Caste morphology and development intermitogetonnr.planus(insecta, isoptera, rhinotermitidae)

Abstract

The termite family Rhinotermitidae displays a wide diversity in its patterns of social organization in castes. The genus Termitogeton probably branched off early in the evolution of this family. We studied the developmental pathways of a putative undescribed species from New Guinea, Termitogeton nr planus. The development begins with two white inactive instars (larvae), the second of which possesses small wing buds. These are followed by a relatively homogenous group of active immature stages (pseudergates) among which a biometric study revealed the presence of four instars. The first of these instars possesses wing buds that regress at subsequent molts. The external morphology of older instars resembles that of higher termite workers. Older pseudergates can differentiate into presoldiers and then into soldiers, but they are also able to molt into a unique stage with long wing pads (nymph), preceding the imago. Colony maturity can be reached with about 10(3) individuals. The sex ratio is near 1:1 in all castes except soldiers, among which females are more numerous than males. The caste pattern of T. nr. planus is reminiscent of those of the Kalotermitidae and Termopsidae, and of Prorhinotermes among the Rhinotermitidae. None of these taxa possess a true worker caste, permanently diverted from imaginal development: social tasks are done by unspecialized immatures that retain a full array of developmental options, including that of proceeding to the imago. The most remarkable trait of T. nr. planus is the presence in all second-instar individuals of wing buds that later regress to reappear in the single nymphal stage. We suggest that the traditional definitions of the terms larvae, nymphs, and pseudergates should be revised because they cannot be satisfactorily applied to the castes of Termitogeton.

Hidden aggression in termite workers: plastic defensive behaviour dependent upon social context

“…In this species, true workers are absent, and elder juveniles, which are referred to as pseudergates (etymologically "false workers"), perform worker tasks. Pseudergates are socially active and potentially capable of developing into imagos (Grassé & Noirot 1947;Noirot 1985;Thorne 1996;Parmentier & Roisin 2003). In H. sjostedti, after hatching from eggs, larvae undergo six moults before developing into pseudergates (Miura et al 2000, Miura et al 2004.…”

Comparative studies on alate wing formation in two related species of rotten-wood termites: Hodotermopsis sjostedti and Zootermopsis nevadensis (Isoptera, Termopsidae)

“…Even outside the family, few termite species are known to produce alates through a single nymphal instar (Miller, 1969;Noirot, 1969;Noirot and Pasteels, 1987). The only exceptions have been reported in Prorhinotermes and Termitogeton in the Rhinotermitidae, both of which show unique wing formation (Roisin, 1988;Parmentier and Roisin, 2003). It would seem erroneous to conclude that the second stage has been skipped in Hodotermopsis, rather that the alate formation has been accelerated and compacted within the final nymphal instar stage.…”

“…In the Rhinotermitidae, two species are reported to have a single nymphal instar: Prorhinotermes inopinatus (Roisin, 1988) and Termitogetonr. planus (Parmentier and Roisin, 2003). Until the present report, all known Kalotermitidae and Termopsidae were reported to have at least two nymphal instars (Noirot, 1985).…”

Ultrastructure of posterior sternal glands of Macrotermes annandalei (Silvestri): New members of the sexual glandular set found in termites (Insecta)

“…Their role remains unknown. PSGs also exist in male alates, on sternites 8 -9 in Prorhinotermes, occupying a basal position in Rhinotermitidae, which is a key taxon in the evolution of termites (Parmentier and Roisin, 2003). PSGs could be considered as relics of an ancestral situation, since in the most basal termite, Mastotermes darwiniensis, seven sternal glands (in a broad sense) are found in males on sternites 3-9 and five sternal glands are found in females on sternites Fig.…”