Palaeontologists have concentrated their attention on those families which are well represented in the fossil record. For some obscure reason few zoologists have taken any interest in ostracods, so despite their abundance, the pelagic species which have such a limited fossil record have received little attention.
G. O. Sars, 1865 described the three species which are common around Norway. Subsequently, much of the pioneering descriptive work was carried out by Claus (e.g. Claus, 1874; Claus, 1890; Claus, 1894) and G. W. Müller, 1894; Müller, 1906; Müller, 1912 on material collected in the Mediterranean and on the major expeditions by German research vessels. Unfortunately, their descriptions were written in archaic German and are extremely difficult to understand even for those who are fluent in the language. Brady and Norman, 1896 dabbled in the planktonic species but the mesh of their nets was too coarse to retain any but the largest species.
The first attempt to look at the vertical distribution of the planktonic ostracods was by Fowler, 1909, who sampled in the Bay of Biscay. The Prince of Monaco made extensive collections in the North Atlantic which were worked up by Granata and Caporaccio, 1949. Unfortunately, the samples, which were dispatched to Italy during the Second World War, disappeared while in transit during an air-raid on Milan railway station. Amazingly, they turned up several months later, but in rather a bad state and some of the material had become muddled; some of the depth records now seem suspect in the light of modern sampling.
Another land-mark study was the treatise by Skogsberg, 1920 whose weighty volume is a excellent cure for insomnia, but includes the description of the nomenclature for the limb setation which is now generally adopted for the halocyprids. The Atlantic was also well sampled during the Dana Expedition, and the reports by Poulsen, 1962; Poulsen, 1969a; Poulsen, 1969b; Poulsen, 1973; Poulsen, 1977 make an important contribution to the zoogeography of the group. It is only in the last couple of decades that the extensive collections made from R. R. S. Discovery ( R.R.S. Discovery Map) have made it possible to produce a fully comprehensive illustrated account of the species inhabiting the waters around Britain.
In the descriptions of the individual species the stations at which each individual species was found are listed before the link to the map.
Abundance of Ostracods
In oceanic waters, planktonic ostracods are surprisingly abundant for such a poorly known group. Our ignorance of them has been partly the result of their relative scarcity in the surface wind-mixed layers of the water column at temperate and higher latitudes during much of the year. But the obscurity of many of the original taxonomic descriptions by Müller and Claus, and the absence of designated type material have also contributed. Moreover, much of these authors' original collections were either lost during the Second World War or have subsequently deteriorated so much, that little of it remains useful for taxonomic comparisons.
In tropical latitudes, the ostracods are often abundant throughout the water column, especially in the surface layers at night. In the upwelling regions along the Gulf of Oman in the North-west Indian Ocean they are numerically dominant.
Around the British Isles
Around the British Isles, although they are frequently the second-most abundant group of macroplankton below the surface 100m, their small size means that their contribution to the biomass of the standing-crop of pelagic community is relatively small. Their high abundance is maintained throughout the deep water column; even at depths of 4000m in the Porcupine Seabight, south-west of Eire they remain second in order of abundance.