Roy L. Caldwell University of California, Berkeley

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Roy L. CaldwellUniversity of California, Berkeley
Mantis shrimp Still the fastest claw in the west!
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The stomatopods are a diverse group with over 500
species
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Aeschronectidids and Palaeostomatopods Diverged
from other Malacostracan stock in the Devonian,
400 million years ago
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Archaeostomatopods Carboniferous origins
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All seven modern extant superfamilies have
Cretaceous origins
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The key innovation in the evolution of modern
stomatopods was the enlargement of the second
thoracopods into lethal raptorial appendages 300
million years ago.
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The first stomatopods had a simple unarmed
raptorial appendage, but many groups have evolved
a barbed dactyl used to spear prey.
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Several times in their history, stomatopods have
evolved a smashing raptorial appendage.
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Stomatopods require a cavity or burrow for
protection, for reproduction and for feeding.
Most aggressive interactions, particularly in
smashers, are over cavities.
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With such lethal weapons, fighting is dangerous.
Up a third of the adults in a population have
wounds.
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Forces at impact and due to cavitation.
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The Strike of a 14 cm male Odontodactylus
scyllarus recorded at 5000 frames/s

• Dactyl speed of 23 m/s
• Peak angular speed of 990 rad/s
• Peak acceleration of 104,000 m/s2
• Duration of strike lt 2 ms
• Recorded force of 1400 N
• Most strikes show cavitation

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The evolution of the raptorial appendage provided
not only an effective feeding apparatus, but also
a potent offensive and defensive weapon that has
influenced just about every aspect of the biology
of modern stomatopods.
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Mating Systems and the Evoluton of Monogamy
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Male
Female
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Many species mate promiscuously whenever they
have the opportunity.
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In many smashing gonodactylid species, males
guard a female for a few days prior to egg
laying. The males then leave.
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In one spearing super family, the
Lysiosquilloidea, the majority of species appear
to be monogamous.
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In monogamous Lysiosquillids such as these 31 cm
L. maculata, males have larger raptorial
appendages and eyes and do most of the hunting,
provisioning their mates.
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Monogamy appears to have evolved in this group
because

• 1. The cost of constructing a new burrow using
  mucus.
• The risk of predation while searchig for a mate.
• It is probably better for a male to remain with
  a female and feed her than it is to search for a
  new mate.

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Pullosquilla thomassini
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One of the smallest of all stomatopods,
Pullosquilla doesnt fit our hypothesis as to why
it is monogamous. Males are highly mobile and
can dig a new burrow in minutes. They also occur
at high density so the cost of searching must be
low.
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The answer lies in the males being able to
provide paternal care. A female often can
produce two large clutches of eggs. She cares
for one, the male cares for the other.
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Sensory Systems
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Chemosensory based individual recognition in
Neogonodactylus
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Test arena for Neogonodactylus festae
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A resident defends its cavity from an intruder.
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Cavity contains clean water
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Cavity contains water from an unknown stomatopod
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Cavity contains water from the container of a
stomatopod that previously defeated the intruder
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Adult stomatopods have apposition compound eyes
made up of hundreds of individual ommatidia, each
with their own optics. In the superfamilies
Squilloidea and Lysiosquilloidea, the eyes are
typically dorsoventrally elongated, extending the
baseline for monocular stereopsis.
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In all stomatopods, a midband made up of rows of
ommatidia bisects the eye. In squilloids the
midband is made up of 2 rows. In gonodactyloids
and lysiosquilloids it has 6 rows.
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When an ommatidium is directly aligned with your
eye (or a camera), no light is reflected back.
This creates a dark pseudopupil. When the
ommatidia of multiple parts of the eye are
directed at the camera, we see multiple
pseudopupils.
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A skewing of the ommatidia in the dorsal and
ventral halves of the eye produces overlapping
fields of vision. The range of an object in view
is, therefore, a simple function of the
particular sets of ommatidia that simultaneously
image it.
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Polarized Signals
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Odontodactylus latirostris displays linear
polarization of the antennal scales.
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In Odontodactylus latirostris, only the males
have polarized antennal scales. These seem to be
involved in courtship.
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The bright / dark blue polarized patches seen in
many gonodactyloids may be structurally produced
and do not fade during a molt.
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In several species of Haptosquilla, the first
maxillipeds possess blue plates that are linearly
polarized. These patches are hidden except when
the animal displays them. The angle at which the
polarized display can be seen is highly
directional.
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In the Peacock mantis shrimp, Odontodactylus
scyllarus, only sexually mature males (gt 12 cm)
have linearly polarized red/clear uropod spines.
In females and juvenile males, the spines are
non-polarized and red.
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Stomatopod Fluorescence
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Lysiosquillina glabriuscula photographed in broad
spectrum white light.
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Lysiosquillina glabriuscula photographed in blue
light.
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Lysiosquillina glabriuscula photographed in blue
light with a yellow filter. Pigments in the
yellow spots fluoresce yellow-green in blue
light. As the animal goes deeper, the species
specific signal remains yellow-green. Receptors
in the eye are tuned to yellow-green.
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Echinosquilla guerinii