Prior exposure to weathered oil influences foraging of an ecologically important saltmarsh resident fish

Estuarine ecosystem balance typically relies on strong food web interconnectedness dependent on a relatively low number of resident taxa, presenting a potential ecological vulnerability to extreme ecosystem disturbances. Following the Deepwater Horizon (DwH) oil spill disaster of the northern Gulf of Mexico (USA), numerous ecotoxicological studies showed severe species-level impacts of oil exposure on estuarine fish and invertebrates, yet post-spill surveys found little evidence for severe impacts to coastal populations, communities, or food webs. The acknowledgement that several confounding factors may have limited researchers’ abilities to detect negative ecosystem-level impacts following the DwH spill drives the need for direct testing of weathered oil exposure effects on estuarine residents with high trophic connectivity. Here, we describe an experiment that examined the influence of previous exposure to four weathered oil concentrations (control: 0.0 L oil m−2; low: 0.1 L oil m−2; moderate: 0.5–1 L oil m−2; high: 3.0 L oil m−2) on foraging rates of the ecologically important Gulf killifish (Fundulus grandis). Following exposure in oiled saltmarsh mesocosms, killifish were allowed to forage on grass shrimp (Palaeomonetes pugio) for up to 21 h. We found that previous exposure to the high oil treatment reduced killifish foraging rate by ~37% on average, compared with no oil control treatment. Previous exposure to the moderate oil treatment showed highly variable foraging rate responses, while low exposure treatment was similar to unexposed responses. Declining foraging rate responses to previous high weathered oil exposure suggests potential oil spill influence on energy transfer between saltmarsh and off-marsh systems. Additionally, foraging rate variability at the moderate level highlights the large degree of intraspecific variability for this sublethal response and indicates this concentration represents a potential threshold of oil exposure influence on killifish foraging. We also found that consumption of gravid vs non-gravid shrimp was not independent of prior oil exposure concentration, as high oil exposure treatment killifish consumed ~3× more gravid shrimp than expected. Our study findings highlight the sublethal effects of prior oil exposure on foraging abilities of ecologically valuable Gulf killifish at realistic oil exposure levels, suggesting that important trophic transfers of energy to off-marsh systems may have been impacted, at least in the short-term, by shoreline oiling at highly localized scales. This study provides support for further experimental testing of oil exposure effects on sublethal behavioral impacts of ecologically important estuarine species, due to the likelihood that some ecological ramifications of DwH on saltmarshes likely went undetected.

A paradox of parasite resistance: Disease-driven trophic cascades increase the cost of resistance, selecting for lower resistance with parasites than without them

Most evolutionary theory predicts that, during epidemics, hosts will evolve higher resistance to parasites that kill them. Here, we provide an alternative to that typical expectation, with an explanation centered on resource feedbacks. When resistance is costly, hosts evolve decreasing resistance without parasites, as expected. But with parasites, hosts can evolve lower resistance than they would in the absence of parasites. This outcome arises in an eco-evolutionary model when four conditions are met: first, resistance has a fecundity cost (here, via decreased foraging/exposure rate); second, resources increase during epidemics via trophic cascades; third, increased resources magnify the benefit of maintaining a fast foraging rate, thereby magnifying the cost of evolving a slower foraging/exposure rate (i.e., resistance); fourth, that amplification of the cost outweighs the benefit of resistance. When these conditions are met, hosts evolve lower resistance than without parasites. This phenomenon was previously observed in a mesocosm experiment with fungal parasites, zooplankton hosts, and algal resources. Re-analyzing this experiment produced evidence for our model's mechanism. Thus, both model and experiment indicate that, via resource feedbacks, parasites can counterintuitively select against resistance.

Effect of probiotic supplement feed on the foraging activity of Indian honeybee (Apis cerana indica F.)

Aim: To investigate the effect of probiotic supplement feed on the foraging behaviour Indian honeybee colonies to resolve the excessive usage of antibiotics. Methodology: The effect of sugar syrup feed (Untreated hives) and sugar syrup + probiotic supplement feed @ 10 ml 100 ml-1 syrup (Treated hives) on Indian honeybees was tested. The foraging activity and foraging rate were recorded and subjected to paired t- test analysis. Results: The present observation showed a significant difference in the foraging rate between the colonies fed with sugar syrup + probiotic supplement (2.33 ± 0.11 min-1) than the colonies that received sugar syrup alone (1.35 ± 0.06 min-1). The highest foraging rate (2.80 ± 0.39 min-1) was recorded in treated hives. Interpretation: The experiment revealed that the brood development was directly proportional to brood pheromone levels, which positively affects the foragers, consequently foraging rate and honey production. Thus, the probiotic supplement feeding may influence the foraging behaviour of honeybee colonies.

Efisiensi Penyerbukan oleh Penyerbuk Liar dan Lebah Tetragonula laeviceps pada Bunga Ranti dan Kacang Panjang

Penyerbukan serangga merupakan salah satu upaya peningkatan efisiensi produksi tanaman berbuah pada lahan terbatas. Penelitian bertujuan mengamati aktivitas dan efisiensi penyerbukan serangga liar dan Tetragonula laeviceps pada tanaman ranti dan kacang panjang dengan sistem tanam tumpang sari di Desa Sukawangi, Kabupaten Sumedang pada bulan September hingga Januari 2020. Pengamatan dilakukan pada pukul 08:00-15:00 WIB selama periode perbungaan. Pengamatan dilakukan pada perlakuan aplikasi T. laeviceps, open-pollination, dan self-pollination, masing-masing perlakuan terdiri atas 100 bunga ranti dan 100 bunga kacang panjang dan dianalisis menggunakan one way analysis of variance (α = 0.05). Aktivitas serangga diukur berdasarkan flower handling time, foraging rate, visitation rate, dan fruit set. Kualitas buah diukur berdasarkan diameter, bobot, panjang, dan oBrix. Hasil penelitian ditemukan masing-masing tiga serangga pengunjung berpotensi polinator pada ranti dan kacang panjang dengan pola kunjungan bervariasi pada open-pollination. Efisiensi fruit set tertinggi ranti terjadi pada perlakuan aplikasi T. laeviceps dan kacang panjang pada perlakuan open-pollination. Terdapat perbedaan nyata pada oBrix buah ranti dan kacang panjang, sedangkan self-pollination hanya menghasilkan buah yang secara signifikan lebih panjang pada kacang panjang. Dengan demikian, T. laeviceps dapat dijadikan salah satu alternatif serangga penyerbuk terdomestikasi dalam upaya efisiensi fruit set dan kualitas buah tanaman ranti dan kacang panjang. Kata kunci: aktivitas serangga, fruit set, kualitas buah

Virulent disease epidemics can increase host density by depressing foraging of hosts

All else equal, parasites that harm host fitness should depress densities of their hosts. However, parasites that alter host traits may increase host density via indirect ecological interactions. Here, we show how depression of infected host foraging rate can produce such a hydra effect. Using a foraging assay, we quantified reduced foraging rates of a zooplankton host infected with a virulent fungal parasite. We then parameterized a dynamical model of hosts, parasites, and resources with this foraging function, showing how foraging depression can create a hydra effect. Mathematically, the hydra arose when increased resource productivity exceeded any increase in resource consumption per host. Therefore, the foraging-mediated hydra effect more likely emerged (1) for hosts which strongly control logistic-like resources and (2) during larger epidemics of moderately virulent parasites. We then analyzed epidemics from 13 fungal epidemics in nature. We found evidence for a foraging-mediated hydra effect: large outbreaks depressed foraging rate and correlated with increased densities of both algae and hosts. Therefore, depression of foraging rate of infected hosts can produce higher host densities even during epidemics of parasites that increase host mortality. Such hydras might prevent collapse of host populations but also could produce higher densities of infected hosts.

Bee species (Hymenoptera: Anthophila) in a Cerrado-Atlantic Forest ecotone: nesting habits related to foraging activity in a degraded forest fragment

The aim of this paper was to determine the species diversity and frequency of foraging performed by bees in fragment of degraded forest in a Cerrado-Atlantic Forest ecotone area, also considering the nesting habit of each species. The foraging frequency of each bee species in the main floral sources was recorded for 12 consecutive months. The nesting site was used to sort the bees into guilds: above-ground nesting bees, ground-nesting bees, and both below and above-ground nesting bees. The guild of ground-nesting bees had 24 species and accounted for 17.48 % of the foraging rate, while above-ground nesting bees were represented by 12 species which made 8.89 % of the foraging rate, and both below and above-ground nesting bees comprised five species which made 0.43 % of the foraging rate. Africanized honeybee performed 73.20 % of the foraging flight, and presented a broad food niche. Therefore, in the forest fragment studied, two types of impacts which make difficult the survival and maintenance of the native bee fauna were observed: the dominance over floral resources by the exotic species the Africanized honeybees; the small number of large trees.

Relative abundance and foraging activity of hymenopteran pollinators in cucurbitaceous vegetables

A study was conducted to investigate the diurnal activity patterns of hymenopteran pollinators in culinary melon and the dynamics of hymenopteran pollinators of five selected cucurbitaceous vegetables viz.,culinary melon, bitter gourd, pumpkin and ridge gourd in 34 locations of Kerala from 06:00 h to 18:00 h with a cone type hand net. The study revealed that Apis cerana indica was dominant in culinary melon, pumpkin and ridgegourd and Tetragonula travancorica was dominant in bitter gourd and ash gourd, A. cerana indica, T. travancorica and Halictus sp. recorded highest foraging speed during 10:00 h to 11:00 h; Ceratina hieroglyphica and Lasioglossum sp. recorded highest foraging speed during 09:00-10:00 h; T. travancorica, C. hieroglyphica and Lasioglossum sp. recorded maximum foraging rate during 10:00 h to 11:00 h; A. cerana indica and Halictus sp. recorded highest foraging rate during 11:00-12:00 h and 09:00-10:00 h.