Spectral responses of the tsetse fly, Glossina morsitans morsitans

Spectral responses of male Glossina morsitans morsitans Westw, were investigated using behavioural and electrophysiological techniques. Phototactic responses to monochromatic lights of different wavelengths but equivalent intensities (measured either in energy or quantal units) were tested in an apparatus which permitted the simultaneous presentation of pairs of lights to groups of flies. Near ultraviolet light was the most attractive, followed by blue and red, with green and far red light giving no significant responses above control levels. The spectral sensitivity of the compound eye was also determined from the electroretinogram (ERG) recorded from electrodes implanted in the eye which was stimulated with flashes of monochromatic light. Three areas of maximum sensitivity were found by this method in the UV, blue/green and red. The relationship between the behavioural and electrophysiological sensitivity characteristics is explained with reference to visual systems of other Diptera which have previously been described.     

Mating,insemination, and ovulation in the tsetse fly, Glossina morsitans

Virgin females of the tsetse fly, Glossina morsitans orientalis, retain their first egg within the right ovary whereas mated females ovulate. The component of the mating act which causes ovulation and thereby initiates the ovarian cycles which follow, is not insemination, the construction of a spermatophore in the uterus, or a humoral factor associated with the testes, accessory glands or ejaculatory ducts of donor males, or ‘full’ spermathecae of donor females. The ovulation rate increases with copulation time and females are shown to ‘add up’ their ‘sexual experience’ independently of that of the males. Inter-specific matings between G. morsitans and G. austeni also result in ovulation, but an unidentified factor associated with the completion of the mating act was also apparent. It is suggested that a ‘mechanical’ factor probably with nervous and endocrine components is responsible for the release of the egg from the ovary. Observations on the construction of empty spermatophores by aspermic males of G. morsitans are included.     

Hormonal control of lipid synthesis in the fat body of the adult female tsetse fly, Glossina morsitans

Aqueous extracts of brain, thoracic ganglion or corpora cardiaca of female Glossina morsitans were shown to contain a substance which inhibited the synthesis of lipid from l[U-¹⁴C] leucine by fat cells incubated in vitro. The highest concentration of this substance was found in the corpora cardiaca; approximately 1 × 10^?6 gland pairs μl^?1 were required for maximum inhibition. At concentrations greater than 1 × 10^?4 gland pairs μl^?1 the lipid synthesis inhibiting factor (hereafter referred to as the LSIF) was inactivated by the presence of a substance which could be removed by gel filtration. The concentration of LSIF in the corpora cardiaca and midbrain varied throughout the reproductive cycle of the female. Net release of LSIF from the midbrain occurred between the 2nd and 7th day of the 9-day reproductive cycle. Net release from the corpora cardiaca began on day 5 and continued until the end of the interlarval period on day 9. Results are consistent with the hypothesis that LSIF is synthesised mainly in the medial neurosecretory cells of the midbrain whereas the corpora cardiaca are the site of storage and release into the haemolymph. LSIF was present in midbrain and corpora cardiaca extracts from male G. morsitans but at lower concentrations than in females. No variation in LSIF concentration could be correlated with the feeding cycle. LSIF activity was not detected in fresh haemolymph but was found at high concentration in boiled haemolymph, suggesting the presence of an inhibitor which was inactivated at high temperature. Preliminary investigations into the nature of LSIF have shown it to be inactivated by proteolytic enzymes and to be recoverable in a single peak from a Sephadex G15 column.Results support the view that LSIF is a peptide hormone which, in conjunction with an inhibitor, controls the lipid synthetic ability of the fat cells of the adult female tsetse fly throughout the reproductive cycle.     

The nutritional importance of dietary blood components for reproduction in the tsetse fly, Glossina morsitans

Females of Glossina morsitans morsitans were fed diets of different composition and their performance in terms of survival, fecundity and offspring size, used as a basis for assessing the nutritional importance of the dietary constituents for reproduction. Diets comprised defibrinated bovine blood from which individual components had been removed, or various fractions of bovine blood mixed in different ratios and combinations.Flies fed serum-free diets (comprising saline-washed bovine erythrocytes) failed to reproduce and their ovaries were atrophied. Attempts were made to correct these symptoms by adding serum components to washed erythrocytes. Results showed that serum albumin and lipoproteins were vital for ovarian growth. The erythrocytes in defibrinated bovine blood could be replaced by preparations of haemoglobin. Dialysis against isotonic sodium chloride, removal of gamma globulins, removal of lymphocytes or heating to 55°C for 2 h did not alter the nutritional quality of defibrinated bovine blood. The qualitative importance of dietary albumin associated lipids and lipoproteins for oöcyte growth suggests a specialisation which may be peculiar to viviparous Diptera. Results are discussed in terms of the development of synthetic diets for tsetse.     

Biosynthesis of contact sex pheromone in the female tsetse fly, Glossina morsitans morsitans Westwood

Injection of [2,3 ¹⁴C] sodium succinate into recently emerged, unfed females of Glossina morsitans morsitans resulted in incorporation of radiolabel mainly into surface cuticular alkanes. In vivo experiments with intact flies showed that the distribution of labelled alkanes depended on fly mobility, the legs of unrestrained flies possessing proportionately larger amounts of radioactive hydrocarbon material than those of flies whose legs were tied together with a silk suture. The heads of both restrained and unrestrained flies contained proportionately more material per unit surface area than did any other body part. However, ablation experiments and in vitro incubation showed that the most active incorporation of label into alkanes occurred in the abdomen and that all dorsal abdominal segments were equally active. The ventral abdomen also incorporated label into cuticular alkanes in vitro, but other body parts were apparently less able to do so. The sex pheromone of G. m. morsitans is a trimethyl-substituted alkane, the labelling of which appeared to be in proportion to the relative abundance of its methyl groups among those of the other alkanes of the cuticle following injection of either intact or legless flies. Hence it is proposed that sex pheromone is synthesized along with other cuticular alkanes mainly by cells closely associated with the abdominal cuticle of females and that it is spread over the external surface both by diffusion and by grooming which leads to accumulations of hydrocarbon material on the legs.     

Influence of diet on synthesis and utilisation of lipids for reproduction by the tsetse fly Glossina morsitans

Fatty acid composition of lipids from adult Glossina morsitans was unaffected by an in vitro fed diet of cow blood which induces production of under-sized offspring compared to that of flies fed on a superior diet of pig blood. The commonest fatty acids were C_16:0, C_16:1 and C_18:1 and only small differences in proportions were detected between virgin and pregnant females. Rate of lipid accumulation by males and females was the same and was unaffected by diet, but males achieved a maximum of 2.5 mg on day 9 while both virgin and fertilised females reached a maximum of 5,0 mg on day 14 of adult life. Lipid content of pregnant flies then fell to 3.0 mg on the day of larviposition and accumulation began again. A cow blood diet reduced the extent to which the lipids were utilised for larval growth and this was reflected in an altered secretory activity cycle in the female uterine gland. However, no effect on the growth of adult fat body was detectable in such flies. Mating and fertilisation, which influence reproductive events through activity of the endrocine system do not seem to affect the acquisition of lipid reserves by female Glossina. However, they clearly exert considerable influence over distribution of such reserves between fat body and uterine gland, which distribution is also affected by diet.     

Experimental and ultrastructural study of the control of ovulation and parturition in the tsetse fly Glossina fuscipes (Diptera)

Injections of haemolymph, organ extracts and various other substances, as well as in vitro experiments, show that ovary and oviduct extracts on the one hand, and dibutyryl cyclic AMP on the other, enhance ovulation, whereas parturition is stimulated by extracts of the brain, thoracic ganglionic mass, nerve XVII, different parts of the genital apparatus and perhaps proctolin. On the contrary, the proximal neurohaemal organs (corpus cardiacum and perisympathetic organs) appear to contain a substance inhibiting parturition. Lastly, normal intact flies cannot respond to extracts facilitating parturition in decapitated flies. Neuromuscular junctions probably containing peptides and neurotransmitters are described in the muscles of the ovaries, oviducts and the vaginal aperture. Other junctions containing neurotransmitters only are present in uterine and intersegmental muscles. The neurohaemal areas of nerve XVII contain 3 types of peptidergic terminals. From our overall results it is concluded that ovulation is regulated by neurosecretory products released at neuromuscular junctions in the ovaries and oviducts. Parturition control is more complicated. A first neurohormone (parturition-stimulating hormone) appears to be produced in the nerve centres and released in neurohaemal areas located on nerve XVII in the vicinity of the uterus; it enhances the contraction of this organ. A second neurohormone, the parturition-inhibiting hormone may be released in the corpora cardiaca and the median perisympathetic organ. A cephalic nervous factor might exert inhibitory action.     

Hormone stimulated lipolysis and proline synthesis in the fat body of the adult tsetse fly, Glossina morsitans

G. morsitans fat cells incubated in vitro with l-[U-¹⁴C]-leucine incorporated the radiolabel, mainly into triglycerides. Aqueous extracts of corpora cardiaca, midbrain, or thoracic ganglion stimulated the release of radiolabelled material from prelabelled fat cells in vitro. Corpora cardiaca extracts were the most active, approx. 1 × 10^?3 gland pairs/μl elicited the maximal response. At concentrations above 1 × 10^?3 gland pairs/μl the activity of corpora cardiaca extracts was inhibited by a substance which could be removed by gel filtration. The stimulatory factor in nervous-tissue extracts was destroyed by proteolytic enzymes and was recoverable in a single peak by Sephadex G15 gel filtration. Results suggest that it is a peptide hormone produced mainly by the median neurosecretory cells of the midbrain with the corpora cardiaca being the site of storage and release. No hormone was detectable in fresh haemolymph, but it was found at high concentration in boiled haemolymph, implying the presence of a heat labile inhibitor.Under the in vitro conditions used the hormone stimulated the synthesis of proline from alanine and the hydrolysis of triglycerides to free fatty acids. The probable functions of the hormone are to stimulate proline synthesis in response to demand for flight and/or to mobilise lipid for larval nutrition. The relative importance of these apparent functions in vivo could not be determined.     

Effects of sodium-transport inhibitors on diuresis and mid-gut (Na+ + K+)-ATPase in the tsetse fly Glossina morsitans

The effects of four inhibitors of specific sodium-transport mechanisms on diuresis in the tsetse fly Glossina morsitans, have been determined. Ouabain (1.0, 0.1 mM) and ethacrynic acid (1.0, 0.2 mM) reduced the rate of water loss, whereas amiloride (1.0 mM) and furosemide (1.0 mM) did not. The effects of ouabain, ethacrynic acid and meal size upon the anterior mid-gut (Na⁺ + K⁺)-ATPase activity were also determined. For ouabain, the negative logarithm causing 50% inhibition of (Na⁺ + K⁺)-ATPase (pI₅₀) was 6.0, whilst ethacrynic acid together with meal size did not affect the activity of this enzyme. These results show that diuresis in this insect involves the active transport of sodium ions by both electrogenic and $\text{Na}{}^{\mathrm{+}}\text{K}{}^{\mathrm{+}}$ exchange pumps.     

Diapause of the southwestern corn borer, Diatraea grandiosella: Further evidence showing juvenile hormone to be the regulator

Further evidence is presented to demonstrate the involvement of juvenile hormone (JH) in regulating diapause in the final larval stage of the southwestern corn borer. Diatraea grandiosella. JH titres in the haemolymph were measured throughout the entire diapause period. Additional results showed that actively secreting corpora allata are necessary to maintain diapause because allatectomized larvae terminated diapause prematurely. A topical application of JH mimic 2 days after the allatectomy prevented this premature termination of diapause. Intact nervous connections between the brain and the corpora allata were necessary for the maintenance of JH secretion. Other surgical work showed that the brains of nondiapausing larvae exhibited a higher ecdysiotropic activity than those of pre-, early-or mid-diapausing larvae.A single application of a JH mimic was more effective in maintaining a diapause-like state in nondiapausing larvae than were repeated topical applications of C₁₈-JH or an implantation of active corpora allata, suggesting that JH was more rapidly metabolized than was the JH mimic. The oxygen consumption of diapausing larvae which had received repeated topical applications of JH mimic was not significantly elevated over that of the controls indicating that treated larvae maintained a low metabolic rate even though they reverted to the spotted morph. A single application of 0.03 μg JH mimic/larva was sufficient to prolong diapause, thereby confirming that JH is necessary for diapause maintenance.     

Song of the finch Lagonosticta senegala: Interspecific mimicry by its brood-parasite Vidua chalybeata and the role of song in the host's social context

The African village indigobird Vidua chalybeata mimics the song of its brood-host, the Senegal firefinch Lagonosticta senegala. Firefinches in large aviaries did not respond to mimicry of their song and calls by indigobirds in the same aviaries. The lack of agonistic reaction by the firefinches is related to the non-agonistic meaning of song in the social behaviour of the firefinches. Song was not given during experimentally induced aggressive behaviour in the firefinches, but was given during courtship and by both male and female firefinches separated from their mates. Thus the main communicative function of song in L. senegala is in pair-bond maintenance.     

Omnivory in the calanoid copepod Temora longicornis: feeding, egg production and egg hatching rates

We measured in laboratory experiments the ingestion, egg production and egg hatching rates of female Temora longicornis as a function of diet. The diets consisted of a diatom (Thalassiosira weissflogii), an autotrophic dinoflagellate (Heterocapsa triquetra), and a bacterivorous ciliate (Uronema sp.) given as sole foods, or combinations of these single-food items: diatom+dinoflagellate, diatom+ciliate, dinoflagellate+ciliate, and diatom+ciliate+dinoflagellate. For the three single-item diets, the functional response was similar; i.e., ingestion rate increased linearly with food concentration (food range: ∼25 to ∼600 μg C l⁻¹). When all diets were considered, maximum daily carbon ration (∼70% of body weight) was independent of food type. However, the maximum daily egg production rate (12% of body carbon) was obtained with the diatom diet. For all diets, both ingestion and egg production rates increased with food concentration. Ingestion and egg production rates were affected differently by the interaction of food concentration and food type: at low food concentrations, ingestion rates were highest on diets containing the diatom. At high food concentrations, egg production rates were highest on the two phytoplankter diets and their combination. The presence of the ciliate in the diet did not enhance ingestion rate or egg production. Mixed-food diets did not enhance egg production relative to single-food diets. Hence, dietary diversity did not appear to be particularly advantageous for reproduction. Carbon-specific egg production efficiency (EPE; egg production/ingestion) was independent of food concentration and type, and equaled 9%. Egg hatching success was low (mean<30%) and independent of food concentration and type, and egg production rates. Our results are consistent with previous observations that egg production in T. longicornis is enhanced during diatom blooms. However, the relatively low EPE and egg hatching success suggest that reproduction and recruitment in this study were severely constrained by the biochemical composition of the diet, or the physiological condition of the females towards the end of their season of growth in Long Island Sound.     

Schistosoma mansoni: Influence of the mouse host's sex,age, and strain on resistance to reinfection

Male and female CBA strain mice varying in age from 2 to 7 months were observed to acquire the same degree of resistance to reinfection with Schistosoma mansoni. Random bred Tyler's Original (TO) strain mice obtained from different commercial suppliers showed significant variation in mortality rate and the levels of resistance they respectively acquired to homologous reinfection with S. mansoni. Measurement of the mandibles of representative mice from the three TO mouse colonies confirmed the presence of genetic differences. A further comparison of seven strains of mice showed there to be significant differences, with respect to resistance to reinfection, between the inbred strains C57BL and C3H. However, in relation to the intermediate responses of other strains, this difference could not be attributed to H-2 specificity. In all of the strains tested there was a significant correlation between the number of worm pairs derived from the primary infection and the degree of resistance to challenge.     

云南元江芒果园桔小实蝇成虫日活动规律及空间分布格局

利用甲基丁香酚引诱剂和黄板对桔小实蝇Bactrocera dorsalis成虫日活动规律及飞行高度进行了研究,同时根据多种聚集度指标对桔小实蝇成虫的空间分布格局进行了分析。结果表明:元江县挂果期芒果园内桔小实蝇日活动量高峰出现在10:00、16:00左右,活动量低谷出现在8:00、14:00和19:00左右,日间温湿度与其日活动量之间无线性相关关系;成虫飞行高度随时间变化,受降雨影响,雌雄成虫飞行高度存在差异。上午、中午成虫多近地飞行,午后多在1.5 m以上高度飞行,降雨导致成虫飞行活动量大幅减退,多分布于1.5 m以上枝叶附近。株高8 m的3a芒果树4 m高度处黄板捕获虫量最大,其次是2 m高处,6m以上虫量较少。雄性成虫在芒果园中呈聚集分布,原因之一是其自身的聚集行为;雌虫空间分布不均,主要呈聚集分布,少数部分为均匀分布,其聚集由环境因素造成。     

转基因鱼试验湖泊铜锈环棱螺种群动态及次级生产力

2008年2月至2009年1月对转基因鱼试验湖泊铜锈环棱螺的种群生态学进行了周年研究.铜锈环棱螺的平均密度和生物量分别为28.96个/m2和17.33 g/m2,丰度最高值出现在4月(34.29个/m2和54.51 g/m2),其次为12月(25.1个/m2和36.18g/m2).试验湖泊中铜锈环棱螺在4-7月繁殖,种群中含有4个年龄组,其中2008年龄组占绝对优势.铜锈环棱螺壳长-体重方程为:lg Ww=2.8791 x 1g SL-3.4227,使用瞬时生长法测算试验湖泊铜锈环棱螺的周年生产量,带壳湿重为12.72g·m-2·a-1,去壳干重为0.74 g·m-2·a-1,P/B系数为0.42.估算试验湖泊2005年至2009年铜锈环棱螺生产量(去壳干重)分别为2.24,2.49,1.50和0.74 g·m-2·a-1.多元逐步回归分析显示总氮对铜锈环棱螺的次级生产量有显著影响,转基因鲤的捕食压力也可能是影响铜锈环棱螺生产量的重要因素.     

Stress-induced accumulation of glycerol in the flesh fly, Sarcophaga bullata: evidence indicating anti-desiccant and cryoprotectant functions of this polyol and a role for the brain in coordinating the response

Nondiapausing larvae of the flesh fly, Sarcophaga bullata, responded to several forms of short-term environmental stress (low temperature, anoxia and desiccation) by accumulating glycerol. Elevation of this polyol, regardless of the type of stress that induced accumulation, conferred cold resistance: larvae with high glycerol levels were 3-4 times more tolerant of a 2h exposure to -10 degrees C than unstressed larvae. Protection against low temperature injury, as well as dehydration, was also attained by injection of exogenous glycerol into third instar larvae. This artificially induced cold hardiness was only temporary: when glycerol-injected larvae were exposed to -10 degrees C immediately after injection, survival was high, but none survived if they were injected and then held at 25 degrees C for 2 days before the -10 degrees C exposure. Larvae ligated behind the brain immediately after low temperature exposure failed to accumulate glycerol, but glycerol did accumulate in larvae ligated 6-24h after cold treatment, thus implying a critical role for the brain in initiating glycerol production. Interestingly, a much shorter exposure (2h) to low temperature was sufficient to reduce the maximum rate of water loss. Collectively, these observations suggest that multiple pathways may be exploited in response to stress: one pathway is most likely associated with rapid cold hardening (RCH) which generates immediate protection, and a second pathway remains activated for a longer period to enhance the initial protection afforded by glycerol.     

Short Communication: Analysis of effective light in different photobioreactors: its influence on growth,photosynthetic activity and glycerol production by the freshwater green alga Chlamydomonas reinhardtii

The unicellular green alga Chlamydomonas reinhardtii synthesizes glycerol as an osmoregulatory metabolite when exposed to high saline concentrations (200 mM NaCl). Response to osmotic stress can be used for biotechnological production of this compound. When synthesis of a substance is linked to photosynthetic capacity and consequently to effective light, the production on a large scale makes an efficient utilization of light necessary. In the present work a model for evaluation of effective light has been tested.     

Natural variation of carotenoids in the eggs and gonads of the echinoid genus, Strongylocentrotus: implications for their role in ultraviolet radiation photoprotection

We examined variability in carotenoid concentration in the gonads and eggs of four sea urchin species (Strongylocentrotus purpuratus, Strongylocentrotus franciscanus, Strongylocentrotus pallidus and Strongylocentrotus droebachiensis) to explore the possible role of carotenes as photoprotectants. Carotene concentrations were measured in gonads and gametes of each species, while in eggs the ultraviolet radiation (UV-R) sensitivity and self-shading capacity by carotenes were calculated. Mean concentrations of carotenes in gonads ranged from 0.13±0.017 mg g⁻¹ dw (S. purpuratus), 0.14±0.019 mg g⁻¹ dw (S. franciscanus), 0.29±0.079 mg g⁻¹ dw (S. pallidus) to 0.36±0.06 mg g⁻¹ dw (S. droebachiensis). In eggs, concentrations ranged from 0.026±0.003 to 0.09±0.034 mg g⁻¹ dw. UV-R sensitivity in eggs was quantified by measuring UV-R induced first-cleavage delay. Intra-specifically, cleavage delay varied significantly between individuals, and could be correlated with carotene concentration. Interspecific differences in cleavage delay and carotene concentrations were not correlated. Using the observed concentration of β, β-echinenone (which makes up between 82.4% and 94.9% of the total carotene concentration in the eggs) and a molar extinction coefficient of ε=13.7×10³ mol⁻¹ cm⁻¹ at 334 nm, we calculated self-shading efficiency in the eggs. Self-shading capacity (J₃₃₄) indicated that the eggs could only screen from 4.6% (J₃₃₄=0.046) down to 1.5% (J₃₃₄=0.015) of UV-R at 334 nm. While not sunscreens, we suggest that carotenes can photoprotective in echinoid eggs, probably by mitigating the effects of reactive oxygen species.     

Subchloroplastic localization of NAD kinase activity: evidence for a Ca2+, calmodulin-dependent activity at the envelope and for a Ca2+, calmodulin-independent activity in the stroma of pea chloroplasts

Chloroplasts were prepared from pea seedlings and tested for NAD kinase activity. More than half of a Ca²⁺, calmodulin-dependent activity and most of a Ca²⁺, calmodulin-independent activity of the homogenate were associated with chloroplasts. The Ca²⁺, calmodulin-dependent activity could be detected by adding Ca²⁺ and calmodulin to the incubation medium containing intact chloroplasts. This activity could not be separated from the chloroplasts by successive washes or by phase partition in aqueous two-polymer phase systems. After chloroplasts fractionation, the Ca²⁺, calmodulin-dependent NAD kinase activity was localized at the envelope, and the Ca²⁺, calmodulin-independent activity was recovered from the stroma. In view of these results and of a previous report [Simon (1982) Plant Cell Rep. 1, 119–122] the occurrence and presumed role of calmodulin in the chloroplast are discussed.