Charles R Seaborn 
gressive behavior and associated skel- 
etal armature are much more devel- 
oped in shrimps limited by nonexpand- 
able holes in coral or rock. 
The giant mantis shrimp discovered 
by Charles and his friends was a Ly- 
siosquilla glabriuscula. The species 
in the genus Lysiosquilla include some 
of the largest known stomatopods, at- 
taining sizes of up to fifteen inches. 
Characterized by toothed claws and 
broad black-and-white or black-and- 
yellow bands across the body, these 
species are rare, and little is known 
of their habits other than that they 
dig vertical burrows in sandy sub- 
strates. 
The discovery of this large Lysio- 
squilla was intriguing since we had 
been studying one of the smallest spe- 
cies of sand-dwelling mantis shrimps, 
Nannosquilla schmitti, in a nearby 
bay. Adults of the latter species are 
white and only about three-fourths of 
an inch long. When placed on a fine, 
sandy substrate, one of these petite 
shrimps will begin digging with its 
pleopods — abdominal flaps that beat 
rapidly, propelling a cloud of sand be- 
hind the animal. As a depression is 
formed, the shrimp arches the middle 
of its back downward; then it dips 
the anterior part of its body into the 
depression, gathers a load of sand in 
its maxillipeds, and flings the particles 
away, thereby enlarging the hole. This 
action is repeated until only the tip 
of the animal’s tail clings to the rim 
of the burrow while its long, thin body 
hangs head-first down into the hole. 
Turning sinuous somersaults inside the 
burrow (which is scarcely wider than 
its body), the shrimp continues to 
gather sand, then emerges head-first 
at the surface, and flings the sand 
onto the small mound accumulating 
outside the entrance. Often the shrimp 
hesitates, peering in various directions 
with its mobile stalked eyes, which 
rotate independently as it surveys the 
surroundings, then somersaults again 
into the narrow burrow. The large Ly- 
siosquilla had presumably excavated 
its burrow in the sandy bottom of the 
bay in a similar manner. 
Recent studies conducted by Ray- 
mond Manning of the Smithsonian In- 
stitution and myself have shown that 
lineages of small stomatopods evolve 
more rapidly than lineages of large 
stomatopods. A few closely related 
species of Lysiosquilla are found in 
all the world’s oceans, suggesting an 
old and slowly evolving group. Nan- 
nosquilla, however, is found only in 
the Americas, and all fourteen small 
species of this lineage have diverged 
into distinct species in either the east 
Pacific or west Atlantic regions since 
the elevation of the Central American 
land bridge about three million years 
ago. We found that these trends in 
evolution held up in all groups of sto- 
matopods. 
I thought about this varied evolu- 
tionary history as I lay on the sandy 
bottom of the bay peering at the iri- 
descent yellowish green eyes, rudder- 
like antennal scales, and folded rap- 
torial appendages of an eight-inch-long 
mantis shrimp. It returned my stare, 
rotating first one eye, then the other, 
appearing unconcerned in its two-inch- 
wide burrow. Charles had been di- 
rected to the shrimp by friends who 
were living on a sailboat in the area. 
Keen observers of the organisms living 
around them, they had watched the 
shrimp as it cleaned its burrow and 
performed its daily routines. As al- 
ready suggested, mantis shrimps learn 
rapidly, and this individual had 
quickly become accustomed to its ob- 
servers. Our friends had supplied us 
with some pieces of squid, and re- 
assured by the serene appearance of 
the shrimp watching me, I extended 
my hand and the piece of squid toward 
41 
