Biological control of water lettuce,Pistia stratiotes [Araceae] byNeohydronomus affinis [Coleoptera: Curculionidae]

Neohydronomus affinis was imported into Australia as a potential biological control agent for the floating aquatic weedPistia stratiotes. Quarantine studies demonstrated that this weevil was host specific toP. stratiotes and it was released into the field in 1982. Subsequently it was released as a control agent for this weed in several other countries. In AustraliaN. affinis reduced infestations ofP. stratiotes by 40% or more within 12–18 months. The results are discussed in relation to its effectiveness in other parts of the world. We concluded thatN. affinis effectively controlsP. stratiotes in tropical regions (to lat. 22°), but in cooler regions its effectiveness fluctuates with seasonal conditions.      

Establishment and Dispersal ofUrophora affinis(Diptera: Tephritidae) andMetzneria paucipunctella(Lepidoptera: Gelechiidae) in Southwestern Virginia

Two European gall-producing insects,Urophora affinisFrfld. (Diptera: Tephritidae) andMetzneria paucipunctella(Zeller) (Lepidoptera: Gelechiidae) were introduced into Virginia in 1986 for biological control of spotted knapweed (Centaurea maculosaLam.). Adults ofU. affinis(n = 2625) andM. paucipunctella(n = 450) were released at two sites in Montgomery County, Virginia, and their populations were monitored yearly by dissecting spotted knapweed flower heads. Beginning in 1992, knapweed samples collected at various distances from the release sites were checked for dispersal.U. affinisis well established and is spreading slowly. The number of larvae per flower head and the seed numbers are inversely related as plants with the greatest number of larvae per spotted knapweed head had the lowest number of seeds. Knapweed density has declined at one of the release sites which had the highest rate of infestation byU. affinis.Establishment of the moth,M. paucipunctella,is less certain as it has been recovered at a very low level from only one site.     

Interactions ofMonoporeia affinis (Lindström) (Amphipoda) with sedentary Chironomidae

Interannual population oscillations ofMonoporeia affinis and sedentary chironomids are negatively correlated in Lake Mälaren. Sedentary chironomid abundance regressed againstM. affinis density was highly significant at a lag response of one year (adj. R²=0.54, P=0.0001). The inverse correlation between Tanytarsini (Micropsectra sp. andTanytarsus sp.) andM. affinis densities supports a recruitment limitation hypothesis,viz. that the growth or survival of early instar chironomids is low at high amphipod densities. Microcosm studies showed density-dependent effects on the growth and survival of second instarCh. riparius larvae across an amphipod density gradient. No significant effects were found on growth or survival of third instars. These findings support the chironomid recruitment limitation hypothesis. Amphipod predation on early instar chironomid larvae is suggested as a population controlling mechanism.     

Partitioning of food resources by sculpins in Lake Michigan

Synopsis Resource partitioning was studied in two benthic Lake Michigan fishes, the deepwater sculpin,Myoxocephalus thompsoni, and the slimy sculpin,Cottus cognatus, that exhibit nearly disjunct distributions along a hypolimnetic depth gradient. Fish were collected in an area of sympatry over two 24 h periods. These sculpins exhibited food segregation—slimy sculpins ate primarilyPontoporeia affinis, deepwater sculpins ate bothP. affinis andMysis relicta — and their depth segregation was associated with the reported abundance of these prey. Different feeding behaviors may be responsible for this association, since slimy sculpins consumed intermediate size ranges ofPontoporeia and deepwater sculpins consumedPontoporeia in a pattern similar to the ambient size distribution. Neither fish showed a daily activity cycle, and both appear food-limited.     

Role of plant phenology in mediating interactions between two biological control agents for spotted knapweed

The role of spotted knapweed phenology on the attack rate of two seed-head insects Urophora affinis and Larinus minutus was assessed in a series of field studies at four study sites in south-eastern British Columbia, Canada. Slow or later developing knapweed plants had more seed heads that contained only single or multiple U. affinis whereas early or faster developing plants had more seed heads containing L. minutus alone or in combination with U. affinis. L. minutus did not distinguish between seed heads with or without U. affinis larvae when laying eggs. However, seed heads with multiple U. affinis present, produced fewer L. minutus adults than expected. The probability of single or multiple U. affinis galls being present increased with seed-head diameter but was not affected by seed-head height. Attack by L. minutus increased with seed-head diameters >5 mm and was lower at plant heights above 50 cm. These results demonstrate two mechanisms that enable U. affinis to successfully coexist with L. minutus: differences between the species in their response to the developmental phenology of knapweed heads, and increased survivorship of U. affinis in heads with multiple U. affinis galls through niche interference competition. These mechanisms provide a possible explanation for the persistence of U. affinis populations on spotted knapweed, in spite of high levels of within seed-head mortality that have been observed with increasing L. minutus populations.     

Effects of large Saduria entomon (Isopoda) on spatial distribution of their small S. entomon and Monoporeia affinis (Amphipoda) prey

We performed laboratory experiments to investigate the effects of predator avoidance and numerical effects of predation on spatial distribution of small Saduria entomon (Isopoda) and Monoporeia affinis (Amphipoda), with large S. entomon as predators. The horizontal distribution and mortality of the prey species, separately and together, were studied in aquaria with a spatial horizontal refuge. We also estimated effects of refuge on mortality of small S. entomon and M. affinis by experiments without the refuge net. In addition, we investigated whether predation risk from large S. entomon influenced the swimming activity of M. affinis, to clarify the mechanisms behind the spatial distribution. Both small S. entomon and M. affinis avoided large S. entomon. The avoidance behaviour of M. fffinis contributed about 10 times more to the high proportion in the refuge than numerical effects of predation. Due to the low mortality of small S. entomon the avoidance behaviour of this species was even more important for the spatial distribution. The combined effect of avoidance behaviour and predation in both species was aggregation, producting a positive correlation between the species in density. M. affinis showed two types of avoidance behaviour. In the activity experiments they reduced activity by 36% and buried themselves in the sediment. In the refuge experiments we also observed avoidance behaviour with the emigration rate from the predator compartment being twice the immigration rate. The refuge did not lower predation mortality in M. affinis, probably due to the small scale of the experimental units in relation to the mobility of the species. Predation mortality in small S. entomon was higher in absence of a refuge and especially high in absence of M. affinis.     

Multiple density dependence in two sub-populations of the amphipod Monoporeia affinis: a potential for alternative equilibria

Possible mechanisms for differences in population densities and dynamics were investigated in the amphipod Monoporeia affinis at two deep sites in the northern Bothnian Sea. The two sites were sampled yearly for 10 years. Average sizes, growth and mortality of the different age-classes were estimated from the cohort structure of the two populations. Laboratory experiments also investigated the ability of the common predatory isopod Saduria entomon to cause densitydependent (DD) mortality of the prey M. affinis. At site A, 43 m depth, the average density of M. affinis was twice as high as at site B, 81 m depth. The fluctuations in density were asynchronous between the two sites. Recruitment and subadult sizes of Monoporeia affinis were density dependent at both sites. The main functional difference between the two populations seemed to be the DD mortality of the 1 + cohort that occurred only at the low-density site B. A corresponding DD mortality was found in the predation experiments at densities of 1 + m. affinis corresponding to those found at site B. The potential importance of the predator was also indicated by a significant negative correlation between the biomass of S. entomon and the rate of change in M. affinis density in the field. The similarities in the abiotic factors between the two sites suggested that differences in carrying capacity should be small. The results could be explained by the predation regulation hypothesis for the low-density population at site B, while at site A M. affinis seemed to be regulated by intra-specific competition and limited by predation. It is suggested that in this simple predator-prey system there is potential for the existence of alternative equilibria.     

The response of three chydorid species to temperature, pH and food

The responses of three chydorid species, Chydorus sphaericus(O.F. Müller), Alona affinis (Leydig) and Alonopsis elongata (Sars) to temperature, pH and food type were examined. Egg development time of all species decreased with increasing temperature, although the degree of change was different for each species. C. sphaericus had the fastest development time at all temperatures, and A. elongata the slowest. pH also affected the egg development time of each species differently. A. elongata failed to reproduce at low and medium pH, the egg development time of C. sphaericus was fastest at high pH while that of A. affinis was fastest at low pH. Food type was found to have significant effects on the population growth of individual species. C. sphaericus populations grew equally well in all three food types provided, and grew more than the other two species when fed on an algae culture, and filtered pond water. A. affinisand A. elongata populations grew best when fed on a detritus food source. The responses of each species to the different variables tested are discussed in relation to field observations of their distribution and abundance.     

The ultrastructure of the eye of the mosquitofishGambusia affinis

Summary The ultrastructure of the tissue components of the eye ofGambusia affinis, excluding the sensory cells, is described. The cornea consists of two different sections of collagenous layers of different density. The choroid includes an argentea composed of- and-melanophores, lipopterinophores and a choriocapillaris associated with the rete mirabile of the choroid body. Bruch's membrane, underlying the retinal pigment layer, can develop complex associations with fibroblasts delimiting the choriocapillaris. The outer section (stroma) of the iris includes several cell types that are not found in the inner or vitread section. In adultGambusia the lens capsule is well developed, but in twoweek-oldSarotherodon larvae the lens epithelium is covered only by a glycocalyx.     

Phenol chromatography,morphology and cytogenetics in three species and natural hybrids ofProsopis (Leguminosae — Mimosoideae)

Three species and two natural hybrids ofProsopis from the Entre Rios province of Argentina are compared morphologically, cytologically and chromatographically. It is possible to identify them by their chromatograms. There is a seasonal variation in about one third of the phenolic compounds analysed, a phenomenon that should be considered for chemosystematical conclusions. The results show many affinities betweenP. alba andP. nigra, whereasP. affinis apparently is more isolated. From the frequence of the hybrids, their fertility and their meiotic behaviour one can evaluate the isolation barriers between these species.     

Some reflections on the structure of the mandibleplate ofEurytemora affinis (Copepoda,Calanoida)

The mandibleplates of several specimen of the copepodEurytemora affinis collected from the Westerschelde and the Gironde estuary were studied. Using the Edge index (ITOH, 1970) this species could be classified as an omnivore. Pictures obtained by light and scanning electron microscopy reveal that the mandible teeth ofE. affinis have a molar-like structure, which likely changes in functional morphology with developmental stage, sex and age of the adults. Based on these observations, the desirability to consider the three dimensional structure of copepod mandibles for feeding mode classification is discussed.Communication no. 540 of the Delta Institute for Hydrobiological Research, Vierstraat 28, 4401 EA Yerseke, The Netherlands.     

Effects of maternal and embryo characteristics on post-fertilization provisioning in fishes of the genus <Emphasis Type="Italic">Gambusia</Emphasis>

Maternal provisioning of embryos in Gambusia (Poeciliidae) entails both production of large, yolky eggs and mother-to-embryo transfer of nutrients, the latter of which is readily quantified using injection of radiolabeled nutrients. We assayed patterns of nutrient transfer in broods of 26 Gambusia geiseri and 23 Gambusia affinis females, using injection of tritiated leucine. We examined maternal and embryo characteristics affecting the instantaneous rate of transfer and characterized the pattern of transfer to individual embryos within broods. Maternal (female size and condition) and brood characteristics (mean embryo size, developmental stage, brood size) did not predict the mean level of nutrient transfer to embryos in a brood for either species. Within broods, individual provisioning of embryos was not related to developmental stage, but was related to embryo mass in G. affinis with nutrient transfer higher to larger embryos. In addition, overall within-brood variation in nutrient transfer, measured as coefficient of variation in embryo radioactivity, was higher in G. affinis than in G. geiseri.     

Phenetic investigation of non-nodulating African species ofAcacia (Leguminosae) using morphological and molecular markers

Morphological and RAPD markers were used to assess the relationships among nodulating and non-nodulating species of AfricanAcacia. Non-nodulating species of AfricanAcacia are only found within subg.Aculeiferum sect.Monacanthea. African species of sect.Monacanthea examined were found to form a group distinct from the other African species examined on a morphological and molecular basis. All lack the ability to nodulate, suggesting that non-nodulation may be used as a taxonomic tool. The species of sect.Aculeiferum were separated by RAPD and morphological analysis into two groups depending on whether they were armed with prickles in pairs and/or prickles in threes, or solitary. A third group of species was identified within sect.Acacia: further subdivision of this group was achieved into subsectt.Pluriseriae andUniseriae. The position ofA. albida relative to other AfricanAcacia species was found to be distinct but not totally independent of the genus. The partitioning and distribution of the genetic variability within the genus is further elucidated by the RAPD analysis of populations ofAcacia species. A population analysis ofA. polyacantha demonstrated geographical and site-specific variation.     

Have introduced fish initiated piscivory among the long-fingered bat?

During the winter of 2003–2004 feces were collected from a winter colony of the long-fingered bat (Myotis capaccinii) in the Hazorea cave (north-west Israel). Of the 1913 feces that were examined, 234 contained scales of Gambusia affinis – a small fish that had been introduced to Israel around 1920 in order to control mosquito larvae. The remains of spiders and five insect orders were also represented in the feces. This is the first report of a piscivorous bat in the Middle East and the first finding of fish remains in the feces of M. capaccinii. The findings show that in the north of Israel this species does not hibernate but remains active throughout the winter. It appears that the consumption of G. affinis reflects a change in the diet of these bats from insectivory to semi-piscivory.     

Copepod biomass in an estuarine and a stagnant brackish environment of the S. W. Netherlands

In the mesohaline zone of the Westerschelde estuaryEurytemora affinis is the dominant copepod, demonstrating large biomass values nearly throughout the year. In the meso-polyhaline Lake VeereAcartia tonsa is abundant, mainly during summer. In spring a small population ofEurytemora americana is found. The tidal estuary harboured far denser copepod populations throughout the year than the stagnant brackish lake water. The average yearly copepodid+adult biomass in the Westerschelde estuary was approx. 850 mg/m³ (wet weight), in Lake Veere approx. 130 mg/m³. Temporarily low oxygen values did not influence negatively the copepod populations in the Westerschelde estuary. The seasonal distribution of the dominant copepods in both areas is explained in the light of recent litterature data. PerennialEurytemora affinis abundance in the Westerschelde estuary must be mainly caused by large concentrations of nannodetritus particles, bacteria included, throughout the year.Acartia tonsa in Lake Veere has to thrive mainly on nannophytoplankton. Communication no. 141 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherland.     

紫翅猪毛菜、钠猪毛菜不同个体大小繁殖分配差异及随海拔的变化

以新疆准噶尔盆地藜科猪毛菜属植物紫翅猪毛菜(Salsola affinis C.A.Mey)、钠猪毛菜(Salsola nitraria Pall)为研究对象,用繁殖分配比例的方法对比分析了两种猪毛菜不同海拔同一种群内不同个体大小繁殖分配的特点,并用异速生长模型分析了不同海拔繁殖生物量与营养生物量之间分配与个体大小的依赖关系。结果发现:1)不同海拔繁殖生物量(R)与营养生物量(V)呈不同程度的异速生长。紫翅猪毛菜随海拔的升高R-V的异速生长斜率显著升高,截距随海拔的升高没有显著增加;而钠猪毛菜的斜率随海拔升高显著降低,截距则显著升高。2)紫翅猪毛菜在较低海拔个体大小与繁殖分配呈负相关,在较高海拔呈正相关;钠猪毛菜在较低海拔个体大小与繁殖分配呈正相关,在较高海拔呈负相关;两种猪毛菜繁殖分配的适应对策相反。3)将同一种群个体大小分成大、中、小3种类型,多重比较发现紫翅猪毛菜在较低海拔,中小个体的繁殖分配显著高于大个体的繁殖分配;在较高海拔,大个体的繁殖分配显著高于中小个体的繁殖分配。钠猪毛菜在较低海拔,大个体的繁殖分配显著高于中、小个体的繁殖分配;在较高海拔,小个体的繁殖分配显著高于大、中个体的繁殖分配。综合分析认为:两个物种随海拔变化产生不同的繁殖分配策略,除遗传效应外,环境和个体大小对钠猪毛菜繁殖分配的变化均产生重要影响,而紫翅猪毛菜繁殖分配的变化主要由海拔差异导致。由于微生境对同一种群的个体大小产生影响,进而产生不同的繁殖分配模式,所以在干旱区更应重视个体大小对繁殖分配的影响。     

Biological control of three floating water weeds,<Emphasis Type="Italic">Eichhornia crassipes,Pistia stratiotes</Emphasis>, and <Emphasis Type="Italic">Salviniamolesta</Emphasis> in the Republic of Congo

Since 1999, four specific weevils (Coleoptera, Curculionidae) were released in the Republic of Congo against three exotic floating water weeds: Neochetina eichhorniae Warner and N. bruchi Hustache against water hyacinth, Neohydronomus affinis Hustache against water lettuce, and Cyrtobagous salviniae Calder and Sands against water fern. Recoveries of exotic weevils were made from all 24 release sites except one, and all four species have established and spread (up to 800 km for water hyacinth weevils). Within a few years of releases, control of water fern and water lettuce was such that fishing and navigation could be resumed, while reductions of water hyacinth populations were only beginning.     

Heterostyly in species ofNarcissus (Amaryllidaceae) andHugonia (Linaceae) and other disputed cases

The hypothesis ofHenriques andFernandes that several Iberian species ofNarcissus (Amaryllidaceae) are tristylous is reconsidered. Contrary to the opinion ofBateman and most subsequent authors, we believe that the available evidence indicates that some populations ofN. triandrus andN. fernandesii, at least, are tristylous; other populations ofN. triandrus are distylous.Hugonia cf.penicillanthemum (Linaceae) from new Caledonia is distylous, but it remains possible that other species ofHugonia are tristylous. The disputed occurrence of heterostyly in S. African species ofBauhinia (Leguminosae),Cleome (Capparaceae) andAneilema (Commelinaceae), and inAgelaea (Connaraceae) is discussed.     

Effect of alphacypermethrin and bifenthrin on the survival of five acarine predators of Halotydeus destructor (Acari: Penthaleidae)

The synthetic pyrethroids, alphacypermethrin and bifenthrin, were evaluated in the laboratory and field for their impact on the survival of five acarine predators of the pasture pest, Halotydeus destructor (Tucker). In laboratory bioassays, alphacypermethrin at the proposed field rate (5 g a.i. ha^-1) for H. destructor and the scarab beetle pest, Aphodius tasmaniae Hope caused medium-high mortality to Walzia australica Womersley (Anystidae), Bdellodes affinis Atyeo (Bdellidae), Balaustium murorum (Hermann) (Erythraeidae) and Parasitus fimetorum (Berlese) (Parasitidae) but was not toxic to Cyta latirostris (Hermann) (Bdellidae). In the field, populations of W. australica and B. affinis treated with this rate were significantly reduced but recovered after 8 weeks. Bifenthrin at 5 g a.i. ha^-1 killed 96–100% of W. australica, B. affinis, B. murorum and P. fimetorum in laboratory bioassays and significantly reduced field populations of W. australica and B. affinis for 17 weeks. In bioassays both products at 2.5 g a.i. ha^-1 permitted 10–30% survival of B. affinis and B. murorum and alphacypermethrin permitted 59% survival of W. australica. A 2.5 g a.i. ha^-1 rate of alphacypermethrin is recommended for control of H. destructor in pasture when A. tasmaniae is not present, thus minimizing the impact of chemical control on the survival of some predatory mite species.     

New species of the genus Scaphocalanus (Calanoida: Scolecithricidae) from the Iskenderun Bay – northeastern Levantine Basin

A new calanoid copepod species Scaphocalanus emine n. sp. is described for the first time from the Iskenderun Bay, northeastern Levantine Basin. S. emine is similar to S. affinis (Sars, 1905) having both identical orientation of the posterolateral corners of the cephalothorax and a median crest on the forehead. The new species is also similar in some features to S. affinis in the structure of Re1P1- lacking the outer marginal spine and by the presence of the rounded apex on the distal internal margin. It differs from S. affinis as the median crest on the forehead is smaller and due to the presence of a rudimentary endopod furnished with an apical spine on the P5. Originality in construction of the P1 and P5 distinguish the new species from other Scaphocalanus species.