Egg Case Protein 3: A Constituent of Black Widow Spider Tubuliform Silk

Spider silk has outstanding mechanical properties, rivaling some of the best materials on the planet. Biochemical analyses of tubuliform silk have led to the identification of TuSp1, egg case protein 1, and egg case protein 2. TuSp1 belongs to the spidroin superfamily, containing a non-repetitive N- and C-terminal domain and internal block repeats. ECP1 and ECP2, which lack internal block repeats and sequence similarities to the highly conserved N- and C-terminal domains of spidroins, have cysteine-rich N-terminal domains. In this study, we performed an in-depth proteomic analysis of tubuliform glands, spinning dope, and egg sacs, which led to the identification of a novel molecular constituent of black widow tubuliform silk, referred to as egg case protein 3 or ECP3. Analysis of the translated ECP3 cDNA predicts a low molecular weight protein of 11.8 kDa. Real-time reverse transcription–quantitative PCR analysis performed with different silk-producing glands revealed ECP3 mRNA is predominantly expressed within tubuliform glands of spiders. Taken together, these findings reveal a novel protein that is secreted into black widow spider tubuliform silk.

Mesoscale structures in amorphous silks from a spider’s orb-web

Of the 7–8 silk fibers making up an orb-web only the hierarchical structural organization of semicrystalline radial fibers -composed of major ampullate silk- has been studied in detail, given its fascinating mechanical features. While major ampullate silk’s nanofibrillar morphology is well established, knowhow on mesoscale (> 50–100 nm) assembly and its contribution to mechanical performance is limited. Much less is known on the hierarchical structural organization of other, generally less crystalline fibers contributing to an orb-webs’ function. Here we show by scanning X-ray micro&nanodiffraction that two fully amorphous, fine silk fibers from the center of an orb-web have different mesoscale features. One of the fibers has a fibrillar composite structure resembling stiff egg case silk. The other fiber has a skin–core structure based on a nanofibrillar ribbon wound around a disordered core. A fraction of nanofibrils appears to have assembled into mesoscale fibrils. This fiber becomes readily attached to the coat of major ampullate silk fibers. We observe that a detached fiber has ripped out the glycoprotein skin-layer containing polyglycine II nanocrystallites. The anchoring of the fiber in the coat suggests that it could serve for strengthening the tension and cohesion of major ampullate silk fibers.

Factors Affecting Egg Deposition of the European Mantis

In this paper, we studied the egg-case (oothecae) deposition of the European mantis, Mantis religiosa (Linnaeus 1758), a predatory insect. We hypothesized that the height of ootheca deposition on a plant reflects the insolation requirements of the species, and would increase when plant cover is denser. We found that the taller the plants nearby, the greater the height of egg deposition. Oothecae were also oviposited higher in denser vegetation. The observed behavior may ensure the proper insolation of developing offspring. To our knowledge, this is the first description of an egg laying strategy of this species under natural conditions. This finding allows for a better understanding of habitat selection and the overall ecology of the European mantis. It may be also useful in identifying the mechanisms of the range extension of this species and is a potential tool to effectively conserve xerothermic ootheca-laying animals. Further studies are required to assess the flexibility of this behavior under different environmental conditions.

Morphology of immature stages of Helophorus (Gephelophorus) auriculatus (Coleoptera, Helophoridae)

The morphology of immature stages of Helophorus (Gephelophorus) auriculatus Sharp, 1884 is described. This is the first description of the larva and pupa of the subgenus Gephelophorus Sharp, 1915. We describe the morphology of the egg-case, all larval stages (first to third instar, including chaetotaxy of the head) and pupa. Morphological transformations between larval instars were examined. Head chaetotaxy was nearly identical between instars. Ventral teeth on the nasale, considered as a useful taxonomic character, were absent in the first instar but well developed in later instars. Chaetotaxy differed among the subgenera Gephelophorus, Helophorus and Lihelophorus in the length and shape of setae on head capsule and maxilla. Pupal morphology was similar to that of previously described pupae: H. (Helophorus) aquaticus (Linnaeus, 1758) and H. (Rhopalohelophorus) orientalis Motschulsky, 1860. A key to families of the Hydrophiloidea of Japan based on larval characters is provided.