The Genus Latrodectus Includes Several Species, Including Spiders Commonly Called

Multiple Choice

The genus Latrodectus includes several species, including spiders commonly called widow spiders. The black widow is perhaps the most notorious member of this genus, and some species of black widows exhibit the familiar red hourglass on their ventral side. Black widows have large venom glands, and their bite can be harmful to humans. However, these bites very seldom lead to death in humans if proper medical treatment is provided. In comparison with females, adult male black widows are often gray or brown in color, rather than black, and they are only about half the size of females. As a result, they have smaller venom glands and tend to be less of a health concern. Black widows produce a neurotoxin called latrotoxin, and as the venom spreads through the body, it causes the release of neurotransmitters, including acetylcholine. Black widows spend their entire lives in their cobwebs, sitting and awaiting predators. When a prey item stumbles into their web, they rush out quickly to subdue it but tend to fatigue quickly and cannot maintain high levels of activity for long periods. As a result, ____________________.

A) they have mostly fast-twitch muscles
B) their muscles have high levels of myoglobin
C) they need a constant supply of oxygen for fast contractions
D) actin and myosin function without calcium