under what conditions would you expect enhanced paternal care to evolve

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under what conditions would you expect enhanced
paternal care to evolve??
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if this is the mating position of assassin bugs...
Bohart Museum of Entomology - UC Davis
shady grove training center
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male assassin bugs stand guard over egg
clutches clutches can contain eggs from up to
5 different females ride on females backs
until they lay their eggs
Rhinocoris annulatus
Viera Vodrazkova
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(No Transcript)
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"Smith argues that because Nepomorpha
heteropterans (the lineage to which belostomatids
belong a group of true bugs) are
phylogenetically constrained to five instars,
selection for large body size in giant water bugs
necessarily resulted in increased egg size. In
fact, belostomatid eggs became so large that
simple diffusion of water-borne oxygen was no
longer enough to prevent drowning. At this point
in their evolution, belostomatids faced an
evolutionary conflict not encountered by the
smaller insects in their sister group, the
waterscorpions (Nepidae) either constrain egg
(and thus body) size to prevent egg drowning or
expose water-adapted eggs to the hazards of
desiccation by ovipositing in open air. The
benefits of large body size forced the basal
belostomatid subfamily, the Lethocerinae, down
the latter evolutionary path. Lethocerine females
crawl out of the water and deposit a clutch of
huge eggs on emergent vegetation. Females do not
select oviposition sites randomly, but seek areas
in which partly submerged males are engaged in
courtship pushups that send signals of their
location over long distances in the water. Once
united, a pair alternates between copulation and
oviposition until the egg clutch is complete. The
job of protecting the huge and very exposed eggs
from desiccation falls to the male from the time
they are laid until they hatch several days
later, the male hydrates the eggs repeatedly,
moving from the water to the eggs and standing in
such a way that water draining off his body runs
over the egg mass. Given the fact that
lethocerines are the largest heteropterans on
earth, it is surprising that emergent brooding in
these bugs was not discovered until recently.
Instead, it is back-brooding behavior in the
Belostomatinae that has held giant water bugs in
the evolutionary limelight for the last 100
years. Courtship and mating in this subfamily are
identical to that of the Lethocerinae, except
that these behaviors take place entirely under
water rather than on emergent vegetation (101,
103). The most significant behavioral difference
between the Belostomatinae and the Lethocerinae
is that, rather than depositing eggs on blades of
vegetation, belostomatine females lay their eggs
on the backs of their mates. With this
fundamental change in oviposition site came an
equally fundamental change in essential paternal
duties males no longer needed to prevent egg
desiccation, but eggs left under water without
aeration were now subject to drowning. To prevent
egg drowning, all back-brooding species aerate
eggs by surface-brooding. That is, males
encumbered with eggs simply float at the
air-water interface, supplying eggs with much
needed oxygen. Males of most back-brooding genera
also aerate eggs through brood pumping, an active
pushup behavior that increases the flow of water
over the surface of eggs. In addition to pushups,
males of a few species also aerate eggs by
brood-stroking, or rhythmically brushing their
hind legs over their charges, again to increase
water flow over the brooded eggs. As with
lethocerines, this paternal behavior provides
belostomatines with a successful mechanism for
achieving great size without sacrificing
offspring survival."
Douglas W. Tallamy. 2001. Evolution of exclusive
paternal care In arthopods. Annu. Rev. Entomol.
4613965
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Douglas W. Tallamy. 2001. Evolution of exclusive
paternal care In arthopods. Annu. Rev. Entomol.
4613965
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Hippocampus abdominalis
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eggs incubated in completely- enclosed sac-like
pouch
eggs incubated in a pouch with folds that
partially or fully enclose the eggs
eggs placed into individual egg compartments
eggs loosely attached to ventral side of male -
no pouch
eggs incubated in a pouch and protected by pouch
plates