A comparison was made between the absolute and actual fecundity of C. taenia and allotriploid Cobitis females from a diploid-polyploid population inhabiting the Bug River, of Vistula R iver basin in Poland. All specimens were measured, weighed and aged. The absolute fecundity was determined by a gravimetric method using 29 ovaries (three of C. taenia, 25 of triploids and one of tetraploid). The actual fecundity was estimated according to the method adopted by Halačka et al. (2000) and used five ovaries of C. taenia and 40 of Cobitis triploids. Absolute fecundity of C. taenia under analysis ranged from 1 819 to 3 302 eggs and equaled 2 487 on average. It was significantly lower than absolute fecundity of an exclusively diploid population in Klawój Lake described previously (Juchno & Boroń 2006a). Absolute fecundity of triploid females ranged from 285 to 3 710, with an average of 1 577 eggs, whereas the fecundity of tetraploid Cobitis female was low, with only 882 eggs. The highest actual fecundity of C. taenia as well as of triploids was observed after they laid their first batch of eggs.
First-stadium juveniles of Polydesmus angustus born each month from May to September were reared throughout their life cycle under controlled seasonal conditions. At maturity, the reproductive patterns of 62 females were studied individually. It was confirmed that females born from May to August have a 1-year life cycle and those born from late August onwards a 2-year life cycle (cohort-splitting). A third type of life cycle - interseasonal iteroparity - was observed in a few females born late in the season. On average, annual females started to reproduce when 11.4 months old and produced 3.6 broods per female over 1.8 months; the later they were born from May to August, the later they reproduced the following year. Biennial females started to reproduce when 19.9 months old and produced 3.8 broods per female over 2.2 months; all reproduced early in the breeding season. These results indicate that only annual females can produce an appreciable proportion of biennial offspring from late August onwards, which rules out direct genetic determination of life-cycle duration. The reproductive characteristics of P. angustus suggest a non-genetic mechanism that can drive cohort-splitting. Because individual females reproduce for about 2 months on average, this automatically results in cyclic variation in life-cycle duration (annual/biennial/annual) in the long-term progeny of any female.
Very little is known about the spawning behaviour of loach fishes, despite the fact that reproduction is one of the most important aspects in the autecology of animals. Here the spawning behaviour of golden spined loaches of the genus Sabanejewia is described for the first time. In opposite to spined loaches of the genera Cobitis and Misgurnus, the spawning partners do some ‘circle swimming’ together prior to spawning and the male does not form a full ring around the female but catches the female with a ‘V’-shaped body. This spawning behaviour explains why males of Sabanejewia, unlike nearly all other genera of Cobitidae, 1) are not significantly smaller than females, a condition that is required only to form a complete ring around the female,and 2) have swellings in the middle of the body instead of specialised rays of the pectoral fins like in most other genera. These swellings are in the part of the body that touches the female during the release of gametes, while the pectoral fins do not reach to female’s body.
The coccinellid H. axyridis shows considerable intraspecific variability of elytral patterns. In this paper, we suggest that a genotype that confers a specific pattern of elytra could also confer other specific autecological attributes. The aim of this paper is to compare fitness parameters of two phenotypes (aulica and nigra). Aulica is a common morph characterized by two light red areas that nearly cover the whole elytra, leaving a narrow black border, whereas nigra is completely black; the latter is a rare morph that was naturally obtained from mass cultures. Intraspecific differences occur between H. axyridis phenotypes. The aulica phenotype is more voracious than nigra. Consumption rate of males is higher in aulica than in nigra, but there is no difference for females. Larval biomass of aulica is generally higher than that of nigra. The maximum body-weights reached by larval instars and adults are significantly higher for aulica. Aulica also has greater longevity and reproductive capacity. Only life stage duration of eggs and pre-pupae differ between the two phenotypes. Nigra shows lower fecundity and fertility. Our study showed that the strong differences in phenotype traits of the coccinellid H. axyridis could affect its fitness.
Flight is important for insects but also incurs costs in terms of reduced reproductive reserves. Recent studies on butterflies have shown that thorax mass and nitrogen content decrease over the adult lifespan, suggesting that flight muscle breakdown may also occur in butterflies. However, unlike other insects known to resorb flight muscles, butterflies will continue to fly throughout the reproductive period. Nonetheless, use of nutrients from flight muscles for reproduction has the potential to improve the reproductive output considerably. In this study we have tested to what extent female Pieris napi L. (Pieridae) butterflies actually do breakdown flight muscles. By comparing muscle mass in recently emerged and older free-flying females we show that mass and nitrogen content of the two most important groups of flight muscles each decrease by more than 50% over the adult lifespan. The significance of this finding is discussed in relation to reproduction and flight in butterflies.
Halobates spp. are the only insects inhabiting the open sea. One sea skater species, Halobates sericeus, was collected at 18 locations in the East China Sea area (27°10´N- 33°24´N, 124°57´E-129°30´E), and H. micans and/or H. germanus at only 8 locations in the area south of 29°47´N, where water temperatures were more than 25°C. At three locations, where the water temperature was less than 23°C, neither H. micans nor H. germanus were caught. The effect of photoperiod on the aggregation and mating behaviour of the sea skater, H. sericeus, was studied under laboratory conditions during a one-month cruise. Adults and 5th instar larvae of H. sericeus, collected between 29°02´N and 30°29´N, were kept under long (14.5L : 9.5D) or short-day (10.5L : 13.5D) conditions at 23 ± 2°C for 20 days. Aggregation and mating behaviour of these sea skaters were recorded over a period of 150 min during the daytime. To analyze the data, the observation period of 150 min was divided into 50 intervals of 3 min. Aggregation was observed more under short than long-days. Duration of a group was much longer under the short (mean ± SD : 43.0 ± 108.1 sec) than long-days (7.6 ± 3.1 sec).
The ruffe Gymnocephalus cernuus L. is an introduced species in Italy. In order to assess the impact of exotic species on native fish communities, the ecology and biology of intruders need to be thoroughly investigated. The aim of this study was to analyse the growth and reproductive biology of the ruffe population in Lake Piediluco. From June 1999 to March 2002, and between July 2004 and May 2005, 1 330 specimens belonging to seven age-classes were captured. Sex was determined in 385 individuals: 327 females and 58 males. The SL-TL relationship for the whole sample was TL = 0.923 + 1.075SL. The SL-W relationship was W = 0.0154 SL3.102 for females and W = 0.0157 SL3.106 for males. The parameters of the von Bertalanffy growth curve for length using back-calculated SL were L∞ = 218.29 mm, k = 0.27 y -1, t0 = -0.61 for females and L∞ = 161.54 mm, k = 0.32 y-1, t0 = -0.70 for males. The results showed that in Lake Piediluco ruffe grow as fast as in their original environments. Seasonal growth and back-calculation showed the possible existence of differential mortality prejudicial to small specimens. Moreover, growth analysis revealed marked sexual dimorphism in growth in the Lake Piediluco population. Sexual maturation occurred in both sexes at the end of the first year of life. Reproduction occurred mostly in May and June. The mean diameter of eggs was 1.12 mm. The mean number of eggs produced by each female was 11 961, and increased with the size of the specimens; with regard to relative fecundity, an average value of 239 eggs g-1 was observed. This analysis reveals some important biological characteristics of the ruffe that were not previously well known with regard to the Italian population of the species.
The aim of this study was to evaluate the effects of different diets on the development and reproduction of Lygus rugulipennis Poppius (Heteroptera: Miridae). Using 2 laboratory generations (F1 and F2) obtained from field-collected L. rugulipennis, the following diets were tested: beans, beans plus Tenebrio molitor (L.) (Coleoptera: Tenebrionidae) pupae, and a commercial artificial diet, which was developed for mass rearing of Lygus hesperus Knight. As oviposition substrates, beans and agar/parafilm rolls were used. Our data show that both the artificial diet and the artificial oviposition substrate were ineffective substitutes for beans for both laboratory generations. Stage-dependent and total survival rates clearly indicated that F1 Lygus bugs survive significantly longer when they are reared on vegetable substrates i.e., beans and beans plus pupae. The differential effects of the diets were more pronounced in the F2 generation, in which the embryonic development was longer for eggs from females reared on the artificial diet than on beans, and in which the second instar nymphs did not survive on the artificial diet. Both the total duration of post-embryonic development and the longevity of F1 males were shorter on the artificial diet than on beans. Female fecundity was affected by diet in terms of total duration of the oviposition period and mean number of eggs laid/female, since these parameters were lower on the artificial substrate, compared with those obtained on the bean substrate. However, the diet did not affect the morphological parameters, as there were no significant variations in weight, width of cephalic capsule, and tibia and hemelytra length. Since L. rugulipennis cannot be reared on the commercially available artificial diet, we discuss the necessity to improve both the artificial diet and oviposition substrate so that this Lygus bug and its specific egg parasitod Anaphes fuscipennis Haliday (Hymenoptera: Mymaridae) can be mass reared.
For the last few decades, many studies have analysed the important influence of environmental conditions on the breeding biology of ungulates. However, with reference to Mediterranean wild boar populations, there are hardly any studies. In this paper, we will research the effect of rainfall over eight years on some reproductive variables in a wild boar population located in a Mediterranean ecosystem. Our results indicated that the percentage of pregnant females was higher in rainy years than in dry ones and females over 2 years of age significantly increased their litter size in these rainy years. In addition, dry summers and autumns determined an early rut period and a high concentration of births. However, rainfall did not influence the foetal sex ratio, although we did observe that the sex of the heaviest piglet within each litter was predominantly male, this circumstance being more significant in dry years than in rainy ones. We believe that these results could be showing the wild boar’s survival strategy in the changeable environmental conditions of Mediterranean ecosystems.
Interclonal variability in the photoperiodic responses of the pea aphid Acyrthosiphon pisum and intraclonal differences between wingless viviparous females (=apterae) and winged viviparous females (=alatae) were studied. In 7 clones collected from peas near St.Petersburg the effect of constant diel photoperiods (from 0L : 24D to 24L : 0D at 20°C) on sexual morph determination and dynamics of morph production were recorded. Apterae of 5 clones and apterae and alatae of 2 clones were studied. The mean and age-dependent fecundity of apterae and alatae were compared. The clones studied in detail can be divided in two groups. The first includes clones that produced winged males and had critical photoperiods for female morph determination around 12L : 12D. The second includes clones with critical photoperiods for female morph determination around 17L : 7D; these clones produced wingless males, and one clone produced only oviparae. The intraclonal differences in the photoperiodic limits for ovipara and male production depended on the clone-specific abundance of males. The shapes of the photoperiodic curves for male production also depended on the clone-specific abundance of males. In short-day conditions alatae produced more oviparae and fewer males, and the range of photoperiods that induced ovipara production in alatae was nearly twice as wide as that in apterae. The photoperiodic limits for ovipara and male production differed for apterae and alatae. The fecundity of alatae was lower, although they reproduced for longer and lived longer than apterae. Both apterae and alatae reproduced more intensively over the first 2 weeks. Apterae and alatae began to produce males at the same age. Because of their late onset of larviposition, the reproductive pause that divides female and male production was obscured in alatae. Both apterae and alatae tended to produce initially and finally batches of viviparous offspring, possibly reflecting age-dependent endogenous changes in the hormonal titres in the parents.