Eight legs Spiders belong to the class of arachnids. All arachnids, have eight legs.
- 0.1 Can a spider have 9 legs?
- 0.2 Why do spiders lose legs?
- 0.3 Do tarantulas have 9 legs?
- 1 Do spiders have lungs?
- 2 Do all spiders have 8?
Can a spider have 9 legs?
All legs come out of the first section of their body called the cephlothorax. If they are missing one or more of their eight legs you will be able to see where the leg once was. They will never have more than eight. These are the rules that people and spiders must adhere to.
Can spiders feel pain?
By Dr. Shelley Adamo, Dalhousie University Do insects feel pain? Many of us probably ask ourselves this question. We swat mosquitoes, step on ants, and spray poison on cockroaches, assuming, or perhaps hoping, that they can’t – but can they? As someone who studies the physiology behind insect behaviour, I’ve wondered about it myself. Are these crickets angry? In pain from being whipped by antennae? How would we know? To find out whether insects feel pain, we first need to agree on what pain is. Pain is a personal subjective experience that includes negative emotions. Pain is different from nociception, which is the ability to respond to damaging stimuli.
- All organisms have nociception.
- Even bacteria can move away from harmful environments such as high pH.
- But not all animals feel pain.
- The question, then, is do insects have subjective experiences such as emotions and the ability to feel pain? We’ve probably all observed insects struggling in a spider’s web or writhing after being sprayed with insecticide; they look like they might be in pain.
Insects can also learn to avoid electric shocks, suggesting that they don’t like being shocked. However, just as I was appreciating how much some insect behaviour looked like our pain behaviour, I realized that Artificial Intelligence (e.g. robots and virtual characters) can also display similar behaviours (e.g.
See ( https://www.youtube.com/watch?v=YxyGwH7Ku5Y ). Think about how virtual characters can realistically express pain in video games such as “The Last of Us” (e.g. https://www.youtube.com/watch?v=OQWD5W3fpPM ). Researchers have developed circuits allowing robots and other AI to simulate emotional states (e.g.
‘joy’, ‘anger’, ‘fear’). These circuits alter how the robot/virtual character responds to its environment (i.e. the same stimulus produces a different response depending on the AI’s ‘emotion’). However, this does not mean that robots or virtual characters are ‘feeling’ these emotions.
- AI shows us that behaviour may not be the best guide to an insect’s internal experience.
- Given that behaviour seemed an unreliable guide, I then looked for neurobiological evidence that insects feel pain.
- Unfortunately, the insect brain is very different from the human brain.
- However, once we understand how our brains perceive pain, we may be able to search for circuits that are functionally similar in insects.
Research in humans suggests that pain perception is created by complex neural networks that link up the necessary brain areas. These types of networks require massive bidirectional connections across multiple brain regions. Insect brains also have interconnections across different brain areas.
However, these interconnections are often quite modest. For example, the mushroom bodies in the insect brain are critical for learning and memory. Although the mushroom bodies contain thousands of neurons, in fruit flies, for example, they have only 21 output neurons. In humans, our memory area, the hippocampus, has hundreds of thousands of output neurons.
The lack of output neurons in insects limits the ability of the insect brain to sew together the traits that create pain in us (e.g. sensory information, memory, and emotion). Finally, I considered the question from an evolutionary perspective. How likely it is that evolution would select for insects to feel pain? In evolution, traits evolve if the benefits of a trait outweigh its costs.
Unfortunately, nervous systems are expensive for animals. Insects have a small, economical, nervous system. Additional neurons dedicated to an ‘emotional’ neural circuit would be relatively expensive in terms of energetics and resources. If it is possible to produce the same behaviour without the cost, then evolution will select for the cheaper option.
Robots show that there could be cheaper ways. The subjective experience of pain is unlikely to be an all-or-none phenomenon. Asking whether insects feel pain forces us to consider what we would accept as a subjective experience of pain. What if it was devoid of emotional content? What if cognition is not involved? If insects have any type of subjective experience of pain, it is likely to be something that will be very different from our pain experience.
- It is likely to lack key features such as ‘distress’, ‘sadness’, and other states that require the synthesis of emotion, memory and cognition.
- In other words, insects are unlikely to feel pain as we understand it.
- So – should we still swat mosquitoes? Probably, but a case can be made that all animals deserve our respect, regardless of their ability to feel pain.
Adamo, S. (2019). Is it pain if it does not hurt? On the unlikelihood of insect pain. The Canadian Entomologist, 1-11. doi:10.4039/tce.2019.49 (Paper made available to read for FREE until Sept.16, 2019 in cooperation with Cambridge University Press) Post Views: 3,750
Can spiders live without a leg?
Abstract – Leg loss is a common phenomenon in spiders, and according to the species 5% to 40% of the adults can present at least one missing leg. There is no possibility of regeneration after adult moult and the animal must manage with its missing appendages until its death.
With the loss of one or more legs, female orb-weaving spiders can be penalized twice: firstly, because the legs are necessary for web construction and secondly, the legs are essential for the control of the prey after its interception by the web. During development, spiders may be also penalized because regeneration has energetic costs that take away resources for survival, growth and reproduction.
All these consequences should influence negatively the development of the spider and thus its fitness. We investigated the impact of leg loss in the orb-weaving spider, Zygiella x-notata by studying its frequency in a natural population and web building and prey capture behaviours in laboratory.
- In field populations, 9.5% to 13%, of the adult females presented the loss of one or more legs; the majority of individuals had lost only one leg (in 48% of cases, a first one).
- Leg loss seems to affect all the adult spiders, as there is no difference of mass between intact spiders and those with missing leg.
Data obtained with laboratory-reared spiders, showed that the loss of legs due to the moult is rare (less than 1%). Considering changes in web design, spiders with missing legs decreased their silk investment, increased the distance between spiral turns but did not change the capture surface of the web.
Why do spiders lose legs?
Many a time, we’ve seen spiders that have lost legs. Some may have lost it in fights, while some may have dropped the legs when escaping from predators that have caught onto their legs. Losing a limb or two, may have just saved the spider’s life then. To cope with this, spiders are able to regrow or regenerate their lost legs after a number of moults.
Do tarantulas have 9 legs?
Identifying Features – A female tarantula has a more stocky body than a male and is covered in a light brown or tan hair (thus it is sometimes called the Arizona Blond Tarantula). The male is thinner and “lankier”, with black hair covering most of the body and reddish hairs on its abdomen.
Do spiders have lungs?
Abstract – Spiders (Araneae) are unique regarding their respiratory system: they are the only animal group that breathe simultaneously with lungs and tracheae. Looking at the physiology of respiration the existence of tracheae plays an important role in spiders with a well-developed tracheal system.
- Other factors as sex, life time, type of prey capture and the high ability to gain energy anaerobically influence the resting and the active metabolic rate intensely.
- Most spiders have metabolic rates that are much lower than expected from body mass; but especially those with two pairs of lungs.
- Males normally have higher resting rates than females; spiders that are less evolved and possess a cribellum have lower metabolic rates than higher evolved species.
Freely hunting spiders show a higher energy turnover than spiders hunting with a web. Spiders that live longer than 1 year will have lower metabolic rates than those species that die after 1 year in which development and reproduction must be completed.
Can spiders see color?
Spotlight on color – Humans and many other primates have exceptional color vision. Most people can see three colors — red, blue and green — and all the hues made from various combos of them. Many other mammals typically see just some shades of blue and green light.
Many spiders also have a crude form of color vision, but for them it’s usually based on green and ultraviolet hues. This extends their vision into the deep violet end of the spectrum — well beyond what people can see. It also covers the blue and purple hues in between. Some jumping spiders see even more.
While at the University of Pittsburgh in Pennsylvania, Morehouse led a team that learned certain species of these spiders have a filter squashed between two layers of green-sensitive light receptors, This allows the spiders to detect red light in a small area at the center of their principal eyes’ field of view.
- This adds red, orange and yellow hues to their world.
- That means their vision includes a broader rainbow of colors than we can see.
- Seeing red can be handy since it’s often used as a warning.
- For jumping spiders, the ability to see red may have evolved as a way to avoid toxic prey.
- But once this new world of color was available to the spiders, Morehouse says, they put it to good use — in courtship.
Using Jakob’s eye tracker, Morehouse is investigating what interests female jumping spiders about the colorful, frenetic dances that males use to woo them. He’s finding that by playing to her various eyes, suitors employ a mix of movement and color to capture and hold a female’s attention.
She can see red, orange and yellow hues only at the center of her principal eyes’ boomerang–shaped view. Unless he can grab the attention of her secondary eyes with movement, she won’t turn her principal eyes toward him. And if she doesn’t, she may never see his fabulously colored features. For the male, this could be a matter of life and death.
Why? An unimpressed female may decide to make a meal of him instead of a mate. The males of one species Morehouse studies have a dazzling red face and beautiful lime-green front legs. Yet the females seem most impressed by the orange knees on the males’ third set of legs.
When a male first spots a female, he raises his front legs like he’s directing a plane into its gate. Then he skitters side to side, hoping to catch the attention of her secondary eyes. When she turns his way, he comes closer and starts flicking the wrist joints at the end of his raised front limbs. You can almost hear him saying, “Hey lady, over here!” A male Habronattus pyrrithrix jumping spider waves his front legs at a potential mate as if to say, “Look at me!” Then he lifts the bright orange knees of two back legs.
The female (foreground) can’t look away. Within minutes, he’s won her over. Once he’s drawn her attention, out come the orange knees. These guys will “move them up behind their back into view in a kind of a peekaboo display,” Morehouse says. To find out exactly what it is about a male’s display that turns a female’s head, Morehouse got clever.
- He doctored videos of males dancing, then played the videos to a female perched in an eye tracker.
- He used it to see how each of a guy’s moves affected her attention.
- If the male has an orange knee hiked up, but he’s not moving, she’s less interested.
- If those knees are moving but the orange color is removed, she’ll look but quickly lose interest.
He’s got to have both the right look and the right moves. “He’s using motion to influence where she’s looking, and then he’s using color to hold her attention,” Morehouse explains. Behavioral ecologist Lisa Taylor of the University of Florida in Gainesville, likens the males’ tactics to those of human advertisers.
Do spiders have 8 legs or 8 arms?
|All spiders have 8 legs, 2 body parts (cephalothorax and abdomen), fang-like “chelicerae,” and antenna-like “pedipalps.” Click on the terms below to learn more about each body part.|
Do all spiders have 8?
How many legs do spiders have? – Most spiders have eight legs, but there are a few species with fewer or more. For example, the daddy longlegs has two very long front legs and six shorter back legs, while the Australian tarantula can have up to 12 legs.
Do spiders use all 8 legs to walk?
Spiders walk by alternating two pairs of legs. While two pairs of legs are in the air, other two stay on the ground and support the body.