Page 6 - Berni_1997

Simone Berni

the sympatric (two or more species which live together) B. whitei with which it mates
regularly, as confirmed by Scali, Mantovani and Tinti (1991: 104). This fact causes a
substantial waste of the insects' reproductive potential, only partly balanced by the sex ratio
in favour of males.
B. whitei, a hybrid of B. rossius redtenbacheri and B. grandii grandii, has lately been
the subject of some interesting studies that ha ve thrown light o n its genetic characteristics.
Such characteristics mean that B. whitei is a taxon that is unique in the whole of the animai
kingdom. By rneans of a series of crosses with the three sub-species of B. grandii,
researchers bave found the contemporaneous presence ofparthenogenesis, hybridogenesis and
gynogenesis, and bave also reported occasionai cases of androgenesis (Scali, Mantovani &

AMPHIGONY
'IEJOSIS Q FEilm..IZAnr5AMPHIMIXIS (l)
• •
••
•
•

P ARTHENOGENESIS

AU!OAcnYATION AND
EMBRYONAL AUI'OREGULATION

GYNOGENESIS
.

0
AUTOAcnYATIO~AND :: • l EMBR.YONAI.:
. ~
EMBR.YONAL ;: • DIVISION
REGULATION BY
SPEKMATOZOON
HYBRIDOGENESIS

ANDROGENESIS
~ FUSION+
DEGENFAATIONOJ ~ ~
CONTENT L9 • RYOGE:NdiS
REGULAll
•
•
OF
SPERMATOZOOWS
PENETR.ATION
OVOCITA
t
DUPUCATION

Figure 3. Reproduction modes in the genus Bacillus; after Tinti in Veroli (1995: 26).

Phasmid Studies, 6(1): 4