BEHAVIOUR

The Behaviour of Gonodactylaceus falcatus has theoretically co-evolved as a product of its ecology and in turn, various morphological and physiological adaptations. Behaviours such as feeding, movement, agonistic interactions, sexual reproduction and courtship all reflect these adapatations and its habitat.

FEEDING



MATING AND REPRODUCTION

The Behaviour of Gonodactylaceus falcatus in courtship rituals and mating.

You would think that mating between Mantis Shrimps would be a dangerous affair….. and, you would be right.  In defending its cavity home, the Mantis Shrimp both male and female will engage in elaborate threatening behaviours - puffing up its various maxilliopeds and pushing its carapace forward. This is all toappear … larger. Studies have shown that size is directly proportional to power amplification of its raptorial appendages, thus bigger here is better (Patek etal., 2008).  Conspecific in-fighting is a regular occurrence in the world of this top predator (Caldwell and Dingle,1976).   And it appears that the females are equally as aggressive as males. One study finding that out of 20/ 22 encounters, females start the fight (Caldwell and Dingle, 1972).

So, how does she let him know she’s there on friendly terms? One would expect ritualistic behavioural displays if potential mates are to copulate and not engage in the usual battle tactics which predominate male – female interactions (Caldwell and Dingle, 1969).  No one said it was easy!  Studies show that males seem receptive to copulation at any time, however females have subtle indications that they are receptive (Serene, 1954, Caldwell and Dingle, 1969). Usually, the area around the ventral side of the telson becomes darker, enlarged with the ovaries and the hepato-pancreas complex and is notably not connected to molting (Schone, 1961). Difficult signs to look for however.  The biggest giveaway however, that she is receptive is that she is receptive … usually this just means she does not fight off his advances and her explosive weapon system becomes idle.

The courtship sequence then usually goes something like stills adapted from the video by Roy. L Caldwell above. From Dingle and Caldwell’s 1969 research, they observed that females would copulate with another male within some minutes.  Males on the other hand, showed no interest in another female even after 24 hours and some for up to a week. 

And where is the complex courtship display in mantis shrimp? Fancy tail displays as in peacocks or lyrebirds or flashy camoflague shows as in cuttlefish or the hopping and well-choreographed dances of some insects.  It seems this complex communication involves simply… not fighting. As Caldwell and Dingle (1972) hypothesise, this simple courtship is a product of living in a cavity. There is limited light for fancy displays and not much room for elaborate dances (Johnson, 1969, Hazlett, 1966).

The simplicity of the mating process is in stark constrast to the vagaries of female spawning and subsequent caring. The defence of eggs comes at a high energetic cost to the mother (Caldwell,1973).  Forgoing food outside the cavity is one such cost.

In sum, Caldwell and Dingle (1972) surmise that the stomatopod’s behavioural repertoire has coevolved with four key aspects of its ecology. Firstly cavity living, cavity defence, courtship and maternal obligations, all of which take place within the little safe haven the stomatopod calls home.

MATERNAL EGG BEARING

After copulation, the male will return to the burrow to share a cavity until the eggs are laid. The female lay circa 50,000 eggs (Ruppert, Fox and Barnes, 2004). Both sexes will take turns in defending its entrance. This behaviour is known as mate guarding and represents the singular instance when two stomatopods share a burrow (Caldwell and Dingle,1972). During this time of cohabitation, the pair may copulate several more times.

After she has laid her eggs, she will banish him unless she is unable to intimidate him, i.e. if he is far larger than she. This period between mating and the appearance of eggs lasts around 10 days (Caldwell and Dingle, 1972).  While the female remains in the cavity with her eggs, she gently agitates them, repeatedly turning them over with her maxilipeds.  This is believed to keep the eggs free from parasites algae and/or ciliates (Kinzie, in Caldwell and Dingle,1972). Now alone in the cavity, the female will defend her territory but must drop the eggs in the back of the hole first.

Interestingly, if presented with an egg mass both males or females will carry them but only for a short period, after their short attention span runs out they will either drop them or eat them (Caldwell and Dingle, 1972).