Spinneret Microstructure of the Silk Spinning Apparatus in the Crab Spider, Misumenops tricuspidatus (Araneae: Thomisidae)

Abstract

The silk spinning apparatus in the crab spider, Misumenops tricuspidatus was studied with the field emission scanning electron microscope (FESEM) and the main microstructural characteristics of the silk glands are presented. In spite of the fact that the crab spiders do not spin webs to trap a prey, they also have silk apparatus even though the functions are not fully defined. The crab spider, Misumenops tricuspidatus possesses only three types of silk glands which connected through the typical spinning tubes on the spinnerets. The spinning apparatus of Misumenops closely corresponds to that of wandering spiders such as jumping spiders or wolf spiders except some local variations. Anterior spinnerets comprise 2 pairs of the ampullates and 48 (±5) pairs of pyriform glands. Another 2 pairs of ampullate glands and nearly 20 (±3) pairs of aciniform glands were connected on the middle spinnerets. Additional 50 (±5) pairs of the aciniform glands were connected on the posterior spinnerets. The aggregate glands and the flagelliform glands which have the function of sticky capture thread production in orb‐web spiders as well as the tubuliform glands for cocoon production in females were not developed at both sexes of this spider, characteristically.

Microstructure of the silk apparatus of the comb‐footed spider, Achaearanea tepidariorum (Araneae: Theridiidae)

“…Based on the morphological characteristics of the silk glands as well as the spinnerets (Coddington 1986), the spinning apparatus of this spider corresponds to the patterns found in Araneidae spiders (Tillinghast & Townley 1986; Moon 1998; Moon & Kim 2005) and other web‐building spiders (Kovoor 1987; Peters & Kovoor 1991; Park & Moon 2002; Moon & An 2005). The two major ampullate glands and the pyriform glands were associated with the anterior spinnerets; the minor ampullate glands and the tubuliform and aciniform glands were associated with the median spinnerets, and the tubuliform, flagelliform, aggregate and aciniform glands were associated with the posterior spinnerets.…”

“…It has been reported that most Araneidae spiders (Tillinghast & Townley 1987; Moon 1998; Park & Moon 2002; Moon & An 2005) as well as Theridiidae spiders (Moon et al. 1998; Casem et al.…”

“…The males of some web‐building spiders lack the organs to produce capture thread. Furthermore, not only wandering spiders such as the wolf spider, Pardosa astrigera (Moon 1998), but also the funnel‐web spider, Agelena limbata (Park & Moon 2002), and the crab spider, Misumenops tricuspidatus (Moon & An 2005), lack these organs in both male and female spiders. In A. tepidariorum males were totally lacking the capture thread‐producing organs (they lacked not only the spigots on the spinnerets, but also the silk glands within the abdomen).…”

“…Variations in the composition of the spinning apparatus of araneid spiders have been studied by many researchers (Candelas & Cintron 1981; Tillinghast & Townley 1987; Peters & Kovoor 1991; Moon et al. 1998; Moon & An 2005). Although the spinning apparatus often undergoes adaptive variations, some basic familial characteristics usually remain unchanged (Kovoor 1987).…”

Microstructure of the silk spigots of the green crab spider Oxytate striatipes (Araneae: Thomisidae)

“…Most eccribellate orb‐web spiders produce a gluey material from a flagelliform and two aggregate glands (Kovoor & Zylberberg 1979; Kovoor 1987; Moon & Kim 2005). However, both sexes of O. striatipes lack these so‐called “triad” spigots (Peters 1987; Peters & Kovoor 1991; Moon & Kim 2005) as do other wandering spiders such as the wolf spider Pardosa astrigera (Moon 1998), the funnel‐web spider Agelena limbata (Park & Moon 2002) and the crab spider Misumenops tricuspidatus (Moon & An 2005).…”