Age variation in the body coloration of the orb-weaver spider Alpaida tuonabo and its implications on foraging

Dumas Gálvez,Yostin Añino,Jorge M De La O

doi:10.1038/s41598-018-21971-0

Abstract

Spiders show a repertoire of strategies to increase their foraging success. In particular, some orb-weaver spiders use attractive body colorations to lure prey. Interestingly, coloration varies with age in many species, which may result in ontogenetic variation of foraging success. By using field observations, laboratory experiments and spectrophotometric analysis, we investigated whether pale juveniles and bright adults of the orb-weaver Alpaida tuonabo use different foraging strategies due to ontogenetic variation in coloration. Field observations revealed that foraging success of juveniles and adults was influenced by web properties. However, foraging success increased with body size only in adults, supporting the idea that larger individuals produce a stronger visual signal for prey. The attractiveness of the adult coloration for prey was confirmed in the laboratory with frame-web-choice experiments, in which webs bearing a spider intercepted more bees than empty webs. Our spectrophotometric analysis suggests that the yellow coloration may produce the deceiving signal for prey. Moreover, we identified potential alternative foraging strategies: cryptic juveniles at higher heights and ‘attractive’ adults at lower heights. This study reveals how ontogenetic colour variation may favour the use of alternative foraging strategies in orb-weaver spiders and reduces intraspecific competition.

Highlights

Spiders exhibit a wide range of foraging behaviours that include active pursuit, sit-and-wait, aggressive mimicry or prey attraction in orb-weaver species through the use of web decorations or body colorations[1]
Since body coloration is likely to function for prey attraction in many orb-weaver spiders[9,10,11]; this difference in coloration may indicate that juveniles and adults occupy different niches, possibly reducing intraspecific competition[12]
The pale-red juveniles tended to show lower foraging success as compared to the yellow-striped adults (3.4 ± 3.3 vs 4.9 ± 3.9 damaged areas, respectively; GLM of pooled data with ontogenetic stage as only variable: Z = −2.8, P = 0.004). This result can be attributed in part to differences in body size since adult spiders were larger than juveniles (3.3 ± 1.5 vs 2.6 ± 0.7 mm respectively; Wilcoxon test = 641, P = 0.04)

Summary

Introduction

Spiders exhibit a wide range of foraging behaviours that include active pursuit, sit-and-wait, aggressive mimicry or prey attraction in orb-weaver species through the use of web decorations or body colorations[1]. A particular ontogenetic change typical to many orb-weaver spiders is the shift in body coloration from juvenile to adult[5,6,7]. Few studies have investigated the ontogenetic variation of foraging strategies in orb-weaver spiders[4,14] or other group of spiders[15]. By using field observations, laboratory experiments and spectrophotometric analysis, we studied the endemic Panamanian orb-weaver Alpaida tuonabo Taczanowski, 1878 to determine whether the noticeable yellow-striped adult females differ in their foraging success and strategies as compared to the cryptic pale-red juveniles. (2) In yellow-striped adults, together with properties of the web, foraging success is influenced by the size of the spider, based on the idea that the visual signal for prey increases with body size and the innate preference of pollinators for the yellow colour[18] The influence of their cryptic coloration, since some insect prey do not seem to locate red colours against a green vegetation background17. (2) In yellow-striped adults, together with properties of the web, foraging success is influenced by the size of the spider, based on the idea that the visual signal for prey increases with body size and the innate preference of pollinators for the yellow colour[18]

Methods

Results

Conclusion