Behaviour
1) Cleaning Fish Behaviour
Similarly to other cleaner shrimps, S. hispidus depend highly on their host to feed themself although they are scavengers to some degree and feed on dead organisms if present (Limbaugh et. al 1961). With the intention of acquiring food S. hispidus and commonly every cleaner shrimp are required to make itself visible and obvious when they are eager to clean.
To achieve this S. hispidus has been observed to execute a dancing behaviour where it place itself in a conspicuous spot near its home on the reef and move its antenna while moving side to side (Becker et. al 2006).
This behaviour so called dancing behaviour was first observed in a laboratory by introduction of a host fish in a tank where two S. hispidus can be observed from the other side. One of the shrimp was normally fed whereas the other was starved. The starved coral shrimp was observed performing the dance more often than the fed coral shrimp (two time more frequently). As a result, in return the host fish was paying much more attention to the starved shrimp and tried to collaborate with it more regularly (Becker et. al 2006).
The results observed in this experiment reveal that the dancing behavior seen in cleaner shrimp is used as a signal to the fishes and let them know that they are ready to commence the cleaning action, in other word to feed. S. hispidus uses its very large chelipeds and three sets of shorter maxillipeds, or claws, fragment and select food and ectoparasites from the hosts mouth compartment and gills.
After the cleaning job is performed the fish will swim away and S. hispidus will continue to dance if hungry or go back to his original habitat.
2) Mating Behaviour 
The molting cycle is crucial for the mating of S. hispidus.That is because mating in S. hispidus takes place only when the female is exposed in the ecdysis period. Females that have recently molt are soft and receptive to mating. They are attractive to males during the 24 hours following molting (Zhang et. al 1998). For successful mating, certain behaviours in which both the male and the female are involved are necessary. Those behaviour can be described using a five step approach.
First step which is called the antennule contact: The male gradually approaches the female and establish antenna contact. They touch each other with a waving movement of the claws.
Second, the female react by erecting her body. The female starts to turn around and bend her body raising her abdomen.
Third is the grasping step. The male get closer to the the female with its abdomen erected and grab the female against him
Fourth is the actual mating where the male turns himself 180 degrees to the female so that its head is beside the female’s tail.
Fifth is the spawning. The male moves away and the female starts to spawn approximately 15 minutes following the mating (Zhang et. al 1998).
Feeding Preferences of the Coral Shrimp, Stenopus hispidus, when no Host are Present.
Introduction
Stenopus hispidus or coral shrimp is worldwide distributed and live in crevices on reefs (Limbaugh et al., 1961). It is largely know to consume and remove injured and dead tissues, ectoparasites, and any food particles from fishes (Johnson, 1977). Feeding behaviour associated with the attraction of a fish have been studied and observed (Becker et al., 2006), suggesting that coral shrimp highly depend on their host for food. Coral shrimps are classified as scavengers and will readily feed on any dead animals and organisms when no host is available (Limbaugh et al 1961). The idea here was to test the feeding preferences of S. hispidus on different diets excluding the option of feeding on a host fish and clean. The experiment took place in Australia on the Great Barrier Reef, on Heron Island.
Materials and Methods.
In this study, three S. hispidus individuals have been used. Two of them were males in normal conditions, and the third shrimp was a pregnant female. We did not manage to collect more coral shrimps after 4 days of intense collection. Shrimps were kept isolated during three days and were not fed.
We set up a tank (100×80×40mm ) where four boulders of approximately 20×20×10mm were placed in the four corners of the tank. Among the four boulders, one was taken from the Heron Island reef and put directly in the tank. The three others were soaked in a bleaching solution for 2 hours to kill every living organism that could interact with the shrimps during the experiment. Out of these three boulders we attached algae to one of them, pilchard fish, Sardinops neopilchardus, was crushed in a little container with holes all over the top and placed underneath the second boulder, and for the last boulder crushed gastropods, Austrocochlea constrica, were placed in a container as describe before and placed underneath.
The shrimps were individually placed in the middle of the tank at the start of each replication test. Each individual has been tested three times, and the different boulders were randomly re-located in the tank after each trial. Individuals were given an hour in the tank, after what they were removed and ‘no feeding’ was recorded. If feeding, the diet they consume was recorded and the shrimp was removed directly to keep them starve.
Results
The first shrimp, the pregnant female, has not been observed to feed in the three trials. During the first trial, the shrimp was swimming around and quickly hide under the untouched boulder, but did not feed. During the second two trials it was not even hiding but just swimming around the tank
The second shrimp first feed on the fish diet after 19m34s. Following this, no feeding was observed in the second trial, and finally feed on fish diet again in the third trial after 33min25s.
The third shrimp fed on fish in the first trial after 44m53s. During the second trial, it was hiding and acting around the algae boulders, although feeding signs were not obvious. Lastly, in the last trial, it was feeding on fish diet again after only 13m36s.
Table 1 is summarising the results found in this experiment.
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Natural diet
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Fish diet
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Gastropod diet
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Algae diet
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Not feeding
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Shrimp 1
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Trial 1
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Trial 2
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Trial 3
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Shrimp 2
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Trial 1
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Trial 2
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Trial 3
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Shrimp 3
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Trial 1
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Trial 2
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Trial 3
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Table 1: Representation of the feeding preferences of three Stenopus hispidus individuals when exposed to different diets. Coloured boxes correspond to the diet chosen by each individual for each trial.
Discussion
One of the shrimp was pregnant which can highly affect the results of the experiment. This shrimp have been recorded to hide under boulders once and to swim around the tank most of the time. This behaviour was not observed in the two other shrimp. It suggests that the shrimp was probably familiarising with this new environment. It is important to note that on the night following the experiment the pregnant coral shrimp spawn. The behaviour observed is thought to be related to spawning, the shrimp was possibly searching a location to set up and spawn. Nevertheless, the results obtained by observing the feeding behaviour of this shrimp were not significant as a major factor has to be considered.
The second individual shows a preference for fish over algae, gastropod and community associated with the untouched boulder. This shrimp was either feeding on fish or not feeding at all. The same results were found for the third individual. It is hard to make general conclusions and statement based on just to individuals. The experiment need to be repeated with a much larger number of individuals to improve the accuracy and significance of the test. However, based on those two individuals, when feeling hungry and no host are present, coral shrimps seem to prefer fish over gastropods, algae and natural communities that appear on its surrounding boulders habitat.
References
Becker et al., (2005), “Cleaner Shrimp Use a Rocking Dance to Advertise Cleaning Service to Clients”, Current Biology, vol. 15, pp. 760-764.
Johnson, V. R., (1977), “Individual recognition in the banded shrimp Stenopus hispidus(Olivier)”, Animal Behavior, vol. 25, pp. 418-428.
Limbaugh, et al. (1961), "Shrimps hat Clean Fishes", Bulletin of Marine Science, vol. 11, no. 1, pp. 237-257. |