay was that of agglutination of cat erythrocytes in the presence of haemolymph from individual flies, also performed in Terasaki plates. This test demonstrated significant increases in the rates of haemagglutination in the haemolymph of O. lienalis infected blackflies. The titre appeared to increase during the initial 5 days of infection up to a level of 1/32+, but then fell between day 5 and 7 to a maximum level of 1/2. The proportion of flies exhibiting haemagglutination also rose following infection. Despite the apparent absence of melanization and encapsulation, simuliids may have at least two humoral haemolymph components available to them for parasite regulation; a fast-acting factor responsible for rapid parasite death, and more specific agglutinins, possibly lectins. The role of the latter in defence is as yet unclear.     

Oviposition response of Simulium reptans (Diptera: Simuliidae) to the presence of conspecific eggs

Abstract.

• 1 The oviposition behaviour of Simulium reptans L. is described from two sites on the River Spey, Scotland. Female aggregations were observed immediately downstream of oviposition sites and were composed mainly of gravid flies (range 60–80%0) together with smaller numbers that were either freshly bloodfed (range 2–17%) or infected with mermithid nematodes (range 0–30%).
• 2 The time from landing on the oviposition sites to the onset of oviposition was recorded. The time in the presence of greater than 1-day-old eggs did not significantly differ from sites with no eggs present. However, the presence of freshly laid or I-day-old eggs significantly shortened the time to onset of oviposition. The cues that elicit oviposition are unknown but it is speculated that they may involve a pheromone.

     

Disturbances in the development of the egg chambers of Galleria mellonella L. (Lepidoptera) after reserpine administration

Reserpine causes some changes in the morphology of developing egg chambers when administered to the last (7th)-instar larvae of Galleria mellonella. Among the alterations, there is a numerical change in the number of egg chambers produced in one ovariole. The number of previtellogenic and postvitellogenic egg chambers was decreased significantly. Histological study revealed a series of pathological alterations in the follicular epithelium, oöcytes and trophocytes. Atrophy or proliferation of follicular cells was often observed. Strong vacuolation of the cytoplasm of cells forming the egg chambers appeared in all developmental stages, mainly at the vitellogenic stage. Changes also occurred in the surface of the ovariole tube.The observed disturbances in the developing ovarioles of the wax moth are probably the consequence of reserpine action on the neuroendocrine system.     

Effect of a juvenoid on the growth and differentiation of the ovary of Corcyra cephalonica (Lepidoptera)

The juvenoid hydoprene (Altozar or ZR-0512) results in various developmental aberrations of the ovary when administered to early last instar larvae of Corcyra cephalonica (Stainton). Among other alterations there is a numerical change in ovarioles in the ovary which in all cases becomes highly voluminous, thus potentially increasing the number of eggs which can be deposited by a female. The importance of the fat body, imaginal discs, RNA and protein synthesis in the development of such changes is discussed. Treatment of 1- and 3-day-old pupae produces severe alterations in ovarian anatomy with histological aberrations in the cell components. The production of only a few fully-grown oöcytes by a female obtained after pupal treatment illustrates the partial sterility of these insects. These defects are possibly caused by the juvenoid inhibiting synthetic activity in the fat body and decreasing the rate of mitosis in the germinal part of the growing ovariole and may also be due to the gonadotropic effect of the juvenoid.     

More on the life cycle of Malamoeba scolyti (Amoebidae: Sarcomastigophora) parasitizing: the bark beetle Dryocoetes autographus (Scolytidae,Coleoptera)

Some new developmental features previously unreported in, the life- cycle of an amoeba Malamoeba scolyti, which cause cysts in Malpighian tubules of the bark beetle Dryocoetes autographus, are described by means of light, phase-contrast, Nomarski interference, and electron microscopy. Two developmental phases are presumed to take place in the life cycle of M. scolyti: a phase with large multinucleate amoebae (trophozoites) developing in the gut and caecum of the host, and a phase (parasitic phase) causing cysts in the Malpighian tubules. Some data on the host-parasite relationship and rate of infection are also discussed.     

The life history of Labiostrongylus eugenii, a nematode parasite of the Kangaroo Island wallaby (Macropus eugenii): development and hatching of the egg and the freeliving stages

Smales L. R. The life history of Labiostrongylus eugenii, a nematode parasite of the Kangaroo Island Wallaby (Macropus eugenii): development and hatching of the egg and the free living stages. International Journal for Parasitology7: 449–456. Labiostrongylus eugenii (Trichonematidae) occurs in the stomach of the Kangaroo Island Wallaby. Egg morphology is similar to that of other strongyloids. When incubated at 25°C embryogenesis is completed in about 30 h. An incomplete moult occurs within the egg, and larvae hatch at a sheathed second-stage $\text{43}\text{1}\text{2}\text{–83}\text{1}\text{2}$ h later. Development occurred at all temperatures between 2° and 37°C with an optimum about 25°C and an upper limit near 37°C. The hatching process is very rapid, taking about 2 min. It is signalled by increased larval activity followed by a change in shell permeability. The larva hatches at that pole of the shell which has become plastic.The sheathed second-stage larva measures 659.50 ± 22.54 μm by 27.98 ± 1.22 μm. Its internal structures are concealed by a mass of opaque granules which were demonstrated as neutral lipid by oil red O staining. A second incomplete moult at 3–4 days results in a doubly sheathed infective larva from which the lipid gradually disappears. The mouth never appears patent and the larvae neither feed nor grow but rather decrease in size with age. Optimal temperatures for larvae range between 15°–25°C with 37°C about the upper limit. The significance of this developmental pattern is discussed.     

Development and ultrastructure of a microsporidian parasite in midgut cells of the larch sawfly, Pristiphora erichsonii (Hymenoptera: Tenthredinidae)

The developmental stages of a microsporidium from larvae of Pristiphora erichsonii were investigated. Meronts appeared to be the only stage containing a diplokaryon. Nuclei of sporonts in a parasitophorous vesicle underwent at least three divisions and uninucleate sporoblasts developed from these multinucleate sporonts. As many as 38 spores were observed with a vesicle. A thin pansporoblastic membrane limited the vesicle and was derived from rough endoplasmic reticulum of the host cell. The microsporidium was tentatively identified as Pleistophora sp. Infection levels of the microsporidium in natural populations of P. erichsonii reached 25%.     

Experiments on the transmission of Babesia divergens to cattle by the tick Ixodes ricinus

A modification of the method of rearing Ixodes ricinus gave a successful method of producing and reliably rearing adequate numbers of this tick for experimental work.Experiments on transmission of Babesia divergens by I. ricinus showed that infections could be initiated only in the adult stage of the tick. Whilst all stages of the F₁ generation of an infected female could transmit infection, larvae and nymphs could not acquire it. Infection persisted throughout the F₁ generation and sometimes up to the F₂ larval stage even when the ticks were maintained on hosts not susceptible to B. divergens. Both parasitaemic and premune carrier hosts were infective to ticks. A single infected adult or nymph could transmit infection.     

Ultrastructure and Sporogony of Eimeria (syn. Epieimeria) anguillae (Apicomplexa) in the Eel (Anguilla anguilla)

ABSTRACT. Ultrastructural studies on Eimeria (syn. Epieimeria ) anguillae (Apicomplexa), parasite of the digestive tract of the eel, have shown that the development of this parasite takes place completely within the host cell. Merogony and gamogony are intracellular but in the epicytoplasmic position. Sporogony is also located within the epithelial cells, which agrees with assignment of this coccidian in the family Eimeriidae. However, depending on the intensity of infection and the physiopathological reaction of the host, the gamont may behave in two ways. 1) In massive infections, gamogony stages cause a genuine destruction of intestinal epithelium. Large numbers of gamonts form nodules and parts of the seriously destroyed epithelium peel off and are released into the lumen of the gut and quickly discharged into the outer environment. This discharged epithelium envelops cells containing immature oocysts that then sporulate outside the host. 2) In light infections, the host cells, which are necrotic due to the presence of a zygote, are pushed between the surrounding intact cells towards the base of the epithelium. Closely above its basal lamella, the oocyst then undergoes sporulation. These results show no taxonomically important biological features (e.g. special mode of implantation to the host cell or active movement of the zygote). Because the morphological characteristics of Epieimeria do not differ significantly from Eimeria , we propose to suppress the genus Epieimeria Dyková and Lom, 1981, and relegate its species into the genus Eimeria .     

性成熟草鱼卵巢发育的年周期变化

产卵前的卵巢同时含有大量4时相卵母细胞及少量2时相和3时相卵母细胞。产后2时相及3时相卵母细胞增多而4时相卵母细胞骤减,8月份4时相卵母细胞的数量又增多,约占卵巢体积的80％,及至11月份其数量又下降。自11月至翌年1月,卵巢中3时相卵母细胞增多而4时相卵母细胞则消失不见。至2月份,新的4时相卵母细胞又开始出现并逐渐增多。性成熟草鱼的卵巢以如此规律周而复始地产生成熟的卵子。卵巢中卵母细胞的发育是不同步的。但在产卵前有大量的3时相卵母细胞向4时相演化,同时有为数不少的发育中的2时相卵母细胞存在。产后卵巢中亦同时存在不同发育时期的卵母细胞。     

Postendocytic vitellin processing in ovarian follicles of the stick insect Carausius morosus (Br.)

Newly laid eggs of the stick insect Carausius morosus contain two native vitellins (Vit A and Vit B). Under denaturing conditions, these vitellins resolved into 3 (A₁, A₂, and A₃) and 2 (B₁ and B₂) polypeptides. All of these polypeptides had counterparts in the female hemolymph from which they were shown to be derived by in vivo labelling. During ovarian development, the 2 vitellins changed both in charge and polypeptide composition. In EV and LV follicles, Vit A resolved into 4 distinct vitellin polypeptides (A₀, A₁, A₂ and A₃). Using a panel of monoclonal antibodies, polypeptide A₀ proved to be immunologically related to polypeptide A₂. In follicles about to begin choriongenesis, polypeptide A₃ was gradually replaced by a lower M_r polypeptide. Over the same time period, polypeptide B₁ changed in charge, but not in M_r. To confirm the existence of a polypeptide processing in C. morosus, ovarian follicles of different developmental stages were exposed in vivo to [³⁵S]-methionine from 6 to 72 h. Data showed that A₀ and B₁ were the polypeptides most heavily labelled after short time exposures to the radioisotope. Polypeptides B₂ and A₃ were also labelled to some extent. With progressively longer exposures, polypeptides A₁ and A₂ also became labelled. In vivo exposure to [³H]-GlcNAc caused all vitellin polypeptides to become heavily labelled. Autoradiographic analysis of ovarian follicles labelled this way showed that, during development, radioactivity was gradually transferred from newly formed yolk spheres in the cortical ooplasm to the central ooplasm. Data were interpreted as suggesting a causal relationship between polypeptide processing and progressive yolk sphere fusion to yield the central ooplasm. © 1993 Wiley-Liss, Inc.     

Potentialities of mermithid nematodes for the biocontrol of blackflies (Diptera: Simuliidae)--a review

Mermithids comprise a family of nematodes which invariably kill/sterilize their insect host(s). These nematodes have considerable potential as biocontrol agents of agricultural insect pests and medically important insect vectors. More specifically, mermithid nematodes appear to regulate natural population of blackflies. The taxonomy of the Mermithidae has been only partially evaluated and the taxonomic status of many representatives is uncertain. At least three mermithid genera and species parasitize North American blackflies, although a more varied mermithid fauna probably exists. The host specificity of mermithid parasites of simuliids is variable, but these nematodes do not appear to infect other stream fauna. The sporadic distribution of mermithid parasites of simuliids among potential biotopes may be associated with a relatively inefficient mode of dispersal for such nematodes. Detailed information is lacking concerning stages in the life cycles of these pathogens and their synchronization with the simuliid host. Mermithids cause pathogenic effects upon several blackfly tissues, although no information is available concerning physiological manifestations of mermithid parasitism in blackflies. A brief review of the present state of knowledge of simuliid taxonomy and bionomics is presented. The physiology of blackflies and their mermithid parasites has been largely ignored. The potentialities of mermithid nematodes for the biocontrol of blackflies are assessed and a feasible research programme presented, in relation to the present state of knowledge of mermithid-simuliid interrelationships and related areas of insect nematology.     

Analysis of growth and rotational behavior of sporangiophores in Pilobolus crystallinus (Wiggers) Tode

The growth and rotation of the sporangiophore of Pilobolus crystallinus, which are important factors in its phototropic behavior, were analyzed throughout its development. The sporangiophore initial emerged from the trophocyst and elongated at the extreme tip without rotating. The elongation rate of the sporangiophore apex then gradually decreased and the apex expanded radially to produce the sporangium, but no rotation occurred. A transient cessation of elongation after sporangium development was followed by resumption of both elongation and radial expansion in the region beneath the sporangium developing the subsporangial vesicle. Rotation was not obvious at this stage. Radial expansion of the subsporangial vesicle continued at a decreasing rate until full size was reached. Elongation then recommenced in the newly established growth zone in the upper region of the sporangiophore just beneath the subsporangial vesicle. During this period of growth, the sporangiophore rotated in a clockwise direction as viewed from above. All growth and rotation ceased about 1 h before ejection of the sporangium into the air. Based on these results, a modified classification of the developmental stages has been proposed.This work was carried out under the Joint Research Program of the Institute of Genetic Ecology, Tohoku University, Japan (892006). The authors please to thank Kaori Koga and Hiroko Kikuchi for their helpful assistance.     

The relationship of age and ovarian development to mating of Delia antiqua (Diptera: Anthomyiidae)

Abstract. The relationship between age and sexual receptivity for male and female onion flies, Delia antiqua (Meigen) (Diptera: Anthomyiidae), and factors affecting ovarian development were examined under various conditions. Confinement in small arenas had a significant negative effect on the rate of oogenesis over the first 10 days of adult life and, in some cases, on the percentage of females inseminated. The rate of oogenesis was not affected by male population density, but high density of females in large arenas appeared to have a priming effect. Few males in single-pair mating bioassays conducted over 24 h were sexually mature at 3–4 days post-eclosion, but > 50% mated when aged 6–7 days. Although females first mated at 3–4 days post-eclosion when confined for 24 h with sexually mature males, most females mated at 6–7 days of age when oocytes in the terminal ovariole position comprised 50% of total egg volume (stage 7 or greater on a 10-stage scale). No females aged 3 days were mated in no-choice and two-choice bioassays with sexually mature males over 24 h. Previtellogenic females (stage 3) were not inseminated, and ovarian development was only correlated weakly ( r = 0.48) with mating. Frequency of mating in mixed-sex groups of twenty flies was comparable with that in single pairs. However, more females were inseminated at 3–4 days, probably as a result of multiple matings by a few precocious males. These results do not support the hypothesis that females mate only when ovarioles are mature.     

Infectivity, growth, development and pathology of Echinostoma caproni (Trematoda) in the golden hamster

Laboratory hamsters (Mesocricetus auratus) were experimentally infected with 75 ± 15 metacercarial cysts of Echinostoma caproni. Worms were recovered from days 7 to 89 post-infection with eight to 90 (average 37) parasites in the small intestine. Worm wet weights averaged 0.85 mg at 10 days, 1.8 mg at 17 days, 3.4 mg at 45 days, and 7.7 mg at 89 days; average dry weights for the identical days were, 0.15, 0.30, 0.70 and 2.2 mg, respectively. The average body area of worms fixed in hot (80°C) alcohol-formalin-acetic acid was 0.21 mm² on day 3, 4.9 mm² on day 10, and 17.7 mm² on day 42. Clinical signs in some hamsters included progressive unthriftiness and watery diarrhea. Gross examination revealed enlarged lymphatic nodules along the length of the small intestine. The histopathological responses of hamsters to the parasite showed erosion of the intestinal villi with lymphocytic infiltration being the primary response; hemorrhagic areas were also observed in the villi.