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1.
Mnemiopsis leidyi: larvae depend on microplankton (<200 µm) prey duringthe first few days following hatching until larvae are >0.5mm in length and can successfully capture and consume mesozooplanktonprey. Feeding and growth rates of newly hatched M. leidyi larvaewere measured in controlled laboratory experiments. When fednatural microplankton assemblages, newly hatched larvae consumedsignificant quantities of both autotrophic and heterotrophicprey, including diatoms, phototrophic, heterotrophic and mixotrophicdinoflagellates, euglenoid flagellates, aloricate and tintinnidciliates, and rotifers. Average per capita clearance rates were1.99–7.59 mL individual–1 h–1 ( = 4.01 mL individual–1 h–1; SD = 1.95)and total per capita ingestion was 0.01–4.70 µgC individual–1 day–1 x 102 ( = 0.83 µg C individual–1 day–1 x 102; SD =1.89). Larval growth rates were –0.13 to 0.56 mm individual–1day–1 (equivalent to –1.72 to 4.33 µg C individual–1day–1) over a range of larval sizes from 0.5 (<0.5µg C) to 5 mm (85 µg C). A diet consisting entirelyof microplankton prey supported larval growth for >2 weeks,and growth rate decreased when larvae reached 4–5 mm inlength, corresponding to the beginning of their morphologicaltransition from tentaculate to lobate feeding mode. The grossgrowth efficiency of larvae fed natural microplankton assemblageswas 3%. 相似文献
2.
Growth and ingestion rates of larval fish populations in the coastal waters of Israel 总被引:1,自引:0,他引:1
Clupeoid larvae were collected on eight cruises between February1984 and February 1985 in the coastal waters of Israel. Fromanalysis of daily growth increments of otoliths, growth ratesof the abundant clupeoids, Engraulis encrasicolus, Sardina pilchardusand Sardinella aurita were found to be 0.55 mm day1,0.67 mm day1 and 0.60 mm day1, respectively, duringthe first month after hatching. Ingestion rates were estimatedusing an equation from the literature relating ingestion andgrowth of larval fish. Ingestion calculated for populationsof fish larvae in pelagic waters ranged from 0 to >23 mgC m2 day1 with maximum rates observed in April.Annual ingestion by larval fish at a pelagic station near Haifawas calculated to be 2.2 g C m2 year1, 1020%of annual primary production estimated from 14C uptake. 相似文献
3.
Short-term variability in vertical distribution and feeding of Atlantic mackerel (Scomber scombrus L.) larvae was investigated while tracking a larval patch over a 48-h period. The patch was repeatedly sampled and a total
of 12,462 mackerel larvae were caught within the upper 100 m of the water column. Physical parameters were monitored at the
same time. Larval length distribution showed a mode in the 3.0 mm standard length (SL) class (mean abundance of 3.0 mm larvae
=75.34 per 100 m3, s=34.37). Highest densities occurred at 20–40 m depth. Larvae <5.0 mm SL were highly aggregated above the thermocline, while
larvae ≥5.0 mm SL were more dispersed and tended to migrate below the thermocline. Gut contents of 1,177 mackerel larvae (2.9–9.7 mm
SL) were analyzed. Feeding incidence, mean number (numerical intensity) and mean dry weight (weight-based intensity) of prey
items per larval gut were significantly dependent on larval size. However, while weight-based feeding intensities continued
to increase with larval length, numerical intensity peaked at 4–4.9 mm SL, indicating a shift in the larval diet. While first-feeding
larvae relied most heavily on copepod nauplii and eggs, larvae ≥5.0 mm SL initiated piscivorous feeding. All identifiable
fish larvae were Atlantic mackerel. Thus, the piscivory was cannibalism. Larval feeding incidence and numerical feeding intensities
peaked during daytime and were reduced at night. Daily ration estimates for first-feeding mackerel larvae <4.0 mm SL were
extremely low
= 1.43% body dry weight, but increased dramatically at 5.0 mm SL, i.e., at the onset of cannibalism, reaching >50% body dry
weight in larva ≥8.0 mm SL.
Received in revised form: 31 October 2000
Electronic Publication 相似文献
4.
Daniel Margulies 《Environmental Biology of Fishes》1990,27(3):187-200
Synopsis The vulnerability of white perch, Morone americana, larvae to yearling bluegill, Lepomis macrochira, predators was examined in relation to larval size, nutritional condition and relative abundance of alternative prey. Short-term
(15 min) predation trials were conducted in 381 tanks in the laboratory. Larval vulnerability was measured as the proportion
of larvae killed and the proportion of successful attacks per predator in each 15 min trial. No significant differences in
vulnerability were apparent among larvae regardless of feeding history at sizes < 6 mm SL. At larval lengths > 6 mm SL, size
of larvae was the crucial determinant of their vulnerability. Percentage of larvae killed in 15 min was nearly 100% at sizes
< 6 mm SL, decreased to 30% at a length of 12.0 mm SL and dropped to 18% at 14.0 mm SL. Larvae initially feeding at low food
levels for 2–4 d exhibited decreased growth of 13–25% over the first 3 wks of life, and simulations based on laboratory results
indicated that these growth deficits could result in 5- to 68-fold decreases in survivorship at 38 days after hatching (DAH).
The relative abundance of alternative prey also had a pronounced effect on mortality of larvae. A 10-fold increase in alternative
prey (Daphnia magna) abundance decreased bluegill predation rates on white perch larvae by 10–20%, while a 100-fold increase in Daphnia density decreased larval mortality by 75–90%. 相似文献
5.
Changes in the spatial distribution of Baltic herring larvaethrough time were investigated in the waters off Helsinki, thenorthern Baltic Sea. The average larval densities were comparableto the relatively low levels (mean around 2 larvae m2)found in other studies in the Gulf of Finland. In shallow baysvirtually no herring larvae were found in early June. In lateJune and early July the densities of larvae longer than 10 mmincreased to 14 larvae m2 in shallow areas (depth<2 m), i.e. to levels higher than those recorded in deeperwaters. In combination with data on the size distributions ofthe larvae, these observations suggest that a significant proportionof the herring larvae are found in shallow water after the yolksac stage. We conclude that shallow coastal waters are potentiallyimportant nursery areas for herring larvae and that this featureof herring larval biology should be taken into account in planningsampling programs for larval herring. 相似文献
6.
A modeling study of the effects of size- and depth-dependent predation on larval survival 总被引:1,自引:0,他引:1
Dekshenieks Margaret M.; Hofmann Eileen E.; Klinck John M.; Powell Eric N. 《Journal of plankton research》1997,19(11):1583-1598
The form of the predation pressure experienced by larval stagesof marine invertebrates is largely unknown. However, it is believedthat the type, timing and rate of larval predation are critical in determining recruitment to adult populations. In thisstudy, a time- and depth-dependent model of the growth and behaviorof larvae of the Eastern oyster, Crassostrea virginica, wasused to investi gate the effects of different forms of size-and depth-dependent predation on larval survivorship. The simulatedlarval survival for a cohort experiencing size-dependent predationshowed that the great est percent of the cohort survived tocompetent settlement size when the predation pressure decreasedwith increasing larval size. Additional simulations that includeddifferent types of depth- dependent predation showed that theinteraction between vertical larval migration behavior and predationdetermined the percent of the cohort that survived to settlementsize. The simulated distri butions show that a higher percentof larvae survive when the predation pressure is concentratedin the surface waters. A lower percent of larvae survive tocompetent settlement size when the preda tion pressure is concentratednear the bottom. The different forms of size- and depth-dependentpred ation result in variations in the number of larvae presentin the water column during each larval development stage. Thus,different forms of predation impact the number of larvae availablefor dis persal throughout the marine environment. These resultshave important implications concerning the exchange of geneticmaterial between populations. 相似文献
7.
Embryonic, larval and juvenile development of the roughskin sculpin,Trachidermus fasciatus (Scorpaeniformes: Cottidae) 总被引:1,自引:1,他引:0
Naohiko Takeshita Norio Onikura Seiichi Matsui Seirô Kimura 《Ichthyological Research》1997,44(2-3):257-266
Embryonic, larval and juvenile development of the catadromous roughskin sculpin,Trachidermus fasciatus, were described using eggs spawned in an aquarium. The eggs, measuring 1.98–2.21 mm in diameter, were light reddish-yellow
and had many oil globules, 0.05–0.18 mm in diameter. Hatching occurred 30 days after spawning at 2.3–11.3°C. The newly-hatched
larvae, measuring 6.9–7.3 mm BL, had a single oil globule, 9–10+25–26=34–36 myomeres and 6 or 7 large stellate melanophores
dorsally along the gut. The yolk was almost resorbed, number of pectoral-fin rays attained 16–17, and two parietal, one nuchal
and four preopercular spines were formed, 5 days after hatching, at 8.2–8.4 mm BL. The oil globule disappeared, and one supracleithral
spine was formed, 11 days after hatching, at 8.9–9.5 mm BL. Notochord flexion began 15 days after hatching, at 9.7–10.3 mm
BL. A posttemporal spine was formed 20 days after hatching, at 10.7–10.9 mm BL. The first dorsal fin spines (VII–VIII), second
dorsal fin and anal fin rays (18–19, 16–18, respectively) appeared 23 days after hatching, at 12.0–13.7 mm BL. The pelvic
fin spine and rays (I, 4) were formed and black bands on the head and sides of the body began to develop 27 days after hatching,
at 13.8–15.8 mm BL.
Newly-hatched larvae swam just below the surface in the aquaria. Preflexion larvae (8.9–9.5 mm BL), in which the oil globule
had disappeared, swam in the middle layer, while juveniles (13.8–15.8 mm BL) began swimming on the bottom of the aquaria.
Swimming behavior observed in the aquaria suggested that the fish started to change to a demersal existence at the juvenile
stage. 相似文献
8.
Incze Lewis S.; Ortner Peter B.; Schumacher James D. 《Journal of plankton research》1990,12(2):365-379
A large ({small tilde}30 ? 75 km) patch of larval walleye pollock,Theragra chalcogramma, was located south of the Alaska Peninsuladuring May 1986. A drifter deployed in this patch followed ananticyclonic path consistent with dynamic topography. Changesin community composition and vertical distribution of microzooplankton>40 µm were sampled for 4 days alongside this drifterto examine feeding conditions for larvae. Biological and physicalchanges during the first 2 calm days revealed substantial small-scalevariability within the larger circulation pattern. Changes duringthe last 2 days were dominated by vertical mixing due to strongwinds. Despite mixing, prey concentrations remained adequatefor feeding by larval pollock as determined by laboratory studies.A satellite-tracked drifter replaced the first drifter and wasstill located within the patch 6 days later. Overall distributionsof larvae and movements of the drifters show a net translationof 7.8 km day1 south-westward, but details of the studyreveal complex interactions between coastal waters and a coastalcurrent. During the 10-day period there was an increase in standardlength of the larval fish population of 0.13 mm day1and a decline in abundance of {small tilde}7.6% day1.Both calculated rates must be underestimates due to continuingrecruitment of small larvae from hatching eggs. 相似文献
9.
Larval age, growth and mortality in the oceanic squid Sthenoteuthis pteropus (Cephalopoda, Ommastrephidae) from the eastern tropical Atlantic 总被引:2,自引:0,他引:2
Laptikhovsky Vladimir V.; Arkhipkin Alexander I.; Golub Alexander A. 《Journal of plankton research》1993,15(4):375-384
An investigation was carried out on larvae of the oceanic tropicalsquid Sthenoteuthis pteropus in the equatorial Atlantic (230'N7S;12W830'E) The age of the larvae was calculated from thestatolith microstructure of 20 larvae; mortality was estimatedfrom the size structure of 1128 larvae. The larval stage lasts3238 days. At ages ranging from 14 to 38 days. the dailyrelative growth rates of mantle length decrease from 7.5 to2.8% day1 and from 1416 to 5.8% of body weightday1 At age 1224 days, mortality rates were estimatedusing both raw catch data and corrected data accounting fornet avoidance. The mean value of raw mortality rates was 0.189,the corrected value was 0.158. During the proboscis division(transformation of the larva into juvenile) at age 2535days, a sharp decrease in larval growth rates and a simultaneousincrease in mortality rates (raw 0.443, corrected 0.379) wereobserved. 相似文献
10.
Rising sea temperatures may potentially affect the dispersive larval phase of sessile marine invertebrates with consequences
for the viability of adult populations. This study demonstrated that the planktonic larvae of Rhopaloeides odorabile, a common Great Barrier Reef sponge, survived and metamorphosed when exposed to temperatures up to 9°C above the annual maximum
(~29°C). Planktonic larval duration of 54 h, at ambient temperatures (~28°C), were reduced to 18 h for larvae exposed to elevated
temperatures (32–36°C). Moreover, at ambient temperatures larvae began metamorphosing after 12 h, but at 32–36°C this reduced
to only 2 h. Larvae survived and could still metamorphose at temperatures as high as 38°C, but were no longer functional at
40°C. These results imply that predicted increases in sea surface temperature may reduce planktonic larval duration and dispersal
capabilities, thereby contributing to population subdivision of the species. 相似文献
11.
Embryonic, larval, and juvenile development of a Myanmarese cyprinid fish, Inlecypris auropurpureus, is described from laboratory-reared specimens. The eggs, measuring 0.9–1.0 mm in diameter, were demersal, almost spherical
in shape, transparent and unpigmented, with a pale yellow yolk without oil globules. Hatching occurred 49–56 h after fertilization
at 26.2°–27.3°C. The newly hatched larvae, measuring 2.9–3.1 mm in body length (BL) with 17 + 19–20 = 36–37 myomeres, had
melanophores on the head and body. A cement organ on the forehead for adhering to objects during the yolk sac and early preflexion
larval stages was distinctive. The yolk was completely absorbed at 3.6–4.0 mm BL. Notochord flexion was initiated at 5.1–5.6 mm
BL and finished at 7.1 mm BL. Aggregate numbers of all fin rays were completed at 14 mm BL. Squamation was initiated midlaterally
on the anterior trunk at 14 mm BL and completed at 27 mm BL. Although the eggs of I. auropurpureus resembled those of the closely related species Chela dadiburjori, Danio rerio, and Devario malabaricus, they differed from those of Danio rerio and Devario malabaricus in having a narrower perivitelline space. The larvae and juveniles of I. auropurpureus were also similar to those of C. dadiburjori, Danio rerio, and Devario malabaricus in general morphology, but they differed from the latter three species in having a series of dark blotches laterally on the
body in the juvenile stage. Moreover, I. auropurpureus differed from C. dadiburjori in having more myomeres and a near-single row of melanophores on the body along the dorsal midline from the yolk-sac to early
postflexion larval stages, from Danio rerio in having a cement organ on the forehead during the yolk-sac and early preflexion larvae, and a single melanophore on the
lower eye margin in the early yolk-sac larvae, and from Devario malabaricus in having a single melanophore on the lower eye margin in the early yolk-sac larvae. The presence of a cement organ on the
forehead indicates a close relationship among the genera Inlecypris, Chela, and Devario. 相似文献
12.
The early life history of the viviparous scorpaenid,Sebastes inermis, in Sendai Bay, Japan, was studied and early development described. Newborn preflexion larvae ofS. inermis were about 5.2 mm BL. Notochord flexion occurred at 5.4–8.0 mm BL and transformation at 14–20 mm BL. Preflexion and flexion
larvae ofS. inermis were distinguished from similar larvae by the pigmentation pattern along the dorsal and ventral midlines of the tail. Pigmentation
inS. inermis was light throughout the larval and early juvenile periods. Planktonic larvae were particularly abundant in coastal waters
of Sendai Bay but not offshore. Vertical and horizontal larval sampling indicated that early larvae occupied near surface
waters and horizontal larval sampling indicated that early larvae shift to a benthic habitat occurred at about 12 mm BL, at
the end of the postflexion larval period.Sebastes inermis do not have a distinct pelagic juvenile stage, unlike many North Pacific species ofSebastes. 相似文献
13.
The tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is an important pest of tomato crops in South America and it has recently arrived in
Europe affecting tomato plantations. The susceptibility of T. absoluta larvae and pupae to three species of entomopathogenic nematodes (Steinernema carpocapsae, Steinernema feltiae and Heterorhabditis bacteriophora) was examined under laboratory conditions. Leaf bioassays were conducted to evaluate the nematode’s capability to reach the
larvae and kill them within the galleries. The efficacy of the three nematode species after foliar application to potted tomato
plants was evaluated under greenhouse conditions. High larval mortality (78.6–100%) and low pupae mortality (<10%) was determined
in laboratory experiments. In the leaf bioassay a high level of larval parasitation (77.1–91.7%) was recorded revealing the
nematode’s capacity to kill the larvae inside the galleries. In the pot experiments nematode treatment reduced insect infection
of tomato plants by 87–95%. The results demonstrate the suitability of entomopathogenic nematodes for controlling T. absoluta. 相似文献
14.
S. D. Kashenko 《Russian Journal of Marine Biology》2009,35(5):422-430
The combined effects of temperatures of 14, 17, 20, 22, and 25°C and salinities of 36–12‰ on embryos and larvae of the sand
dollar Scaphechinus mirabilis was studied. Embryonic development is the most sensitive stage in the early ontogenesis of S. mirabilis. It is completed at a temperature of 14–20°C in a salinity range of 36–24‰ and at temperature of 22°C to 26‰. The fertilization
proceeds in wider ranges of temperature and salinity. Among the swimming larvae, blastulae showed the greatest resistance
to variations of these environmental factors. All the larvae survived at a temperature of 14–22°C and a salinity of 36–20‰,
and more than 70% of them at 18‰. The pluteus I is the most vulnerable stage; probably this is related to the formation of
the larval skeleton and transition to phytoplankton feeding. The survival of larvae at the age of 20 days was 100% at 14–22°
C and a salinity of 36–24‰, most of them survived at 14–20°C and a salinity 18‰. The temperature 25 ° C is the most damaging
for early development of S. mirabilis. The duration of development of that species lasts 28.5–29 days at 20°C and a salinity of 32.2–32.6‰. At 20 and 22°C, the
larvae settled and completed metamorphosis more quickly if sand from the parental habitat was present. The larvae did not
settle during the experiment (14 days) at 14 ° C and in the absence of sand. 相似文献
15.
Klaus Anger Eduardo Spivak Tomás Luppi Claudia Bas Deborah Ismael 《Helgoland Marine Research》2008,62(2):93-102
The semiterrestrial crab Neohelice (=Chasmagnathus) granulata (Dana 1851) is a predominant species in brackish salt marshes, mangroves and estuaries. Its larvae are exported towards coastal
marine waters. In order to estimate the limits of salinity tolerance constraining larval retention in estuarine habitats,
we exposed in laboratory experiments freshly hatched zoeae to six different salinities (5–32‰). At 5‰, the larvae survived
for a maximum of 2 weeks, reaching only exceptionally the second zoeal stage, while 38% survived to the megalopa stage at
10‰. Shortest development and negligible mortality occurred at all higher salt concentrations. These observations show that
the larvae of N. granulata can tolerate a retention in the mesohaline reaches of estuaries, with a lower limit of ca. 10–15‰. Maximum survival at 25‰ suggests that polyhaline conditions rather than an export to oceanic waters are optimal for
successful larval development of this species. In another experiment, we tested the capability of the last zoeal stage (IV)
for reimmigration from coastal marine into brackish waters. Stepwise reductions of salinity during this stage allowed for
moulting to the megalopa at 4–10‰. Although survival was at these conditions reduced and development delayed, these results
suggest that already the zoea-IV stage is able to initiate the reimmigration into estuaries. After further salinity reduction,
megalopae survived in this experiment for up to >3 weeks in freshwater, without moulting to juvenile crabs. In a similar experiment
starting from the megalopa stage, successful metamorphosis occurred at 4–10‰, and juvenile growth continued in freshwater.
Although these juvenile crabs showed significantly enhanced mortality and smaller carapace width compared to a seawater control,
our results show that the late larval and early juvenile stages of N. granulata are well adapted for successful recruitment in brackish and even limnetic habitats. 相似文献
16.
Some biological characteristics of early larvae Dacodraco hunteri (Notothenioidei: Channichthyidae) in the western Ross Sea 总被引:1,自引:0,他引:1
Ichtyoplankton surveys were carried out in the western Ross Sea by the R/V Italica in the austral summer 1996 and 1997–1998
to study species composition and spatial distribution of larval stages of fish. One of the most abundant icefish caught was
Dacodraco hunteri, a poorly known channichthyid inhabiting the high-Antarctic Zone. Based on 382 yolk-sac larvae and 13 preflexion larvae,
the study was focused to estimate spatial distribution and abundance, as well as diet and growth rate. The pigmentation pattern
and some morphometric measurements were also recorded for comparative purposes. The specimens were caught in relatively restricted
areas located in Terra Nova Bay and north of the Ross Ice Shelf on the Challenger and Joides Basins. The standardized abundance
of early larvae ranged between 0.03 and 1.72 individuals 10−3 m3 in 1996 and 0.16–4.53 individuals 10−3 m3 in 1997–1998, respectively. Fitting a linear model to the mean length increase in larvae collected in subsequent catch dates,
the growth rate was estimated to be approximately 0.11 mm/day. Based on back calculation of growth rate and presumed hatch
size of 11 mm, larval hatching probably took place in mid-December. Diet of preflexion larvae consisted exclusively of larvae
of the pelagic nototheniid Pleuragramma antarcticum, a key species of the high-Antarctic pelagic food web. Hence, D. hunteri probably plays a more important role than previously thought in the pelagic community of the Ross Sea. 相似文献
17.
Trophodynamics of the plankton community at Dogger Bank: predatory impact by larval fish 总被引:2,自引:1,他引:1
The trophodynamics of a coastal plankton community were studied,focusing on fish larvae and their copepod prey. The major objectiveswere to describe distributional overlap and evaluate the predatoryimpact by larval fish. The study was carried out across DoggerBank in the North Sea, August-September 1991. Sampling transectscrossed tidal fronts off the Bank and plankton at all trophiclevels showed peak abundance within frontal zones. Also Verticallythere was a significant overlap in distributional patterns ofthe plankton. Seven species of fish larvae were abundant, ofthese sprat (Sprattus sprattus) dominated. The abundance ofone group of fish larvae peaked in the shallow water close tothe Bank, whereas other species, including sprat, were foundin deeper water. Prey preference and predation pressure of fishlarvae were assessed using information on prey sizes and growthrates of larvae and the copepod prey. We estimated larval removalof preferred prey sizes to 34% day1, counterbalancedby a 37% day1' replenishment from copepod productionand growth. Additional predation pressure on copepods by aninvertebrate predator was estimated to 13%day1.In conclusion, the dynamics of fish larvae and other zooplankterswere closely linked. At peak abundances of fish larvae (>35mg dry weight m2), the accumulated predation on specificsize ranges of copepods, exerted by larvae and other predators,could exceed the ability of copepod replenishment and intra-/interspecificcompetition among predators might take place. 相似文献
18.
A patch of herring larvae located within 24 h of hatching froma spawning bed on the shelf west of the Outer Hebrides, wasfollowed for 7 days. Dispersion of the larvae was modelled usingsimple turbulent diffusion theory. The mortality rate, estimatedfrom the rate of decrease in the total population size, was2% day1 over the tracking period which is verymuch less than rates calculated for herring larvae in otherareas by previous investigators. Successive observations ofthe length, weight, and the incidence of food in the intestinesof larvae, indicated that feeding commenced 5 days after hatchingand that the growth rate was 0.17 mm day1. 相似文献
19.
In 1996 Montgomery proposed an ontogenetic shift in the use of visual and non-visual senses in Antarctic notothenioid fishes,
with visual dominance in larval fishes giving way to non-visual senses in adults. One prediction of the hypothesis is timing
differences in the development of the respective sensory systems, with the visual system expected to develop earlier than
the other systems. The volume of certain brain centres can be determined from fixed material and should correlate with sensory
development. This study determined the relative volumes of visual and lateral line brain areas, and relative eye size as a
function of fish length in Pleuragramma antarcticum.The relative volume of optic tectum was largest in larval fish, exhibiting a negative allometry with growth. The eminentia granularis, and crista cerebellaris (lateral line associated areas) were not recognisable in the smallest larvae; they became differentiated at standard lengths
of 10–20 mm and their relative volumes continued to increase over the size range of fish studied (up to 150 mm standard length).
Relative eye diameter decreased dramatically over the size range 5–25 mm and then increased such that relative eye diameter
doubled over the size range 25–30 mm. A similar, but less extreme, pattern was seen over the size range 30–60 mm. Above 60
mm relative eye diameter increased slightly with size. Our interpretation is that eye growth and somatic growth are on separate
trajectories, and the breaks in the relative eye diameter curve result from overwinter periods when somatic growth is static,
but the eye continues to grow. These results provide support for the ontogenetic shift hypothesis, and indicate that the timing
of the shift probably occurs after the second winter.
Received: 22 October 1996 / Accepted: 10 January 1997 相似文献
20.
Biological activity assays with RH 5849 and RH 5992 indicated that both compounds affected growth and development of last-instar
larvae ofSpodoptera exigua (Hübner) (Lepidoptera: Noctuidae) in a dose-dependent manner. Within the first 24 h after treatment by continuously offering
leaves dipped in a water solution of ≥50 mg/l RH 5849 and ≥0.5 mg/l RH 5992, symptoms of a prematurely induced larval moult
and head capsule apolysis were visible. Intoxicated larvae died shortly afterwards, showing signs of unsuccessful ecdysis.
LC50-values of RH 5849 and RH 5992 for fifth-instarS. exigua larvae were 110 and 2.5 mg/l, respectively. Pyriproxyfen alone affected the larval stage and disturbed normal metamorphosis.
One supernumerary larval instar occurred occasionally. LC50-value for pyriproxyfen was 1.7 mg/l. Larvae simultaneously treated with RH 5849 or RH 5992 and pyriproxyfen, continued to
grow until they attained a size and weight about 2–3 times that of the controls. This growth was accompanied by at least one
and sometimes two supernumerary moults.
Concerning thein vivo imaginal wing disc growth and development, only in larvae treated with 10 and 50 mg/l RH 5849 or 0.5 mg/l RH 5992, tracheole
migration was observed earlier than in the controls. When applying 300 mg/l RH 5849 or 3–7 mg/l RH 5992, the discs remained
small and no signs of tracheole migration were observed. In larvae simultaneously treated with RH 5849 or RH 5992 and pyriproxyfen,
tracheole migration was not prematurely induced and a pupal cuticle was produced in the discs of larvae, undergoing a supernumerary
moult. No clear signs of evagination were observed. 相似文献