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1.
The life-cycle of Apatania fimbriata (Pictet, 1843) (Trichoptera: Limnephilidae) was studied in the Breitenbach (Hesse, Federal Republic of Germany) and in the laboratory at 6 °C, 10 °C and 14 °C at 14 h day length. Embryogenesis was mainly temperature dependent in the 4 °C–18 °C range. At a constant 22 °C embryos developed to well-differentiated larvae which did not hatch. In the laboratory experiments, developmental rates increased with increasing temperature (6 °C, 10 °C and 14 °C); larvae went through a dormancy in the third and fourth larval instars; in the field this occurred between November and February. The dormancy synchronized the larval development. Laboratory studies led to the conclusion that the dormancy was not temperature dependent but endogenously determined. The emergence pattern of adults showed a clear diurnal pattern, with a maximum emergence approximately two hours after sunset. A comparison of several years emergence studies showed a decreasing number of females with increasing distance from the spring. A comparison of the dry weight of females between two traps at the stream showed a significantly higher weight from the downstream site. For males no between-site differences were observed.  相似文献   

2.
Michael Marten 《Hydrobiologia》1990,199(2):157-172
Embryonal development of the five congeners Protonemura auberti Illies, 1954, P. hrabei Rauser, 1956, P. meyeri (Pictet, 1841), P. nitida (Stephens, 1835), and P. praecox (Morton, 1894) was studied under various laboratory temperatures and different photoperiods.Mean number of eggs in field collected batches was between 470 (P. praecox) and 1211 (P. auberti). Spring species had smaller egg batches than autumn species (Table 1). Mean hatching success in the laboratory was 50–100% at 2–18 °C. In most species hatching success decreased slightly with increasing temperature (Figs. 1a-e). None of the eggs incubated at 24 °C developed. Hatching pattern followed an asymmetric frequency distribution. In general, the hatching periods were the shorter the higher the incubation temperature.Embryonic development of all five species was inversely temperature dependent (Figs. 2a-e), and well described by a power law relationship (Figs. 3a-e). Interspecific differences in incubation periods were notable at nearly all temperatures (Fig. 4). There was a distinct interspecific sequence in length of incubation period (with steps of about 4 days), which was the same as can be seen in the flight periods: The later the species flies the longer the incubation period. Temperature fluctuations and variations in photoperiod had no influence on incubation and hatching periods or hatching success.The thermal demand of the egg stage neither explains the recent geographical distribution of the Protonemura species, nor does it directly correspond to the field temperatures common during their egg development. However, it is optimal in respect to resource partitioning between the five species, with the consequence of temporal displacement of life cycles.Derived from Brittain's (in press) proposal to compare the two constants a and b of the regressions describing the temperature dependence of embryonal development, a new index (Integral Development Time, IDT) indicating the thermal demand was created for easier comparison of numerous species (Table 2). Evaluation of the IDT for various species of Plecoptera (Fig. 5) suggests that species belonging to the family group Systellognatha generally have higher thermal requirements in the egg stage than species belonging to the Euholognatha.  相似文献   

3.
Eggs of Pteronarcys californica Newport were incubated at fixed temperatures between 5 and 20°C in the laboratory and at field temperatures in the Crowsnest River, Alberta. The regression of rate of development on temperature between 5–15°C gave a developmental zero of 3.125°C. Within the range 10–20°C, highest hatching success and fewest days to median hatch occurred at 15.0 or 17.5°C, but physiological time (day-degrees) for egg hatching increased with temperature throughout, markedly so above 15°C. A minimum of 182 days was required for 50% hatch in the laboratory, with no observable development for approximately 80 days. Eggs placed in the river on 25 May 1993 started to hatch on 17 October 1993, and the pulse of larval recruitment in the field population occurred between April and August, 11 to 15 months after oviposition. Eggs hatched over periods of 130–322 days at different temperatures in the laboratory, and over an 11-month period in the field. The placement of diapause early in embryonic development is suggested as a cause of extended recruitment. The variety of embryonic development in Plecoptera is briefly reviewed.  相似文献   

4.
Laboratory‐validated data on the survival, development and hatching responses of fertilized Pacific cod Gadus macrocephalus eggs from the northern Japan stock were determined through an incubation experiment. The optimum temperature for survival until hatching ranged from 4 to 8° C. No significant difference in development rates was found between the populations from Mutsu Bay, Japan, and western Canadian coastal waters even though the samples may belong to different G. macrocephalus stocks. Gadus macrocephalus larvae hatched asynchronously from egg batches despite incubation under the same environment during their development. Both incubation temperature and temperature‐mediated hatch rank affect size and yolk reserve. These data suggest that variations in water temperatures within an ecological range markedly influence the development rates, survival and hatching of the eggs, as well as the stage at hatch larvae of G. macrocephalus. Asynchronous hatching and the production of offspring with variable sizes and yolk reserves are considered evolutionary bet‐hedging strategies that enable the species to maximize their likelihood of survival in an environment with variable temperatures.  相似文献   

5.
Unlike most embryos that hatch on a predetermined timetable, California Grunion Leuresthes tenuis can prolong the embryonic period up to three times longer than the time required for hatching readiness. L. tenuis are teleosts that spawn tidally around the highest spring tides of spring and summer, incubating eggs above the water line. Embryos are competent to hatch in 10 days, however they do not hatch until triggered by an environmental cue, agitation in seawater, as the next spring tides rise. This study examined the growth and survival of L. tenuis embryos and larvae that were all fertilized on the same day, then triggered to hatch after different durations of incubation, up to 35 days post fertilization. L. tenuis embryos that survive extended incubation had decreased yolk reserves and did not advance appreciably in morphological development, even when incubation time was extended to its upper limit. After extended incubation, length of hatchlings was significantly longer than hatchlings from the primary incubation time. Regardless of the duration of incubation, larvae provided food ad libitum grew rapidly and were not significantly different in length at three weeks post hatch. Dry mass increased over time and was not significantly different between larval groups within any post-hatch age. Larval growth and survival after one additional tidal cycle of incubation are not adversely affected, but longer incubation significantly decreases embryonic and larval survival. Large reproductive output, environmentally cued hatching, and plasticity in incubation duration enable L. tenuis to reproduce successfully in the unpredictable sandy intertidal ecosystem.  相似文献   

6.
Abstract.
  • 1 The egg masses of Simulium ornatum, S.equinum and S.vernum are described and information is given on numbers of eggs per egg mass and the size and number of batches laid by individual females.
  • 2 The oviposition sites were studied in relation to water velocity, wind speed and direction.
  • 3 The incubation periods at different river temperatures and the effects of desiccation on percentage hatch and incubation times were investigated.
  • 4 The numbers of eggs laid were assessed for the winter generations of S. ornatum and S.equinum. The relevance of these to the overall production estimates is discussed
  相似文献   

7.
The effect of incubation temperature (2, 4, 6, 8 and 10° C) on haddock Melanogrammus aeglefinus development and growth during the embryonic period and in subsequent ontogeny in a common post‐hatch thermal environment (6° C) was investigated. Hatching times were inversely proportional to incubation temperature and ranged from 20·3 days at 2° C to 9·1 days at 10° C. Growth rates were directly proportional to incubation temperature during both the embryonic and larval periods. There was a significant decline in growth rates following hatch in all temperature groups. Compared to the endogenously feeding embryos, growth rates in the exogenous period declined by 4·4‐fold at 4° C to 3·9‐fold at 8° C, indicative of the demarcation between the endogenous and exogenous feeding periods. Yolk utilization varied from 17 days at 2° C to 6 days at 10° C and followed a three‐stage sigmoidal pattern with the initial lag period inversely proportional to incubation temperature. Time to 50% yolk depletion varied inversely with temperature but occurred 1–1·5 days post‐hatch at all temperatures. Additionally, the period between 10 and 90% yolk depletion also decreased with increased temperature. Overall developmental rate was sequential with and directly proportional (2·3‐fold increase) to incubation temperature while the time spent in each developmental stage was inversely proportional to temperature. Larger embryos tended to be produced at lower temperatures but this pattern reversed following hatch, as larvae from higher temperature groups grew more rapidly than those from other temperature groups. Larvae from all temperatures achieved a similar length (c.total length 4·5 mm) upon complete yolk absorption. The study demonstrated the significant impact that temperature has upon developmental and growth rates in both endogenous and exogenous feeding periods. It also illustrated that temperature changes during embryogenesis had significant and persistent effects on growth in subsequent ontogeny.  相似文献   

8.
Sibling (cannibalism among siblings) and non-sibling cannibalism (cannibalism among non-siblings) were studied in a natural population of a lady beetle, Harmonia axyridisPallas . Of all the eggs laid (n=2269), 24.76% (n=562) were killed by sibling cannibalism and 36.10% (n=819) were killed by non-sibling cannibalism. Sibling cannibalism occurred constantly and intensively in most egg batches throughout the entire oviposition period. On the other hand, non-sibling cannibalism was more intense in the middle and late oviposition periods, and when the egg batches were close to an aphid colony. This may be due to the high density of H. axyridis larvae relative to aphid density in the middle and late oviposition periods and also the larvae searching intensively near an aphid colony.  相似文献   

9.
J. M. Elliott 《Ecography》1986,9(2):113-116
Gravid females of Capnia bifrons (Newman) from Windermere (English Lake District) were almost completely ovoviviparous, the eggs hatching within 15 min after oviposition in the water. When kept in the laboratory at constant temperatures between 3.8 and 19.8°C, few females survived to lay eggs at temperatures above 12.1°C. The relationship between air temperature (T°C) and the egg incubation period (Y days between fertilisation and oviposition) was given by the regression equation: Y = 316.4 T−0.9996 (r2= 0.957, p < 0.001). This equation successfully predicted egg incubation periods for gravid females kept in cages in the field.
Comparisons with similar studies on four non-ovoviviparous species of Plecoptera showed that egg development was rarely more rapid in C. bifrons . It was also shown that the hypothesis of ovoviviparity being an adaptation to combat low water temperatures could be rejected for C. bifrons from Windermere.  相似文献   

10.
A staging table for yolk‐sac larvae of Atlantic cod Gadus morhua was developed and applied to determine the development stage at hatch. Larvae ( n  = 20) were sampled during the period from 50% hatch to first‐feeding from four temperature treatments ( c . 2, 4, 8 and 12° C). Data recorded included standard length, development stage, yolk‐sac area and evidence of feeding by larvae. The results indicated that the stage of development at hatch was positively correlated to larval size. Furthermore, developmentally based changes in morphology shortly after hatch reduced much of the initial difference in size, although some difference still existed. No relationship between size at hatch and the incidence of first‐feeding larvae was found. Based on these observations, it is recommended that the development stage of hatching larvae be reported in studies investigating size and morphological differences when observing individual larval fish that originate from different populations, batches or species.  相似文献   

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