Tag Archives: beautiful sea creatures

Friday Fellow: Sea Swallow

by Piter Kehoma Boll

As the second species of today, I’m bringing a terrible but beautiful predator of the Portuguese man o’ war, the sea swallow Glaucus atlanticus, which is, in my opinion, one of the most beautiful sea creatures.

Glaucus_atlanticus

Isn’t it a magnificent creature? Photo by Sylke Rohrlach.*

Also known as blue dragon, blue glaucus and many other names, the sea swallow is a small sea slug that measures up to 3 cm in length as an adult. This species is pelagic, meaning that it lives in the open ocean, neither close to the bottom nor close to the shore.  Although it is found in all three oceans, genetic evidences indicate that the populations from the Atlantic, the Pacific and the Indian oceans have diverged more than 1 million years ago.

The sea swallow has a gas-filled sac in the stomach that makes it float upside down in the water, meaning that its ventral side is directed upward. The wide blue-bordered band running along the body, as seen in the picture above, is the slug’s foot. It’s dorsal side, which is directed downward, is completely white or light gray.

Being a carnivorous species, the sea swallows feeds on several cnidarian species, especially the Portuguese man o’ war. It usually collects the cnidocytes (the sting cells) of its prey and put them on its own body, so that it becomes as stingy as or even stingier than its prey. If you find one lying on the beach, be careful.

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References:

Churchull, C. K. C.; Valdés, Á.; Foighil, D. Ó (2014) Afro-Eurasia and the Americas present barriers to gene flow for the cosmopolitan neustonic nudibranch Glaucus atlanticus. Marine Biology, 161(4): 899-910.

Wikipedia. Glaucus atlanticus. Available at < https://en.wikipedia.org/wiki/Glaucus_atlanticus >. Access on June 18, 2017.

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Friday Fellow: Branching Vase Sponge

by Piter Kehoma Boll

A fascinating group of animals that has not yet joined the Friday Fellows are the sponges. Different from all other animals, sponges have a unique body structure that behaves more like a plant or fungus. They grow in irregular or radial ways and are usually branched. More than that, they have thousands of small mouths along their bodies, called pores, that suck water from the environment in order to filter food from it.

But let’s talk about our species. Living in the Caribbean Sea, its name is Callyspongia vaginalis, commonly known as branching vase sponge. Its usual shape is that of a tube or set of tubes, sometimes branched, that may reach several centimeters in length and usually abour 3 cm in diameter. The color may vary from pink or lavender to duller colors, such as brown or gray.

callyspongia_vaginalis

A lavender pipe of Callyspongia vaginalis. Photo by Mark Rosenstein*.

As most sponges, the branching vase sponge feeds on small particles and microorganisms that it filters from water. As the concentration of particles in the water increases with depth, organisms growing deeper usually grow faster due to the higher food availability.

The main predators of the branching vase sponge are fishes. They actually act more like herbivores eating plants, as they don’t eat the whole sponge and usually do not kill it, but bite its surface, taking off pieces.

callyspongia_vaginalis2

A large and branched individual of the branching vase sponge. Photo by Paul Asman and Jil Lenoble.**

Bristlestars, especially of the genus Ophiothrix, such as Ophiothrix lineata, are frequently found living inside the main cavity of the sponge. There, these animals find shelter from predators and, at night, when the environment is safer, they extend their arms outside and clean the sponge from large organic particles, feeding on them. It’s a mutually benefitial association.

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ResearchBlogging.orgReferences:

EOL – Encyclopedia of Life. Callyspongia vaginalis. Available at <http://eol.org/pages/1163688/overview&gt;. Access on January 12, 2017.

Hendler, G. (1984). The Association of Ophiothrix lineata and Callyspongia vaginalis: A Brittlestar-Sponge Cleaning Symbiosis? Marine Ecology, 5 (1), 9-27 DOI: 10.1111/j.1439-0485.1984.tb00304.x

Hoppe, W. (1988). Growth, regeneration and predation in three species of large coral reef sponges Marine Ecology Progress Series, 50, 117-125 DOI: 10.3354/meps050117

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**Creative Commons License
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Friday Fellow: Glacial calanus

by Piter Kehoma Boll

Today’s Friday Fellow comes swimming tinily through the freezing waters in the north. It is a small crustacean, more precisely a copepod, and its name is Calanus glacialis. It lacks a common name, but I adapted it as the “glacial calanus”.

Tiny, but beautiful. Credits to University of Alaska Fairbanks*.

Tiny, but beautiful. Credits to University of Alaska Fairbanks*.

Found in the Arctic Ocean and the northernmost areas of the Atlantic and Pacific Oceans, the glacial calanus is one of the most abundant polar species of copepods and one of the main components of the zooplancton in this region. As a result, it is an important food source for other animals, such as fish, birds and even whales.

The life cycle of the glacial calanus varies from 1 to 3 years and depends on the temperature and food availability. Most of its development occurs in summer, when the water is warmer and there is plenty of food, which for our fellow consists mainly of algae, such as diatoms. In autumn, the glacial calanus starts to accumulate lipids and then migrates downwards to deep waters and becomes dormant to survive the long, dark and food-poor winter.

As its life cycle depends on such seasonal variations, global warming may have profound impacts on the populations of the glacial calanus and on that of other species that depend on it as food.

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References:

Kosobokova, K. N. 1999. The reproductive cycle and life history of the Arctic copepod Calanus glacialis in the White Sea. Polar Biology 22:254–263. DOI: 10.1007/s003000050418.

Søreide, J. E.; Leu, E.; Berge, J.; Graeve, M.; Falk-Petersen, S. 2010. Timing of blooms, algal food quality and Calanus glacialis reproduction and growth in a changing Arctic. Global Change Biology 16:3154–3163. DOI: 10.1111/j.1365-2486.2010.02175.x

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