The Cladocera of Suffolk.

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SUFFOLK CLADOCERA CHECKLIST

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THE CLADOCERA OF SUFFOLK ADRIAN CHALKLEY The aim of this article is to stimulate interest in the recording of Cladocera or water fleas in our county. In order to do this it is best to outline the ecological importance of these relatively overlooked and unappreciated animals, this will be followed by a brief glimpse of their geological past and some details of general Cladoceran life histories. Information about recording and a provisional Suffolk species list concludes the introduction and finally there is a review of all species in the British list showing those that have been recorded in Suffolk or may be possible to find in the future, whilst putting them in context with national records as far as is known. Cladocera and the Ecology of Freshwaters Water fleas (Crustacea: Branchiopoda: Cladocera) occupy a wide range of niches globally and are some of the most successful invertebrates found in freshwater ecosystems. Cladocerans can be found within the zooplankton of all types of freshwaters from puddles to large lakes, from ditches to major rivers. As a group they are of prime importance within aquatic food webs across the globe often occurring in high abundance, showing a marked degree of morphological diversification and species richness. Whilst there are some species which predate other zooplankton the majority of cladocera feed on phytoplankton; to be eaten in turn by higher invertebrates, amphibians and fish. Unlike most freshwater plankton, Cladocera have the distinction of being widely known to the general public as ‘Daphnia’. In reality this recognition can be more of a disadvantage since the Daphnia are but one of the 14 families that make up the Cladocera Crustacea. In this article I will outline some of the reasons for studying these tiny, but vital, members of the Freshwater food chain. Cladocera through time The cladoceran fossil record is neither very extensive nor, until recently, very well researched and the pre-quaternary record is generally relatively sparse. After all they are tiny, the majority being less than 1mm with an exceptional few reaching 5 to 6mm, and are difficult to identify from compression fossils in sedimentary rocks. However recent research mostly using fossil ephippia (resting eggs) has extended this sparse record back into the Jurassic (Van Damme & Kotov 2016). These tantalizing micro fossils show that the basic cladoceran body plan and life history was well established at least before the majority of dinosaurs appeared. Then having survived the mass extinction which wiped out the dinosaurs cladocera have continued to the present day in a remarkably unbroken manner. Generalised Cladoceran life history For a large proportion of the year dipping a fine mesh net into most water bodies will rarely catch anything but female water fleas. These are parthenogenetic females which spend their short lives feeding and giving birth to many more parthenogenetic females. Overwintering females or resting eggs may well be in relatively small numbers but exploit spring blooms of phytoplankton. This enables large populations to quickly establish which are exploited in turn by a host of carnivorous members of Trans. Suffolk Nat. Soc. 56 (2020)


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The Cladocera of Suffolk. by Suffolk Naturalists' Society - Issuu