No abstract

Despite the remarkable evolutionary success of insects at colonizing every conceivable terrestrial and aquatic habitat, only five Halobates (Heteroptera: Gerridae) species (~0.0001% of all known insect species) have succeeded at colonizing the open ocean-the largest biome on earth. this remarkable evolutionary achievement likely required unique adaptations for them to survive and thrive in the challenging oceanic environment. For the first time, we explore the morphology and behavior of an open-ocean Halobates germanus and a related coastal species H. hayanus to understand mechanisms of these adaptations. We provide direct experimental evidence based on high-speed videos which reveal that Halobates exploit their specialized and self-groomed body hair to achieve extreme water repellence, which facilitates rapid skating and plastron respiration under water. Moreover, the grooming behavior and presence of cuticular wax aids in the maintenance of superhydrophobicity. further, reductions of their body mass and size enable them to achieve impressive accelerations (~400 ms −2) and reaction times (~12 ms) to escape approaching predators or environmental threats and are crucial to their survival under harsh marine conditions. These findings might also inspire rational strategies for developing liquid-repellent surfaces for drag reduction, water desalination, and preventing bio-fouling. The proliferation of invertebrate taxa in the ocean during the Cambrian explosion eventually led to their colonization on land, where insects first appeared ~479 million years (Myr) ago 1 to eventually dominate various terrestrial ecosystems 2,3. With an estimated ~5.5 million extant species 4 , insects comprise 80% of all known metazoans, making them the dominant animals on Earth 5. Despite their successful colonization of both terrestrial and aquatic habitats, only a small number of insects (~0.5% of total species) have been found in marine environments, mostly in nearshore habitats, with only a handful of Halobates (~0.0001% of insect species) ultimately colonizing the open ocean, the largest biome on Earth 6-8. Halobates is a member of the family Gerridae, which evolved nearly 55 Myr ago 6,9. Some 48 species of Halobates are known to occur in tropical and subtropical seas and oceans that cover more than 70% of the Earth's surface. Most of these species are found in mangrove and near-shore habitats and two even live in freshwater, whereas five live on the surface of the open ocean. The fact that only a mere 0.0001% of insect species were able to colonize the largest habitat on Earth indicates that there must have been formidable environmental challenges for oceanic Halobates to overcome in order to live there. Halobates most likely evolved from an estuarine or mangrove ancestor that was washed out to the sea and became adapted to survive in the open ocean 8,10. Freshwater relatives of sea-skaters are often found on placid water bodies such as small ponds, lakes or slow-flowing streams, whereas many tropical species can be found

Drain flies, Pshycoda spp. (Order Diptera, Family Psychodidae), commonly reside in our homes, annoying us in our bathrooms, kitchens, and laundry rooms. They like to stay near drains where they lay their eggs and feed on microorganisms and liquid carbohydrates found in the slime that builds up over time. Though they generally behave very sedately, they react quite quickly when threatened with water. A squirt from the sink induces them to fly away, seemingly unaffected, and flushing the toilet with flies inside does not necessarily whisk them down. We find that drain flies’ remarkable ability to evade such potentially lethal threats does not stem primarily from an evolved behavioral response, but rather from a unique hair covering with a hierarchical roughness. This covering, that has never been previously explored, imparts superhydrophobicity against large droplets and pools and antiwetting properties against micron-sized droplets and condensation. We examine how this hair covering equips them to take advantage of the relevant fluid dynamics and flee water threats in domestic and natural environments including: millimetric-sized droplets, mist, waves, and pools of water. Our findings elucidate drain flies’ astounding ability to cope with a wide range of water threats and almost never get washed down the drain.

No abstract

We investigated the occurrence of the sea skater Halobates spp. from samples collected at a fixed time series station and from six cruises along the north-south extend of the Red Sea during 2016-2018. Halobates germanus White, 1883 was the only species found during our study, its distribution ranging between 17 • 9 N and 27 • 27 N and between 35 • 67 E and 41 • 49 E. Total H. germanus abundance ranged between zero to 158,610 individuals km −2 with a considerable temporal (at the fixed station) and spatial (cruises) variation. In general, nymphs of different instar stages dominated the population, followed by females and males. The sex ratio was female-biased, with a higher number of females than males. Presence and prevalence of eggs, exuviae (molts), and early nymphal stages indicate a year round breeding cycle by H. germanus. The apparent optimum temperature for H. germanus occurrence in the central Red Sea was at 28.2 • C, corresponding to peak abundances in spring and fall. Absence of any significant correlation of the abundances with environmental parameters indicate relative resilience of H. germanus to changes in environmental conditions.