Factors influencing spawning and pairing in the scale worm Harmothoe imbricata (Annelida: Polychaeta)

Endocrine and environmental factors control reproduction of the polynoid scale worm Harmothoe imbricata. We confirmed that the rate of vitellogenesis was greater in winter specimens transferred from ambient regimes of photoperiod and temperature to a light:dark (LD) photoperiod of 16:8 at 10 degrees C and showed that the number of females spawning was significantly greater than for those transferred to LD8:16 at 10 degrees C. The endocrine mediation of this response was investigated using prostomium implantations. Significantly more LD8:16 females implanted with prostomia from LD16:8 conditioned females spawned than LD8:16 females implanted with LD8:16 prostomia. Females without prostomia failed to spawn. LD16:8 exposure may increase levels of a possible "spawning hormone" in the prostomium. Spawning proceeded in these LD16:8 females and allowed spawning to occur in LD8:16 females implanted with LD16:8 prostomia. In LD8:16 prostomia, titers of the spawning hormone reached the threshold in significantly fewer individuals, so that significantly fewer females implanted with LD8:16 prostomia spawned. Using Y-maze choice chambers, pair formation was shown to be under pheromonal control, with males being attracted to mature females but not to females carrying fertilized oocytes or to LD8:16 conditioned females. Production of this attraction pheromone can, therefore, be manipulated through photoperiodic control, suggesting a link between oogenesis, spawning, and pheromone production.     

Some environmental factors affecting the reproduction of Aphanius dispar (Rüppell, 1828)

In order to determine the suitability of thecyprinodont fish Aphanius dispar as a biologicalcontrol agent for mosquito larvae, the effects oftemperature, salinity, feeding rate and photoperiod onits reproductive condition were studied. The factorsexamined were the gonado-somatic index (GSI) and fourdistinct stages of cell maturation in the ovaries(oogonia, primary oocytes, secondary oocytes andmature ova). The fish were found to be tolerant to awide range of the examined factors. GSI's were notaffected by ambient temperatures over the range of18 °C to 37 °C. However, oocyte maturationstages increased as temperatures rose from 18 °Cto 27 °C, with mature ova first being found at thelatter temperature. No significant differences amongmaturation stages were found between27 °C–37 °C. At salinities ranging from of0 ppt to 56 ppt, no significant differences were found betweenmean GSI's, except for the two extremes of the testrange. The ovaries of fish kept in distilled watercontained primordial germ cells only. In feedingexperiments, significant differences were found onlybetween the ovaries (GSI's and oocyte maturationstages) of fish deprived of food and those fed at1% body weight per day. Regarding photoperiod,a decrease in day length from 14L:10D (the longest dayof the year) to 10L:14D (the shortest) caused adecrease in oocyte maturation stages. Fish at theintermediate level (12L:12D) still had ovariessuitable for spawning, whereas those at 10L:14D didnot. The results of this study show that limitinglevels for adequate reproductive condition were foundfor some of the factors investigated, however, rangesof the factors above these levels were relativelylarge. That Aphanius dispar's reproductivecondition may be controlled in an artificialenvironment is essential for it to be mass produced,and a prerequisite for its use in the biologicalcontrol of mosquito larvae.     

Photoperiod and temperature affect reproductive and nonreproductive functions in male prairie voles (Microtus ochrogaster)

Adult male prairie voles (Microtus ochrogaster) were housed for 10 wk and exposed to long (16L:8D) or short (8L:16D) photoperiods at 21 degrees or 5 degrees C. Maintenance in short day lengths reduced testicular, epididymal, and seminal vesicle mass and also significantly depressed spermatogenic activity. Cold ambient temperature further suppressed gonadal size in voles exposed to short days. Several pelage characteristics were affected by photoperiod, but not by temperature. Increased fur density, fur depth, and length of guard hair and underhair were observed in voles exposed to short days. Intrascapular brown fat and gonadal fat pad mass as well as body mass were significantly less in voles housed in cold temperatures than in voles exposed to warm ambient temperatures; photoperiod did not affect these parameters. Approximately 30% of the male voles exposed to short days maintained their reproductive systems, yet they clearly processed photoperiodic information; all short-day males, regardless of reproductive condition, had comparable winter pelage development. Our results suggest that in prairie voles, photoperiod may be a predictive cue for reproductive function in nature; however, it appears that pelage development is a more obligatory response to photoperiod than is reproduction.     

Coping with resource variation: Effect of constant and variable intervals between feeding on reproductive performance at first spawning of female three-spined sticklebacks

Female three-spined sticklebacks Gasterosteus aculeatus exposed to spring conditions (14) C and a photoperiod of 16L: 8D), and fed 6% of initial body weight per day of enchytraeid worms (controls) over 56 days, or either at regular 3-day or variable 1–5-day intervals between feeds, did not differ significantly in the proportion spawning (72%), in time to first spawning (24·5 days), in fecundity at first spawning (34) or in egg diameter (1·4 mm) at first spawning. There was no significant effect of feeding regime on lipid concentration of females immediately after first spawning (18·8% dry weight), but the experimental females had a slightly lower dry matter content and lower fresh and dry liver weight than controls. Eggs of females on the variable-interval regime had a higher lipid content than eggs from other groups. Days to spawning was correlated inversely and fecundity positively with initial length. Females adjusted their food intake to compensate for short periods of food deprivation, allowing them to maintain their reproductive performance at first spawning.     

Effects of cold storage on field and laboratory performance of Trichogramma carverae (Hymenoptera: Trichogrammatidae) and the response of three Trichogramma spp. (T. carverae, T. nr. brassicae, and T. funiculatum) to cold

Delaying emergence of Trichogramma spp. is critical for commercial production. Here, diapause induction was considered for three species (Trichogramma nr. brassicae Bezdenko, Trichogramma carverae Oatman & Pinto, and Trichogramma funiculatum Carver), and the effect of storage temperature (4 degrees C, 8 degrees C, and 10 degrees C) and time (1-8 wk) was investigated for T. carverae. For all species, percentage of emergence was lowered after an initial diapause induction period (28 d at 14 degrees C and a photoperiod of 8:16 [L:D] h) and lowered further after 1-mo storage at 3 degrees C and a photoperiod of 0:24 (L:D) h. No wasps emerged after 2 mo of storage, suggesting that true diapause was not induced. The effect of 1-8-wk storage on wasp quality was investigated for T. carverae both in the laboratory and the field. Initial fieldwork suggested that this species could be successfully stored at 10 degrees C under continuous light (after 5-d development at 25 degrees C and a photoperiod of 16:8 [L:D] h) without reducing the ability of wasps to parasitize eggs in the field. In a second experiment, storage temperatures lower than 10 degrees C and storage times 3 wk or longer had a negative impact on emergence and longevity, and effects were not additive. Negative effects may partly reflect size changes, because size decreased in response to storage time, and there was an interaction between time and temperature effects on size. Storage time was the major factor influencing fecundity and field success; both fitness measures were reduced after storage of 3 wk or longer. T. carverae can therefore be successfully stored for up to 2 wk without detrimental effects, and 10 degrees C is the preferred storage temperature. T. carverae seems to survive unfavorable temperature conditions by entering a state of quiescence.     

Development, survivorship, and reproduction of Helicoverpa armigera (Lepidoptera: Noctuidae) under constant and alternating temperatures

Laboratory studies were conducted to assess the effect of temperature on the survival, development, fecundity, and longevity of Helicoverpa armigera (Hübner) at 11 constant temperatures ranging from 12.5 to 40 degrees C, as well as at five alternating temperature regimes (25-10, 30-15, 32.5-17.5, 35-20, and 35-27.5 degrees C) and under a photoperiod of 16:8 (L:D) h. H. armigera reared at constant temperatures did not develop from egg to adult (emergence) outside the temperature range of 17.5-32.5 degrees C. The alternating conditions expanded this range from 10 to 35 degrees C. The lowest developmental thresholds of the immature stages were estimated by a linear model and ranged from 10.17 (pupal stage) to 11.95 degrees C (egg stage) at constant temperature regimes and from 1.1 to 5.5 degrees C, respectively at alternating temperatures. The values of developmental thresholds estimated using the nonlinear (Lactin-2) model were lower than those estimated by the linear model for constant and alternating temperature regimes except for larval and pupal stages at constant temperatures. Mean adult longevity fluctuated from 34.4 d at 15 degrees C to 7.6 d at 35 degrees C. Females reared under all alternating temperature regimes laid more eggs than females reared at any, except the 25 degrees C, constant temperature treatment. The intrinsic rate of increase was highest at 27.5 degrees C, at both the constant and the corresponding alternating temperature regimes (0.147 and 0.139, respectively). Extreme temperatures had a negative effect on life table parameters.     

Effects of photoperiod and temperature on reproductive diapause in Ophraella communa (Coleoptera: Chrysomelidae), a potential biocontrol agent against Ambrosia artemisiifolia

Abstract To investigate the seasonal adaptation strategies of Ophraella communa to new habitats, the effects and regulation mechanisms of photoperiod and temperature on the reproductive diapause in a population collected from Changsha, Hunan were examined. Adults showed obvious reproductive diapause, which was regulated by photoperiod and temperature. At 30°C, there was no adult diapause occurring under either long‐day or short‐day conditions; at 25°C the pre‐oviposition period was short and fecundity was high in adult females under L : D 16 : 8 h, whereas under L : D 12 : 12 h, a few females entered reproductive diapause; at 20°C under short‐day conditions, all female adults entered diapause. The pre‐oviposition period was significantly prolonged when the pupae and adults were transferred from long‐days to short‐days, but the day length influence was not obvious when they were transferred only in the adult stage. However, the fecundity dropped greatly no matter whether the photoperiod shifted to short‐days only in the adult stage or whether the shift occurred in both the pupal and adult stage. The fecundity was extremely low when photoperiod shifted from long‐days to short‐days in both pupal and adult stages. This was an indication that the pupal and adult stages were the photoperiod‐sensitive stage for adult reproductive diapause. This was especially true for the photoperiod in the pupal stage, which has a distinctly significant regulative effect on reproductive diapause. Additionally, this article also addresses the reason for different photoperiodic response patterns in reproductive diapause induction between the Changsha strain and the Tsukuba strain (Japan) of O. communa.     

Effect of spawning number and ration on reproductive performance of the batch-spawning three-spined stickleback Gasterosteus aculeatus

An experiment quantified the effect of food ration and spawning number on the breeding season reproductive performance of batch-spawning, female three-spined sticklebacks Gasterosteus aculeatus . Individually housed females were maintained on fixed rations of 2, 4, 8 or 16% of their initial postspawning mass of live enchytraeid worms from immediately after their first spawning until they ceased spawning. Number of spawnings correlated positively with ration. Total breeding season reproductive investment (total wet mass of eggs produced as a percentage of initial postspawning female mass) ranged from 38% at the 2% ration to 147% at the 16% ration. At the lower rations, postspawning mass, batch fecundity and wet and dry masses of the batch declined over successive spawnings, with the rate of decline inversely related to ration. At the highest ration, there was no decline in batch fecundity and postspawning mass increased over successive spawnings. Mean reproductive investment per inter-spawning interval was higher at the highest ration, but at all rations declined over successive spawnings. Mean reproductive effort per inter-spawning interval (wet mass of eggs spawned as a percentage of the wet mass of food consumed over the inter-spawning interval) was inversely related to ration. At the higher rations, reproductive effort showed no trend over successive spawnings. Neither spawning number nor ration had a systematic effect on egg diameter, wet mass per egg, dry mass per egg or total lipid content of the eggs. If the rate of food intake was insufficient, although batch fecundity declined, the main adjustment was a reduction in the number of spawnings in the breeding season.     

Seasonal Variations and Diurnal Rhythms of Gonadotropin (GtH2) Levels in Immature and Mature Female Carp (Cyprinus carpio L)

Daily changes of gonadotropin (GtH2) blood levels of immature and mature carp females were investigated in four seasons during the year: spring, summer (spawning period) and in autumn and winter (“resting” period). GtH2 levels were measured using ELISA method. The maturity stage of oocytes was determined histologically and on the base of germinal vesicle position in the oocyte. It appeared shown that GtH2 levels changed daily during the year in the range of 3.56 to 6.61 ng/ml, regardless of the state of ovarian maturity. Cosinor analysis and ellipse of errors revealed the presence of a circadian rhythm in GtH2 levels only in mature females during the reproduction period (L:D=16:8, water temp. 20 to 22°C).     

Photoperiod influences the critical caloric intake necessary to maintain reproduction among male deer mice (Peromyscus maniculatus).

The concept of critical day length is well established among rodents; reproductive function is maintained when day lengths are greater than some specific threshold. In addition to day length cues, seasonal breeding in deer mice can also be regulated by food availability. The caloric threshold necessary to support reproduction remains unspecified for seasonally breeding rodents. The present study examined the interaction between photoperiod and food availability on reproductive function in adult male deer mice (Peromyscus maniculatus). A critical caloric intake profile was constructed in long (16L:8D) and short (8L:16D) photoperiods; groups of deer mice in both photoperiods either received food ad libitum or 90, 80, or 70% of their individual ad libitum food intake for 10 wk. At autopsy, paired testes, epididymides, and seminal vesicles were removed and weighed. Body mass, total body fat, and total body water contents were also obtained. Short, as compared to long, day lengths inhibited the reproductive systems of male deer mice. However, food consumption interacted with photoperiod to affect reproductive function. Significant reductions in reproductive organ size as well as spermatogenic activity were observed among short-day mice after a 10% reduction in ad libitum food intake. Long-day animals required a 20% reduction in caloric intake to depress reproductive function. Body mass and total body water content were generally unaffected by either photoperiod or food consumption. Total body fat content was reduced in short- as compared to long-day mice. Individual reproductive responsiveness to short days increased as food availability decreased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interaction of Nosema pyrausta and temperature on Ostrinia nubilalis egg production and hatch

Nosema pyrausta is an obligate pathogen causing reduced fecundity and longevity of Ostrinia nubilalis. This study was conducted to determine the combined effects of N. pyrausta infection and temperature on O. nubilalis egg production and hatch. N. pyrausta-infected and noninfected O. nubilalis were maintained in two different temperature regimes. The first regime allowed females to oviposit under optimum conditions (27 degrees C, 65% RH, 16:8 (L:D)), while females in the second regime were held initially under the same humidity and light conditions, but a constant temperature of 16 degrees C for 1 week after which they were transferred to optimum ovipositional conditions. Studies were performed initially with O. nubilalis populations and later with individual mating pairs. In studies with O. nubilalis populations, the mean number of eggs laid per female under optimum conditions was 660, while N. pyrausta-infected females held initially at 16 degrees C laid 116 eggs per female. In studies with individual mating pairs, N. pyrausta infection reduced egg production per female 53 and 11% in the 16 and 27 degrees C temperature regimes, respectively, compared to noninfected females under optimum conditions. Exposure to 16 degrees C temperatures early in the ovipositional period had a more profound impact on reducing egg production in N. pyrausta-infected than noninfected O. nubilalis.     

Age at puberty, fertility and litter size of ewe lambs reared under different photoregimens

Age at puberty, fertility and litter size of ewe lambs of synthetic sire and dam strains raised under different photoregimens were determined. The lambs were bred during January, May or September at 30 to 32 weeks of age. Irrespective of birth date, the lambs were reared under continuous light from birth to 5 weeks of age. From 5 to 20 weeks of age, they were kept under 16 hours of light dairy (16L:8D; Treatment A), 8 hours of light daily (8L:16D; Treatment B), or a split photoperiod of 8 hours total light daily (7L:9D:1L:7D; Treatment C). Subsequently, all lambs were exposed to 9 hours of light daily until after breeding. Lambs were exposed to rams for two estrous periods after treatment with fluorogestone acetate-impregnated intravaginal sponges and pregnant mares' serum gonadotropin (PMSG) to induce synchronized estrus. Although the age at puberty (174 days) was similar among treatments, the incidence of puberty prior to progestagen sponge treatment was higher ( approximately 50%) for lambs reared under Treatments A and C than under Treatment B. Fertility and litter size of lambs were not influenced by the previous photoperiod history or by sexual maturity, i.e., puberal or prepuberal, at the start of the sponge treatment. However, strain, age and weight of lambs at breeding influenced significantly the reproductive outcome.     

Cue hierarchies and testicular development: is food a more potent stimulus than day length in an opportunistic breeder (Taeniopygia g. guttata)?

Opportunistic breeders inhabit areas with unpredictable changes in environmental conditions. In such places favorable breeding conditions can occur during any time of year, and one prediction is that individuals should attend to photoperiod less than to more immediate cues to time reproduction. This study tests whether zebra finches utilize photoperiod independently of other proximate cues, specifically food availability. We transferred semi-domesticated male Lesser Sundas zebra finches (Taeniopygia guttata guttata) from 8 h light, 16 h dark per day (8L:16D) with ad libitum food availability to 20L:4D with ad libitum food (LD ad lib group) or food restriction (LD restricted group). A third group remained on 8L:16D with ad libitum food availability (SD ad lib group). Testis volume in LD ad lib males increased and was larger than other groups within 30 and 60 days of photostimulation. By contrast, LD restricted males and SD ad lib males did not exhibit significant gonadal growth. However, both LD groups increased mass irrespective of food availability. Surprisingly, at the end of the experiment the SD ad lib group sang the most undirected song. Our data demonstrate that long days alone are not sufficient to drive reproductive development in this opportunistically breeding species. Rather, it appears that reproductive development is stimulated by extended feeding times or increased food abundance during long days, and not by changes in day length per se. These data lend support to the proposition that photoperiod acts as a supplementary cue or permissive factor in this system, and thus represents the possibility of a reversal in the hierarchy of cue sensitivity.     

The effects of climate change on the reproduction of coastal invertebrates

Environmental cues control or synchronize the reproductive cycle of many marine invertebrates. Of these environmental cues, photoperiod and temperature have been shown to moderate reproduction either individually or in combination. In addition, they may act directly or, in the case of photoperiod, set circannual clock mechanisms. These environmental cues may affect a number of reproductive parameters, including sex determination, gametogenesis and spawning. Gonadotrophic and spawning hormones appear to act as the transducers between the environment and the gamete, and limited evidence indicates that temperature and photoperiod can alter levels of these. Such processes occur in a range of estuarine invertebrates that constitute important components of the diets of overwintering birds. Global warming is likely to uncouple and alter the phase relationship between temperature and photoperiod and this is likely to have significant consequences for animals that develop gametes during the winter and spawn in the spring in temperate northern latitudes. Species that cue reproduction to photoperiod are likely to be particularly vulnerable. Although this is unlikely to lead to extinctions, it may cause local extirpations. However, this will depend on speed of adaptation to changing climate in relation to speed of climate change and the degree of mixing between populations across the range of the species. More likely will be significant impacts on fecundity, spawning success and recruitment, and this may have significant implications for overwintering birds of national and international importance, and, ultimately, on the conservation status of estuaries such as the Humber in the UK.     

Influence of a new slow-release GnRH analogue implant on reproduction in the Budgerigar (Melopsittacus undulatus, Shaw 1805)

The neuroendocrine conditioning of reproduction in birds could perform a very important role in captive breeding, especially in endangered species. Whereas in domestic and wild mammals pharmacological reproductive conditioning is well developed, in birds an effective method is not available. The aim of this study was to test the influence of a new slow-release GnRH analogue (buserelin acetate) implant on the reproductive activity of the Budgerigar (Melopsittacus undulatus), used as model species for captive-bred endangered birds. The effects were assessed by looking at reproductive parameters (egg-laying rate, egg fertility rate) and measuring excreted sex steroid metabolite concentrations in male and female birds. Modification of reproductive parameters and steroid metabolites excretion patterns were observed among birds administered with a GnRH analogue implant and maintained under artificial photoperiod (group I; 16L:8D). Implanted birds showed higher rates of egg-laying, potentially a higher proportion of fertile eggs and higher excreted steroid metabolite concentrations than birds maintained under natural photoperiod (group II; 10L:14D) and birds maintained under artificial photoperiod (group III; 16L:8D). Thus, it is concluded that the new slow-release GnRH analogue implant may represent an innovative and practicable treatment to rapidly induce reproductive activity in the Budgerigar, and that excreted sex hormone metabolites detection permits to monitor male and female gonadal activity.     

Thermoregulatory responses to manipulations of photoperiod in wood mice Apodemus sylvaticus from high latitudes (57°N)

1. 1. The thermoregulatory responses to manipulations of photoperiod in wood mice (Apodemus sylvaticus), which were drawn from a population living at a high latitude (57°N) were studied.

2. 2. Mice captured in spring were acclimated to two different photoperiod regimes 16L:8D and 8L:16D at a constant ambient temperature of 24°C, for 3 weeks.

3. 3. Daily rhythms of body temperature, oxygen consumption and body temperature at various ambient temperatures, nonshivering thermogenesis (the response to a noradrenaline injection) and body mass were measured. Minimal overall thermal conductance was calculated for both groups.

4. 4. Acclimation to long photophase increased the thermoregulatory abilities at relatively high ambient temperatures while that of long-scotophase increased thermoregulatory abilities at low ambient temperatures.

5. 5. Changes in photoperiod may therefore be used as cues for seasonal acclimatization of thermoregulatory mechanisms in this population of wood mice.

     

Effects of different photoperiods on the reproduction of the barbel, Barbus barbus (L.), reared at constant temperature

The role of photoperiod as an environmental factor controlling reproduction, particularly the duration and ending of the breeding season, in the barbel was investigated by tank experiments. The experiments used a population of barbel matured in captivity which were stripped of eggs at frequent intervals: 10–15 'spawnings'for each female were obtained at 15-day intervals.
A decreasing photoperiod (16·5 light: 7·5 dark→8L: 16D), for an annual cycle contracted to 6 months duration, inhibited the spawning of both female and male fish. This allowed two periods of reproduction (February-May and September-November) within one year. Under natural or constant (10L: 14D) photoperiod conditions, spawning came to an end spontaneously. The rate (accelerated, slow or natural) of daylength increase did not affect the onset of spawning.     

Female reproductive biology of the sand smelt in brackish lagoons of southern France

The breeding season of Atherina boyeri living in the brackish lagoons of Mauguio, Pérols and Méjean (Hérault, southern France) was very protracted (February-September). The peak of the reproductive effort occurred in April, May and June. Larger fishes started spawning earlier, and stopped later, than smaller ones. Batch fecundity varied from 4 to 447 oocytes and was positively related to female length and weight. Monthly mean fecundity increased at the beginning of the breeding season and decreased between June and July. Individual mean oocyte diameter ranged from 1.34 to 1.94 mm and was not related to fish length. Monthly mean oocyte size declined throughout the breeding season as water temperature rose. There was no trade-off between number and egg size. The strategy of these sand smelts seemed well adapted to ensure spawning success without endangering their survival. The highest reproductive effort period occurred in such a way that environmental conditions were suitable to the best survival and growth of hatched larvae. When breeding ceased, fishes, particularly the youngest ones, had enough time to improve their condition before overwintering.     

Comparative study on biological parameters of Bemisia tabaci (Genn.) collected on four host plants from Varamin-Iran

During 2003 biological parameters of sweetpotato whitefly, B. tabaci (Genn.) (Horn. Aleyrodidae) as a major pest of field crops, vegetables and ornamentals were studied. In this study, the infested leaves of cucumber (Cucumis sativus L.) zucchini (Cucurbita pepo L.) eggplant (Solanum melongena L.) and cotton (Gossypium hirsutum L.) with whitefly nymphs and pupae were collected from Varamin-Iran, and were transferred to the laboratory. The newly emerged males and females of each population were released separately into a large cage set on cotton plants. Experiments were carried out in a growth chamber on cotton, (Varamin 76 variety) at 24+/-2 degrees C, 55+/-3% RH and 16:8 h (L: D) photoperiod. The adults of every collected population after emergency were reared in the large cages (40 x 50 x 70) containing pots of cotton plant. The preimaginal developmental time and reproductive parameters of 40 mated females were calculated for each population. The results revealed that the intrinsic rates of increase (r(m)), on cucumber, zucchini, eggplant and cotton were 0.093, 0.068, 0.085 and 0.078 respectively, gross fertility rate, were 67.92, 59.08, 76.13 and 63.14 respectively and mean generation time (T(c)) were 27.4, 27.74, 27.73 and 27.52 days respectively. Other demographic parameters such as intrinsic birth rate (b), intrinsic death rate (d), finite rate of increase (lambda), doubling time (DT), net fecundity rate, net fertility rate , gross fecundity rate, mean age gross fecundity and fertility, mean age net fecundity and fertility, mean age hatch, number of eggs/female/day and daily reproductive rate were also calculated. The results revealed that there were not significant differences between parameters of demography in different populations and the host plant has no significant influence on biological parameters.     

光照时间对双尾新小绥螨生长发育及种群参数的影响

【目的】为了进一步明确光照时间对双尾新小绥螨Neoseiulus bicaudus Wainstein生长发育的影响。【方法】在实验室恒温条件下,采用生命表研究方法,研究在不同光照时间下,双尾新小绥螨捕食土耳其斯坦叶螨的生长发育情况。【结果】双尾新小绥螨在不同光照时间段下均能完成世代周期。在光照时数小于12 h时,从卵发育至成螨的各个发育阶段所需时间均呈缩短趋势,当光照时数大于16 h后各个发育阶段所需的时间又呈增长趋势。产卵期在12L︰12D光照时数下最长为20.74 d,且同其他光照条件均存在显著性差异(P<0.05)。产卵后期、寿命、总产卵量均表现在16L︰8D光照时数下最长,分别为11.93 d、31.05 d和42.4粒。双尾新小绥螨种群的净增值率(R_0)在16L︰8D时达到最大值33.88,在8L︰16D时最低为14.97。【结论】光照时间在12~16 h范围内最适合双尾新小绥螨生长发育。