Glaucus spend their entire lives in the open oceans and so not much is known about their living conditions. It can be expected though that as they live in temperate waters it is likely they would be prone to violent storms.

These nudibranchs are at the will of the currents and wind and it is these forces that push them in-land and onto coastal beaches throughout the year. The specimen studied for this page were collected at the Gold Coast Spit mid-May of 2015 but are found all throughout the tropics of Queensland during summer months, including Herron Island.

It would be easy to assume that these tiny delicate little slugs would have significant bodily harm after being pushed around and tumbled in the shore break. This is not the case. During extreme aggravation Glaucus constrict themselves into atight ball, release their air bubble so that they sink and escape the worst ofthe waves without major harm. Although they look delicate they very rarely experience dramatic damage and if they do they are able to regenerate most areas of the body.

These slugs are at the mercy of winds and currents in the open ocean however they are able to swim by flapping their ‘arms’ in a coordinated manner to rotate themselves in a clockwise or anticlockwise direction. It would seem though from observation that they are unable to use their appendages or tail like structures to move in a purposeful or directional way and simply flap about until they bump into either a prospective mate or prey. As seen below.

Blue sea slugs use rhinophores (from the Greek words rhino meaning nose and phore meaning carrier) to essentially smell their way to their venomous prey in the open ocean. These smelling receptors send the information to the slugs’ brain, just as our olfactory system does for humans, and then they attempt to travel in the direction the scent is coming from. Once they have found their prey they latch on with razor sharp teeth and immediately begin to feed on the living organism.This would be a challenge of not for the design of their jaws and teeth which allow them to latch onto even the most gelatinous of victim. Their teeth are made of a tough chiton which they also steal from one of their prey; the violet snail. All of their tiny teeth (denticles) are serrated and lock together like azipper would once Atlanticus closes its jaws. 

Sea swallows are unique in the way they defend themselves. These sea slugs hunt other venomous pelagic organisms which drift nearby such as the violet snail (Janthina janthina), the blue button jellyfish (Porpitaporpita) as well as blue bottles (Physalia utriculus) and the nutilise their stinging cells as their own after eating them. The stolen stinging cells are known as kleptocnide and are transported through the gut without being digested in a still unknown mechanism to be stored in the cerate.

Cerate (figure 8) – are blood filled finger like appendages on the Glaucus found on the end of its appendages. As with other Aeolids, Glaucus cerate contain a duct connected to the digestive tract which terminates with a cnidosac at the very tip of the‘finger’. This sac is where the nematocysts from the Physalia are stored for defence. Interestingly the cerate of Glaucus are not in fact blue as they appear but actually transparent; the cause of the dark blue colouration comes from the blue Physalia on which they feed.

Glaucus have another unique personality trait, they are veracious predators and it has been theorised that they may in fact be cannibalistic. This behaviour will be explored in more detail to hopefully prove or disprove their response to interaction with another of the same genius.

The experiment to investigate these behaviours was very simple in design; place the two Glaucus in an enclosed environment with some food and observe the behaviour.

Prior to filming, the two species were kept separated in lightly filtered tanks with Physalia so that they could feed. The tanks had no artificial lighting and the water was supplied directly from where the specimen were collected; the Gold Coast Sea Way. The water was maintained at approximately 25 degrees using aquarium heaters. It was noted in the 24 hours before the experiment was conducted that Glaucus seem to be more active at night although they were still willing to feed during the day. For this reason the experiment was conducted in the evening hours around 6pm so that the subjects would hopefully be more active and light was used with a filter so as to not disturb the natural behaviours.

The hypothesis was that Glaucus were only cannibalistic if there was a shortage of their preferred food source, Physalia and thus if Physalia was available to Glaucus then there would be no aggression toward others of the same family. 

This did not prove to be the case, it seems that Glaucus will eat anything it bumps into and has no preference over Physalia to its own kind. As can be seen in the video below, when Glaucus Marginatus comes into contact with Glaucus Atlanticus there are two behaviours that occur. The first shown is unexpected, with Marginatus exposing its penis upon contact with Atlanticus (figure 10) suggesting that these two species would be able to produce hybrid offspring if Atlanticus was willing to accept Marginatus. Marginatus continued this reproductive behaviour for nearly 5 minutes before reverting to a much more aggressive approach toward Atlanticus. Its behaviour changed to that of a predator and Marginatus began to attack and eat Atlanticus. The attacking Marginatus focused on the tips of the cerate where the nematocysts are condensed, eating first the dark blue tips of its victim. The result of the 15 minute attack can be seen in the image below (Figure11).

This is an interesting experimental outcome in itself as it is now confirmed that Glaucus are in fact cannibalistic. However, based on the unexpected behaviour seen during this experiment of Marginatus presenting its penis for copulation, it is proposed that experimentation into the hybridization of the two species could be investigated and their behaviour in open water further explored.