 The other two thirds of their length lies free along the operculum.The total length of the opercular spines is approximately 27 mm.The spine itself is “covered by an integumentary sheath”.⁠⁠ If this sheath ruptures because there is force applied to the spine, it allows the venom to leak from the venom gland cells and to run through a deep groove along the spine and into the wound caused by the sting.