Transcript Mantis shrimp: Still the fastest claw in the west!

Mantis shrimp:
Still the fastest
claw in the
west!
Roy L. Caldwell
University of
California, Berkeley
The stomatopods are a diverse
group with over 500 species
Aeschronectidids and Palaeostomatopods:
Diverged from other Malacostracan stock
in the Devonian, 400 million years ago
Archaeostomatopods: Carboniferous
origins
All seven modern extant superfamilies
have Cretaceous origins
The key innovation in the evolution of
modern stomatopods was the enlargement
of the second thoracopods into lethal
raptorial appendages 300 million years ago.
The first stomatopods had a simple unarmed
raptorial appendage, but many groups have
evolved a barbed dactyl used to spear prey.
Several times in their history, stomatopods have
evolved a smashing raptorial appendage.
Stomatopods require a cavity or burrow for protection,
for reproduction and for feeding. Most aggressive
interactions, particularly in smashers, are over cavities.
With such lethal weapons, fighting is dangerous. Up
a third of the adults in a population have wounds.
Forces at impact and due to cavitation.
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 < 2 ms
• Recorded force of 1400 N
• Most strikes show cavitation
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.
Mating Systems and the Evoluton
of Monogamy
Male
Female
Many species mate promiscuously
whenever they have the opportunity.
In many smashing gonodactylid species, males
guard a female for a few days prior to egg laying.
The males then leave.
In one spearing super family, the Lysiosquilloidea, the
majority of species appear to be monogamous.
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.
Monogamy appears to have evolved in this group because:
1. The cost of constructing a
new burrow using mucus.
2. 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.
Pullosquilla thomassini
One of the smallest of all stomatopods, Pullosquilla
doesn’t 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.
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.
Sensory Systems
Chemosensory based individual
recognition in Neogonodactylus
Test arena for Neogonodactylus festae
A resident defends its cavity from an intruder.
Cavity contains clean water
Cavity contains water from an unknown stomatopod
Cavity contains water from the container of a
stomatopod that previously defeated the intruder
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.
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.
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.
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.
Polarized Signals
Odontodactylus latirostris displays linear
polarization of the antennal scales.
In Odontodactylus latirostris, only the males have
polarized antennal scales. These seem to be
involved in courtship.
The bright / dark blue polarized patches seen in many
gonodactyloids may be structurally produced and do not
fade during a molt.
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.
In the Peacock mantis shrimp, Odontodactylus scyllarus,
only sexually mature males (> 12 cm) have linearly
polarized red/clear uropod spines. In females and
juvenile males, the spines are non-polarized and red.
Stomatopod Fluorescence
Lysiosquillina glabriuscula photographed in
broad spectrum white light.
Lysiosquillina glabriuscula photographed in blue light.
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 yellowgreen. Receptors in the eye are tuned to yellow-green.
Echinosquilla guerinii