Logan Steele
The scorpion body is divided into two major parts: the prosoma (cephalothorax) and the opisthosoma (abdomen). The scorpion's tail, or metasoma, is divided into five segments, plus the telson. The telson is a stinging structure that consists of a bulbous base, called the vesicle or ampulla, and a curved, sharply pointed terminal spine, the aculeus. The vesicle contains a pair of venom glands and associated musculature. The telson flexor system is homologous to the fast flexor system of anterior ganglia. The telson reflex habituation in Limulus polyphemus (horseshoe crab) has been observed to exhibit muscle correlates of reflex telson movement. The telson is also associated with the uropod RS muscle in sand crabs.
| Characteristics | Values |
|---|---|
| Telson | A stinging structure found at the posterior end of the metasoma (tail-like postabdomen) of scorpions |
| Telson Flexor System | Homologous to the fast flexor system of anterior ganglia, with differences in connections to telson motor giants and non-giant fast flexor motor neurons |
| Telson Muscles | Innervated by 11 paired neurons in the terminal (sixth) ganglion and axons in the sixth nerve, including the posterior, ventral, and anterior telson flexors |
| Telson Reflex Habituation | Observed in Limulus polyphemus (horseshoe crab) with repetitive tactile stimulation of the gills |
| Telson Muscle Structure | Thick filament structure studied through immunohistochemical and ultrastructural methods, with insights from tarantula muscle filaments |
| Telson Muscle Energy Utilization | Phosphorylargine utilization (delta PArg) and chemical efficiency vary with contraction type and length |
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What You'll Learn
- The telson is a stinging structure at the end of the scorpion's tail-like postabdomen (opisthosoma)
- Telson flexor muscles do not contract during naturally elicited LG tail flips
- Telson RS muscle in sand crabs may have evolved from the wayward positioning of a rotator muscle fibre
- Telson reflex habituation in Limulus polyphemus (horseshoe crab) was recorded using microelectrodes
- Telson muscles have a chemical efficiency of 31% during slow isovelocity contractions
The telson is a stinging structure at the end of the scorpion's tail-like postabdomen (opisthosoma)
The scorpion body is divided into two major parts: the prosoma (cephalothorax) and the opisthosoma (abdomen). The opisthosoma is further divided into the mesosoma (preabdomen) and the slender, tail-like metasoma (postabdomen). The scorpion's postabdomen, or metasoma, ends in a stinging structure called the telson. The telson is composed of a bulbous base, known as the vesicle or ampulla, and a sharply pointed, curved terminal spine called the aculeus. Additionally, the telson may also feature a small, median subaculear tubercle or accessory spine just below the aculeus.
The vesicle houses a pair of venom glands and associated musculature. The venom glands can vary in structure, ranging from simple sac-like forms to more intricate, folded shapes with pouch-like extensions that significantly increase the surface area of the secretory epithelium. The venom is discharged through the contraction of muscles surrounding the glands, which compresses them against the vesicle wall.
The telson flexor system, which is responsible for the scorpion's stinging motion, shares similarities with the fast flexor system of anterior ganglia. However, there are important distinctions in the connections to the telson motor giants (MoGs). These differences are observed in the connections to the telson non-giant fast flexor (FF) motor neurons and the telson flexor inhibitor (FI). The telson FF motor neurons in ganglion 6 (G6) receive inputs similar to those in G4 and G5.
The scorpion's ability to sting is a result of the coordination between its telson structure and the associated musculature. The scorpion's stinger, located at the end of its tail-like postabdomen, is a specialized structure for delivering venom to defend against predators or capture prey. The scorpion's stinger is a crucial adaptation that enhances its survival capabilities in various ecological niches.
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Telson flexor muscles do not contract during naturally elicited LG tail flips
The telson is a stinging structure found in scorpions and crayfish. The scorpion's body is divided into two major parts: the prosoma (cephalothorax) and the opisthosoma (abdomen). The opisthosoma is further divided into the mesosoma (preabdomen) and the metasoma (postabdomen), which is also known as the "tail". The metasoma bears the telson at its posterior end.
The telson flexor system is a neuromuscular system found in crayfish. It is homologous to the fast flexor system of anterior ganglia. However, there are important differences in connections to the telson motor giants (MoGs). The telson FF motor neurons in ganglion 6 (G6) receive inputs similar to those in G4 and G5. The escape command neurons (lateral giants, LGs, and medial giants, MGs) provide weak disynaptic input via the telson segmental giant (SG6) and strong tri-synaptic input via SG2, SG3, and the corollary discharge interneurons 12 and 13.
The telson flexor muscles are predicted not to contract during naturally elicited LG tail flips. This is due to the presence of feedforward inhibition, which prevents disruption of the expected behavior pattern from LG commands. The sensory input that recruits the LG also recruits inhibition of the telson FF motor neurons, reducing the probability of their firing.
The telson flexor neuromuscular system in crayfish consists of three paired phasic telson muscles: the posterior and ventral telson flexors, and the anterior telson muscle. These muscles are innervated by 11 paired neurons located in the terminal (sixth) ganglion, which provides input via the sixth nerve.
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Telson RS muscle in sand crabs may have evolved from the wayward positioning of a rotator muscle fibre
The scorpion body is divided into two major parts: the prosoma (cephalothorax) and the opisthosoma (abdomen). The scorpion's tail, or "metasoma", is divided into five segments, ending in a stinging structure called the telson. The telson consists of a bulbous base, called the vesicle or ampulla, and a curved, sharply pointed spine, the aculeus. The vesicle contains a pair of venom glands and associated musculature.
The telson flexor system is homologous to the fast flexor system of anterior ganglia, but there are important differences in connections to the telson motor giants. The telson FF motor neurons in ganglion 6 receive inputs similar to those in G4 and G5. The escape command neurons in common provide weak disynaptic input via the telson segmental giant, and relatively strong trisynaptic input via SG2, SG3, and the corollary discharge interneurons 12 and 13.
The RS muscle in sand crabs is so small and inconspicuous that it was overlooked until an anomalous tiny branch from the nerve innervating the uropod remoter muscles in the sixth abdominal segment was traced. These folds turned out to be a few short muscle fibers converging to an attachment on the dorsal arthrodial membrane of the uropod joint, a position corresponding precisely to that of the massive RS muscle of hippid crabs. The RS muscle's dorsal position in the telson and insertion adjacent to the complex tendon of the uropod rotator musculature in abdominal segment 6 suggest that it may have evolved from the wayward positioning of a rotator muscle fiber.
The few, short muscle fibers of the albuneid RS muscle appear to have no mechanical action on the uropod and do not seem capable of stiffening the joint. Their appearance in sand crabs that tailflip was presumably the result of an ontogenetic error in the common ancestor of hippids and albuneids that, while serving no function, had no detrimental effect and became fixed in the lineage.
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Telson reflex habituation in Limulus polyphemus (horseshoe crab) was recorded using microelectrodes
The telson is a stinging structure found at the posterior end of the metasoma, or "tail", of scorpions and other arthropods. It consists of a bulbous base, known as the vesicle or ampulla, which contains a pair of venom glands and associated musculature. The telson also includes a sharply pointed terminal spine, called the aculeus, and may sometimes bear a small, median subaculear tubercle or accessory spine.
The telson flexor system is a neuromuscular system found in arthropods such as scorpions, sand crabs, and crayfish. This system is responsible for the rapid movement of the telson, which can be used for defence or prey capture. The telson flexor muscles are connected to the telson motor giants (MoGs) and receive input from escape command neurons, including lateral giants (LGs) and medial giants (MGs).
In a study on the energy utilization of the Limulus telson muscle, researchers found that thick filament shortening required little to no energy expenditure during rapid contractions. However, the chemical efficiency of the telson muscles during slow isovelocity contractions was measured at 31% for groups shortening equivalent distances from starting lengths of 1.6 and 1.3 Lo, and 15% for the group shortening from 1.1 Lo.
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Telson muscles have a chemical efficiency of 31% during slow isovelocity contractions
The scorpion body is divided into two major parts: the prosoma (cephalothorax) and the opisthosoma (abdomen). The scorpion's tail, or metasoma, is divided into five segments, plus the telson. The telson consists of a bulbous base, called the vesicle or ampulla, and a curved, sharply pointed terminal spine, the aculeus. The vesicle contains a pair of venom glands and associated musculature.
The telson flexor system is homologous to the fast flexor system of anterior ganglia. The escape command neurons in the telson flexor system provide weak disynaptic input via the telson segmental giant and relatively strong trisynaptic input via SG2, SG3, and the corollary discharge interneurons. The compound PSP produced in telson FFs by a single LG or MG impulse was suprathreshold in only five of 55 experiments in isolated abdominal nerve cords. However, the probability that a motor neuron would fire increased with additional giant axon impulses, showing that temporal summation of excitation outweighed the possible recruitment of inhibition.
The telson muscles' chemical efficiency during slow isovelocity contractions is 31% in groups shortening equivalent distances (0.5 Lo) from starting lengths of 1.6 and 1.3 Lo. This efficiency is measured by the utilization of phosphorylarginine (delta PArg) in the muscle during isometric and isovelocity contractions at various lengths. The thick filament shortening does not require a significant amount of energy expenditure, as indicated by the lack of significant delta PArg measurements during rapid shortening at long or short lengths.
The telson muscles' chemical efficiency during slow isovelocity contractions is essential for understanding the energy utilization and contractile properties of these muscles. The lack of energy expenditure during thick filament shortening suggests that the muscle's efficiency may be primarily influenced by other factors, such as the length-tension relationship and the activation of skinned fiber bundles. Further research in this area can provide valuable insights into the unique characteristics of telson muscles and their contractile behaviour.
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Frequently asked questions
A telson is a stinging structure found at the posterior end of the metasoma or "tail" of scorpions.
Yes, a telson is a type of muscle. Telson muscles are found in scorpions, crayfish, and crabs.
Telson muscles are involved in the escape responses of scorpions and crayfish. They also play a role in tailflip behavior in sand crabs.
Telson muscles are innervated by neurones that have somata in the terminal ganglion and axons in the sixth nerve. The contraction of these muscles is controlled by the telson flexor neuromuscular system, which involves the activation of various neurones and inhibition pathways.
Yes, there are three types of telson muscles: the posterior telson flexor, the ventral telson flexor, and the anterior telson muscle.
