Biology subjects

Dahake, A.

Publications and source records attributed to Dahake, A..

4 recordsLinked to original sources

bioRxiv2025

Squash flowers as microhabitats: the effects of floral temperature and humidity on pollen viability and visitor behavior

Flowers represent intricate microcosms shaped by their chemical and micrometeorological properties. Notable examples include thermogenic flowers that create a warm microclimate for visitors and residents. We document a distinct microclimate within the large flowers of both wild and domesticated squashes (Cucurbita spp.). Unlike thermogenic flowers, squash flower temperatures remain near ambient, but their humidity consistently exceeds ambient levels from bud to senescence, resulting from stomatal and petal transpiration rather than nectar evaporation. Experimentally reducing humidity in greenhouse-grown male squash flowers results in significant pollen tube rupture, directly impacting plant fitness. To explore the role of floral humidity within a broader ecological context, we performed similar humidity manipulations on squash farms to assess impacts on the behavior of their specialist squash bee pollinator (Xenoglossa pruinosa), generalist pollinators (bumblebees, honeybees), and specialist herbivores (cucurbit beetles). Experimentally reduced floral humidity lower visitation frequency by squash bees but have no effect on generalist pollinators. Manipulation of floral humidity did not influence the foraging duration of any pollinators but impacted the residence of male squash bees in wilted flowers compared with unmanipulated flowers. Finally, there was a positive correlation between the dryness of the ambient air and the abundance of squash bees and cucurbit beetles residing in the humid wilted floral chambers. In conclusion, our findings showcase squash flowers as a humid microhabitat that influences reproductive success directly by affecting pollen viability and indirectly by altering interactions with squash bees, their specialist pollinators.

ecology↗

bioRxiv2023

Dying of thirst: Osmoregulation by a hawkmoth pollinator in response to variability in ambient humidity and nectar availability

Climate-induced alterations in flowering phenology can lead to a temporal mismatch between pollinators and the availability of floral resources. Such asynchrony may be especially impactful in desert ecosystems, where flowering time and pollinator emergence are particularly sensitive to rainfall. To investigate the osmoregulation of a desert-living hawkmoth pollinator Manduca sexta, we sampled hemolymph osmolality of over 1000 lab-grown moths held at 20%, 50%, and 80% ambient humidity. Under starvation, the hemolymph osmolality of moths remained within a healthy range from days 1-3, regardless of ambient humidity. However, osmolality levels increase steeply from a baseline of 360-370 mmol/kg to 550 mmol/kg after 4-5 days in low and intermediate humidity and after 5 days in high humidity. Starved moths exposed to low humidity conditions died within 5 days, whereas those in high humidity conditions lived twice as long. Moths fed either synthetic Datura wrightii nectar, synthetic Agave palmeri nectar, or water, maintained osmolality within a healthy baseline range of 350-400 mmol/kg. The same was true for moths that fed on authentic floral nectars. However, moths consumed higher amounts of synthetic nectar, likely due to the non-sugar nectar constituents in the authentic nectar. Finally, simulating a 4-day mismatch between pollinator emergence and nectar availability, we found that a single nectar meal can osmotically rescue moths in dry ambient conditions. Our findings indicate that hemolymph osmolality provides a rapid and accurate biomarker for assessing both the health and relative hydration state of insect pollinators.

physiology↗

bioRxiv2022

Floral humidity as a signal--not a cue--in a nocturnal pollination system

Although visual and olfactory floral signals attract pollinators from a distance, at the flowers threshold, pollinators can use floral humidity as an index cue for nectar presence. We evaluate the role of floral humidity in the Datura wrightii-Manduca sexta nocturnal pollination system. In addition to our finding that M. sexta shows strong innate attraction toward humid flowers, we identify the hygrosensing sensillum on their antennae, demonstrate its extreme sensitivity to minute changes in RH, and observe the elimination of moths behavioral preference towards humid flowers following experimental occlusion of the sensilla. Despite Manducas attraction toward humid flowers, we find that floral humidity is not a reliable cue for nectar presence in this system. While Datura floral headspace sustains an enormous humidity gradient, it is not a consequence of nectar evaporation, but an outcome of gas exchange through floral stomata and is decoupled from nectar presence. Using interdisciplinary tools, we demonstrate the function of floral humidity as an attractive signal, not a cue, in this pollination system, thus showcasing an underappreciated modality by which flowers may manipulate their visitors.

ecology↗

bioRxiv2018

Independent control of slow and fast flight manoeuvres in insects: the roles of vision and antennal mechanoreception

Flying animals need constant sensory feedback about their body position and orientation for flight control. The visual system provides essential but slow feedback. In contrast, mechanosensory channels can provide feedback at much shorter timescales. How the contributions from these two senses are integrated remains an open question in most insect groups. In Diptera, fast mechanosensory feedback is provided by organs called halteres, and is crucial for the control of rapid flight manoeuvres, while vision controls manoeuvres in lower temporal frequency bands. Here we have investigated the visual-mechanosensory integration in an insect which lacks halteres: the hawkmoth Macroglossum stellatarum. They represent a large group of insects that use Johnstons organs in their antennae to provide mechanosensory feedback on perturbations in body position. High-speed videos of freely-flying hawkmoths hovering at stationary or oscillating artificial flowers showed that positional fidelity during flight was reduced in flagella ablated animals, but was recovered after flagella re-attachment. Our experiments show that antennal mechanosensory feedback specifically mediates fast flight manoeuvres, but not slow ones. Differences in the latency of visual feedback (in different light intensities) affected all antennal conditions equally, suggesting there was no compensatory interaction between antennal and visual feedback under the tested conditions. These results establish the importance of antennal mechanosensors in providing rapid mechanosensory feedback for finer control of flight manoeuvres, acting in parallel to visual feedback.

neuroscience↗