Biology Reference
In-Depth Information
that “
Atractaspis
spp. appear to represent the evolutionary endpoint of a functional
conflict between envenomation and transport in which a rear-fanged envenomating
system has been optimized at the expense of most, if not all, palatomaxillary transport
function” (Deufel and Cundall, 2003). Therefore, although all of the fossorial and/or
nocturnal genera included in this group share many traits: slender body form with short
tails, and lacking a loreal scale; possessing smooth, shiny scales; relatively small heads
and eyes (Shine et al., 2006; see
Plate 1.1A
), and their monophyly is supported by
morphological and molecular data (McDowell, 1986; Underwood and Kochva, 1993;
Vidal et al., 2008; Zaher, 1999; Zaher et al., 2009), some genera possess markedly dif-
ferent dentitional morphology that notably influences their potential medical impor-
tance. Bites from
Atractaspis
spp. have caused serious envenomings (Kochva, 1998;
Kurnick et al., 1999; Wagner et al., 2009; Warrell et al., 1976a), while the medical
importance of uncommonly encountered genera such as
Homoroselaps
and
Macrelaps
is unclear. Bites from
M. microlepidotus
have been reported to cause loss of conscious-
ness, and the species is considered “potentially lethal” by some authors (Vitt and
Caldwell, 2008), although all of these cases are anecdotal, without any formal medi-
cal evaluation or verification (Branch, 1982; Chapman, 1968; FitzSimons, 1919, 1962;
FitzSimons and Smith, 1958; Visser and Chapman, 1978). FitzSimons (1919) stated
that
M. microlepidotus
bites were insignificant, and Chapman (1968) described a bite
with minimal local effects. Similarly, the single well-documented bite from a dwarf-
spotted garter snake (
Homoroselaps lacteus
) consisted of only local pain and edema
(Branch, 1982). Thus, the atractaspidids are a distinctive series of snakes assigned to a
shared taxonomic status on the basis of strong morphological and molecular systematic
evidence. However, this taxonomy has placed together several species previously con-
sidered either “colubrids,” elapids, or viperids. Therefore, the revised biological classi-
fications of many species previously considered part of the “Colubridae” may result in
reassignments that can impact their perceived clinical importance by altering previous
taxonomic relationships, or by formulating new perceptions on the basis of relation-
ships to newly reassigned taxa.
It must be noted that to date, some of these reassignments (such as those involving
Atractaspis
spp.) are not universally adopted or recommended by consensus and
may be subject to further changes or returned to their previous classification(s).
Therefore, the clinician must be proactive in seeking a thorough biological history
(through consultation with a knowledgeable toxinologist or professional herpetolo-
gist and/or via current literature) for any colubroid of unknown clinical importance
involved in a medically significant bite. This may provide clues about the potential
medical importance of the species involved as derived from observations of bites by
related taxa. It emphasizes the need for careful verification of recommended taxo-
nomic reassignments prior to their publication and general adoption. Such a standard
may frustrate taxonomists eager to achieve recognition of their findings, but this cau-
tion may also temper incorrect, premature assertions that can affect categorization of
an “envenomed” patient.
