Neotenic Phenotype and Sex Ratios Provide Insight into Developmental Pathways in Reticulitermes flavipes (Isoptera: Rhinotermitidae).

Jian Hu,Brian T Forschler

doi:10.3390/insects3020538

Abstract

Several thousand Reticulitermes flavipes (Kollar) including worker, nymph, soldier, neotenic and alate castes were collected from three pine logs brought into the laboratory on dates five years apart. The neotenics, all nymphoid, were divided into three groups based on the extent of cuticle pigmentation and termed regular neotenics (RN), black-headed neotenics (BHN) or black neotenics (BN). All castes, from Log A, in 2008, provided a neutral sex ratio except BHN (N = 378) and BN (N = 51) which were exclusively male while the soldiers (N = 466) were female-biased. This information suggests that there is a sex-linked bifurcation along the path for termite development with a male-biased neotenic or female-biased soldier as the choice. In contrast, termites collected in 2004 from Log B provided sex ratios that included a female biased RN (N = 1017), a neutral soldier (N = 258) and male biased BHN (N = 99) and workers (N = 54). Log C, collected in 2009, provided female biased soldiers (N = 32), RNs (N = 18) and BHNs (N = 4) and only male BN (N = 5). Eight laboratory cultures, ranging in age from five to 14 years old, also were sampled and all castes sexed. The census included a 14-year old queen-right colony, an 8-year old polyandrous colony and six colonies provided nymphs and male-biased worker populations. Together these data indicate a flexible caste determination system providing a unique opportunity for a better understanding of the flexible developmental options available in R. flavipes that we discuss relative to the literature on Reticulitermes ontogeny.

Highlights

Termites are social insects that undergo paurometabolous development and have morphologically distinct castes [1,2]
The nymphoid neotenics found in this collection included three phenotypes that were differentiated based on the degree of pigmentation: regular neotenics (RN), black-headed neotenics (BHN) or black neotenics (BN) (Figure 1)
All neotenics from the Log collections were brachypterous nymphoids and this is the first report of neotenic forms differentiated based on degree of pigmentation believed to be a result of tanning/sclerotization (Figure 1)

Summary

Introduction

Termites are social insects that undergo paurometabolous development and have morphologically distinct castes [1,2]. They are generally divided into two groups with the higher termites, members of the family Termitidae, representing a diversity of derived species while the remaining families, considered the ancestral lines, are termed the lower termites. The literature hints at an ontogeny complicated by flexibility. This confusion is exemplified by the fact that there have been at least nine versions of the life cycle proposed for the economically important pest genus Reticulitermes [2,6,12,13,14,15,16,17,18]

Methods

Results

Discussion

Conclusion