Table 2. Ethogram based upon observations of laboratory populations of the clam shrimp Eulimnadia texana
Behavior
Description
Behaviors performed by both hermaphrodites and males:
Feeding
Clam shrimp are filter feeders. Rapid beating of the legs creates a current pulling microscopic
particles toward the clam shrimp. Clam shrimp feed almost constantly.
Lying on Bottom
Molting
Out of View
Struggling
Lying on the substrate at the bottom of the tank. The legs mayor may not be still.
Process of shedding old exoskeleton.
Individual clam shrimp not visible. Possibly burried in the substrate.
Rapid movements of the body in an attempt to disengage a clasping male.
Swimming
Locomotion around tank using antennae. It is difficult to distinguish this behavior from feeding
behavior because the two may occur simultaneously.
Hermaphrodite-only behaviors:
Digging
Performed by gravid hermaphrodites only. The gravid hermaphrodite will dig in the substrate at
the bottom of the tank. A hermaphrodite may dig continuously for up to several hours.
Dropping a clutch
Release of the eggs from the brood chamber. This may occur in the substrate after digging.
Male only behaviors:
Aggressive interaction
Clasping
Tagging Along
Takeover
Thrusting
An interaction between a male clasping a hermaphrodite and another male attempting to interfere
with the pair. These interactions involve bodily contact between males, such as pushing.
Male clasps the carapace of another clam shrimp with the first two pair of thoracic appendages.
Outcrossing is always preceded by this behavior. Males also clasp other males, as well as gravid
or unreceptive hermaphrodites at times.
One male is clasped to a hermaphrodite and another male clasps onto him forming a 'train'.
A male takes a hermaphrodite away from another male as a result of an aggressive interaction.
Male clasped to a hermaphrodite forces the lower portion of his body up into the hermaphrodite's
carapace near the paired ovaries and makes pulsating motions. Sperm transfer is assumed to be
taking place.
80 .-------------------------------------------------~
(/)
Z
o
:cc
&;
UJ
U)
III
o
70
60
50
40
30
LI. 20
o
';If!. 10
o
Feeding &
Swimming
Lying on Clasping
Bottom
Being
Clasped
II Hermaphrodites
[J Males
Out of
View
Digging
BEHAVIORS
Molting
77
Fig. 1. Behavioral time budget for an androdioecious clam shrimp Eulimnadia rexana. The bars indicate the average frequency of each
behavior when compared to the total number of behaviors observed. Darker bars represent behaviors performed by hermaphrodites. Lighter
bars represent behaviors performed by males.
Behavior
Description
Behaviors performed by both hermaphrodites and males:
Feeding
Clam shrimp are filter feeders. Rapid beating of the legs creates a current pulling microscopic
particles toward the clam shrimp. Clam shrimp feed almost constantly.
Lying on Bottom
Molting
Out of View
Struggling
Lying on the substrate at the bottom of the tank. The legs mayor may not be still.
Process of shedding old exoskeleton.
Individual clam shrimp not visible. Possibly burried in the substrate.
Rapid movements of the body in an attempt to disengage a clasping male.
Swimming
Locomotion around tank using antennae. It is difficult to distinguish this behavior from feeding
behavior because the two may occur simultaneously.
Hermaphrodite-only behaviors:
Digging
Performed by gravid hermaphrodites only. The gravid hermaphrodite will dig in the substrate at
the bottom of the tank. A hermaphrodite may dig continuously for up to several hours.
Dropping a clutch
Release of the eggs from the brood chamber. This may occur in the substrate after digging.
Male only behaviors:
Aggressive interaction
Clasping
Tagging Along
Takeover
Thrusting
An interaction between a male clasping a hermaphrodite and another male attempting to interfere
with the pair. These interactions involve bodily contact between males, such as pushing.
Male clasps the carapace of another clam shrimp with the first two pair of thoracic appendages.
Outcrossing is always preceded by this behavior. Males also clasp other males, as well as gravid
or unreceptive hermaphrodites at times.
One male is clasped to a hermaphrodite and another male clasps onto him forming a 'train'.
A male takes a hermaphrodite away from another male as a result of an aggressive interaction.
Male clasped to a hermaphrodite forces the lower portion of his body up into the hermaphrodite's
carapace near the paired ovaries and makes pulsating motions. Sperm transfer is assumed to be
taking place.
80 .-------------------------------------------------~
(/)
Z
o
:cc
&;
UJ
U)
III
o
70
60
50
40
30
LI. 20
o
';If!. 10
o
Feeding &
Swimming
Lying on Clasping
Bottom
Being
Clasped
II Hermaphrodites
[J Males
Out of
View
Digging
BEHAVIORS
Molting
77
Fig. 1. Behavioral time budget for an androdioecious clam shrimp Eulimnadia rexana. The bars indicate the average frequency of each
behavior when compared to the total number of behaviors observed. Darker bars represent behaviors performed by hermaphrodites. Lighter
bars represent behaviors performed by males.