Kofyar cash-cropping: Choice and change in indigenous agricultural development

Amid discussions of an agricultural crisis and the failure of largescale, mechanized, capitalintensive development schemes in Nigeria, the Kofyar of Plateau State provide a case study of farmers spontaneously expanding food crop production for the market, using indigenous lowenergy technology. Temporary, followed by permanent, migration from the Jos Plateau homeland to frontier settlements on the fertile Benue plains has been accompanied by a change from initial shifting cultivation in forest clearings to permanent, intensively tilled and fertilized homestead fields. Labor is organized primarily in households that have grown in size and complexity. Cooperative and exchange work groups are also important for meeting seasonal bottlenecks and providing the careful, disciplined cultivation that intensive agriculture requires. Kofyar now devote up to 50% of their labor to cash crops, and they purchase considerable quantities of manufactured goods and medical services. Their uncoerced adaptation to an environment of new land resources and market incentives suggests both the advantages of indigenous development with a minimum of state control or interference and the limitations of a conventional dependency theory perspective.     

Sucrose response thresholds of honey bee (Apis mellifera) foragers are not modulated by brood ester pheromone

Division of labor is a hallmark of eusocial insects and their ecological success can be attributed to it. Honey bee division of labor proceeds along a stereotypical ontogenetic path based on age, modulated by various internal and external stimuli. Brood pheromone is a major social pheromone of the honey bee that has been shown to affect honey bee division of labor. It elicits several physiological and behavioral responses; notably, regulating the timing of the switch from performing in-hive tasks to the initiation of foraging. Additionally, brood pheromone affects future foraging choice. In honey bees, sucrose response threshold is a physiological correlate of age of first foraging and foraging choice. Brood pheromone has been shown to modulate sucrose response threshold in young bees, but its effects on sucrose response thresholds of bees in advanced behavioral states (foragers) are not known. In this study we examined the sucrose response thresholds of two different task groups, foragers (pollen and non-pollen) and non-foraging bees, in response to honey bee brood pheromone. Sucrose response thresholds were not significantly different between brood pheromone treatment and controls among both non-pollen and pollen foragers. However, the sucrose response threshold of non-foraging bees was significantly higher in the brood pheromone treatment group than in the control group. The switch to foraging task is considered a terminal one, with honey bee lifespan being determined at least partially by risks and stress accompanying foraging. Our results indicate that foragers are physiologically resistant to brood pheromone priming of sucrose response thresholds.     

Reciprocal indirect interactions between Tetranychus urticae and Aphis gossypii mediated by cucumber plant

Induced plant responses to herbivory can alter plant quality and influence subsequent interactions with organisms that use that plant as food source. In this study, we conducted several experiments in order to understand whether preference and performance of the cotton aphid, Aphis gossypii (Hem: Aphididae) and the spider mite, Tetranychus urticae (Acari: Tetranychidae) are affected by the previous herbivory of conspecific or heterospecific species on cucumber plants. Longevity, fecundity and pre-imaginal development time were measured as performance criteria. In addition, we explored whether these effects are local or systemic. In the case of performance experiments, the results varied from negative to neutral depending on the performance criteria, no positive effect was observed in studied interactions. Also, depending on performance criteria, the previous herbivory affected the plant systemically, or locally. Results of preference experiments indicated that mites and aphids prefer to settle and produce offspring on control leaf disc to prevent detrimental effects of the previous herbivory. Spider mites showed a stronger preference than aphids in the detection of induced leaf discs, which resulted in more mites being present and laying more egg on control leaf disc in both local and systemic treatments. Performing both preference and performance experiments, not only reveals the effect of herbivores on each other's mediated by the plant but also reveals more information about the sensitivity of herbivores to change in the quality of their host.     

Herbivore and phytohormone induced defensive response in kale against cabbage butterfly, Pieris brassicae Linn

The constitutive and induced resistance were studied in two varieties (Khanyari and Kawdari) of kale, Brassica oleracea var. acephala in response to cabbage butterfly, Pieris brassicae infestation and exogenous application of jasmonic acid (JA) and salicylic acid (SA). Phenols, condensed tannins, flavonoids and proteins were measured at six days after JA (1?mM) and SA (1?mM) application and/or insect infestation. Plant damage and larval weights were also recorded. Khanyari variety showed highest amounts of phenols (208.23?μg/g FW), condensed tannin (347.76?μg/g FW), flavonoids (175.61?μg/g FW) and proteins (0.71?mg/g FW) in plants pre-treated with JA and infested with insects. The PAL activity was high in response to JA application followed by insect infestation. Insects reared on Khanyari and Kawdari plants pre-treated with JA prior showed significantly reduced larval weights (97.88 and 102.46?mg, respectively). Damage was low in plants pre-treated with JA in Khanyari at 3, 6 and 9?days after treatment (10.52%, 8.52%, and 5.30%, respectively). Thus, JA can play an important role in plant defense in kale against P. brassicae.     

Ungulate browsing affects subsequent insect feeding on a shared food plant,bilberry (Vaccinium myrtillus)

Browsing by ungulates may induce plant responses and affect subsequent plant food quality for other animals. Populations of many deer species have increased to unprecedented levels in Europe and North America. In Norway, population densities of red deer (Cervus elaphus) have increased over the past decades, but little is known about how increased deer browsing pressure may change the palatability of key food plants for other taxa in the boreal ecosystem. We conducted a cafeteria experiment to assess if long-term deer-browsing intensity affected the palatability of bilberry (Vaccinium myrtillus) leaves for leaf-eating larvae (mainly Lepidoptera). We found that leaf-eating insect larvae preferred bilberry leaves from the lightly browsed bilberry plants; the larvae consumed twice as much leaf biomass from the lightly browsed plants than from the unbrowsed and moderately browsed ones, and four times more than from highly browsed plants. Larvae never selected leaves from highly browsed plants as their first choice. Our study suggests that browsing-induced changes in the quality of shared food plants may be important in mediating indirect interactions between browsers of widely separated taxa. Whereas low levels of long-term red deer browsing increases the palatability of bilberry leaves for leaf-eating larvae, high browsing pressure reduces food consumption. Whether changes in palatability lead to changes in population densities of leaf-eating larvae remains to be studied, but any such adverse effects could have cascading ecological consequences for insectivorous birds and mammals.     

Save your host,save yourself? Caste‐ratio adjustment in a parasite with division of labor and snail host survival following shell damage

Shell damage and parasitic infections are frequent in gastropods, influencing key snail host life‐history traits such as survival, growth, and reproduction. However, their interactions and potential effects on hosts and parasites have never been tested. Host–parasite interactions are particularly interesting in the context of the recently discovered division of labor in trematodes infecting marine snails. Some species have colonies consisting of two different castes present at varying ratios; reproductive members and nonreproductive soldiers specialized in defending the colony. We assessed snail host survival, growth, and shell regeneration in interaction with infections by two trematode species, Philophthalmus sp. and Maritrema novaezealandense, following damage to the shell in the New Zealand mud snail Zeacumantus subcarinatus. We concomitantly assessed caste‐ratio adjustment between nonreproductive soldiers and reproductive members in colonies of the trematode Philophthalmus sp. in response to interspecific competition and shell damage to its snail host. Shell damage, but not parasitic infection, significantly increased snail mortality, likely due to secondary infections by pathogens. However, trematode infection and shell damage did not negatively affect shell regeneration or growth in Z. subcarinatus; infected snails actually produced more new shell than their uninfected counterparts. Both interspecific competition and shell damage to the snail host induced caste‐ratio adjustment in Philophthalmus sp. colonies. The proportion of nonreproductive soldiers increased in response to interspecific competition and host shell damage, likely to defend the parasite colony and potentially the snail host against increasing threats. These results indicate that secondary infections by pathogens following shell damage to snails both significantly increased snail mortality and induced caste‐ratio adjustments in parasites. This is the first evidence that parasites with a division of labor may be able to produce nonreproductive soldiers according to environmental factors other than interspecific competition with other parasites.     

Plant water stress and previous herbivore damage affect insect performance

1. Short‐term changes in plant resistance traits can be affected by abiotic factors or damage by herbivores, although how the combined effects of abiotic factors and previous damage affect subsequent insect larval development is not well understood. 2. Complementary glasshouse and field experiments were conducted to evaluate whether plant water stress and previous herbivore damage influenced monarch (Danaus plexippus) larval development on common milkweed, Asclepias syriaca. 3. In the glasshouse, water stress altered a suite of A. syriaca functional traits but did not affect nutrient content, whereas herbivore damage increased leaf nitrogen (N) and reduced the carbon:nitrogen (C:N) ratio. A bioassay experiment showed that monarch larval survival was lower on well‐watered plants that were previously damaged by monarch larva than on damaged and drought‐stressed plants. Bioassay larvae consumed less leaf tissue of previously damaged plants, whereas monarch larval mass was affected additively by water stress and previous damage, after correcting for the amount of leaf tissue consumed. 4. In a 2‐year field experiment, monarch larval performance was higher on previously damaged A. syriaca plants that received experimentally reduced rainfall, relative to plants receiving ambient rainfall. 5. Collectively, these results from glasshouse and field experiments suggest that insect performance was highest on previously damaged plants under water stress and highlight the additive and interactive roles of abiotic and biotic factors on herbivore performance.     

Feeder-free Derivation of Melanocytes from Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs) represent a platform to study human development in vitro under both normal and disease conditions. Researchers can direct the differentiation of hPSCs into the cell type of interest by manipulating the culture conditions to recapitulate signals seen during development. One such cell type is the melanocyte, a pigment-producing cell of neural crest (NC) origin responsible for protecting the skin against UV irradiation. This protocol presents an extension of a currently available in vitro Neural Crest differentiation protocol from hPSCs to further differentiate NC into fully pigmented melanocytes. Melanocyte precursors can be enriched from the Neural Crest protocol via a timed exposure to activators of WNT, BMP, and EDN3 signaling under dual-SMAD-inhibition conditions. The resultant melanocyte precursors are then purified and matured into fully pigmented melanocytes by culture in a selective medium. The resultant melanocytes are fully pigmented and stain appropriately for proteins characteristic of mature melanocytes.