Proboscia macintyrei sp. nov. (Bacillariophyceae) from the subarctic Pacific, and new observations on P. eumorpha

Abstract

Light and scanning electron microscope observations on filtered water samples, collected during the subarctic Pacific cruises of the R/V Vema (VEMA 20; May–July 1964) and R/V Robert D. Conrad (CONRAD 10; June–August 1966), have revealed the presence of two seasonal forms of Proboscia macintyrei sp. nov. The ‘spring’ and ‘winter’ cells of the new species are both solitary (lacking claspers), with the ‘spring’ form possessing a much shorter and more domed proboscis. Proboscia macintyrei usually differs from other living Proboscia species by possessing 1–2 thin, long polar spinulae at the proboscis tip, usually situated on one side, to the left of the longitudinal slit (rimoportula). The proboscis of the P. macintyrei ‘winter’ form normally bears longitudinal crease-like ridges, but without the thinner transverse ribs of P. subarctica. The morphology of these two species suggests they are living representatives of the ‘barboi’ lineage. Proboscia eumorpha is sometimes present on the filters, with the ‘winter’ form being documented herein in detail for the first time.

Keywords:

• diatom ecology
• distribution
• membrane filters
• polar diatoms
• seasonality

Acknowledgements

The authors would like to thank the captains, crews and scientists of the R/V Vema and R/V Robert D. Conrad for their help in acquiring the samples, and particularly Andrew McIntyre. We are also grateful to Kyoko Hagino for sending us the filter samples. Finally, we would like to thank the two reviewers for their helpful comments, which significantly improved our manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental data

Supplemental data for this article can be accessed at https://doi.org/10.1080/0269249X.2021.1872708

Additional information

Funding

This research was carried out under the auspices of the ‘Super Warm Earth Project’, organized by The Center for Advanced Marine Core Research (CMCR) of Kochi University, and is funded by the Joint Usage/Research Center for Drilling Earth Science (JURC-DES), Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.