Stomatopod Biology

A Pictorial Primer on Stomatopod Sex

Click on the pics below to view detailed images. Narrative and pictures courtesy of Dr. Roy Caldwell.

Odontodactylus mating.

Pair of Odontodactylus scyllarus copulating.

"Only a few species of stomatopod that I have studied are promiscuous and mate readily in captivity. Those that
mate almost any time a male and female are introduced are Odontodactylus sycllarus, Gonodactylus smithii, and
Pseudosquilla ciliata. Other species appear to have specific periods of female receptivity just before she lays her
eggs. You can usually tell if a female is going to mate by examining her cement glands. If they are packed with a
white material, she is getting ready to reproduce and probably will mate.

"Even in the promiscuous species, mating doesn't always go smoothly and a fight may break out at any time. If you
try to introduce two animals, have net handy to intervene if they start fighting."


Scanning electron micrograph of the sex organs of a small Gonodactylus

"Stomatopods have internal fertilization just like mammals and like marsupials, they have a pair of penises. Each penis is attached to the inside base of the last pair of walking legs. Often you can see these tubes hanging down between the legs. In Pseudosquilla ciliata and Odontodactylus scyllarus, they are dark in color and about a third of the length of the leg, so they are easy to see. In some other species, they are clear an a bit harder to get a look at. The presence of the penises makes it much easier to sex a male than a female, so if you are sure there are no penises, you have a female.

"Stomatopod penises are erectile just like mammals. When the male is ready to mate, they become slightly longer
and much stiffer (They are usually quite flaccid.). During copulation, the male mounts the female, grasps her
carapace with his maxillipeds, and partially turns her over so that her ventral thorax is pressed against his ventral
thorax. In other words, they mate belly to belly. He then makes several vigorous thrusts to insert the penises and
then pumps rapidly for several seconds until he ejaculates. The ejaculate comes out like toothpaste out of a tube
and often after copulation you can see threads of ejaculate hanging out of the female's gonopores.

"Between the female's first pair of walking legs are her gonopores, the opening into which the male inserts his
penises. The eggs will also be extruded through these openings."



Male penises

Female gonopores


Squilla empusa eggs

Lysiosquillina sulcata eggs

Gonodactylus chiragra eggs

Females with Eggs

"Once the animals have mated, the female eventually will lay eggs. We are not sure how long they can store sperm, but I have recorded fertile eggs from females that had not mated for three months.

"The eggs are extruded through the oviducts and out through the gonopores. Near the genital openings, they are
exposed to the stored sperm where fertilization takes place. Cement glands on the ventral thorax produce a
gummy cement that the female uses to mold the eggs in to a mass - usually a disk-shaped glob that she can carry
in her maxillipeds, but can put down if necessary. The eggs are cared for by the female for from 10 days to a
couple of months. When they hatch, in gonodactylids the female remains with the larvae for another week. In most other species, the larvae leave the cavity or burrow almost immediately.

The female Squilla empusa on the upper right was photographed while laying eggs and molding them into a disk.


Web Site Author: A. Sunjian
Site Created February 3, 1998
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