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2 Posts tagged with the crustacea tag
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Different ideas of the relationship between the crustacea (crabs, barnacles, copepods and others) and insects have been discussed at length over the past century. The emergence of more and better DNA information is allowing the evolutionary relationships to be explored and clarified.


Ronald Jenner (Zoology) co-authored a first phylogenomic test of the recent hypothesis of a sister group relationship between hexapods (insects) and remipede crustaceans. Numerous data and testing of different interpretations led the authors to robustly find hexapods and remipedes as sister groups.


Remipede crustaceans were first described as Carboniferous fossils in the 1950s (around 310 million years old).  However, living species have been discovered since 1979, living only in underground aquifers connected to the sea. They are slow-moving with relatively basic segmented body plans, but can have specialised characteristics such as poison fangs and advanced sense of scent, important for securing prey in their unusual habitat.

 

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A Remipede from Mexico

 

The paper looks at the idea of the Pancrustacea - a large group containing both crustaceans and insects.  The data support the idea that the Pancrustacea can be divided into two major groups.  In the first are the marine decapods (crabs, prawns and lobsters), barnacles and copepods.  In the second group are found the freshwater Branchiopoda (such as the familar waterflea Daphnia), the Remipedes and the insects.  This supports the insects as a part of the Pancrustacea, possibly as part of a subgroup that moved from shallow marine environments to specialist freshwater, groundwater and terrestrial habitats.

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von Reumont, B. M., Jenner, R. A., Wills, M. A., Dell’Ampio, E., Pass, G., Ebersberger, I., Meyer, B., Koenemann, S., Iliffe, T. M., Stamatakis, A., Niehuis, O., Meusemann, K. and Misof, B. Early online. Pancrustacean phylogeny in the light of new phylogenomic data: support for Remipedia as the sister group of Hexapoda. Molecular Biology and Evolution (doi:10.1093/molbev/msr270)  Abstract

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There is considerable international interest in the impacts of invasive species on biodiversity.  Species are described as being invasive when they cause impacts on biodiversity outside their normal range as a result of introduction or spread as a consequence of human activity.  This impact can lead to loss of native species, spread of disease, impacts on native habitats or other effects.  They are often described as invasive alien species. In the marine environment this can happen as a result of transport by ships in ballast water, or migration through new sea routes such as the Suez Canal.


Recent work from the Museum provides more evidence that the flood of invasive Red Sea species entering the Mediterranean via the Suez Canal includes fish parasites.  Dr Hoda El-Rashidy (who obtained her PhD while researching in the Zoology Department at the NHM) and Prof Geoff Boxshall (Zoology) have described two more new species of parasitic copepods from Egyptian Mediterranean waters off the coast of Alexandria.

 

Their hosts, two species of Red Sea rabbitfish (Siganus luridus and S. rivulatus) have established populations in the Mediterranean. Invasive species often leave their parasites behind, due to the sampling effect of passing through a small founder population, but the continuing discovery of invasive parasitic copepods combined with the absence of any genetic evidence of a bottleneck in their host populations, highlights the remarkable scale of the faunal invasion of the eastern Mediterranean.

 

International concern and efforts to monitor and control impacts of invasive species are significant, with an EU Strategy,  a major focus from the Convention on Biological Diversity, and a UK Non-Native Species Secretariat.  Even on a city level here in London there is coordination on selected species such as Japanese knotweed and various invasive crayfish.


El-Rashidy, H.H. & Boxshall, G.A.  2011. Two new species of Parasitic Copepods (Crustacea) on two immigrant fishes from the Red Sea of Family Siganidae. Systematic Parasitology 19: 175-193. DOI 10.1007/s11230-011-9298-7