Friday Fellow: Portuguese Man o’ War

by Piter Kehoma Boll

And so we finally reached the 100th Friday Fellow! In order to commemorate, we will have two Friday Fellows today, just as we had during the 50th one. And to start I chose a cnidarian that always caught me attention.

Living in the Atlantic Ocean and known popularly as Portuguese man o’ war, its binomial name is Physalia physalis, both words derived from the Greek word for bubble, physalis. And the Portuguese man o’ war is, in fact, like a floating bubble with some stuff attached, or at least it looks like that.

A Portuguese man o’ war lying on the beach. Photo by Anna Hesser.*

Most people may think that the Portuguese man o’ war is a jellyfish due to its looks, but it is actually part of another group of cnidarians, the siphonophores. Their body is not a single individual, but rather a colony of several smaller animals, called zooids, which are speciallized to have different functions within the colony and cannot live separately. They are all derived from the same embryo, thus being clones from each other.

The upper portion of the Portuguese man o’ war has a gas-filled sack, which is called the pneumatophore and is the original organism derived directly from the embryo. Below the pneumatophore there are several different kinds of organisms, such as nectophores for swimming, dactylozooids for defense and capture of prey, gonozooid for reproduction and gastrozooids for feeding. The long tentacles, which reach more than 10 m in length, are composed by dactylozooids and fish for prey throughout the water.

Floating on the sea. Photo by Regine Stiller.*

As other cnidarians, the Portuguese man o’ war has nettle-like cells which sting and inject venom. In humans, the venom usually cause pain and let whip-like marks on the skin where the tentacles touched. Sometimes more severe complications will results and in rare cases it may result in death.

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References:

Stein, M. R.; Marraccini, J. V.; Rothschild, N. E.; Burnett, J. W. (1989) Fatal portuguese man-o’-war (Physalia physalis) envenomation. Annals of Emergency Medicine 18(3): 312–315.

Wikipedia. Portuguese man o’ war. Available at <https://en.wikipedia.org/wiki/Portuguese_man_o%27_war&gt;. Access on June 16, 2017.

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Friday Fellow: Divergent Dinobryon

by Piter Kehoma Boll

Let’s return once more to the troublesome and neglected protists. This time I’m bringing you another tiny but beautiful alga, more precisely a golden alga. Its name is Dinobryon divergens and as usual there is no common name, so I invented one by simply translating the scientific name, thus I’ll call it the divergent dinobryon.

The divergent dinobryon is part of the class Chrysophyceae, commonly known as golden algae. Measuring about 50 µm in length, it lives in temperate lakes around the world and forms colonies composed of about 6 to 50 ovoid cells that are surrounded by a vase-like shell (lorica) of cellulose, as seen in the picture below.

A branching colony of Dinobryon divergens. The cells are clearly visible inside the lorica. Photo by Frank Fox.*

During colony formation, an original cell divides and one of the two daughter cells slides to the opening of the lorica and starts to construct a new one. It starts by creating the base of the lorica, which has a funnel shape and is attached to the inner wall of the original lorica. With further divisions, the colony starts to grow in a tree-like form. And the most interesting part is that the cells have two flagella and use them to swim, pulling the whole colony through the water.

As with other golden algae, the divergent dinobryon produces an internal siliceous structure that is globose, hollow and has a single opening connecting to the outside. This structure is called a statospore or stomatocyst and allows the cell to enter a resting state (cyst). The statospore is an important structure to help distinguish different species of golden algae.

The divergent dinobryon is a mixotrophic organism, meaning that it feeds by photosynthesis and by ingesting food too, especially bacteria. Kind of an interesting fellow, don’t you think?

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References:

Franke, W., & Herth, W. (1973). Cell and lorica fine structure of the chrysomonad alga, Dinobryon sertularia Ehr. (Chrysophyceae) Archiv für Mikrobiologie, 91 (4), 323-344 DOI: 10.1007/BF00425052

Herth, W. (1979). Behaviour of the chrysoflagellate alga, Dinobryon divergens, during lorica formation Protoplasma, 100 (3-4), 345-351 DOI: 10.1007/BF01279321

Karim, A., & Round, F. (1967). Microfibrils in the lorica of the freshwater alga Dinobryon New Phytologist, 66 (3), 409-412 DOI: 10.1111/j.1469-8137.1967.tb06020.x

Sandgren, C. (1981). Characteristics of sexual and asexual resting cyst (statospore) formation in Dinobryon cylindricum Imhof (Chrysophyta) Journal of Phycology, 17 (2), 199-210 DOI: 10.1111/j.1529-8817.1981.tb00840.x

Sheath, R., Hellebust, J., & Sawa, T. (1975). The statospore of Dinobryon divergens Imhof: Formation and germination in a subarctic lake Journal of Phycology, 11 (2), 131-138 DOI: 10.1111/j.1529-8817.1975.tb02760.x

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Friday Fellow: Deep-sea marr

by Piter Kehoma Boll

Looking like some sort of tribal mystic rattle, our newest Friday Fellow comes from the deep waters in the northern hemisphere. Its scientific name is Marrus orthocanna, and I adapted a common name as “deep-sea marr”. I think it sounds cool.

A magic rattle from the deep sea. Photo by Kevin Raskoff.

The deep-sea marr is a siphonophore cnidarian, and as all siphonophores, it is a colonial organism rather than a single individual. It is composed by several specialized organisms (zooids) linked together by a long “stem” and unable to live independently. It is a free-swimming organism, swiming in a pulsative way through the dark deep sea waters.

At the front or upper side of the colony is the pneumatophore, a gas-filled float that is the primordial organism in the colony, the one that originated directly from the embryo. After it, there are several bell-shaped translucent organisms, the nectophores, which are specialized in locomotion, making the colony move by contractions. The last part of the body, the siphosome, contains a series of different zooids, including individuals specialized to capture prey, to digest food and to reproduce.

The deep-sea marr is found mainly in Arctic waters, but sometimes occurs more southwards, down to the Mediterranean Sea. It may grow to several meters in length and its diet most likely includes small crustaceans. It is a weird, but certainly beautiful creature.

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References:

EOL –  Encyclopedia of Life: Marrus orthocanna. Available at: < http://eol.org/pages/1005745 >. Access on April 21, 2016.

Wikipedia. Marrus orthocanna. Available at: <https://en.wikipedia.org/wiki/Marrus_orthocanna >. Access on April 21, 2016.