Cockroache; Ecology, behavior & history - W.J. Bell

Mastotermes (Fig. 9.7) is the only isopteran with the latter,
which it shares with all examined Blattaria (Bandi et
al., 1995; Lo et al., 2003a). Mastotermes has additional
characters that ally the taxon with cockroaches, including
a well-developed anal lobe in the hindwing and the packaging
of eggs in an ootheca (Watson and Gay, 1991;
Nalepa and Lenz, 2000; Deitz et al., 2003).
The bacteroid-uric acid circulation system was in place
when termites evolved eusociality (Fig. 9.1), possibly allowing
for the mobilization of urate-derived nitrogen
from the fat body and its transfer among conspecifics via
coprophagy and trophallaxis (Chapter 5). The endosymbiosis
was subsequently lost in other termite lineages
when these diverged from the Mastotermitidae (Bandi
and Sacchi, 2000). Other termites sequester uric acid in
the fat body, but without bacteroids, individuals lack the
ability to mobilize it from storage. Stored reserves can
only be used by colony members via cannibalism or
necrophagy. Once ingested, the uric acid is broken down
by uricolytic bacteria in the hindgut (Potrikus and Breznak,
1981; Slaytor and Chappell, 1994). Bacteroids were
likely lost in most termites because two aspects of eusocial
behavior made fat body endosymbionts redundant.
The recycling of dead, moribund, and sometimes living
nestmates, combined with the constant flow of hindgut
fluids among nestmates via trophallaxis, allowed uricolytic
gut bacteria to be a more cost-efficient option
(Bandi and Sacchi, 2000). It is of note, then, that after eusociality
evolved, the storage and circulation of uric acid
and its breakdown products changed from one that occurs
primarily at the level of individual physiology to one
that occurs at the colony level. It is also of interest that
proctodeal trophallaxis, a behavior linked to the presence
of the hindgut symbionts, may have been influential in
the loss of the fat body endosymbionts.
EVOLUTION OF EUSOCIALITY 1:
BASELINE
Fig. 9.7 Male and female dealate primary reproductives of
Mastotermes darwiniensis. Photo by Kate Smith, CSIRO Division
of Entomology.
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 symbionts
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
TERMITES AS SOCIAL COCKROACHES 161