An examination of the potential role of spider digestive proteases as a causative factor in spider bite necrosis.

Tissue necrosis following spider bites is a widespread problem. In the continental United States, the brown recluse (Loxosceles reclusa), hobo spider (Tegenaria agrestis), garden spider (Argiope aurantia) and Chiracanthium species, among others, reportedly cause such lesions. The exact mechanism producing such lesions is controversial. There is evidence for both venom sphingomyelinase and spider digestive collagenases. We have examined the role of spider digestive proteases in spider bite necrosis. The digestive fluid of A. aurantia was assayed for its ability to cleave a variety of connective tissue proteins, including collagen. Having confirmed that the fluid has collagenases, the digestive fluid was injected into the skin of rabbits to observe whether it would cause necrotic lesions. It did not. The data do not support the suggestions that spider digestive collagenases have a primary role in spider bite necrosis.

Water-soluble luminal contents of the gut of the earthworm Lumbricus terrestris L. and their physiological significance.

In the post-gizzard gut of the earthworm Lumbricus terrestris, distinguishing the functions of the luminal epithelium from those of the chloragogenous tissue has been hindered by the close apposition of these two tissues. Moreover, both tissues may have different functions from the anterior to the posterior of the animal. We analyzed the gut luminal contents of L. terrestris so as to gain a better understanding of the function of the luminal epithelium. The intestine was divided into four regions from anterior to posterior, and the water-soluble portion of the luminal contents of these four regions was analyzed for protease and amylase activity, calcium and ammonium ions, and protein. The same four regions of the gut wall were analyzed for glutamate dehydrogenase (GDH) and serine dehydratase (SDH) to determine their location with reference to the site of ammonia production. We observed high levels of proteases, amylase, protein and calcium ions in the gut luminal contents of the first two regions, and a significant decline of all four variables in region III. Conversely, ammonia was low in the gut contents of regions I and II but rose sharply in region III, which was also the region to which the tissue enzymes GDH and SDH were localized. The ammonia content of earthworm casts was observed to be much higher than that of the surrounding soil. These data are presented as partial evidence for the proposal that the excretory ammonia produced by feeding earthworms is a product of the luminal epithelium of region III of the gut. It is also proposed that ammonia and calcium may function as ion-exchangers in the absorptive function of the earthworm gut.

Moult-related changes in ampullate silk gland morphology and usage in the araneid spider Araneus cavaticus.

Major ampullate (MaA) and minor ampullate (MiA) silk glands of juvenile Araneus cavaticus (third to penultimate instars) were examined by dissection at various times relative to ecdysis. Several days before ecdysis the larger pairs of MaA and MiA glands become non-functional and remain so until ecdysis. Nevertheless, proecdysial spiders are able to draw ampullate fibres due to the presence of smaller pairs of MaA and MiA glands which are functional at this time. Indeed, it appears that these smaller ampullate glands are intended for use only during proecdysis. Thus, larger MaA and MiA glands and smaller MaA and MiA glands are typically not used concurrently (a brief transitional period is an exception). The smaller ampullate glands functioning in one juvenile stadium regress in the following stadium and become (what have previously been referred to as) accessory MaA and MiA glands. These nonfunctional accessory ampullate glands do not re-develop into functional smaller ampullate glands until the following stadium. Thus, a given pair of smaller MaA or MiA glands is only functional in every other juvenile stadium. However, because there are two sets of smaller/accessory MaA and MiA glands which function alternately, the spider is able to produce ampullate fibres during the proecdysial portion of each stadium. A new terminology for the larger, smaller and accessory ampullate glands is proposed which emphasizes the kinship between the two sets of smaller/accessory ampullate glands.

Identification of proctolin in the central nervous system of the horseshoe crab, Limulus polyphemus.

A proctolin-like peptide was isolated from the prosomal CNS of the chelicerate arthropod, Limulus, and purified using size exclusion, ion exchange and high performance liquid chromatography. Coincident bioassay (cockroach hindgut) and radioimmunoassay were employed to identify fractions which contained proctolin-like material. Proctolin-like activity coeluted with synthetic proctolin with all three chromatographic techniques employed. When applied to either the Limulus heart or hindgut preparations, purified Limulus proctolin produced excitatory responses which were indistinguishable from those produced by the synthetic peptide. Purified samples of the Limulus proctolin-like peptide were subjected to Edman degradation and tandem mass spectrometry and the amino acid sequence of the Limulus peptide was determined to be identical to that of cockroach proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH). The presence of proctolin in the Limulus CNS and its biological action on the isolated heart and hindgut suggest a physiological role for this peptide in the regulation of cardiac output and hindgut motility.