Geology Reference
In-Depth Information
gained unil around 1964, when intensive field
studies were inaugurated by zoologists from the
universiies of Dar es Salaam and Copenhagen.
Since then collecing acivities have been
extended, especially by the former group, to many
areas and bioic regions in Tanzania, giving for
the first ime a base-line concept of the East Afri-
can diplopod fauna from which to extract and
contrast the true montane fauna.
At the present, approimately 212 nominal spe-
cies are known from Tanzania and about twice
that number are sill undescribed: extrapolaion
allows an esimate of at least 1000 endemic
Tanzanian millipede species, the majority of them
probably being montane species. During the early
period of alpha taxonomy in this group and
region, roughly 1864-1964, the majority of spe-
cies were described (and have remained known)
from single specimens with faulty or inadequate
locality data. Only through the recent efforts ofK.
M. Howell and his colleagues and students has it
been possible to perceive the remarkable biogeo-
graphic-evoluionary potenial of this very rich
and diversified fauna. Specialists working in
better-known groups of both animals and plants
are especially reminded that so far only one
modem revision of an African family of
Diplopoda has been published, and that, perforce,
the few recent generic revisions have been of
limited biogeographic significance.
lifestyle, render millipedes useful for studies of
evolution and dispersal, the more so since all are
intolerant of exposure to seawater and most to the
smallest desiccaion. Altenaively, they share with
other organisms the ability to eploit adapive
opportuniies by both symparic and allopatric
mechanisms, and impressive bursts of speciaion
can occur within the same higher taxa that include
stabilised and even relictual species.
In other respects millipedes exhibit a wide
range of anatomical and biological singulariies.
They are the only arthropods in which the original
body somites have become fused in pairs, forming
diplosomites provided with two pairs of legs. The
majority of species are equipped with serially seg-
mental defence glands, producing allomones cap-
able of discouraging predators as well as
inhibiing fungal growth. Each order of millipedes
produces highly characterisic allomones, and the
spectrum includes such ingredients as hydrogen
cyanide, hydrochloric acid, quinones and phenols.
Only the merest beginning has been made so far
n exploring the variety, uses and manufacture of
these bizarre compounds: some may yet be shown
to possess medical properies. Many of the larger
species discharge their allomone readily when
picked up, someimes (as in Dendrostrep tus macra-
canthus Attems) in the form of a fine spray. Aside
from this fairly passive means of defence, mil-
lipedes are totally non-aggressive creatures: they
do not bite, sing, transmit diseases, nor - except
in unusual cases - eat the crops.
The procedures of reproducion are airly
standardised throughout the class. All species
pracise intenal ferilisaion and the young hatch
from shelled eggs, usually in a larval stage with
three pairs of legs. Subsequent growth occurs
through a number of stadia and periods of
diapause, during which addiional segments are
produced in a posterior germinaion area
(teloblasty); legs are then provided for the new
segments of the previous moult. Some species
pass through six or seven immature stages and
become sexually mature at the last moult, when
one or two pairs of legs are dramaically trans-
formed (in the males) into copulatory organs of
someimes surpassing compleity. The outer ends
of the oviducts are correspondingly equipped with
About Diplopoda
Millipedes, in general, comprise one of the least
known of the larger classes of arthropods - the
present total of nearly IO 000 species is organised
into no fewer than 115 families and 15 orders -
despite which our knowledge of the group
remains at a level approimated by entomology
150 years ago. Millipedes are racheate arthro-
pods and virtually all of them eist as deriivores
in the moist litter and upper soil horizons of
deciduous forests around the globe. Their fossil
record, although fragmentary, extends back to the
Lower Devonian and some groups appear to have
changed but little down to the Recent. Such long
lineages and evoluionary stabiliy, plus their
somewhat parochial preferences of biotope and
Search WWH ::

Custom Search