Memories from 2004
Walter Dioni Cancún - México
With some notes on marine algae, diatoms, foraminifers, peritrichs, and mystery worms


The first image is not mine. It's the artistic work of Lucy Nieto and I've used it with her authorization (and modified it somewhat) from her page in Flickr. But it fits very well in the mood of my old night at the beach. Photomicrographs were shot with the 0.4 MP camera on my National Optical microscope. I took the other pictures with my Canon Powershot A300. Most of the photomicrographs and the most important part of the text were posted, in 2004, at Microscopies, a French Forum for Microscopy.

Key words: Cancún, coralline sand, formaminifers, polysiphonia, cladophora, cothurnia, Vaginicolidae

The night before, there was no moon. Seated on the tenuous sand of the beach, with the dim lights from the distant city over my shoulders, I had the sensation of being inside a black diamond. The absolute transparency of the atmosphere let me enjoy the incessant and caressing murmurs from the small and soft waves, and of the gilded twinkle of the stars on the black and perfect smoothness of the firmament.

A pair of distant tourist ships were reflecting their lights on the wavelets, and, as if it was brought by the marine waves, a faint sound of music was arriving to me intermittently. I really enjoyed that moment on my first vacation in several years. And, feeling me happy, I sank my hands in the still lukewarm sand.

And, inevitably, my biologist conscience appraised the smoothness of the grains, and evaluated the slow, constant and timeless work of the waters on the dead coral skeletons, rolling them, time and time again, with infinite patience, to produce this strange sand that never burns you. Over which it is possible to walk with the naked feet for many hours, in the heat of the noon, with a torrid sun, without feeling nothing else than a comfortable tepidity.

Of course! I took a sample to examine it later! And dreaming about the incredible blue of the oligotrophic Caribbean waters, which, I hoped would be waiting for me the following morning, I went away to sleep.

The wind began to blow at night. At dawn the waves struck and crowded on the beach, with a dull and threatening rumor of military drums. With the first light, gray and threatening shredded clouds could be seen, flowing swiftly in the sky over the lead colored sea. My day was going to ruin. But just towards mid-morning the sky was clear, the wind asleep, and the only witness of the nocturnal fury which remained was the still turbulent sea, with an opaque bluish-milky color due to the amount of suspended fine sand.

I was seated again on the desolate beach that began to be filled with visitors. The crest of the waves, now calmed, had an untidy aspect, by the seaweed that floated whole or in pieces, uprooted by the violence of the waves at night. The sea did not invite to a visit.

But for my grandsons this was really indifferent. And soon they were jumping around me, with their small buckets full of trophies robbed from the waters.

The sample tools

I quickly saw the delicate hairs of the red and green seaweeds, and .... those cylindrical gelatinous bodies. 'Bad Waters', grandfather, 'bad waters'!, (Mexicans call 'bad waters' those containing jellyfish). Were the boys thinking that the small gelatinous pieces were the little stinger jellyfishes which often invade waters near the shore? What would they be? Because certainly, jellyfish they were not.

Of course, I kept some samples to examine them later. Biology and microscopy have priority over vacations!!! I was aware of these contradictory desires before coming to the beach.


Seated, later, at the microscope I first examined the seaweeds. I could identify them quickly. The red one was a Polysiphonia of which I show an exicata of Polysiphonia and the most characteristic traits of its structure.

Images above in order: 1 – A Polysiphonia branch with  tetrasporangia. 2 – High power tetrasporangia view.
3 – long and thin, very transparent trichoblast at the end of a branch.
4 – end of the branch, oblique lighting, with epiphytic diatoms


Jean Marie Cavanihac and Jean Parmentier, have presented two beautiful photographic studies of this genus, which can be seen HERE and HERE

The green alga was a Cladophora. That I also show in the following pictures. See the characteristic chloroplasts and branching of the thin filaments.



Most interesting, on the seaweeds, were the epiphytes. Abundant diatoms and protozoa use them as a substrate. I believe that the festive spirit of the previous night celebration had influenced its behavior, because, evidently, they imitate the fire-works (image below) that had arisen intermittently from the tourism ships. Mexicans love the fire-works, and they always include them in the tourist's 'Mexican nights'. Apparently, the exuberant architecture of those agglomerations is due to a special diatom of the genus Climascosphenia,) (thanks to Dominique Voisin for confirming the identification).



Clusters of diatoms fixed to the algae and a lateral view of one Climacosphaenia.


There were also some Vorticella and Epystilis, peritrich protozoans, scarcely distributed in the spaces that the diatoms left free.

But the most interesting and abundant guest hid itself, imitating water by its transparency. In tiny transparent glasses, lodged transparent tiny bodies, extended like trumpets, with the widened end surrounded by a circular crown of cilia, generally clinging by pairs in their crystalline cockpits, firmly adhered to the algae by short stalks.


Six images of the transparent protozoa on its transparent substratum.


They prefer to adhere to the trichoblasts, also themselves transparent, of Polysiphonia. The corresponding genus is Cothurnia, and belongs to a group of peritrichs that normally amateurs have difficulties in identifying.


One individual colored electronically to make it more evident.

I present in an Appendix a key, which should allow the careful microscopist to clearly identify the genera of the family Vaginicolidae, which are relatively frequent in the samples taken from fresh water or from marine water. The genera Cothurnia and Pyxicola , are quite often mistaken, as it can also happen with Pseudocothurnia and others.

According to the illustration in the on-line facsimile of Kahl’s 'Wimpertiere oder Ciliata', perhaps the Cothurnia of Cancúns Polysiphonia can be identified as Cothurnia ovata.


As I often remark, it's very difficult for an amateur to apply the correct specific name. The original descriptions are not very often available, the suitable publications are generally in scientific journals to which the amateur does not have access,
protozoologists use now special silver staining techniques to distinguish the details of the ciliar system, and they generally resort to the scanning electron microscope to obtain suitable three-dimensional images.


As is the case for rotifers (see my article in the November 2008 issue of Micscape), microscopes with Differential Interference Contrast (DIC - Nomarski), and the electronic flash, could offer spectacular images of these cryptic inhabitants of my seaweeds. So far my cothurnias must be satisfied being known as Cothurnia cf. ovata. The abbreviation cf, interposed between the genus and the species means: 'Confer', that is 'Compare it with' or, efectively stating, it is a declaration of the biologist who implies: ' this species probably is ......, but I am not sure'.


Finally, I dedicated my attention to the sand and I had my moments of excitation when I could identify between the blunt and light colored grains the characteristic shells of some dead Foraminifers, (with an exception, a single live specimen of Allogromia). But the small sample did not show a great species richness.

1 – Allogromia sp. alive. 2 and 3 – Probably Quinqueloculina. 4 – Probably Elphidium


Nevertheless, gliding smoothly over the glass slide, between the small and irregular coralline grains, it appeared a vermiform organism of doubtful affiliation. So doubtful that it demanded days for me to reach a conclusion on its probable lineage. I enclose here the first snapshot that I took of it. And I will share next month my research on its micro-anatomy, even if that allowed me a taxonomic approach still less exact than that of my cothurniae. Sometimes this happens.





Some of them are very rare, i.e. Cothurniopsis, Pseudothuricola and Pachytroca


1 (2)

Flat lorica , laid down and cemented to the substrate. It does not have an operculum. It can have a short ascending neck, and, generally, it lodges two inhabitants that adhere directly to the end of the lorica


2 (1)

The lorica is more or less vertical, it is not laid down on the substrate. With or without a stalk


3 (8)

The front opening of the lorica is open when the infusorian is contracted


4 (5)

The lorica is cylindrical or vase shaped, but does not have a stalk and its end is directly joined to the substrate


5 (4)

The lorica has a stalk. It can be only external, or have a portion, inside the lorica, that joins to the end of the protozoa


6 (7)

Lorica remains open when the protozoan contracts


7 (6)

The infusorian has adhesions to the rim of the lorica's mouth and this is closed by folding of the edge towards the interior


8 (3)

As the infusorian contracts the lorica is closed by means of a secreted thick cover, a thin membranous cover, or a cytoplasmic thickening



The lorica is closed by a cytoplasmic thickening of the forward edge


10 (9)

The lorica is sealed by a membranous cover, adhered to the mouth rim, or to the inside of the wall. Or by an pseudochitinous operculum


11( 12)

Lorica closed by a hard pseudochitinous cover, (operculum) attached laterally to the forward end of the peritrich


12 (15)

The cover is a membrane adhered internally, towards the 2/3 of the lorica's height. It could be overlooked if special attention is not put on it


13 (14)

Lorica without a stalk, and adhered to the substrate by a curved or flat base


14 (13)

Lorica with a stalk. Sometimes a long stalk, and even partially internal


15 (10)

The membrane of the cover articulates on the rim of the lorica



  Comments to the author, Walter Dioni , are welcomed.


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