The only benthic species of the marine dinoflagellate Polykrikos, P. lebourae. Note: This is the heterotrophic form with some food bodies and is devoid of plastids so is rightly designated Polykrikos herdmanae n. sp. (2).

"Polykrikos (from Greek “poly” - many, and “krikos” – ring or circle) is one of the genera of family Polykrikaceae that includes athecate pseudocolony-forming dinoflagellates. Polykrikos are characterized by a sophisticated ballistic apparatus,[2] named the nematocyst-taeniocyst complex, which allows species to prey on a variety of organisms. Polykrikos have been found to regulate algal blooms as they feed on toxic dinoflagellates. However, there is also some data available on Polykrikos being toxic to fish (1). Polykrikos was first seen in 1868 by Uljanin and was mistakenly considered as a metazoan larva of a turbellarian flatworms. In 1873 Butschili re-examined the specimen and concluded that the cell was an unusual ciliate, and Bergh later, in 1881, clarified Polykrikos dinoflagellate affinities" (1).

"The most distinctive feature of the athecate dinoflagellate genus Polykrikos Butschli is the formation of multinucleated ‘pseudocolonies’ comprised of an even number of zooids that are otherwise similar in morphology to individual dinoflagellates in external view. The zooid sulci are fused together, but every zooid has its own cingulum and pair of flagella. A pseudocolony often has half the number of nuclei than it has zooids. Trichocysts, nematocysts, taeniocysts, mucocysts, and plastids have all been reported from different members within the group. The genus currently comprises four species: P. schwartzii Bu ̈ tschli — the type species, P. kofoidii Chatton, P. lebourae Herdman, and P. grassei Lecal. The morphological features, systematic history, and taxonomic issues within the polykrikoid dinoflagellate species is summarized elsewhere (Hoppenrath and Leander 2007). All known polykrikoid species are marine and planktonic, except P. lebourae, which inhabits sandy interstitial environments" (2). Some species are heterotrophic while others are photosynthetic (3).

In my sample from the sandy benthos of the estuary Accabonac Harbor, I found numerous polykrikoid dinflagellates whose morphology and their being found in the sandy benthos are both consistent with P. lebourae. According to Hoppenrath and Leander (1), P lebourae has both photosynthetic and heterotrophic forms. These workers historically discussed P. lebourae: "Polykrikos lebourae has pseudocolonies convisible borders between zooids (Balech 1956; Dragesco 1965; Herdman 1923; Hoppenrath 2000; Fig. 1A—D). Moreover, although a heterotrophic form has been described and is included in the original species description, P. lebourae was in most cases described as photosynthetic (Balech 1956; Dragesco 1965; Herdman 1923; Hoppenrath 2000). A potential to disassemble into smaller zooid stages with only one nucleus, as described for P. kofoidii and P. schwartzii (e.g., Nagai et al. 2002), has not been recorded for P. lebourae. The heterotrophic form of P. lebourae (almost) always contains complex extrusomes or ‘taeniocyst—nematocyst complexes’, which have been occasionally observed in photosynthetic forms as well (Dragesco 1965; Hoppenrath 2000). It is unclear whether the photosynthetic and heterotrophic forms of P. lebourae constitute two separate lineages or represent variability within one species (1).

 They studied both forms of this only known marine benthic (sand-dwelling) species of Polykrikos, P. lebourae, using light and electron microscopy and molecular phylogenetic analyses. Their abstracted findings were: " The pseudocolonies usually contained eight integrated zooids and two nuclei. Pseudocolonies consisting of four or five zooids and one nucleus were observed for the first time for this species; some of these reduced pseudocolonies contained plastids, while others were heterotrophic and contained taeniocyst—nematocyst complexes. The ultrastructure of the plastids in P. lebourae did not conform to the organization of thylakoids and enveloping membranes present in the peridinin-containing plastids of other photosynthetic dinoflagellates (i.e. stacks of 3 thylakoids and 3 outer membranes). Instead, the plastids in P. lebourae had thylakoids arranged in pairs and appeared to be enveloped by only two membranes(2).

The "molecular phylogenetic data using small subunit rDNA demonstrated that the photosynthetic and heterotrophic forms of P. lebourae represent two distinct clades. The more inclusive clade containing both forms of P. lebourae was most closely related to heterotrophic polykrikoids, namely P. kofoidii. These results led us to conclude that the photosynthetic and heterotrophic forms of P. lebourae are in fact two distinct lineages, and the heterotrophic form is described here as Polykrikos herdmanae n. sp."(1). Thus Hoppenrath and Leander erected a new species for the heterotrophic form of P.lebourae: Polykrikos herdmanae n. sp.

This is the heterotrophic form with nematocysts and some food bodies and is devoid of plastids so is rightly designated Polykrikos herdmanae n. sp. (2).

1. https://en.wikipedia.org/wiki/Polykrikos
2. Morphology and Phylogeny of the Pseudocolonial Dinoflagellates Polykrikos lebourae and Polykrikos herdmanae n. sp. Mona Hoppenrath and Brian S. Leander. Protist, Vol. 158, 209—227, April 2007
3. CHARACTER EVOLUTION IN POLYKRIKOID DINOFLAGELLATES. Mona Hoppenrath and Brian S. Leander. J. Phycol. 43, 366–377 (2007). DOI: 10.1111/j.1529-8817.2007.00319.x