ONTOGENETIC CHANGES IN THE CUTICULAR SCALES OF A JUMPING SPIDER V. R. Townsend, Jr., andB. E. Felgenhauer

Department of Biology, University of Southwestern Louisiana, Lafayette, Louisiana 70504-245 1

Introduction

adult Corythalia canosa (Araneae, Salticidae) are covered in dense patches of black, gold and white chitinous, cuticular scales. During ontogeny, the colors and densities of the cuticular scales of this spider have been observed to vary dramatically I . Early instar spiders have relatively few scales that are predominantly white in color. Later instar spiders have progressively more scales and eventually possess the gold and black scales that are common for adults. In general, very little is known about the morphology of the cuticular scales of salticid spiders 2,3 . Only the morphology of the scales of adult spiders in a few genera of Nearctic jumping spiders has been previously described 2,3 .

The dorsal and lateral surfaces of the prosoma (cephalothorax), opisthosoma (abdomen) and walking legs of

Materials and Methods

dehydrated in ethyl alcohol, and chemically dried with hexamethyldisilazane. Specimens were mounted on aluminum stubs and sputter-coated with gold for 2 min. Using a JEOL 6300F Field Emission SEM, we examined the spiders at accelerating voltages of 15-20 kV.

We collected adult and immature spiders in Lafayette, Louisiana. Spiders were fixed in Trump's fixative,

Results and Discussion The morphology of the cuticular scales of Corythalia canosa varies dramatically with ontogeny. Individuals

examined immediately after hatclung lacked scales entirely. Individuals allowed to molt once or twice after hatchmg possessed only a few, whlte, elongate scales (Fig. 1 A). Later instars possessed a greater number of white, black and gold scales. The scales of these spiders occurred in dense patches on the prosoma and opisthosoma but were only sparsely distributed on the walking legs. Scales were morphologically differentiated with respect to location on the body (i.e., prosomal scales exhibited a distinct morphology in comparison with opisthosomal scales). In these spiders, different scale types occurred in mixed patches (Figs. 1 B, C) on both the prosoma and opisthosoma. Most scales in these patches exlubited the typical adult morphology (Fig. 1 D), although a few scales had elongate shafts, a morphological characteristic shared by the scales of earlier instars.

these jumping spiders are covered in small, predominantly spatulate scales (Fig. 1 E). Adult spiders often have six different types of cuticular scales, three distinct types occurring on the dorsal surface of the prosoma (Fig. 1 F). We found no relationship between scale morphology and scale color in adults.

hypotheses concerning the functional significance of cuticular scales in spiders appear applicable to this phenomenon '. First, if scales function in intraspecific communication, then the presence of different scale types, colors and densities during ontogeny may allow individuals to accurately assess the age, size and sexual maturity of rival conspeclfics in agonistic encounters. Second, if scales function in a thermoregulatory capacity, changes in scale morphology may be correlated with changes in microhabitat use and or activity cycle. Finally, if scales function defensively (either as a physical barrier to predatory attacks or in crypsis), ontogenetic changes in scale colors, densities and morphology may coincide with changes in the risks of predation by different predators, such as wasps and other spiders. Future studies examining the functions of scales in jumping spiders are needed to evaluate these hypotheses.

Following the terminal molt and subsequent sexual maturity, the prosoma, wallung legs and opisthosoma of

The functional significance of such a dramatic change in scale morphology during ontogeny is unclear. Several

References 1. Crane, J. (1 948) Comparative biology of salticid spiders at Rancho Grande, Venezuela I. Systematics and life hstories in Corythalia. Zoologica, 33 : 139- 145. 2. Hill, D. E. (1979) The scales of salticid spiders. 2001. J. Linn. SOC., 65: 193-218. 3. Felgenhauer, B. E. (1 998) Araneae. In: Microscopic Anatomy of the Invertebrates, 8 (in press), Wiley-Liss Publishers, Inc.

Received and accepted 7 November 1997.

MICROSCOPY RESEARCH AND TECHNIQUE 40:79–80 (1998)

r 1998 WILEY-LISS, INC.

Fig. 1. SEM micrographs of the cuticular scales of early instar, lateinstar and adult Corythalia canosa. A. Elongate scales of an earlyinstar spider. 3800. B. Elongate and short scales from the prosoma ofan immature spider. 31,000. C. Patch of elongate and short scalesfrom the opisthosoma of an immature spider. 3850. D. Close-up of the

dorsal surface of the cuticular scales on the prosoma of an immaturespider. 31,800. E. Scales from the prosoma of an adult spider. 31,000.F. Distribution of scales on the dorsal surface of the prosoma of anadult spider. 343.

80 V.R. TOWNSEND, JR. AND B.E. FELGENHAUER