Dataset: RHB_ostracods
Deployment: RHB0603

Ostracods were identified by microscopic examination of specimens for previously-documented diagnostic morphological characters. Identification was done of living specimens prior to preservation in 95% ethanol. For DNA extraction and processing details, see Nigro et al (2016).

P.I. Notes:

The total number of species sorted from the samples and identified during the cruise was 80. There will have been several which could not be identified onboard ship so the final number will probably approach 90. This includes 6-8 species that are either certainly or probably novel, which all came from the deep tows. These new species increase the number of species currently known to inhabit the Atlantic (140) by nearly 6%. For example three individuals of the seven specimens belonging to the deep-living genus Bathyconchoecia are each representatives of previously undescribed species; two of the others are strikingly sculptured specimens of a species that has previously been collected at depths of 4000m off NW Africa, but still remains undescribed. The same is true for the 20 or so specimens of a Fellia species taken in the deep nets at stations 4 and 5.

A number of other notable species, which are rare in oceanographic collections, were taken in the deep tows, including:

1. Gigantocypris dracontovalis, which is smaller than its better known and more abundant congener G. muelleri (of which only a single specimen was recorded) and has golden reflectors in its large naupliar eyes;
2. Mollicia tyloda that has only been recorded a couple of times since it was first described by G.W.Muller in 1906, and
3. Macroconchoecia macroreticulata and M. spinireticulata only recently described from deep water in the NE Atlantic, which were both abundant in the deeper MOC-10 samples.

Seventeen of the species were collected at all five stations, but a further four that were not recorded at station 4 are likely to be in those samples, increasing the number of ubiquitous species to 21. Eleven species were collected for the first time at station 5, including the largest of the halocyprids, Alacia valdiviae, which is over 6 mm long and bright red in color, and so unlikely to have been overlooked previously.

There were considerable changes in the species dominance. Orthoconchoecia secernenda that had been the commonest large ostracod was replaced by O. atlantica, Halocypris globosa by Halocypria inflata, and Orthoconchoecia secernenda by O. atlantica.

Before the cruise began, I set a target of 50 species to be sequenced. Thanks to the large number of species that made their first appearance at station 5, the target was exceeded. In all, 58 species were picked out for sequencing and these are the first halocyprids ever to be sequenced. They represent 39% of the species known to occur in the whole of the Atlantic (now 148, which includes the new species collected on the cruise) and 25% of the global inventory of planktonic ostracods (230). Hence we have already achieved substantial progress towards providing a powerful identification tool for planktonologists studying this abundant group that has largely been overlooked because of the problems associated with their identification.

** For station 3 cast 5, changed instrument from MOC-10 to MOC-1 because the station number and cast number don't match. Net could have spent most of its time at 200 m. None of nets worked right.