Geophilomorph centipedes and the littoral habitat - Books and ...

24 A.D. Barber / Terrestrial Arthropod Reviews 4 (2011) 17–39
Geophilomorph centipedes, both terrestrial and littoral have been shown to be
more tolerant of immersion than lithobiomorphs (Hennings, 1903 Plateau, 1890 ).
Schubart ( 1929 ) found that submerged specimens of Pachymerium ferrugineum
(C.L.Koch,1835) from Germany survived 7-68 days at room temperature (16-18 o C)
whilst Suomalainen ( 1939 ) reported 24-95 days at 19-27 o C and 68-178 days at 6-12 o C
for Finnish animals. Binyon and Lewis ( 1963 ) reported on survival times for animals
immersed in sea-water for Strigamia maritima , Hydroschendyla submarina
Stigmatogaster subterranea with the latter having much reduced survival times compared
with the two littoral species. Th e two halophiles were able to maintain their body
fl uid concentrations more or less constant for 14 hours whilst in Stigmatogaste r this
rose signifi cantly. Th ere appears to have been little subsequent work on osmoregulation
in littoral centipedes.
Gaseous exchange
Unlike some spiders which are able to trap bubbles of air in their nests and use these
either as a direct resource or as a physical gill or remain in air pockets trapped in some
other way e.g. in empty barnacle shells (McQueen and McLay, 1983 ; Roth and Brown,
1975 ; Rovner, 1987 ) there is little clear evidence of geophilomorphs doing this even
though Bonnel ( 1929 ) had reported that Mixophilus indicus (Silvestri, 1929 ) trapped a
bubble of air in a loop in the posterior end of its body. Rajalu ( 1972 ) was unable to
confi rm this and as Lewis ( 1962 ) pointed out, although newly immersed specimens of
Strigamia maritima have bubbles of air on their surface these are likely to be rapidly
dispersed by movement. Nor is there any evidence of centipedes occupying air fi lled
burrows. However there have been suggestions that air bubbles could be trapped in
spiracles and might act as physical gills (Laloy, 1904 ; Suomalainen, 1939 ) and there is
some evidence for this (Lewis, 1960).
Alternatively either the general body surface or some part of it might allow gaseous
exchange directly with sea water (Rajalu, 1972 ). Manton ( 1965 ) argued that closure of
the spiracular atrium when burrowing allowed respiration to continue and that the
atrial cuticle facilitated respiration under wet soil (and hence, possibly, sea water)
conditions.
Tolerance of more or less severe hypoxia in insects (which would be advantageous
during submergence) is greater than in most vertebrates (Hoback and Stanley, 2001 ;
Schmitz and Harrison, 2004 ) and the apparent capacity of at least some centipedes to
build up an oxygen debt which is subsequently “paid off ” is indicated by experiments
with Mixophilus indicus (Rajalu, 1970 ). A similar phenomenon has been found when
measuring oxygen consumption in the terrestrial lithobiomorph Lithobius agilis (Ivan
Kos, pers. comm.)
Problems of defi ning halophiles
One of the problems associated with gaining a clear picture of the variety and numbers
of shoreline animal species is that of defi nition of the terms “littoral” and “sea shore”
which, in some accounts, can include areas of land close to the beach itself. For instance,
and