Loricate choanoflagellates (Acanthoecida) from warm water seas. VIII. Crinolina Thomsen and Diaphanoeca Ellis

Jette Buch Østergaard,Helge Abildhauge Thomsen

doi:10.1016/j.ejop.2021.125791

Jette Buch Østergaard, Helge Abildhauge Thomsen

Open Access

https://doi.org/10.1016/j.ejop.2021.125791

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Abstract

The loricate choanoflagellate genera Diaphanoeca Ellis and Crinolina Thomsen encompass a total of ten species. The majority of these are recorded from the warm water regions reported on here. A distinct morphological dichotomy characterizes the genus Diaphanoeca as currently circumscribed. The species distribute themselves within a ‘D. grandis subgroup’ and a ‘D. pedicellata subgroup’ distinguished on e.g., the position of the protoplast inside the lorica chamber and the elaboration of the anterior projections. We are, while awaiting in particular further molecular evidence, taking a conservative approach and abstain from dealing with the subgroup issue at the generic level. The examination of material from the warm water regions of the world’s oceans has resulted in the description of D. sargassoensis sp.n., D. pseudoundulata sp.n., and D. throndsenii sp.n., and a thorough re-examination of D. undulata. Species of Crinolina share multiple features with in particular the D. grandis species subgroup. It is yet relevant, both in a morphological and molecular perspective, to retain the genus Crinolina which remains unambiguously defined based on the posteriorly open lorica. A high level of agreement is found when contrasting morphological and molecular based phylogenetic schemes.

Highlights

In an ongoing effort (Thomsen and Østergaard 2019a, Thomsen and Østergaard 2019b, Thomsen and Østergaard 2019c, Thomsen and Østergaard 2019d, Thomsen and Østergaard 2019e, Thomsen et al 2020a, Thomsen et al 2020b) to provide a first comprehensive overview of warm water loricate choanoflagellate diversity, based on a traditional microscopical approach, we here deal with species of the tectiform genera Diaphanoeca Ellis, 1929, and Crinolina Thomsen, 1976
A lorica mesh has, to the best of our knowledge, not been reported from species of Crinolina. Considering that such a lorica lining has been repeatedly observed in D. grandis and the fact that C. isefiordensis is in essence a posteriorly truncated version of the D. grandis lorica it is surprising, despite having access to numerous highresolution images, that we have been unable to pinpoint a lorica membrane in either species of Crinolina
The apparent absence of a lorica lining membrane, and the flagellar anomaly perhaps indicates that feeding behaviour in species of Crinolina somehow deviates from what is meticulously described from D. grandis (Nielsen et al 2017)

Summary

Introduction

In an ongoing effort (Thomsen and Østergaard 2019a, Thomsen and Østergaard 2019b, Thomsen and Østergaard 2019c, Thomsen and Østergaard 2019d, Thomsen and Østergaard 2019e, Thomsen et al 2020a, Thomsen et al 2020b) to provide a first comprehensive overview of warm water loricate choanoflagellate diversity, based on a traditional microscopical approach, we here deal with species of the tectiform genera Diaphanoeca Ellis, 1929, and Crinolina Thomsen, 1976. Species allocated to these genera are fairly large and, in some cases, even exceeding 100 mm in length.

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