Current Research
Jumping spiders experience REM sleep-like state!
While filming adult jumping spiders throughout the night in the hanging position (see research below), we discovered that they experience phases of twitching and muscle atonia. Muscle atonia is characterized by curling of the legs towards the sternum likely as a result of pressure loss due to muscle atonia in the prosoma. During these phases, which happened in regular intervals and with robust durations, we further noticed twtiches of limbs, spinnerets and abdomen that seemed rather uncontrolled, resembling REM states in other animals. We then filmed newly emerged spiderlings, which are temporarily translucent and thus allowed us to directly observe their eyes, that is their retinal tubes. Incredibly, all phases of twitching and/or leg curling were accompanied by retinal movements. This provides the first evidence of an REM sleep-like state in a terrestrial arthropod and we are beyond excited. There is going to be numerous research directions from here, including taking this research into the field - stay tuned for more soon and check out the videos (News & Outreach or directly on twitter)! Get in touch if you want to chat about snoozing (dreaming!?) spiders!
If you want to know where this discovery fits into the bigger picture of REM sleep in the animal kingdom, I highly recommend giving this beautiful Commentary in PNAS by Barrett A. Klein a read.
Jumping spiders experience REM sleep-like state!
While filming adult jumping spiders throughout the night in the hanging position (see research below), we discovered that they experience phases of twitching and muscle atonia. Muscle atonia is characterized by curling of the legs towards the sternum likely as a result of pressure loss due to muscle atonia in the prosoma. During these phases, which happened in regular intervals and with robust durations, we further noticed twtiches of limbs, spinnerets and abdomen that seemed rather uncontrolled, resembling REM states in other animals. We then filmed newly emerged spiderlings, which are temporarily translucent and thus allowed us to directly observe their eyes, that is their retinal tubes. Incredibly, all phases of twitching and/or leg curling were accompanied by retinal movements. This provides the first evidence of an REM sleep-like state in a terrestrial arthropod and we are beyond excited. There is going to be numerous research directions from here, including taking this research into the field - stay tuned for more soon and check out the videos (News & Outreach or directly on twitter)! Get in touch if you want to chat about snoozing (dreaming!?) spiders!
If you want to know where this discovery fits into the bigger picture of REM sleep in the animal kingdom, I highly recommend giving this beautiful Commentary in PNAS by Barrett A. Klein a read.
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Jumping spiders! Behavior, signals, cognition, anti-predator adaptations
When we think about anti-predator adaptations, we often first think about morphological characteristics such as camouflaging colors or warning signals as well as behavioral strategies. In my current research, I investigate the role of cognition in anti-predator strategies. Using jumping spiders as a model system, I am looking into whether and how jumping spiders recognize predators to inform an appropriate behavioral response. To do this, we have developed a novel experimental paradigm which we will soon make openly accessible in both a fancy 3D-printable as well as a low cost paper version! Stay tuned! |
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Jumping spider night life
Being highly visual and diurnal animals, jumping spiders are not really active at night. In fact, we found that some jumping spiders seem to sleep in the most peculiar way. Evarcha arcuata, while perfectly capable of building classic silk retreats, like to spend their night hanging upside down suspended on a silk thread (Fun fact: we found way more spiders by searching for them hanging in the grass at night than by trying to find them during the day!). This way of resting may be more common than we think, as by now we have received several photos and observations from across the globe. We think that there may be a sensory advantage to spending the night on a silk line. When vision is limited, this way of resting a) keeps the animals out of reach of potential predators, and b) if a predator approaches from overhead, the spider is able to sense the vibration and drop to the ground. I'm broadly interested in how animals, otherwise relying heavily on vision, have evolved strategies to safely spend their nights- a potentially risky and vulnerable time. Sensory switching as suggested by hanging jumping spiders may be one way of dealing with this. But there are likely many more interesting adaptations out there... |
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Past Research
Predator identification from DNA traces left on artificial prey (clay models) Predator-prey interactions are a vast field in ecological research and many mechanisms thereof are crucial to understand natural selection, trait functions, cognition of traits and hence their evolution. However, for many taxa predator-prey interactions are difficult to study because field observations of predation events are rare. Predation is based on perception of stimuli, in many cases visual cues. To understand the effects of different visual cues on predation, such as coloration or patterns of prey animals, many studies use artificial prey to collect information. Although widely deployed, this method largely lacks standardization of attack identification. In a new approach, we tested whether DNA of predators can be isolated from bite and peck marks found on clay models to ultimately allow precise and robust identification of the attacker. In a pilot study, we placed more than 800 models of European fire salamanders (Salamandra salamandra) in the field to collect information on predation. Attack marks on models were first analyzed visually. Subsequently, we successfully isolated and sequenced DNA of more than 6 different species of attackers from the marks left on clay models. Our results not only underline the problem of misidentification of attacks by vision alone, but also offer an intriguing method to gain robust data on predators of artificial prey. Furthermore, the method opens up new possibilities beyond the standard use of clay model studies to date, including a potential use in invasive species monitoring and species inventories. https://doi.org/10.1111/2041-210X.13459 For a commentary on the use of clay model studies with implications for improvements and future directions see: https://doi.org/10.1186/s40850-018-0033-6 |
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Function of red sole coloration in diurnal, toxic harlequin toads (genus Atelopus)
Many animals have evolved remarkable strategies to avoid predation. In diurnal, toxic harlequin toads (Atelopus) from the Amazon basin, we find a unique colour signal. Some Atelopus populations have striking red soles of the hands and feet, visible only when walking. When stationary, the toads are hard to detect despite their yellow-black dorsal coloration. Consequently, they switch between high and low conspicuousness. Interestingly, some populations lack the extra colour display of the soles. We found comprehensive support that the red coloration can act as an aposematic signal directed towards potential predators: red soles are significantly more conspicuous than soles lacking red coloration to avian predators and the presence of the red signal significantly increases detection. Further, toads with red soles show bolder behaviour by using higher sites in the vegetation than those lacking this signal. Field experiments hint at a lower attack risk for clay models with red soles than for those lacking the signal, in a population where the red soles naturally occur. We suggest that the absence of the signal may be explained by a higher overall attack risk or potential differences of predator community structure between populations. https://doi.org/10.1038/s41598-018-37705-1 |
