N. Abramson, V. Alekseev

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Mechanisms and peculiarities of dormancy in
veretebrates and invertebrates?????????????
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• N. Abramson, V. Alekseev
• Zoological Institute RAS

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Terms and definitions
Laudien 1973

• Keilin (1959)

Active lifenormal metabolism
Induced directly by unfavorable
conditions and development is resumed soon after
return to favorable conditions
includes a complicate internal hormonal
mechanism that needs in time both for beginning
and finishing its work. As result diapause starts
before really harsh conditions and can not be
immediately broke even if favorable conditions
return
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• The first researches on the diapause were carried
  out at the beginning of the 20th century on the
  silkworm (Bombix mori). The neologism diapause
  was subsequently extended from insects to other
  taxa which exhibited a similar kind of adaptation
  in many details, including hormone identity or
  level of metabolic depression these included
  porifera, turbellaria, briozoa, rotifera,
  oligochaeta, tardigrada, crustacea and collembola.

4
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The diapause may occur at different development
stages
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Hibernation in mammals

• Hibernation is an adaptive strategy that
  is used by species in several mammalian orders to
  conserve energy in cold or inhospitable
  environments. During hibernation these mammals
  dramatically lower their metabolic, heart, and
  respiratory rates as well as their body
  temperature in a precisely controlled manner. In
  species with winter hibernation the body
  temperature usually falls below 10 ?. Minimal
  temperature in 3? was recorded in arctic ground
  squirrel Spermophilus undulates, though in
  majority of this species do not fall below 5?.

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Remarkably hibernation occurs in seven different
orders of mammals
insectivores
bats
primates
monotremes
rodents
marsupials
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two hypothesis explaining the interspersed nature
of the distribution of extant hibernating species
through Mammalia
common ancestor is a hibernator
common ancestor is not a hibernator
Lineages where the ability to hibernate partially
lost or completely lost
Lineages where hibernation must have arisen
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Expression of PDK-4 during the hibernation
season. (A) Northern blot of total RNA from the
hearts of active and hibernating 13-lined ground
squirrels. (B) Bar graph summarizing PDK-4 mRNA
levels in the hearts of sibling and nonsibling
ground squirrels (C) Tissue distribution of PDK-4
mRNA from a single hibernating animal sacrificed
in January during hypothermic torpor (Tb 5 5C).
Tissues are as indicated above each lane
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cDNAs encoding human and ground squirrel PTLs
expressed inthe yeast P.pastorisboth human and
ground squirrel PTL perform remarkably well at
low temperatures. At 0?C, the enzyme from ground
squirrel still maintains 48 and 33 of the
maximal activity (seen at 37?C) with tributyrin
and triolein respectively. Human PTL showed 42
maximal activity at 0?C using tributyrin and an
amazing 55 maximal activity using triolein. This
result shows that the low-temperature catalysis
seen with a protein in hibernators is also found
in humans.
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Model depicting the central role of differential
gene expression during hibernation. Single arrows
indicate direct effects, whereas multiple arrows
indicate an effect that requires multiple
intermediate events
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similar or close in vertebrate and invertebrates

• Displayed independently in different sometimes
  very distant orders under the influence of
  environmental factors
• occur at different development stages (e.g. eggs,
  embryos, juveniles or adults)
• Suppression of metabolism (in diapause is 3-6
  times lower than in in active at the same
  ambient temperature) and characteristic features
  of development (period of preparing, gradual
  suppression of metabolic functions, refractory
  phase, ,exit)
• The duration of refractory phase usually do not
  exceed 3 months, after that they could be
  reactivated by transfer to favorable conditions.
  This period coincides with the period of activity
  of diapause inhibiting hormone as it was shown
  for decapodes (Alexseev, 1998).
• There is significant similarity in chemical
  mechanism of hormonal control of resting phase in
  these animals ???????,

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