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

Fig. 6.10 Comparison of total radiolabel content of Blattella
germanica females and the oothecae they produced while feeding
on either a dog food (25% crude protein) or a 5% protein
diet; these females were mated to virgin males that had been simultaneously
injected with 3 H leucine (a representative amino
acid) and 14 C hypoxanthine (a purine converted to uric acid in
vivo). Dog food fed-females and their oothecae contained 17%
of the male contributed radiolabel. Those on the low-protein
diet contained 63% of the radiolabel made available to them at
mating. Values are mean SEM. a vs. b, p 0.005; c vs. d, p
0.027; e vs. f, p 0.007 (Student’s t-test). From Mullins et al.
(1992), courtesy of Donald Mullins and with permission from
the Journal of Experimental Biology.
ination system unavailable to females and juveniles. From
the female perspective, it was suggested that a spermatophore
slathered with an excretory product would be
an unattractive meal, and prevent her from consuming it
before the sperm moved into storage (Roth, 1967, 1970a).
An alternative suggestion was that the uric acid may function
as a mating plug that deters additional inseminations
(Cornwell, 1968). In species such as Miriamrothschildia
( Onychostylus) notulatus, Lophoblatta sp., Cariblatta
minima, Amazonina sp., and Dendroblatta sobrina, so
much uric acid is applied by males that the female genital
segments gape open (Roth, 1967c).
The most strongly supported hypothesis is that the uric
acid transferred during mating acts as a nuptial gift. In B.
germanica, radiolabeled uric acid can be traced from the
male to the female, and subsequently to her oocytes; the
transfer occurs more readily when the female is maintained
on a low-nitrogen diet (Fig. 6.10). The urates are
probably ingested by the female, along with the spermatophore,
but it is possible that a small fraction may
enter via her genital tract (Mullins and Keil, 1980). An
analogous urate transfer and incorporation occurs in X.
hamata. In this case, the female turns, post-copulation,
and feeds on a urate-containing slurry produced and offered
by the male (Schal and Bell, 1982). After copulation
the male raises his wings, telescopes his abdomen, widens
the genital chamber, exposes a white urate secretion, and
directs it toward the female, who ingests it. Females feed
for about 3.5 min. As in B. germanica, females on nitrogen-deficient
diets transfer to their maturing oocytes
more male-derived uric acid than do females on highprotein
diets. The magnitude of the gift offered by males
of these two species depends on a combination of male
age, size, diet, and frequency of mating. The uricose
glands of newly emerged male B. germanica contain little
or no secretion; they become filled in one or two days
(Roth and Dateo, 1964). The glands are nearly emptied at
each copulation (Roth and Willis, 1952a).
Male to female transfer of uric acid probably occurs in
all cockroach species that possess male uricose glands. A
recently mated female Blattella humbertiana was observed
removing excess uric acid with her hind legs, then
eating some of the material before it hardened (Graves,
pers, comm. to LMR in Roth, 1967c). In three species of
Latiblattella the male’s genitalia and posterior abdominal
segments are covered with “chalky white secretion” after
mating, and females of Lat. angustifrons have been observed
applying their mouthparts to it after mating
(Willis, 1970).
Paternal Investment or Mating Effort?
A nuptial gift can benefit a male in two ways. The gift can
function as paternal investment, where transferred nutrients
or defensive compounds increase the number or
quality of resultant offspring, or it can function as mating
effort, which increases the male’s fertilization success
with respect to other males that mate with the same female
(Eberhard, 1996). The hypotheses are not mutually
exclusive, and there is debate on the distinction between
them, centering mainly on the degree to which a donating
male has genetic representation in the offspring that
benefit from the gift. The latter is dependent on female
sperm-use patterns, the length of her non-receptive period
following mating, and the time delay until the female
lays the eggs that profit from the male’s nutritional contribution
(reviewed by Vahed, 1998).
The incorporation of male-derived urates into oothecae
of B. germanica suggests paternal investment, supported
by three lines of evidence (Mullins et al., 1992).
First, urate levels in eggs steadily decrease during development.
This strongly suggests that the uric acid is metabolized
during embryogenesis (Mullins and Keil, 1980),
presumably via bacteroids transmitted transovarially by
the female (e.g., Sacchi et al., 1998b, 2000). Second, 14 C
radioactivity not attributable to 14 C urate is present in tissue
extracts of oothecae (Mullins and Keil, 1980; Cochran
and Mullins, 1982; Mullins et al., 1992). As pointed out by
Mullins and Keil (1980), however, the 14 C radiolabel
reflects pathways involving carbon atoms and not neces-
100 COCKROACHES