In an earlier post I described the fascinating world of soldier aphids. There are also some aphids that might, with a little bit of imagination, be called sailor aphids. I first came across the phenomenon of aquatic aphids when I was doing my PhD at the University of East Anglia in the late 1970s. At the time I was working on a beautiful little aphid, the bird cherry-oat aphid, Rhopalosiphum padi , which characteristically has a rusty-brown bum.
At the time, the foyer of the Biological Sciences building was graced by the presence of a large aquarium. One day whilst waiting for my lab mates to join for the long trek to coffee, I was amusing myself by teasing the fish and noticed a number of aphids feeding on the water-lilies. Two things piqued my curiosity, one they vaguely looked like my beloved study aphid and secondly they were feeding on the submerged stems, rather than on the leaves. It turned out that they were indeed related to my aphid, I identified them as Rhopalosiphum nymphaeae the water-lily aphid, or more prosaically, the reddish-brown plum aphid! They are known to be able to feed underwater for some time as they are able to trap air on their bodies using specialised hairs and when large numbers of aggregate on a submerged stem, the trapped air bubble sometimes covers the entire colony. They can also apparently walk on water. Unfortunately I did not have a camera with me and have so far not been able to find a picture demonstrating this phenomenon or their ability to remain submerged whilst feeding. They are regarded as a bit of pest by some gardeners although they can also be used as a biological control agent.
Another aphid which might more appropriately be called a sailor aphid, is Pemphigus trehernei, which feeds on sea asters in the salt marshes of Western Europe, including those on the Norfolk coast in East Anglia (Foster & Treherne, 1975). As you might expect given its habitat, it is able to survive being submerged during high tides, but what I really find amazing is that the first instar nymphs disperse by floating away on the sea, hoping to bump into another suitable sea aster on which to establish a new colony (Foster & Treherne, 1978). Optimistic indeed, although I guess as they are still with us it is effective enough. There is yet another intertidal aphid, Staticobium limonii, which is also able to withstand being submerged by high tides, but does not have the same ability as P. trehernei, 50% of them being dead after 20 hours and all being dead after a mere 48 hours under water, compared with the 400 hours plus that some 10% of P. trehernei can manage (Foster & Treherne, 1976). A pretty good attempt at holding their breath I reckon and a good reason to describe them as sailor aphids, although submariners might be a better description. And of course, yet another reason why I love aphids so much.
Centre, T.D., Dray, F.A., Jubinsky, G.P. & Grodowitz, M.J. (1999). Insects and Other Arthropods That Feed on Aquatic and Wetland Plants. United States, Department of Agriculture, Agricultural Research Service Technical Bulletin 1870
Foster, W.A. & Treherne, J.E. (1975). The distribution of an intertidal aphid, Pemphigus trehernei Foster, on marine saltmarshes. Oecologia, 21, 141-155.
Foster, W.A. & Treherne, J.E. (1976). The effects of tidal submergence on an intertidal aphid, Pemphigus trehernei Foster. Journal of Animal Ecology, 45, 291-301.
Foster, W.A. & Treherne, J.E. (1978) Dispersal mechanism in an intertidal aphid. Journal of Animal Ecology, 47, 205-217.