Biology Reference
In-Depth Information
Plate 4.77
Maxilla of the wandering garter snake (
Thamnophis elegans vagrans
),
Sandoval, New Mexico, USA.
Several slightly enlarged, ungrooved posterior maxillary teeth
are present. Bites by this species have uncommonly produced mild-to-moderate edema, pain,
and hemorrhagic blistering (see text). AMNH #R148051, photo copyright to Arie Lev.
In a detailed morphological comparison of Duvernoy's glands of three
Thamnophis
taxa, Taub (1967) reported that
T. sirtalis
had a thin gland capsule and a moderate num-
ber of thin-walled trabeculae, while the glands of
T. elegans
and
T. cyrtopsis
(black-
necked garter snake) exhibited heavy-to-thick capsules and many moderately thick
trabeculae. Other significant differences among these glands were noted. The glands of
T. elegans
and
T. cyrtopsis
were composed of columnar cells, but there were pyrami-
dal cells in the
T. sirtalis
gland (Taub, 1967). About 10% of the tubules in the
T. sirta-
lis
gland were lumenate, in comparison to 50% and 90% of the tubules present in the
glands of
T. elegans
and
T. cyrtopsis
, respectively. The glands of
T. sirtalis
and
T. cyr-
topsis
were moderately vascular, whereas that of
T. elegans
was highly vascular (Taub,
1967). The
T. elegans
gland contained a mixture of serous and mucous cells; that of
T. cyrtopsis
had mucous cells common throughout; and the
T. sirtalis
gland lacked
mucous cells. None of these taxa had a mucous supralabial gland associated with the
serous Duvernoy's gland (Taub, 1967). Fry et al. (2008) reported that the
T. elegans
gland contained isolated mucoid cells or patches and a relatively large ovoid duct.
Kardong and Luchtel (1986) performed a gross and ultrastructural study of the
Duvernoy's gland of
T. elegans vagrans
and reported that the gland was encased by
a thin coat of collagenous connective tissue. The gland was multilobulated, and these
consisted of numerous acini (
secretory units containing serous cells). These authors
reported absence of any significant secretion storage volume, although there were vari-
ably sized lumenae defined by the acini (Kardong and Luchtel, 1986). A main duct
contained the only mucous cells found within the gland and, along with scattered
serous cells, comprised the simple columnar epithelium lining the duct. The duct ulti-
mately emptied into the buccal cavity near the posterior maxillary teeth. The study
demonstrated that the ultrastructure of the
T. e. vagrans
Duvernoy's gland closely com-
pared with that of another natricid, the medically important
R. tigrinus
. The glands
of both taxa exhibit serous and myoepithelial cells, but lack mitochondrial-rich cells;
secretory granules of the serous cells are abundant and homogenously dense (Kardong
and Luchtel, 1986; Yoshie et al., 1982; see the subsection on
R. tigrinus
in Section 4.3).
Unlike in
R. tigrinus
, the serous cells of
T. e. vagrans
have endoplasmic reticulum and
Golgi complexes that lack extensive cisternae (Kardong and Luchtel, 1986; Yoshie
et al., 1982). Similar to
D. typus
and
N. tessellata
, the serous cells of
T. e. vagrans
