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

sequently incorporated it into their oothecae. The source
of the leucine-derived materials is unknown, but the authors
suggested that it may have originated from the spermatophore
or seminal fluids.
Spermathecae
Our understanding of the functional anatomy of the female
cockroach reproductive tract in relation to cryptic
mate choice languishes behind that of some other insect
groups. The shape, number, elasticity, duct length, coiling
pattern, musculature, presence of valves or sphincters,
and chemical milieu of spermathecae play a strong role in
sperm selection by females (Eberhard, 1996). Multiple
sperm storage sites are particularly important in allowing
females to cache and use the ejaculates of different
males selectively (Ward, 1993; Hellriegel and Ward,
1998). Sperm storage organs in cockroaches have not received
much consideration since McKittrick (1964), who
demonstrated a great deal of variety in the form, number,
and arrangement of spermathecae (Fig. 6.15). In Cryptocercus
the spermatheca is forked, with the branches terminally
expanded; the single spermathecal opening lies
in the roof of the genital chamber. The spermatheca of
Lamproblatta has a wide, sclerotized basal portion and a
slender forked distal region. Within the Polyphagidae,
Arenivaga has a single, unbranched spermatheca, but
Polyphaga has a small tubular branch coming off about
halfway up the main duct. In the Blattellidae the spermathecal
opening is shifted to a more anterior position
on the roof of the genital chamber, far in advance of the
base of the ovipositor. Some species of Anaplecta have, in
addition, a pair of secondary spermathecae that open separately
on the tip of a small membranous bulge, the genital
papilla, that lies at the anterior end of the floor of the
genital chamber (Fig. 6.15F). The cockroaches of this
genus thus have either one or three spermathecae. The
Pseudophyllodromiinae, Blattellinae, Ectobiinae, Nyctiborinae,
and Blaberidae have secondary spermathecae
only. The spermathecal pores in these may be widely
spaced (Fig 6.15G—Pseudophyllodromiinae except Supella)
or more closely situated within a spermathecal
groove (Fig 6.15H—Supella, Pseudomops), thought by
Snodgrass (1937) to function as a sperm conduit. One
pair of spermathecae, each with a separate opening, is
typically present in Pseudophyllodromiinae, but the Blattellinae
may have two (Fig. 6.15I) or more pairs, each with
a separate opening. Xestoblatta festae averages 10 or 11
spermathecal branches, but these converge into just two
exterior openings (Fig. 6.16K). Nyctibora sp. (Fig. 6.15J)
and Paratropes mexicana have three pairs of spermathecae.
All Blaberidae have a single pair of spermathecae that
open on the genital papilla or directly into the common
oviduct; in most species they are accompanied by a conspicuous
pair of spermathecal glands (McKittrick, 1964).
Spermathecal Glands
Initially, the energy necessary for sperm maintenance and
motility is provided in the semen. The seminal fluid of P.
americana contains small amounts of protein, substantial
glycogen, and some glucose, phospholipid, and other
PAS-positive substances (Vijayalekshmi and Adiyodi,
1973). Females are presumably responsible for fueling the
long-term metabolic needs of sperm, as well as for creating
a favorable environment for extended storage. In Periplaneta,
for example, a female mated during her first preoviposition
period can produce fertile eggs for 346 days
subsequent to her first ootheca (Griffiths and Tauber,
1942a). Parcoblatta fulvescens females can produce more
than 30 oothecae without remating (Cochran, 1986a). It
is possible, however, that at times stored sperm are neglected,
digested, or destroyed; Breland et al. (1968) noted
that the sperm in cockroach spermatheca are sometimes
degenerated.
Spermathecal walls are typically glandular, a trait functionally
associated with providing for the maintenance
requirements of the enclosed sperm. In some species the
storage and secretory functions are largely separated via
the development of one or more spermathecal glands
(Gillott, 1983). Because cockroach spermathecae are also
secretory, however, it has been difficult to make a distinction
between spermathecae and spermathecal glands
without direct observation of the location of stored
sperm. An example is P. americana, whose spermatheca
has two branches, both of which are muscular and secretory.
The first spermatheca (“A” of Lawson and Thompson,
1970) is an S-shaped capsular branch that terminates
in a large swelling lined with a dense and deeply pigmented
cuticular intima. It has a thick, underlying muscular
layer and a smooth surface facing the lumen. Spermatheca
“B” is a long, slender, tightly coiled branch with
a thinner lining and strongly rugose inner surface. Secretory
cells with collection centers fed by microvilli are far
more numerous in the former than in the latter. The two
spermathecae join basally to form a common duct. For
many years, the slender, coiled branch was thought to be
a spermathecal gland, until sperm were found in both
branches following copulation (Marks and Lawson, 1962;
Lawson and Thompson, 1970). Lawson thought that “B”
served as a secondary storage reservoir for sperm. Hughes
and Davey (1969) noted that the tubular branch seemed
to release sperm more slowly than the capsular branch, or
only after the capsular branch had finished discharging
them. If so, sperm from the capsular branch may fertilize
the majority of the female’s eggs, and a multiply mated female
may bias paternity via differential sperm storage.
MATING STRATEGIES 111