Stomatopod Mating Habits
Mantis with Eggs by A. Scott Johnson
The male mantis struggles feebly against the female's tightening grip, its own raptorial appendages chopping weakly as its strength slowly ebbs. The large female jaws open and close, the male goes limp, and then....
Ooopss sorry! Wrong critter!
Stomatopod mating behavior varies considerably between different species, as befits a group of animals with such diverse habits. In this article we'll take a look at some representative mating habits in mantis shrimps, from the promiscuous systems practiced by species such as Oratosquilla to strictly monogamous stomatopods like Lysiosquillina.
First, some general info on stomatopod reproduction:
The life cycle of mantis shrimps involves an egg stage; a series of free-swimming, plankton-feeding larval stages; a series of immature (subadult) growth stages; and finally a sexually mature (reproductive) adult stage. Mantis larvae are efficient, scary-looking predators of the planktonic world, miniature ogres with fearsome raptorial appendages to make mama and papa proud.
In many stomatopods, the sexes associate only briefly during mating, and the females bear most of the costs of producing young. Since many mantis shrimps are solitary, one or the other sex has to search for a potential mate during mating. There is some risk involved in doing this, since a mantis shrimp far out of its home is potentially snack food for larger fishes. After finding a potential mate, an elaborate courtship ritual may be performed by the visiting mantis to assure the other that "love, not war" is the assignment of the day --- this ritual is particularly important in the case of those mantis shrimps who normally fight each other over a limited supply of potential homes.
During mating , the sperm of the male is briefly stored in the seminal receptacles of the female. The female extrudes her eggs and fertilizes them, stucking the eggs together using an adhesive secretion from special glands on her thorax. The egg mass is then carried by the front thoracic appendages and constantly cleaned and turned until they hatch. The female refrains from eating anything during the brooding process. In many mantis shrimps the male stands guard over the female before spawning, and only leaves to find another cavity when the female spawns. Finally, egg hatching occurs when the currents are strong enough to transport the larvae away from the shallow reefs or intertidal habitats of the adults.
In the smasher Gonodactylus bredini, both males and females may search for mates, although in the majority of times it is the male who does the searching. In this species, the female breeding cycle is very tightly coupled to the lunar cycle, and females may start searching for mates in order to assure that they can mate during the new moon tides when they are fertile (females in this species can store sperm, but can only produce one fertile clutch of eggs per mating/cycle). Females tend to select for males who are larger than themselves when a guest comes a-courting. After courtship, the male mates repeatedly with the female and then defends her and the nest cavity until the females extrudes her eggs. The male then leaves to search for a new cavity, probably because the old cavity may be too small to hold both male and female, as well as the eggs.
In the smasher Haptosquilla, the limited number of available cavities (possible homes) in their natural habitat heavily influences its mating habits. Competition for available living cavities is ferocious in this case. In this species, only males go out in search of females, and courtship may last for up to 30 minutes as the male has to convince the female of its "good" intentions (ie., "I'm a lover, not a fighter!", sort of thing). In addition, the female selectively choses males smaller than herself (again, probably to make sure she is not driven out of her home), and the male leaves immediately after mating.
The "swingers" of the stomatopod world include the spearer Oratosquilla, which lives off the coast of Japan, and where promiscuity in mating is the rule. Females mate repeatedly with males of any size, and they can store the sperm for many months after mating. On their end, males do not go to the trouble of guarding females but repeatedly wander around in search of more females. In this case, the fact that these spearers live in non-limiting burrows in the mud and thus do not compete for homes (as well as the fact that this critter lives in turbid waters where predation may be less of a factor) may contribute to this lifestyle.
Finally, the moral platform in mantis shrimps goes to the spearers of the genus Lysiosquilla, who form tight, monogamous relationships even before individuals are sexually mature. The males ambush fish that come too close to their burrows, and thus have larger eyes and raptorial appendages. The pair lives in sandy burrows that may be up to 10 m long. The lifestyle may have been selected for due to the fact that these mantis shrimps have reduced armor and are particularly vulnerable to predation if they have to leave their homes to search for mates. In this case the mantis live long and monogamous lives. Dr. Roy Caldwell notes that he has followed a monogamous pair of Lysiosquillina maculata for 20 years.
Christy J.H. and Salmon, M. (1991). Comparative Studies of Reproductive Behavior in Mantis Shrimps and Fiddler Crabs. Amer Zool 31:329-337.
Web Site Author: A. San Juan
Site Created February 3, 1998