# Prorocentrum | Algae ID

Source: https://algaeid.com/identification/prorocentrum/

[ID guide](https://algaeid.com/identification/) › Dinoflagellates

# *Prorocentrum* sp.

A common benthic genus. Some species make okadaic acid in the wild.

I find benthic *Prorocentrum* in sand samples from nearly every tank I look at. Most of the time they sit at low levels and most people never notice them, but they can bloom. I do not have enough data to say how hard a *Prorocentrum* bloom is to deal with, and aquarists report different experiences.

**About toxins.** Some *Prorocentrum* make okadaic acid, which causes diarrhetic shellfish poisoning in the wild. The genus falls into two major groups: a more symmetrical one, and one that is less symmetrical and often has a little spike (like some of the cells in the pictures below). The *Prorocentrum* we see in home aquaria are not thought to make okadaic acid, but it is very hard to say conclusively that any species does *not* make toxins, because it can be hard to get them to express toxins in the lab. I have not met anyone who has observed toxic effects from *Prorocentrum* in their aquarium.

## How to recognize it

- **Size and shape.** Individual oval, round, or heart-shaped cells, larger than small-cell [Amphidinium](https://algaeid.com/identification/amphidinium/) (roughly 20 to 60 µm). Large-cell Amphidinium can be close in size, so use the other clues too.
- **A large central pyrenoid.** A big, perfectly round circle in the middle of the cell.
- **The nucleus (dinokaryon).** It fans out behind the pyrenoid.
- **Movement.** Usually none, or the tumbling swim typical of most dinoflagellates. They do *not* glide along surfaces like Amphidinium.
- **The apex.** *Prorocentrum* cells have two halves (valves). One valve has a notch at the apex, and the two different flagella come out of pores in that notch.

People often confuse *Amphidinium* and *Prorocentrum*, since both are oval. Size, the pyrenoid, the motion, and the two narrow folds at the top of an *Amphidinium* cell are how to tell them apart.

*Prorocentrum*: mostly two big plates (valves). The grooves have shrunk into a notch at the apex, and there is no upper half.

![Prorocentrum cells at 630X](https://algaeid.com/img/pro-2925.jpg)

An undescribed species of *Prorocentrum* isolated from a marine aquarium, 630X. A large central pyrenoid is visible and the dinokaryon fans out below it.

![Prorocentrum cells at 630X](https://algaeid.com/img/pro-2928.jpg)

Same isolate, 630X. The pyrenoid is the large round structure in the middle of each cell.

![Two Prorocentrum cells, one focused on the pyrenoid and one on the nucleus](https://algaeid.com/img/pro-dinokaryon.jpg)

An undescribed *Prorocentrum* from a home aquarium (collected April 2012 by a marine aquarium hobbyist), 630X on a Zeiss Axioskop with a Canon EOS 5D Mark II. The cell rests on its left valve while the microscope is focused through the right valve, which is missing a notch at the apex. In *Prorocentrum* taxonomy the plates arranged in that notch matter, and the two different flagella emerge from pores there. The upper cell has the pyrenoid in focus; the lower cell has the dinokaryon in focus. The suture between the valves shows as a halo around the lower cell.

![Oval Prorocentrum cells with central pyrenoids](https://algaeid.com/img/prorocentrum-photo-1.jpg)

Prorocentrum in close-up: oval cell with a round central pyrenoid. Image courtesy of a hobbyist.

![Oval Prorocentrum cells with central pyrenoids](https://algaeid.com/img/prorocentrum-photo-2.jpg)

A field of Prorocentrum cells. Image courtesy of a hobbyist.

![Oval Prorocentrum cells with central pyrenoids](https://algaeid.com/img/prorocentrum-photo-3.jpg)

Prorocentrum cells, a second field. Image courtesy of a hobbyist.

## More species

### *Prorocentrum levis*

Often seen in stacked clusters, with large central pyrenoids that look segmented.

![Prorocentrum levis](https://algaeid.com/img/plevis-2678.jpg)

Stacked clusters of *Prorocentrum levis*. Large central pyrenoids are visible.

![Prorocentrum levis](https://algaeid.com/img/plevis-2679.jpg)

*Prorocentrum levis* at 630X. The central pyrenoid is segmented.

![Prorocentrum levis](https://algaeid.com/img/plevis-2652.jpg)

*Prorocentrum levis* at 630X.

![Prorocentrum levis](https://algaeid.com/img/plevis-2662_cropped.jpg)

*Prorocentrum levis* at 630X, cropped.

### *Prorocentrum hoffmanianum*

Light micrographs from low to high magnification, then scanning electron micrographs. Species identification of *Prorocentrum* often depends on the pores in the plates and the plates in the apical notch, which you cannot see with a light microscope.

![Prorocentrum hoffmanianum at 10X](https://algaeid.com/img/phoff-10x.jpg)

*Prorocentrum hoffmanianum* at 10X magnification.

![Prorocentrum hoffmanianum at 40X](https://algaeid.com/img/phoff-40x.jpg)

*Prorocentrum hoffmanianum* at 40X magnification.

![Prorocentrum hoffmanianum at 630X](https://algaeid.com/img/phoff-630x.jpg)

*Prorocentrum hoffmanianum* at 630X magnification.

![SEM of Prorocentrum hoffmanianum](https://algaeid.com/img/phoff-sem-1500.jpg)

*Prorocentrum hoffmanianum*, scanning electron micrograph at 1500X. Scale bar 10 µm.

![SEM close-up of the apex of Prorocentrum hoffmanianum](https://algaeid.com/img/phoff-sem-6800.jpg)

Scanning electron micrograph at 6800X showing the apical notch and the pores in the thecal plates of *P. hoffmanianum*. Scale bar 10 µm.

### An undescribed *Prorocentrum* from an aquarium

This is the isolate shown above, collected from a hobbyist's aquarium and photographed at several magnifications.

![Prorocentrum sp. at 10X](https://algaeid.com/img/prorocentrum-sp-10x.jpg)

Prorocentrum sp. at 10X magnification.

![Prorocentrum sp. at 20X](https://algaeid.com/img/prorocentrum-sp-20x.jpg)

Prorocentrum sp. at 20X magnification.

![Prorocentrum sp. at 40X](https://algaeid.com/img/prorocentrum-sp-40x.jpg)

Prorocentrum sp. at 40X magnification.

![Prorocentrum sp. at 60X](https://algaeid.com/img/prorocentrum-sp-60x.jpg)

Prorocentrum sp. at 60X magnification.

![Prorocentrum sp. at 630X](https://algaeid.com/img/prorocentrum-sp-630x.jpg)

Prorocentrum sp. at 630X magnification.

### A newer aquarium: *Prorocentrum arenarium*?

In 2012 a hobbyist sent me this one, from an aquarium only a few months old. Snails and a sand-sifting goby would not graze on it, and he thought some snails died after grazing on it. I tentatively identified it as *P. arenarium*, but I could not be sure from pictures alone.

![Living Prorocentrum cell](https://algaeid.com/img/arenarium-live.jpg)

A *Prorocentrum* isolated from a new aquarium in 2012 (tentatively *P. arenarium*), living cell.

![Prorocentrum left valve](https://algaeid.com/img/arenarium-left.jpg)

Left valve of the same isolate.

![Prorocentrum right valve](https://algaeid.com/img/arenarium-right.jpg)

Right valve of the same isolate.

### A variety from culture collections

In 2011 I bought a variety of dinoflagellates, mostly *Prorocentrum* species, from culture collections. They show how different *Prorocentrum* cells can look, and that they are flat: some are pointed, some round, and some carry a spine. The species were not recorded in my notes.

![Pointed oval dinoflagellate cell](https://algaeid.com/img/culture-2572.jpg)

A pointed oval cell, one of several *Prorocentrum*-type dinos I bought from culture collections in 2011. The species was not recorded here.

![Oval cell with a central pyrenoid and pores along the rim](https://algaeid.com/img/culture-2682.jpg)

Another culture-collection cell: a larger oval with a central pyrenoid and a row of pores along the edge of the plate.

![Pale oval cell with an apical notch](https://algaeid.com/img/culture-2726.jpg)

A paler oval cell. The notch at the apex (at the bottom of this picture) is where the grooves and flagella are crammed in.

![Slender pointed dinoflagellate cell with a spine](https://algaeid.com/img/culture-2617.jpg)

A slender, pointed cell with a spine at one end.

![Slender dinoflagellate cell with a spine and a flagellum](https://algaeid.com/img/culture-2728.jpg)

A slender cell with a spine and a trailing flagellum.

![Round dinoflagellate cell with a thick wall](https://algaeid.com/img/culture-2734.jpg)

A round cell with a thick wall. Cultures often contain cells in different stages like this.

![Oval dinoflagellate cell with orange-red bodies](https://algaeid.com/img/culture-2744.jpg)

A cell with orange-red bodies inside, as seen in older or stressed cultures.

### Scanning electron microscope views

The scanning electron microscope shows what you cannot see in an ordinary microscope: the pores in the plates, and that the cell is a flat disc when seen from the edge.

![SEM of a Prorocentrum cell seen edge-on](https://algaeid.com/img/sem-edge-on.jpg)

A scanning electron micrograph of a *Prorocentrum* seen from the edge. It is flat, a thin disc made of two plates. Scale bar 10 µm.

![SEM of a Prorocentrum cell from the face](https://algaeid.com/img/sem-oval-1.jpg)

The same kind of cell seen face on, with the pores in its plate. Scale bar 10 µm.

![SEM of a spiny Prorocentrum cell](https://algaeid.com/img/sem-spiny.jpg)

A scanning electron micrograph of a pointed *Prorocentrum* with a spine at one end. Scale bar 10 µm.

### Fluorescence

![Fluorescence micrograph of Prorocentrum with blue nuclei and red chloroplasts](https://algaeid.com/img/micans-dapi.jpg)

Epifluorescence microscopy of *Prorocentrum micans* stained with DAPI. Nuclei appear blue from the DAPI; chloroplasts glow red from autofluorescence. The characteristic bi-lobed nucleus is visible.

## Video from another aquarist

A home-aquarium sample with *Prorocentrum*, shared with me in 2018.

[Video: Prorocentrum from a home aquarium](https://www.youtube.com/watch?v=eOgmZGuhFQc)

Prorocentrum from a home aquarium [Watch on YouTube](https://www.youtube.com/watch?v=eOgmZGuhFQc)