城市生活垃圾自动分选技术

迅速而巨量增长的城市生活垃圾给我国带来了严峻的社会、环境压力;城市生活垃圾的资源化、无害化综合利用,对于改善人民群众生活环境、减少资源浪费、发展循环经济,都具有十分重要的意义。要使城市垃圾综合利用目的得以实现,必须突破制约垃圾处理的瓶颈问题——垃圾分类技术这一世界难题。在分析垃圾特点和各种垃圾处理方法优势的基础上,经过多年的探索与研制,开发了一种新型的用于城市生活垃圾资源化综合利用的自动分选技术。     

Red-winged blackbird parental investment following brood parasitism by brown-headed cowbirds: is parentage important?

Parental investment by red-winged blackbirds (Agelaius phoeniceus) in response to natural and experi‐mental parasitism by brown-headed cowbirds (Molothrus ater), and in response to freeze-dried, female cowbird mounts presented near redwing nests during the egg-laying period was measured. Two measures of redwing parental investment were used: nest defense effort toward a model predator, and rate of feeding nestlings. There were no significant differences in levels of parental investment among unparasitized nests, naturally parasitized nests, or experimentally parasitized nests. Similarly, parental investment did not differ between redwings that were exposed to the cowbird mount and those that were not exposed to the mount, or among redwings exposed to the cowbird mount at different distances from the nest. This suggests that red-winged blackbirds do not recognize when they have been parasitized, and hence do not associate parasitism with a decrease in their parentage, or that parentage is not an important predictor of parental investment in this species. Received: 24 January 1997 / Accepted after revision: 7 June 1997     

Brood size manipulation affects frequency of second clutches in the blue tit

The reproductive trade-off hypothesis predicts that the investment made in current reproduction determines the breeders’ future fitness as a consequence of intra-or inter-generational reproductive costs. Long-lived species are expected to favour their own reproductive value at the expense of their offspring, hence incurring in inter-generational costs, whereas short-lived species are expected to invest in the current breeding attempt even at the expense of their own survival, thus incurring in intra-generational costs. We tested whether intensity of current reproductive effort has intra-or inter-generational costs in a short-lived bird, the blue tit Parus caeruleus, with a brood size manipulation experiment. We expected more intra-generational (parental reproduction and/or survival) than inter-generational (offspring quality and survival) reproductive costs. We found that parental effort, measured as the hourly rate of parental visits to nests, increased gradually with experimental manipulation. Brood size manipulation resulted in a gradual increase in the number of fledglings per nest from reduced to increased treatments. We found an effect of the manipulation on the probability of making a second clutch, with adults rearing enlarged broods being less likely to undertake such a second reproduction during the season compared to those rearing control or decreased broods. We found no evidence of other reproductive costs; neither as adult weight after manipulation, apparent parental local survival, apparent offspring local survival or local recruitment. Although the results seem to support the a priori expectations, alternative explanations are discussed.Communicated by M. Soler     

Why are larger convict cichlid (Cichlasoma nigrofasciatum) fry sometimes adopted into broods of smaller fry?

Females of Elasmucha grisea defend their eggs and small nymphs against invertebrate predators. Females sometimes guard their clutches side by side on the same birch leaf. We studied benefits of this joint guarding both in the field and in the laboratory. We found that adjacent females had significantly larger clutches than solitary females. In the laboratory, we studied the effectiveness of joint versus single defence against ant (Formica uralensis) predators. We established female pairs from initially singly guarding females by cutting off pieces of leaves with egg clutches and pasting them beside another female guarding her clutch. In the control group the females with their clutches were similarly cut off but these clutches were placed on another leaf without any female. The birch twigs where females guarded their clutches were placed in cages in close proximity to laboratory ant nests. In the experimental treatment, two females guarded their clutches together and at the same nest there was another birch twig without a female. In the control treatment two twigs with one female on each were placed close to another ant nest. Two females defended their clutches significantly more successfully, losing fewer eggs than did the single females. This primitive form of female sociality in parent bugs resembles colonial nesting in birds, where communal defence is also important. However, to our knowledge this is the first experiment where the benefit of joint guarding has been tested directly by manipulating the size of the breeding group rather than by measuring the risk of predation in groups of different size.     

Sex ratio and the sexual conflict about brood care in a biparental mouthbrooder

The pay-off of deserting and leaving a mate to care for the offspring alone is generally assumed to depend mainly on the availability of alternative mating partners and on the potential spawning rate of males and females. Eretmodus cyanostictus is a monogamous mouthbrooding cichlid in which the clutch is successively incubated first by the female and then by the male. It has been suggested that parents are constrained to monogamy due to low remating probabilities for both sexes. We tested this hypothesis by varying the sex ratio experimentally. Mate desertion by either sex was not significantly higher when additional potential mates were present (males: 8.3%, females: 0%) than when there were no other same-sex conspecifics present (males: 0%, females: 0%). Males lost their mate to a male intruder during their incubation in 26.7% of cases. Pair members were more active and showed more aggression when same-sex conspecifics were present. Behavioural differences between treatments were strongest during the incubation period of a given sex. If no desertion takes place, sexual conflict may be expressed also on a second level, the amount of parental care each parent provides. Indeed, males took the offspring later when additional females were present, although male incubation time did not differ between treatments. A hitherto undescribed display behaviour of females was clear evidence of a conflict about the timing of shift of young. In conclusion, offering alternative mating opportunities did not strongly favour mate desertion in E. cyanostictus. It rather revealed a conflict between mates about when to shift the young.Communicated by M. Abrahams     

Quasi-parasitism in birds

Our view of avian mating systems has been revolutionised by the use of molecular tools that have provided evidence supporting theoretical predictions that extrapair paternity (EPP) and intra-specific brood parasitism (IBP) would be widely observed alternative mating strategies in socially monogamous species. Quasi-parasitism (QP) is a third type of alternative mating strategy, where a female lays an egg in another females nest and that egg is fertilised by the male partner at the parasitised nest. In contrast to both EPP and IBP, QP has been reported in only 12 species to date. We explore reasons for the apparent rarity of QP in birds and conclude that it is only likely to be adaptive in a fairly restrictive set of circumstances. We also review all of the evidence for the occurrence of QP in birds and find that it is far more limited than generally believed, as many apparent examples may be explained by rapid mate--switching or errors in molecular analysis of parentage. We suggest a number of criteria that need to be met for an unequivocal demonstration that QP has actually occurred.Communicated by: A. Cockburn     

Micro-evolutionary change in host response to a brood parasite

The relationship between brood parasites and their hosts is usually assumed to result in coevolution, and documentation of changes in extant populations should thus be possible. Here we describe how the ejection rate of eggs of an obligate brood parasite, the great spotted cuckoo Clamator glandarius, by its host, the magpie Pica pica, has recently increased in an area in southern Spain. The ejection rate of great spotted cuckoo eggs in naturally parasitized nests of the magpie increased at a rate of 0.5% year' during the period 1982–1992. This result was verified in a number of field experiments using nonmimetic and mimetic model eggs. The rate of increase in ejection rate was 4.7% year^-1 for mimetic eggs and 2.3% year^-1 for nonmimetic eggs. There were clear differences in parasitism by the great spotted cuckoo between study plots and years, which makes comparisons of rates of parasitism between areas difficult without considering temporal variation. The recent increase in the ejection response of magpies to great spotted cuckoo eggs was not due to magpies using the abundance of cuckoos as a cue to the intensity of parasitism.     

Reproductive biology of the spiny lobster, <Emphasis Type="Italic">Panulirus Penicillatus</Emphasis>, in the southeastern coastal waters off Taiwan

The reproductive biology of spiny lobster, Panulirus penicillatus, was studied based on 2,068 lobsters, ranging from 34.28 to 131.60 mm carapace length (CL), sampled in Taitung coastal waters from September 2003 to December 2004. The overall sex ratio approximated 1:1 (χ² = 0.02, P > 0.05), but the monthly sex ratios in 2004 showed significant differences and males were predominant in sizes larger than 80 mm CL. Reproductive activity, assessed using histology, a gonadosomatic index and percentage of ovigerous females, indicated that the mature females could be found in every month and that the major spawning occurred from May to September. The presence of re-developing/re-ripe ovaries by month and size-specific spawning time suggest that larger mature females (>60 mm CL) spawn at least three times a year while smaller new mature females spawn at least once a year. For females, the estimated sizes at 50% physiological and functional maturity were (mean ± SE) 56.46 ± 0.56 mm CL and 66.63 ± 1.07 mm CL. The estimated sizes at functional maturity were between 72 and 74 mm CL for males. The number of eggs per spawning event (brood size, BS) was related to CL by the equation Y _BS = 2.4 × 10^-3CL^4.18 (r ² = 0.902, n = 12). Female lobsters with CL ranging from 60 to 80 mm made the greatest contributions to egg production because of their high brood size and active reproductive activity. A minimum legal size should be established for the fishery to protect egg production potential of lobster population in the southeastern coastal waters off Taiwan.     

The dynamics of brood desertion among communally breeding females in the treehopper, Publilia concava

In species that exhibit extended parental care, females sometimes lay eggs communally in order to redistribute the costs of offspring care. Communal egg-laying often involves redundancy in female effort, such that the number of females contributing to reproduction is more than is needed to provide adequate parental care. As a result, a subset of females will often abandon the communal brood, with the time of departure ranging from immediate abandonment after egg-laying (brood parasitism) to delayed abandonment with prolonged care (cooperative breeding). In this paper I approach the parental care dynamics of female-female broods as a desertion game similar to that of mate desertion in species with bi-parental care. I describe a field study of the insect Publilia concava (Hemiptera: Membracidae), a species that exhibits communal oviposition and a full range of egg guarding. This species exhibits full redundancy in female care, with no difference in survival between singly and doubly guarded broods. I find that double guarding is extremely rare in the population, with most communal broods having only one female guard. While this guard was usually the female that initiated the brood, these same females were more likely to abandon when secondary females arrived and when secondary females exhibited longer guarding durations. Paradoxically, the secondary females usually abandoned the broods they visited, resulting in up to 50% of broods with double abandonment. These unguarded broods suffered a 50% reduction in hatching success, reflecting an important risk for primary females that abandon egg masses to secondary females. Overall, P. concava exhibits desertion dynamics similar to mate desertion in vertebrates and it is likely that the theoretical work in this area will be useful for future work that addresses the allocation of parental care among communal breeders.     

Isolating fetal nucleated red blood cells from maternal blood: The baylor experience—1995

In our previous work we have isolated fetal cells from maternal blood and used fluorescent in situ hybridization (FISH) for chromosome-specific probes to detect aneuploidy. Current efforts in the Baylor College of Medicine programme are focusing on obtaining consistency in flow-sorting methodology and on determining sensitivity and specificity. To this end, systematic evaluation of five glycophorin A (gly A) antibodies all produced agglutination, leading us to abandon the use of gly A antibodies for positive selection of fetal cells. Conversely, we have found LDS-751 to be useful for nuclear selection. CD45 negative selection can best be accomplished by the use of flasks coated with goat antibodies against mouse antibodies. Positive selection by flow sorting for either CD71⁺ cells or gamma-globin-positive cells seems to be successful. Using these two approaches, we have recently detected male (fetal) cells in pregnancies in which the fetus was 46, XY in 10 of 18 and in 12 of 14 cases, respectively.