Evolution Of Eusociality 1 Baseline

A detailed examination of the biology of colony initiation in Cryptocercus lends itself to a logical, stepping-stone conceptual model of the evolution of the earliest stages of termite eusociality, with a clear directionality in the sequence of events. Female C. punctulatus lay a clutch of from one to four oothecae. Unlike other oviparous cockroaches (Fig. 7.1), nymphs do not hatch from the ootheca simultaneously. The majority of egg cases require 2-3 days for all neonates to exit (Nalepa 1988a). Laboratory studies further suggest that there is a lag of from 2-6 days between deposition of successive oothecae (Nalepa, 1988a, unpubl. data). Consequently, there can be an age differential of 2 or more weeks between the first and last hatched nymphs in large broods. These age differentials are corroborated by field studies. Families collected during autumn of their reproductive year can include second, third, and fourth instars (Nalepa, 1990), at which point development is suspended prior to the onset of their first winter.

Nymphs in these families hatch without the gut sym-bionts required to thrive on a wood diet; consequently, they rely on trophallactic food and fecal pellets (Fig. 5.4) from adults for nutrients. Parents apparently provide all of the dietary requirements of first-instar nymphs, and some degree of trophallactic feeding of offspring occurs until their hindgut symbioses are fully established. Individual nymphs probably have high nutritional requirements, since they gain considerable weight and go through a relatively quick series of molts after hatch. The young are potentially independent at the third or fourth instar (Nalepa, 1990, Table 2), but the family structure is generally maintained until parental death. Adults do not reproduce again. Because of their extraordinarily long developmental times (up to 8 yr, hatch to hatch, depending on the species—Chapter 3), adult Cryptocercus rarely, if ever, overlap with their adult offspring (CAN, unpubl.). In addition to providing food and microbes, parental care includes gallery excavation, defense of the family, and sanitation of the nest (Cleveland et al., 1934; Seelinger and Seelinger, 1983; Nalepa, 1984,1990; Park et al.,2002). This degree of parental care exacts a cost. If eggs are removed from Cryptocercus pairs, 52% are able to reproduce during the following reproductive period. If parents

Fig. 9.8 Trophic shift model for transition from subsociality to initial stages of eusociality in a termite ancestor. (A) Baseline conditions. A series of egg cases are laid over a short period of time, resulting in age differentials within the brood. Adults feed all offspring; cost of parental care results in reproductive arrest.

Juveniles develop slowly but progressively toward adulthood. (B) Transition to eusociality. Fourth instars begin feeding younger siblings; cost of alloparental care results in developmental arrest of juvenile caregivers. Female resumes oviposi-tion. After Nalepa (1988b, 1994).

Fig. 9.8 Trophic shift model for transition from subsociality to initial stages of eusociality in a termite ancestor. (A) Baseline conditions. A series of egg cases are laid over a short period of time, resulting in age differentials within the brood. Adults feed all offspring; cost of parental care results in reproductive arrest.

Juveniles develop slowly but progressively toward adulthood. (B) Transition to eusociality. Fourth instars begin feeding younger siblings; cost of alloparental care results in developmental arrest of juvenile caregivers. Female resumes oviposi-tion. After Nalepa (1988b, 1994).

are allowed to take care of neonates for 3 mon prior to brood removal, however, only 12% oviposit the following summer. This suggests that parental care may deplete reserves that were accumulated over the course of their extended developmental period and are not easily replaced. Under the constraint of a wood diet, their apparent semelparity in the field can be attributed to the need for, and cost of, long-term parental care of the young (Nalepa, 1988b). The life history of a subsocial termite ancestor similar to that of Cryptocercus is depicted in Fig. 9.8A.

Was this article helpful?

0 0
Oplan Termites

Oplan Termites

You Might Start Missing Your Termites After Kickin'em Out. After All, They Have Been Your Roommates For Quite A While. Enraged With How The Termites Have Eaten Up Your Antique Furniture? Can't Wait To Have Them Exterminated Completely From The Face Of The Earth? Fret Not. We Will Tell You How To Get Rid Of Them From Your House At Least. If Not From The Face The Earth.

Get My Free Ebook


Post a comment