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

Fig. 5.7 Phylogeny of dictyopteran species and a comparison with the phylogeny of endosymbiotic
Blattabacterium spp. The host phylogeny was based on a combined analysis of 18S rDNA and mitochondrial
COII, 12S rDNA, and 16S rDNA sequences. Tree length: 2901, consistency index: 0.55. Bold
lines indicate those dictyopteran taxa that harbor Blattabacterium spp., and that were examined in
host endosymbiont congruence tests. The asterisk indicates the only node in the topology that was in
disagreement with that based on host phylogeny. From Lo et al. (2003a), reprinted with permission
from Nathan Lo and the journal Molecular Biology and Evolution.
Urate Management
Nitrogen excretion in cockroaches is a complex phenomenon
that differs from the expected terrestrial insect pattern
of producing and voiding uric acid. Several different
patterns are apparent. The majority of species studied
(thus far 80) do not void uric acid to the exterior even
though they may produce it in abundance (Cochran,
1985). When cockroaches are placed on a diet high in nitrogen,
urates accumulate in their fat body (Mullins and
Cochran, 1975a); they are typically deposited in concentric
rings around a central matrix in storage cells (urocytes)
adjacent to bacteriocytes (Cochran, 1985) (Fig.
5.6B). When the diet is deficient in nitrogen or individual
nitrogen requirements increase, bacteroids mobilize the
urate stores for reuse by the host, and the fat body deposits
become depleted. Uric acid storage thus varies directly
with the level of dietary nitrogen and is not excreted
under any conditions. Even when fed extremely high levels
of dietary nitrogen, American and German cockroaches
continue to produce and store uric acid in the fat
body and other tissues, ultimately leading to their death
(Haydak, 1953; Mullins and Cochran, 1975a). At least
three other patterns of urate excretion are found in the
family Blattellidae. In the Pseudophyllodromiinae, the
genera Euphyllodromia, Nahublattella, Imblattella, and
probably Riatia sparingly void urate-containing pellets,
with urates constituting 0.5–3.0% of total excreta by
weight (Cochran, 1981). Feeding experiments showed
that high-nitrogen diets did not change urate output in
Nahublattella nahua, but did increase it in N. fraterna in
a dose-dependent manner. In both cases diets high in nitrogen
content led to high mortality. The genus Ischnoptera
(Blattellinae) excretes a small amount of urates
(2% by weight) mixed with fecal material; this pattern is
similar to that of other generalized orthopteroid insects,
except for the very small amount of urates voided (Cochran
and Mullins, 1982; Cochran, 1985).
84 COCKROACHES