Structure of the ovaries of the Nimba otter shrew, Micropotamogale lamottei, and the Madagascar hedgehog tenrec, Echinops telfairi

The otter shrews are members of the subfamily Potamogalinae within
the family Tenrecidae. No description of the ovaries of any member
of this subfamily has been published previously. The lesser
hedgehog tenrec, Echinops telfairi, is a member of the subfamily
Tenrecinae of the same family and, although its ovaries have not
been described, other members of this subfamily have been shown to
have ovaries with non-antral follicles. Examination of these two
species illustrated that non-antral follicles were characteristic
of the ovaries of both species, as was clefting and lobulation of
the ovaries. Juvenile otter shrews range from those with only small
follicles in the cortex to those with 300- to 400-mu m follicles
similar to those seen in non-pregnant and pregnant adults. As in
other species, most of the growth of the oocyte occurred when
follicles had one to two layers of granulosa cells. When larger
follicles became atretic in the Nimba otter shrew, hypertrophy of
the theca interna produced nodules of glandular interstitial
tissue. In the tenrec, the hypertrophying theca interna cells in
most large follicles appeared to undergo degeneration. Both species
had some follicular fluid in the intercellular spaces between the
more peripheral granulosa cells. It is suggested that this fluid
could aid in separation of the cumulus from the remaining granulosa
at ovulation. The protruding follicles in lobules and absence of a
tunica albuginea might also facilitate ovulation of non-antral
follicles. Ovaries with a thin-absent tunica albuginea and
follicles with small-absent antra are widespread within both the
Eulipotyphla and in the Afrosoricida, suggesting that such features
may represent a primitive condition in ovarian development.
Lobulated and deeply crypted ovaries are found in both groups but
are not as common in the Eulipotyphla making inclusion of this
feature as primitive more speculative. Copyright (C) 2005 S. Karger
AG, Basel.