Content
- Spider classification
- How many eyes does a spider have?
- spiders' vision
- The Jumping Spider Vision
- spider anatomy
- How many legs does a spider have?
- How long does a spider live?
Among the more than 40 thousand species of spider around the world, it is not always easy to know if we are facing a poisonous one or not, but we always know that it is a spider. Relatively small in size, big in fame, these predators command respect just by hearing. It's easy to imagine one, isn't it? Those articulated little legs, unmistakable agility and imaginary fantasies worthy of Hollywood. But when you think of a spider, how do you imagine its eyes? How many eyes does a spider have? And legs?
In this post by PeritoAnimal we answer these questions and explain the basic anatomy of a spider, so that you know how to recognize one well, even in your imagination.
Spider classification
Different species of spiders can be found around the world, always in terrestrial habitats. . There are currently about 40,000 species of spiders cataloged but it is believed that less than a fifth of the existing spider species are described. In other words, many of them are not yet known.
Spiders are arthropod insects of the class Arachinida, order Araneae, which includes species of spiders whose families can be classified into suborders: mesothelae and Opisthothelae.
Although the classification of spiders can vary, it is common to group them according to patterns in their anatomy. the number of eyes of a spider is a relevant factor in this systematic classification. The two suborders currently cataloged are:
- Opisthothelae: it is the group of crabs and other spiders that we are used to hearing about. In this group, the chelicerae are parallel and point downward.
- Mesothelae: this suborder includes spiders that are rarer, extinct families, and older species. In relation to the previous group, they can be differentiated by the chelicerae that move only longitudinally.
How many eyes does a spider have?
THE most have 8 eyes, but among the more than 40 thousand species of spiders there are exceptions. In the case of the family Dysderidae, they can only have 6, spiders of the family tetrablemma they may only have 4, while the family Caponiidae, can only have 2 eyes. There are also spiders that don't have eyes, those who live in caves.
The spider's eyes are on the head, as are the chelicerae and pedipalps, often positioned in two or three curved rows or on an elevation, which is called a eye bund. In larger spiders it is possible to see how many eyes a spider has even with the naked eye, as shown in the photo.
spiders' vision
Despite so many eyes, the number of them is not what really leads them to their prey. most of the spiders don't have a developed vision, since it is practically a secondary sense for these arthropods. Possibly they don't see more than shapes or changes of light.
The spiders' secondary sense of sight also explains why many of them hunt in the evening or at night. What really allows them to move around precisely is their supersensitivity due to the hairs spread all over their bodies, detecting vibrations.
The Jumping Spider Vision
There are exceptions and the jumping spiders, or flycatchers (Salticide), are one of them. The species that belong to this family are seen most during the day and have a vision that allows them to recognize predators and enemies, being able to detect movement, direction and distance, assigning different functions to each pair of eyes.
spider anatomy
The legs, segmented body and articulated limbs are the characteristics of a spider most visible to the naked eye. Spiders don't have antennas, but they have well-developed central nervous system, as well as the reflective and legs that allow them to explore and recognize the environment, even in the case of those spiders that don't have eyes.
THE basic anatomy of a spider consists of:
- 8 legs structured in: thigh, trochanter, femur, patella, tibia, metatarsus, tarsus and (possible) nails;
- 2 tagmas: cephalothorax and abdomen, joined by the pedicel;
- Thoracic fovea;
- Reflective hairs;
- Carapace;
- Chelicerae: in the case of spiders, they are claws that inject poison (venom);
- 8 to 2 eyes;
- Pedipalps: act as an extension of the mouth and help in capturing prey.
How many legs does a spider have?
Most spiders have 8 legs (four pairs), segmented in 7 parts: thigh, trochanter, femur, patella, tibia, metatarsus, tarsus and (possible) nails, with the middle nail touching the web. So many legs for a not-so-big body have a function beyond agile displacement.
The first two pairs of the front legs are the ones most used to explore the environment, using the layer of hair that covers them and their sensory capacity. On the other hand, tufts of hair under the nails (scopules) help in the adhesion and stability when spiders move over smoother surfaces. Unlike other arthropods, however, instead of muscles, spiders' legs extend due to a hydraulic pressure which is typical characteristic of these species.
As for sizes, the largest and smallest known species are:
- Biggest spider: Theraposa blondi, it can measure up to 20 cm in wingspan;
- Smallest spider:Patu digua, size of the head of a pin.
How long does a spider live?
Out of curiosity, the spider life expectancy can vary greatly depending on the species and conditions of its habitat. While some species have a life expectancy of less than 1 year, as in the case of the wolf spider, others can live for 20 years, as in the case of the trapdoor spider. The spider known as 'number 16' became famous after breaking the record for the oldest spider in the world, she is a trapdoor spider (Gaius villosus) and lived for 43 years.[1]
If you want to read more articles similar to How many eyes does a spider have?, we recommend that you enter our Curiosities section of the animal world.