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1.
Summer ichthyoplankton surveys were conducted in the northern Gulf of Mexico from 2007 to 2010 to characterize the distribution and abundance of tuna larvae. Larval assemblages of tunas were comprised of four genera: Thunnus, Auxis, Euthynnus, and Katsuwonus. Thunnus were the most abundant and four species were detected; T. atlanticus [blackfin tuna], T. obesus [bigeye tuna], T. albacares [yellowfin tuna], and T. thynnus [bluefin tuna]. Intra- and inter-annual variability in the distribution and abundance of Thunnus species were observed with higher densities in 2008 and 2009, with a decline in abundance observed in 2010. Distribution and abundance of Thunnus larvae were influenced by physical and chemical conditions of the water mass, notably sea surface temperature and salinity. Distinct species-specific habitat preferences were observed and the location of mesoscale oceanographic features influenced larval abundance with higher densities of T. atlanticus, T. obesus, and T. albacares near anticyclonic (warm core) regions and the Loop Current, while T. thynnus was observed in higher densities near cyclonic (cold core) regions. This study demonstrates that spatial and temporal variability in the location of mesoscale oceanographic features may be important to partitioning nursery habitat among Thunnus species.  相似文献   

2.
Abundance of 2 ixodid tick species, Ixodes (Exopalpiger) trianguliceps Birula, 1895 and Ixodes (Ixodes) persulcatus Schulze, 1930 was studied during 6 years, in 1998–2001 and 2003–2004, at a research station in Gomselga Village (central Karelia, Kondopoga District, 62°04′N, 33°55′E). New data on host species composition and ixodid tick abundance were obtained from 4 forest plots at different stages of reforestation (secondary succession) following felling that occurred 7–14, 12–19, 25–32, and 80–87 years ago. Individuals of I. persulcatus predominated and constituted 73% of the total ticks collected. The occurrence rates of different developmental stages were shown to fluctuate in the course of reforestation both in I. trianguliceps (larvae, 2.8–5.3; nymphs, 1.5–2.2; adults, 0–0.09) and in I. persulcatus (larvae, 4.3–10.6; nymphs, 0.6–4.2).  相似文献   

3.
The organic matter content in the eggs and early larvae of the ctenophores Mnemiopsis leidyi and Beroe ovata from the Black Sea was determined using the adapted microtechnique of dichromate oxidation. The content of organic matter in the eggs of M. leidyi (0.25 μg/indiv.) was 5 times less than in B. ovata (1.28 ± 0.29 μg/indiv.). The somatic content of organic matter was 0.25 ± 0.09 μg/indiv. (25.1 ± 8.3 μg/mg, wet wt) for 2-day-old larvae of M. leidyi (0.2–0.3 mm in body length) and 1.37 ± 0.19 μg/indiv. (67.1 ± 5.7 μg/mg wet wt) for larvae of B. ovata (0.4 mm in body length). The specific organic content of larvae of both species steadily decreased with an increase in ctenophore body size and weight, approaching 3–4 μg/mg of wet weight for 2 mm specimens of M. leidyi and 3–5 μg/mg of wet weight for 6 mm B. ovata. The specific organic content of early larvae was 20–30 times higher than that of adult ctenophores. The results of this investigation could be useful in the evaluation of the energy budget for somatic growth and generative production in these species. Calculations indicate that with specific wet weight growth rates of 0.43/day for M. leidyi larvae and 0.29/day for B. ovata larvae, their true organic increases are respectively 30 and 38% less, i.e., no more than 0.31/day for the former and 0.18/day for the latter species.  相似文献   

4.
Three species of cecidomyiid midges (Diptera: Cecidomyiidae), whose larvae overwinter in the soil, can cause significant yield losses on wheat in Europe: the orange wheat blossom midge, Sitodiplosis mosellana (Géhin), the yellow wheat blossom midge, Contarinia tritici (Kirby), and the saddle gall midge, Haplodiplosis marginata (von Roser). The biological control of wheat midges by their parasitoids can contribute to reduce the midge populations. Soil samples were collected in several fields in Belgium in 2012–2014 in order to characterize the parasitism rates and parasitoid complexes in overwintering larvae. The parasitism rates varied greatly between the sampled fields: 3–100, 0–100 and 2% for S. mosellana, H. marginata and C. tritici, respectively. The parasitism rate was not related to the larval density of wheat midge. The three wheat midges have totally distinct parasitoid complexes in Belgium. Eight species (Hymenoptera: Pteromalidae and Platygastridae) were found as parasitoid of S. mosellana: Macroglenes penetrans (Kirby), Amblypasis tritici (Walker), Euxestonotus error (Fitch), Euxestonutus sp. Fouts, Leptacis sp. Foerster, Platygaster gracilipes (Huggert), Platygaster nisus Walker, and Platygaster tuberosula (Kieffer). According to their abundance, M. penetrans, E. error and P. tuberosula appeared as the main parasitoids of S. mosellana in Belgium. For the two other wheat midges, only one species of the family Platygastridae was found for each midge: Platygaster equestris (Spittler) for H. marginata and Synopeas myles (Walker) for C. tritici.  相似文献   

5.
Data on the species composition and distribution of ichthyoplankton in Onega Bay of the White Sea are presented for June–July 2007, 2010–2012, and 2015–2016. In the ichthyoplankton, the specimens of the early developmental stages of 21 fish species were registered; the larvae of the White Sea herring Clupea pallasi marisalbi, capelin Mallotus villosus, and Pacific sand lance Ammodytes hexapterus were the most abundant. It is shown that the northwestern and southeastern zones, distinguished in Onega Bay by hydrophysical parameters, also differ in species composition and in ichthyoplankton abundance.  相似文献   

6.
The ichthyofauna of the narrow coastal zone of southwest Crimea in 2003–2004 was represented by 79 fish species belonging to 36 families. The structure of the species composition of eggs, larvae, and adult fish in these years indicated to its restoration in comparison with the late 1980s to early 1990s. The abundance of commercial fish increased: Engraulis encrasicolus ponticus, Trachurus mediterraneus ponticus, and Mullus barbatus ponticus. The quantity of migratory fish increased: Pomatomus saltatrix and Sarda sarda. The presence in winter catches of Trachurus mediterraneus ponticus and Pomatomus saltatrix indicated favorable conditions for their wintering off South Crimea. Appearance in catches of the fish of elder age groups is evidence of the restoration of their age structure. The competitor for food Mnemiopsis leydyi still influences the food resources of the fish and, thus, their survival. If they appear in plankton simultaneously, the abundance of larvae drastically decreases. The obtained data indicate to the vulnerability of coastal biocenoses to anthropogenous impact and to the necessity of monitoring of fish resources and of their protection.  相似文献   

7.
Rabbit neutrophils peptide-1 (NP-1) is a type of defensin that possesses a broad spectrum of antimicrobial activity. Chlorella ellipsoidea is a new eukaryotic expression system for exogenously producing NP-1. The NP-1 transgenic C. ellipsoidea can be directly added into feed as antimicrobial agent without any purification procedure for the NP-1 peptide. However, the effects of C. ellipsoidea and NP-1 on the host gut microbiota should be explored before application. In this study, diets containing different concentrations (1.25, 2.5, and 5 %) of C. ellipsoidea and NP-1 transgenic C. ellipsoidea were administered to male Sprague–Dawley rats. Compared with the chow diet control group, none of the experimental groups showed any significant differences in their growth indices, and no histopathological damage was observed. The phylotypes of gut microbiota in the control group, the 5 % C. ellipsoidea diet group and the 5 % NP-1 transgenic C. ellipsoidea diet group were determined by 16S rRNA sequencing. The results showed that both 5 % experimental groups had shifted community memberships of gut microbiota. In particular, the 5 % NP-1 transgenic C. ellipsoidea diet exhibited an increased abundance of most Gram-positive bacterial taxa and a reduced abundance of most Gram-negative bacterial taxa, and it promoted the growth of some lactic acid bacterial genera. Lactic acid bacteria, especially the Bifidobacterium and Lactobacillus, have been widely reported to be benefic effects on the host. Thus NP-1 transgenic C. ellipsoidea is promising feed additive and gut regulator, as it have the potential to increase the abundance of Bifidobacterium and Lactobacillus in gut microbiota of animal.  相似文献   

8.
Research on the Morava River floodplain mosquito fauna was carried out from April to October in 2009 and 2010. Altogether, 5864 adults were collected and identified from 12 selected sites. The presence of 28 mosquito species belonging to 6 genera were confirmed in the study area. The floodplain of the Morava River is known for its frequent inundation every year. The floods are quite irregular and often followed by the mass production of mosquitoes. The most abundant species were Aedes vexans (41.4%), Ae. cinereus (7.5%), Ae. rossicus (16.7%), Ochlerotatus sticticus (20.5%), and Culex pipiens (3.1%). Ae. vexans and Oc. sticticus are typical outbreak species for the Morava River floodplain. The years 2009 and 2010 differed in the number of floods, which influenced the mosquito faunal composition and abundance during the year.  相似文献   

9.
Amending a peat-based growing medium with 10% v/v spent mushroom compost, a source of fungal chitin and other nutrients, prolonged the persistence of entomopathogenic fungi (Metarhizium brunneum Petsch and Beauveria bassiana (Balsamo) Vuillemin; Hypocreales: Clavicipitaceae). This resulted in improved efficacy of M. brunneum against black vine weevil, Otiorhynchus sulcatus F. (Coleoptera: Curculionidae) larvae compared with using inoculum without spent mushroom compost. B. bassiana only controlled larvae when used in combination with spent mushroom compost (75?±?7% reduction in live larvae). Mixing entomopathogenic fungal inoculum with spent mushroom compost and growing medium was as effective in controlling black vine weevil larvae as using spent mushroom compost colonised with M. brunneum or B. bassiana in the growing medium (80?±?12% reduction in live larvae). The former method is preferable since it does not require production and storage of colonised spent mushroom compost, or registration of new substrate formulations of M. brunneum or B. bassiana.  相似文献   

10.
The larval morphology of the gastropod Cryptonatica janthostoma inhabiting the Northwest Pacific was described for the first time. Hatched planktotrophic veligers of C. janthostoma had shells 250 μm in height with 0.8 whorls, a bilobate velum with a dark brown pigmentation band shaped along its edge, pair of eye spots, tentacles and statocysts. The surface of the embryonal shell (protoconch 1) was covered with fine granules extended at the dorsal side and rounded at lateral surfaces. Concentric crests and growth lines occurred on part of the shell of late free-swimming larvae (protoconch 2) The velum of the C. janthostoma larvae remained bilobate during the pelagic stage of development, whereas it was divided in 4 lobes during larval development in most of the other species of the Naticidae family. The veliger of C. janthostoma was similar to that of Natica montagu from Danish waters [16] by its shape, pigmentation, shell sculpture and velum structure.  相似文献   

11.
Vertical distribution and diel vertical migration of a zooplankton community were studied at two stations off Central Peru in April 2006. Zooplankton was collected at five depth strata by vertical hauls with Hydo-Bios multinet (300-μm mesh, 0.25-m2 mouth size). The zooplankton community was distributed in relation to a strong, shallow oxycline (1 ml l?1 oxygen isopleth generally above 36 m). The highest total abundance was always in the upper, well-oxygenated layer. The most important species were: Acartia tonsa (72.86%), Centropages brachiatus (7.5%), and Paracalanus parvus (3.1%); Acartia tonsa was the dominant species at all times. Larvae of the polychaete Magelona sp. (7.5%) and larvae of the brachiopod Discinisca lamellosa (3.5%) were numerically dominant in April and small copepods e.g. Oncaea venusta (3.88%) were numerically dominant during August. Five distinct patterns of vertical distribution and migration in relation to the oxygen minimum layer were distinguished in this study: (1) Ontogenetic vertical migration through the oxycline (Acartia tonsa adults, nauplii, and copepodids), (2) permanent limitation to layers above the oxycline (e.g. Oikopleura sp., most invertebrate larvae), (3) distribution mostly below the oxycline with occasional migration into the layers just above the oxycline (Eucalanus inermis), (4) Diel Vertical Migration (Centropages brachiatus), and (5) reverse Diel Vertical Migration (larvae of the polychaete Magelona sp.).  相似文献   

12.
We investigated the environmental drivers of larval abundance of anchovy Engraulis encrasicolus and sardine Sardinops sagax in Algoa Bay, Eastern Cape (South Africa). This study comprised a pre-drought post-drought time period, comparing the responses of the fish larvae to different factors before and after the drought. The current study presents, for the first time, which environmental variables are affecting the anchovy and sardine larvae populations in the region. Easterly wind speed and zooplankton density were the only environmental variables that presented a significant change between the pre- and post-drought periods, increasing after the drought. Generalized additive models (GAMs) were used in order to explore the effects that environmental factors might have in the abundance of anchovy and sardine larvae in Algoa Bay. Specifically, the GAM that best explained the deviance of the anchovy larvae dynamics included the covariates rainfall, easterly wind speed, Chl a concentration, sardine larvae abundance and the interactions SST*Chla and sard*SST. The GAM best explaining sardine larvae abundance included only the easterly wind speed as a covariate. This model showed that there was a positive relationship between the higher values of wind speed and sardine larvae abundance.  相似文献   

13.
Understanding the environmental factors that affect the distribution and abundance of rare and threatened species can help identify priority sites for conservation action such as habitat management. The moth Cucullia lychnitis is identified in UK legislation as a priority species for conservation. Its conspicuous larvae feed on a patchily distributed host plant Verbascum nigrum, but are entirely absent from some host plant patches within the species’ range. Environmental variability among patches was investigated to understand factors affecting (i) patch occupancy by C. lychnitis and (ii) abundance of C. lychnitis, where present. Occupancy of individual V. nigrum plants within occupied patches was also investigated. The likelihood of patch occupancy increased with patch size, and decreased with patch isolation. Abundance of C. lychnitis was negatively correlated with patch isolation and with abundance of the weevil Cionus nigritarsis, which exploits the same host plant and may be a competitor. Within occupied patches, larvae of C. lychnitis were significantly more likely to be found on taller plants with more flower spikes; such plants are typical of established rather than newly-created patches. These results may help to guide efforts to conserve C. lychnitis, highlighting the importance of habitat connectivity and indicating potential management actions to promote features positively associated with larval incidence and abundance.  相似文献   

14.
Diadema antillarum was once ubiquitous in the Caribbean, but mass mortality in 1983–84 reduced its numbers by >97%. We measured Diadema abundance on back reefs and patch reefs that have been well studied for >25 years. From June 2000 to June 2001, populations on back reefs have increased >100% (June 2001 mean densities 0.004–0.368/m2), while patch reef populations increased >350% (June 2001 densities 0.236–0.516/m2). Populations are dominated by small urchins, suggesting high recent recruitment. Increased Diadema densities appear to be affecting macroalgae abundance. The general spatio-temporal pattern of recovery around St. Croix seems to be following that of the die-off, suggesting that the same oceanographic features that spread Diadema's pathogen are now carrying urchin larvae.  相似文献   

15.
Aedes aegypti (L.) is the main vector of tropical diseases such as dengue, chikungunya and Zika. Due to the overuse of insecticides, Ae. aegypti resistant populations have increased. Biological control with Lysinibacillus sphaericus (Ahmed) has been used against Culex sp. and Anopheles sp. Although Ae. aegypti is refractory to the binary toxin of L. sphaericus spores, vegetative cells have been shown to be effective against Ae. aegypti larvae. In this work, the effect of L. sphaericus vegetative cells on Ae. aegypti temephos-resistant larvae was assessed under lab and simulated field conditions. L. sphaericus caused about 90% mortality of insecticide-resistant Ae. aegypti larvae under simulated field conditions. Likewise, Ae. aegypti larvae were more sensitive to mixed cultures of L. sphaericus than to individual strains; then, the most effective mixed culture exhibited an LC50 of 1.21 × 105 CFU/mL with Rockefeller larvae and 8.04 × 104 CFU/mL with field-collected larvae. Additionally, we found that mixed cultures composed of two L. sphaericus strains were more effective than a culture formed by the three strains. Our results suggest that mixed cultures comprising L. sphaericus vegetative cells could be useful for controlling temephos-resistant populations of Ae. aegypti, as evidenced by the effectiveness demonstrated under laboratory and simulated field conditions.  相似文献   

16.
Invasive predators can have dramatic impacts on invaded communities. Extreme declines in macroinvertebrate populations often follow killer shrimp (Dikerogammarus villosus) invasions. There are concerns over similar impacts on fish through predation of eggs and larvae, but these remain poorly quantified. We compare the predatory impact of invasive and native amphipods (D. villosus and Gammarus pulex) on fish eggs and larvae (ghost carp Cyprinus carpio and brown trout Salmo trutta) in the laboratory. We use size-matched amphipods, as well as larger D. villosus reflecting natural sizes. We quantify functional responses, and electivity amongst eggs or larvae and alternative food items (invertebrate, plant and decaying leaf). D. villosus, especially large individuals, were more likely than G. pulex to kill trout larvae. However, the magnitude of predation was low (seldom more than one larva killed over 48 h). Trout eggs were very rarely killed. In contrast, carp eggs and larvae were readily killed and consumed by all amphipod groups. Large D. villosus had maximum feeding rates 1.6–2.0 times higher than the smaller amphipods, whose functional responses did not differ. In electivity experiments with carp eggs, large D. villosus consumed the most eggs and the most food in total. However, in experiments with larvae, consumption did not differ between amphipod groups. Overall, our data suggest D. villosus will have a greater predatory impact on fish populations than G. pulex, primarily due to its larger size. Higher invader abundance could amplify this difference. The additional predatory pressure could reduce recruitment into fish populations.  相似文献   

17.
Maeto K  Ozaki K 《Oecologia》2003,137(3):392-398
Quercus crispula (=Q. mongolica var. grosseserrata) is the predominant tree species in cool temperate, mixed broadleaf/conifer forests in northern Japan. We compared 11 years of data on acorn production in a population of Q. crispula, with data on seed-insect populations, to try to answer the following questions: (1) Does Q. crispula show a regular pattern of masting? (2) How long do principal seed predators remain in diapause? (3) How do the seed predators affect the pattern of predator satiation? Q. crispula showed a tendency to alternate bearing, with significant synchrony between individual trees. The principal acorn-feeding insects (Curculio spp. weevils), which infested 25%–70% of matured acorns, generally exhibited a prolonged diapause of 2 years. No significant negative relationship was found between the rate of injury by the weevils and the density of mature acorns, indicating that simple predator satiation fails due to the synchrony of the life-cycle of acorn-feeding insects and the periodical production of acorns. However, the rate of injury by the weevils was negatively correlated with the relative abundance of mature acorns to the number of weevil larvae that had matured 2 years previously. Thus, the proportion of sound acorns notably increased in a rich crop after a disturbance in alternate bearing. Prolonged diapause of specific seed predators is critical in determining the peak year of sound-seed production.  相似文献   

18.
The sweet potato Ipomoea batatas (L.) Lam., which has extrafloral nectaries, was visited by nine indigenous ant species in south Kyushu, Japan. These ant species were evaluated for their ability to remove the eggs of two lepidopteran species—Aedia leucomelas (Linnaeus) and Spodoptera litura (Fabricius)—through ant-exclusion experiments. The results showed that Tetramorium bicarinatum (Nylander), one of the dominant ant species, is an efficient predator of lepidopteran eggs. This ant species removed A. leucomelas eggs from ant-visited plants in six trials conducted from mid-July to mid-October, with high removal rates (90–100%) occurring from mid-September onward. On ant-excluded plants, only 0–18% of exposed eggs were removed by ants that accidentally invaded the plants. Tetramorium bicarinatum also removed egg masses and the hatchlings of S. litura. The mean percent area of egg-laden leaves eaten by S. litura larvae was lower on ant-visited plants (0.9%) than on ant-excluded plants (57.3%). In contrast, Formica japonica Motschulsky, another dominant ant species, was not observed removing the eggs or larvae of the lepidopteran species. These results show that certain indigenous ant species are efficient as biocontrol agents. Thus, individual ant species need to be investigated for their ability to control insect pests in various crops.  相似文献   

19.
The tamarisk leaf beetle (Diorhabda carinulata), introduced from Eurasia in 2001 as a biological control agent for the invasive plant Tamarix ramosissima, has spread widely throughout the western USA. With D. carinulata now very abundant, scientists and restoration managers have questioned what influence this introduced arthropod might have upon the avian component of riparian ecosystems. From 2009 through 2012 we studied the consequences of biological invasions of the introduced tamarisk shrub and tamarisk leaf beetles on the diets of native birds along the Dolores River in southwestern Colorado, USA. We examined avian foraging behavior, sampled the arthropod community, documented bird diets and the use of invasive tamarisk shrubs and tamarisk leaf beetles by birds. We documented D. carinulata abundance, on what plants the beetles occurred, and to what degree they were consumed by birds as compared to other arthropods. We hypothesized that if D. carinulata is an important new avian food source, birds should consume beetles at least in proportion to their abundance. We also hypothesized that birds should forage more in tamarisk in the late summer when tamarisk leaf beetle larvae are more abundant than in early summer, and that birds should select beetle-damaged tamarisk shrubs. We found that D. carinulata composed 24.0 percent (±?19.9–27.4%) and 35.4% biomass of all collected arthropods. From the gut contents of 188 birds (25 passerine species), only four species (n?=?11 birds) contained tamarisk leaf beetle parts. Although D. carinulata comprised one-quarter of total insect abundance, frequency of occurrence in bird gut contents was only 2.1% by abundance and 3.4% biomass. Birds used tamarisk shrubs for foraging in proportion to their availability, but foraging frequency did not increase during the late summer when more tamarisk leaf beetles were present and birds avoided beetle-damaged tamarisk shrubs. Despite D. carinulata being the most abundant arthropod in the environment, these invasive beetles were not frequently consumed by birds and seem not to provide a significant contribution to avian diets.  相似文献   

20.
Long-term data on the composition and absolute and relative abundance of eight bat species hibernating in artificial caves of Samara Luka are considered. About 13 000 hibernating individuals are annually accounted there. The relative abundance of the species decreased in the following order: Myotis brandtii (35%), Plecotus auritus (20%), M. daubentonii (13%), M. mystacinus (13%), Eptesicus nilssonii (8%), M. dasycneme (8%), and M. nattereri (2%). Singular E. serotinus were recorded not every year. The number of hibernating animals in pits was proportional to their size and the number of shelters. Bats used previously chosen shelters and were never found in adjacent caves. The maximum species diversity (H’) and evenness (E) were observed in bat communities in medium-sized caves. One of the main factors of increasing abundance of hibernating bats in abandoned pits is their gradual colonization by the animals.  相似文献   

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