Voracious Species Research Articles

Stable Isotopes Reveal Algal Assimilation in the Carnivorous Sea Slug Pleurobranchaea maculata (Quoy & Gaimard, 1832) on Patagonian Coasts

Exotic species that achieve successful invasions often show considerable dietary plasticity in resource choice, sometimes adjusting their diet to new or variable resources. This can increase species' impact in the recipient environment. In this study, we explore the diet of the invasive gray side-gilled sea slug Pleurobranchaea maculata (Quoy & Gaimard, 1832) in two environments with contrasting presence of algae (different depths) on northern Patagonian coasts, by means of stable isotope analysis. Results showed the most probable prey contribution to the diet of shallow individuals of P. maculata to be algae, whereas colonial tunicates were the preferred prey in deep environments. Therefore, we suggest that P. maculata behaves as an omnivorous species in the receiving community, because it consumes and assimilates the algae, which represents a dietary shift compared to their original feeding habits (carnivorous). This species exhibited the ability to adapt to different dietary resources by showing significant differences in niche locations, niche breadth, and exhibiting little to no overlap between different environments, which supports the previous description of P. maculata as a generalist consumer. Pleurobranchaea maculata's dietary plasticity might drive ecological consequences in the invaded community. Thus, it is important to monitor for future changes in the benthic community to develop efficient programs for the management of this invasive voracious species.

Influence of ground beetles (Carabidae) as biological agent to control of the Mediterranean fruit fly pupae, Ceratitis capitata, in Iranian citrus orchards

• High diversity and density of Carabidae observed with eliminated pesticide spray. • Instead pesticide, mineral oil spray led conserving the carabids species. • Seasonal density fluctuation of Carabidae was observed, increasing in spring. • Highest population of Carabidae with the peak of fruit fly damage in September. • H. rufipes, B. karelinii and Pterostichus macer were the most voracious predators. Damage by Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in the northern Iranian citrus orchards has been led to spray by different chemical pesticides. The present study was conducted in the citrus orchard in Mazandaran province of Iran where with the exception of mineral oil treatments for scale insects, had not been sprayed with synthetic insecticides for six years. The purpose of this study was initially to investigate faun and seasonal activity of predaceous ground carabid beetles in the citrus orchards. Additionally, their role as predators of Ceratitis capitata (Wiedemann) pupae was evaluated under laboratory and field conditions. Predation in laboratory was evaluated by no choice feeding experiments while predation under field conditions was evaluated by molecular detection of the pest DNA in the gut contents of field-collected Carabids. A total of 3,437 beetles of ten carabid species were collected from a non-chemical treatment citrus orchard. The results of the seasonal density fluctuation indicated increasing population in spring reaching the highest in September, simultaneously with the peak of fruit fly damage, and thereafter decreasing during winter when the pest was overwintering. However, three species, Harpalus rufipes, Broscus karelinii and Brachinus brevicollis were most abundant in the field collection but the results of no-choice experiments in the laboratory indicated H. rufipes, B. karelinii and Pterostichus macer were the most voracious predators on pupae. Results of gut content analysis of the voracious species indicated the positive testing for pest DNA in 79.16 % of H. rufipes , 76.92% of B. karelinii and 75% of P. macer of analyzed beetles. The results of the study strongly indicated that in citrus orchards where intensive spraying is eliminated, natural enemies such as Carabid beetles could play an important role in reducing pests such as medfly.

First Record of Oleacina cyanozoaria (Gundlach in Pfeiffer, 1857) Feeding on a Eleutherodactylus Frog in Pico San Juan, Cumanayagua, Cienfuegos Province, Cuba

Around twenty species of the landsnail subfamily Oleacininae inhabit Cuba. However, only five species were found in south-central region of the island. Despite the frequency of Oleacina in Cuba, these species have been poorly studied and little is known about their ecology, ethology and carnivorous feeding preferences. This field study is the first record showing Oleacina cyanozoaria to be an active predator on a small Eleutherodactylus frog. Small vertebrates have not been previously noted to be part of these voracious species’ diet.

Predation rate and performance of three ladybirds against the green peach aphid Myzus persicae in sweet pepper

AbstractMyzus persicae (Sulzer) (Hemiptera: Aphididae) is one of the most common and harmful pest species attacking sweet pepper. Here, we compared the predation rate and performance of Adalia bipunctata (L.), Hippodamia variegata (Goeze), and Scymnus interruptus Goeze (Coleoptera: Coccinellidae) fed on M. persicae infesting sweet pepper. In the laboratory, when offered 150 aphids daily, A. bipunctata was the most voracious species (predation per adult female of 122.7 aphids per 24 h) followed by H. variegata (87.7) and S. interruptus (27.3). When offered 50 aphids, 92% of the S. interruptus larvae developed to adults, 48% of H. variegata, and only 7% of A. bipunctata. In greenhouse experiments, A. bipunctata completely eradicated the aphid population within 2 days following release, whereas H. variegata and S. interruptus initially reduced the aphid population; however, in the long‐term, the infestation was not controlled. Adults of A. bipunctata remained on the plants even in the absence of prey but they laid almost no eggs. Very few adults of H. variegata and S. interruptus were recorded on the plants despite the presence of prey, yet egg laying was observed. Overall, A. bipunctata had an immediate impact on the aphids and is more suitable for curative releases. However, it showed limited potential to establish in the crop. Due to their capacity to complete development with low prey availability, the potential of H. variegata and S. interruptus for preventative releases against aphids in greenhouse crops should be studied further.

Study of trophic relationships between diaspididae family species -host plants -predators and parasitoids in Algeria

The use of parasitoids and predators in biocontrol contribute to the development of sustainable agriculture, respects environment and human health. In this context, we undertook the identification of natural Diaspididae enemies located on the Algerian territory. Results highlight three predatory families: Coccinellidae, Nitidulidae and Coniopterygidae families, the first represented by the most voracious species as Rhyzobius lophantae living on 19 Diaspines observed on 121 plants, from the northern, and two parasitoid families lived on 39 Diaspididae species affecting 125 plants and were represented by four genera and 23 species such as Aphytis and Encarcia (Aphelinidae) lived on 31 diaspididae species found on 125 host plants. The most voracious and polyphagous species identified are interesting for IPM. Keywords : Diaspididae, Predators, Parasitoids, Host-plant, Algeria

Prospects for predatory mirid bugs as biocontrol agents of aphids in sweet peppers

In recent years, biological control strategies to control many major horticultural pests have been successfully implemented in the Eastern Mediterranean basin. However, the management of some pests, such as aphids in sweet pepper crops, can still be improved. The goal of this study was to examine the potential of the omnivorous predatory mirids Nesidiocoris tenuis, Macrolophus pygmaeus, and Dicyphus maroccanus as biocontrol agents of aphids in sweet pepper crops. First, the capacity to detect Myzus persicae-infested and un-infested plants was studied in a Y-tube olfactometer. Females of the three species of predatory mirids were strongly attracted to the odor of infested M. persicae plants. Second, the prey suitability of young and mature nymphs of M. persicae for these three mirid species was studied. The three species actively preyed on M. persicae, although D. maroccanus resulted the most voracious species preying both young and mature nymphs. Finally, the capacity of the three omnivorous predators to reduce M. persicae in heavily infested plants was determined in semi-field conditions. The three species of mirids could reproduce on aphids and establish on sweet pepper plants. Mirids significantly reduced the number of M. persicae per leaf, reaching levels of aphid reduction close to 100 % when compared to the untreated control. These results suggest that mirids might play a major role in aphid management in sweet peppers. The potential implementation methods of predatory mirids for the biological control in sweet peppers are discussed.

The invasion of Lake Orta (Italy) by the red swamp crayfish Procambarus clarkii (Girard, 1852): a new threat to an unstable environment

Procambarus clarkii is an invasive, prolific and aggressive species introduced into Italy for commercial use since the 1980s. In November 2010, this red swamp crayfish was detected in Lake Orta, a large, deep, Italian subalpine lake. Well-known for its 80year heavy pollution by copper, Lake Orta has been gradually colonized by biota, after its chemical recovery in the 1980s. The lake is still far from being comparable to other subalpine lakes for taxa composition and seasonal dynamics. Lake Orta may be regarded as an unstable environment, in which the invasion by this voracious species deserves particular attention. After the present early detection, we plan to perform interventions to minimize negative impacts of P. clarkii to both the ecology and economy of the region. The latter may be particularly important in the case of the Lake Orta because of a persistence of heavy metals in the sediments.

Inorganic and methylmercury: Do they transfer along a tropical coastal food web?

Methylmercury (MeHg) and inorganic mercury (Hginorg) were evaluated in the water of a Brazilian estuary, with two size classes of plankton and seven fish species of different feeding habits. Water partition coefficients (PCs) in microplankton were fourfold higher for MeHg than for Hginorg; and water PCs in mesoplankton were 26 times higher for MeHg than Hginorg. Difference between microplankton and mesoplankton MeHg bioaccumulation factor (BAF) was higher (0.60log units) than Hginorg BAF (0.24log units), indicating that trophic transfer of MeHg between planktonic organisms is more efficient than Hginorg transference. MeHg concentrations, proportion of mercury as MeHg and its biotransference factors (BTFs) in the microplankton, mesoplankton and fish increased with increasing trophic level while biotic concentrations of Hginorg and proportion of mercury as Hginorg decreased thus indicating that MeHg was indeed the biomagnified species of mercury. MeHg reflected the vertical trophic guilds distribution, due to the fact that the top predator fish presented the highest concentration (0.77μgg−1d.w.), followed by the less voracious species (0.43μgg−1d.w.); while planktivorous fish presented the lowest concentrations (0.044μgg−1d.w.). Hginorg did not present the same behavior. Results suggest that feeding habits and trophic guild are important parameters, influencing biotransference and biomagnification processes.

Influence of Ground Predators on the Survival of the Mediterranean Fruit Fly Pupae, Ceratitis capitata, in Spanish Citrus Orchards

A survey of predaceous ground arthropods was conducted in two citrus orchards in Valencia, Spain, and their role as predators of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) pupae was evaluated under field and laboratory conditions. A total of 2959 predaceous arthropods were collected in pitfall traps in the two orchards from July 2003 to September 2004. Ants (Hymenoptera) were the most abundant group (83.61%), followed by Staphylinidae (7.77%), Araneae (5.24%), Dermaptera (2.13%), Carabidae (0.64%) and Cicindelidae (0.61). Pupae disappearance rates were higher during the warmer months of the year, from May to October, and in the orchard with the largest ant population. In the warm season, the mean survival of C. capitata pupae was 35.7±6.2% and 14.3±6.7%, respectively, in both orchards. Patterns of predation, inferred from broken or abnormal pupae, were more frequently observed in the colder months, from November to April, when spiders, Staphylinidae and other predators were present. In the cold season, the combined effect of predation and low temperature led to an adult emergence rate of 26.7±9.9% and 13.0±7.5% in both orchards. In no-choice laboratory trials, all predator species tested fed at significantly different rates on C. capitata pupae. Preliminary data show that the Carabids, Pseudophonus rufipes (Duftschmid) and Harpalus distinguendus (Degeer), were the most voracious species, consuming more than one pupa per day.

Are grazer-induced adaptations of bacterial abundance and morphology timedependent?

Predation by protists is a well known force that shapes bacterial communities and can lead to filamentous forms and aggregations of large cell clusters. These classic resistance strategies were observed as a direct consequence of predation by heteroand mixotrophic flagellates (the main group of bacteria predators in water) on natural assemblages of bacteria and on single plastic strains. Recently it was shown that a long time exposure (about 30 days) of a bacterial strain, characterized by high degree of phenotypic plasticity, to flagellates, without direct predation, enhanced the formation of resistant forms (filaments) in a continuous culture system. Target prey populations and predators were separated by a dialysis membrane. Moreover, the positive impact on bacterial growth, due to the chemical excretes released by flagellates was demonstrated for exudates of photosynthetic activity. The same positive impact may also be seen in response to exudates related to grazing. In this study, two short-term experiments (<100 hours) were conducted to test for modifications in the morphology and productivity of three different bacterial strains that were induced by the presence of active predators, but without direct predation. The growth and morphological distribution of each of the selected strains was tested separately using batch cultures. Cultures were either enriched with carbon in the presence or absence of flagellate predators, or included pre-filtered exudates from flagellate activity. In a second experiment, bottles were provided with a central dialysis bag that contained active flagellates, and were inoculated with the selected bacterial strains. In this way, bacteria were exposed to the presence of predators without direct predation. The bacterial strains used in this experience were characterised by a high degree of phenotypic plasticity and exhibited different successful strategies of resistance against grazing. The flagellates selected as predators belong to two voracious species: Spumella sp. and Ochromonas sp., strictly heterotrophic and mixotrophic, respectively. For all the treatments, it was impossible to find any clear evidence of a morphological adaptation stimulated by the mere presence of flagellates. On the other hand, for all bacterial strains the enrichment of the media due to the release of exudates, resulted in higher growth rates and higher abundances, confirming that grazers are fundamental actors involved in the inner recycling of the microbial loop.

Biotic communities and feeding habits of Litopenaeus vannamei (Boone 1931) and Litopenaeus stylirostris (Stimpson 1974) in monoculture and polyculture semi-intensive ponds

Zooplankton, macrozoobenthos and feeding habits of Litopenaeus stylirostris and L. vannamei in monoculture and polyculture semi-intensive experimental ponds were evaluated. Zooplankton was more abundant in monoculture of L. stylirostris (1002±670 organisms (org.) L−1) than in monoculture of L. vannamei (470±37 org. L−1), and polyculture (321±188 org. L−1). The main zooplanktonic groups were polychaeta larvae, nauplii, copepods and polychaeta. Macrozoobenthos was more abundant in polyculture (6898±11 137 org. m−2) compared with monoculture of L. stylirostris (3201±350 org. m−2) and L. vannamei (2384±3752 org. m−2). The main benthic groups were copepods, polychaeta, ostracods, nematodes and insects. Differences in feeding habits were found between species and regimes. Litopenaeus vannamei showed to be a more voracious species and fed mostly on organic detritus and benthos in both culture regimes. Litopenaeus stylirostris had a more restricted sources of feed in the ponds. The major component in the stomach content of both species was detritus. Macroalgae, sand, exuvia, formulated feed, prey and microalgae were minor components for both species (<7%). Ingestion of formulated feed was <4% for L. stylirostris and was not detected for L. vannamei. The stomach repletion rates were larger for L. vannamei (55.6% and 48.8%) than for L. stylirostris (43.75% and 44.89%). Litopenaeus stylirostris grew better in polyculture (10.3±3.4 g) that in monoculture (9.0±3.8 g). Litopenaeus vannamei grew better in monoculture (16.1±4.8 g) than in polyculture (13.4±4.5 g). For both species, feed conversion ratio was lower in polyculture.

Observation of epigeic predators and predation on artificial prey in a cereal field

AbstractPredation activity of different epigeic predators on artificially supplied prey was studied in a cereal field during several 24 h periods from spring to early summer 1993. Carabids were the most frequently observed predators. Among them Poecilus cupreus was the most voracious species during day‐time, and Agonum muelleri during night‐time. Predation rates were highest between 10.00 and 18.00 h and lowest between 02.00 and 10.00 h. Linear regressions showed significantly positive relations between temperature and predation rates, and between predation and activity density of epigeic predators. The latter relation was stronger when only activity density of predators which were observed to consume baits was included. Quadrat sampling and pitfall sampling showed that with the former only a small proportion of bait‐consuming predators were caught whereas with the latter method this proportion was high.

Predator Complex of the Green Peach Aphid 1 on Sugarbeets: Expansion of the Predator Power and Efficacy Model 2

A model to evaluate potential reductive impact of populations of green peach aphid, Myzus persicae (Sulzer), by predators was generalized to include effects of temperature on the rate of aphid reproduction and the functional response of the predator complex. Coccinella transversoguttata richardsoni Brown was the most abundant predator in field experiments with large numbers of green peach aphids on sugarbeet plants, Beta vulgaris , L., Geocoris pallens Stal, syrphids, and Scymnus marginicollis Mannerheim were also abundant. Predators had a major role in determining the abundance of aphids, but their effect was greater at the higher densities because the more voracious species responded preferentially to high aphid populations.

Etude du regime alimentaire de l'Aigle de mer, Myliobatis aquila (L., 1758) des cotes tunisiennes

Myliobatis aquila, the Eagle Ray, is a voracious species which feeds all the year round. The stomach contents of 523 fishes (males 281, females 241) have been examined. Benthic invertebrates are found in the stomachs more frequently than any other group: there is no specific choice for them. The proportion of teleosts in the stomach contents of M. aquila increases with the length of the ray. This is most evident in females which normally reach a larger size than males. The eagle ray provides an example where a change from a demersal to a semi-pelagic mode of life is associated with a change in diet which reflects the fauna of the new environment.

On Fish and Mosquitos in Palestine

One of the greatest difficulties of anti-mosquito work in Palestine is that there are a series of swamps in the littoral plain, lying almost at sea level and prevented from draining into the Mediterranean by sand-dunes and sand-bars which block their outlet channels. It appears that cutting channels through the coastal dunes is a task which would have to be repeated at very frequent intervals, and until some-what large sums of money are available the pumping of these numerous swamps into the sea cannot be undertaken. There are, moreover, other rather large areas of marsh, notably Lake Huleh, Beisan marsh and the Marj Sanour, the proper drainage of which is at the moment beyond the financial resources of the country. We have therefore to rely for the moment on ameliorative measures which are admittedly not sufficiently radical. Among other things, I have begun a study of our native fish, hoping to find some small and voracious species that breeds rapidly and is able to live in waters of different degrees of salinity. The results which I have obtained are perhaps discouraging, but certainly interesting.