Haker, ’90). There is no demonstration that females
provide nutrition to the developing young after yolk
is exhausted (and Fachbach indicated that a large
amount of yolk is available to late “larvae”), so I
suspect that the subspecies is ovoviviparous, and
simply retains its young through metamorphosis
most of the time, as members of several subspecies
of S. salamndra are known to do occasionally. Fully
metamorphosed young are born of S. atra after a
lengthy gestation period; larvae are born at diverse
stages in most of the ovoviviparous species. Retention
has therefore evolved only in “end taxa” of one
lineage of salamanders. The live-bearing salamanders
live in the Alps and adjacent mountain ranges.
Caecilians, too, have performed relatively few reproductive
“experiments,” but the few are very successful,
and are the predominant reproductive
modes. All caecilians practice a unique mode of internal
fertilization. Males evert the rear part of the
cloaca, which effects an intromittent organ that is
inserted into the vent of the female so that sperm
is transported directly, without being strewn into
water. Of the six families of caecilians, the three
most primitive (one in northwestern South America,
two in southeast Asia) lay eggs on land, the
female guards them until they hatch, and the larvae
wriggle into streams. The larvae spend perhaps
a year in their aquatic phase, then metamorphose
abruptly (Wake, ’89), spending the rest of their lives
on land. One family, the paraphyletic, world-wide
Caeciliaidae, includes species with free-living larval
stages, others with direct development, and yet
others that are obligately oviductal egg retainers
that provide maternal nutrition after the yolk supply
is exhausted (viviparity). All members of the
two remaining families, the aquatic Typhlonectidae
of northern and central South America and the
Scolecomorphidae of east and west Africa, apparently
are obligately viviparous. There are no species
that appear to be ovoviviparous, or retained
but dependent only on yolk for nutrition. Viviparity
has evolved at least twice, once in the Old World
and once in the New World, and there may have
been additional events. I can only speculate about
this until the systematics of caecilians in general
and caeciliads in particular are better understood