Short Communication |
Corresponding author: Karolina Fučíková ( karolina.fucikova@gmail.com ) Academic editor: Endymion Cooper
© 2015 Karolina Fučíková.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Fučíková K (2015) A new record of the rare alga Pachycladella P. C. Silva (Chlorophyceae) in New England. PhytoKeys 56: 19-27. https://doi.org/10.3897/phytokeys.56.6268
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A rarely reported taxon, the microscopic green alga Pachycladella, was found in a pond in Connecticut. Due to an unresolved taxonomic debate within the genus, the species-level identity of the newly discovered population cannot be determined with absolute certainty. However, according to the currently accepted classification the Connecticut specimens best match Pachycladella zatoriensis, heretofore only known from Europe. The find represents not only the first record of Pachycladella in Connecticut, but also in the entire New England region. This study highlights the need for continuing floristic surveys even in regions previously well explored.
Connecticut, floristics, microalgae, plankton
USA’s New England region, which encompasses the states of Connecticut (CT), Maine, Massachusetts, New Hampshire, Rhode Island and Vermont, has certainly received plenty of floristic attention over the past century. Freshwater algal floristic works in this region, however, have dwindled in recent years. In 1984, a 1020 pages long list of New England algal records and the related literature was compiled by
The genus Pachycladella was originally described from Palisades Interstate Park in New York by
Pachycladella and the species within it have a somewhat convoluted taxonomic history (
The present study contributes a new record of Pachycladella cf. zatoriensis from the USA, and is the first report of the genus Pachycladella for CT and for New England. Given the past taxonomic confusion it is difficult to interpret all historical records with certainty, but it is possible that this study also represents the first record of P. zatoriensis in the United States. Continuing survey studies will be necessary to understand the occurrence patterns of Pachycladella and its species.
In 2014 and 2015 I conducted a survey of selected lakes, streams, and wetlands in northeastern CT and recorded the algal diversity in these habitats. Samples were collected using a 10 µm mesh plankton net, stored in small Ziploc bags, and examined microscopically using an Olympus BX60 microscope with Nomarski DIC optics equipped with an Olympus DP25 digital camera (Olympus Imaging America, Center Valley, PA, USA). The Olympus CellSens software was used to capture images and measure cell dimensions. Georeferenced records of observed algae, accompanied by micrographs where possible, have been deposited in iNaturalist (https://www.inaturalist.org/projects/freshwater-algae-of-new-england). Most algal species were identified using North American and New England taxonomic literature (
On August 4th 2015, I collected a plankton sample from a pond on Bonemill Rd., Storrs, CT (41°48'12", -72°16'48") and in it found a population of a species I had not seen in any previous collection, including a 2014 sample from the same pond. I identified the alga as Pachycladella umbrina based on the unmistakable reddish-brown cell wall processes (Fig.
Light micrographs of Pachycladella cf. zatoriensis found in Connecticut. A gross morphology of a vegetative cell B same cell as in A, with focus on process apices C small vegetative cell with a clearly bifurcated process apex (enlarged in the inset) D an unusual cell with a fifth, irregularly placed and colorless appendage E high-magnification micrograph showing the hollow bases of cell wall processes as well as their dark coloration F same cell as in E with focus on the cell surface and attachment of the fourth process. Scale bars represent 10 µm in all images.
I collected an additional sample on August 12th. In both samples, Pachycladella occurred infrequently but consistently: I usually saw 5-10 specimens on every slide. Other algae abundant in the planktonic community included nonmotile colonial chlorophytes resembling Chlamydocapsa planktonica (West & G.S. West) Fott, members of the chlorophycean family Hydrodictyaceae, the large dinophyte Ceratium hirundinella (O.F. Müller) Dujardin, alongside diatoms (e.g., Cymbella C. Agardh, Eunotia Ehrenberg, and Melosira C. Agardh), synurophytes (Mallomonas Perty and Synura Ehrenberg), and euglenoids (Euglena Ehrenberg, Lepocinclis Perty, Phacus Dujardin, and Trachelomonas Ehrenberg).
The observed Pachycladella cells were spherical and 8–11.5 µm in diameter, and possessed one chloroplast with a single pyrenoid (not always visible). Cell wall was protracted into four (rarely five, Fig.
Globally, Pachycladella has been reported broadly but infrequently. For some time, the genus and its sole species were only known from North America (e.g., as noted by
Based on past records and newly collected data,
In the USA, Pachycladella has been heretofore reported from Alabama, Kentucky, New York, North Carolina, Tennessee, and from the Great Lakes region, and has been noted to be rare or uncommon (e.g.,
The population of Pachycladella newly found in CT morphologically matched the original description of P. umbrina except for having appendages consistently in a tetrahedral orientation, rather than being mostly cruciate (
The rarity of Pachycladella combined with difficult-to-interpret past records makes species-level taxonomy in this genus quite tricky. DNA barcode data are available only from SAG 10.85, and therefore genetic comparisons of morphologically and geographically distinct populations are not possible at present. A morphological study aided by a molecular phylogeny would help deciding which traits should be considered taxonomically informative. Because even morphologically distinct taxa can be non-monophyletic (e.g.,
It is possible that this interesting alga had been overlooked in past floristic studies or misidentified as another taxon, despite its distinct morphology. Pachycladella could conceivably be mistaken for Treubaria triappendiculata Bernard, a species reported from Massachusetts by
It may be somewhat surprising to see a new genus record in a region so well studied – and particularly in CT, which of all the New England states likely has the best documented freshwater algal microflora, perhaps only rivaled by Rhode Island (
Despite past taxonomic confusion and uncertainty about the classification and specific diversity of Pachycladella, this study presents a new record of an alga that matches the original generic description perfectly, best matching the species P. zatoriensis. As such, it is the first record of Pachycladella in New England and possibly the first record of P. zatoriensis in North America.
The author was supported by the NSF grant DEB-1354146. Many thanks for constructive comments on the manuscript go to Drs. Pavel Škaloud and Endymion Cooper.