Tag Archives: Fish

Going deep with your guts full of microbes: a lesson from Chinese fish

by Piter Kehoma Boll

All around the world, many animal species have adapted to live in cave environments, places that are naturally devoid of light, either partially or entirely, and are, therefore, nutrient-poor habitats. The lack of light makes it impossible for plants and other photosynthetic organisms to survive and, as a result, little food is available for non-photosynthetic creatures. They rely almost entirely on food that enters the cave from the surface by water or animals that move between the surface and the depths.

Due to the lack of light in caves, animals adapted to this environment are usually eyeless, because seeing is not possible anyway, and white, because there is no need for pigmentation on the skin to protect from radiation or to inform anything visually. On the other hand, chemical senses such as smell and taste are often very well developed.

All these limitations make cave environments relatively species-poor when compared to surface environments. Or at least that is what it looks like at first. There are, of course, much less macroscopic species, such as multicellular animals, but those animals are themselves an environment and they may harbor a vast and unknown diversity of microrganisms inside them.

As you may know, most, if not all, animals have mutualistic relationships with microorganisms, especially bacteria, living in their guts. Those microorganisms are essential for many digestive processes and many nutrients that animals get from their food can only be obtained with the aid of those microscopic friends. The types of microorganisms in an animal’s gut are directly related to the animal’s diet. For example, herbivores usually have a high diversity of microorganisms that are able to break down carbohydrates, especially complex ones such as cellulose.

A recent study, conducted in China with fishes of the genus Sinocyclocheilus, compared the gut microbial diversity of different species, including some that live on the surface and some that are adapted to caves. All species of Sinocyclocheilus seem to be primarily omnivores but different species may have preferences for a particular type of food, being more carnivorous or more herbivorous.

The study found that cave species of Sinocyclocheilus have a much higher microbial diversity than surface species. But how can this be possible if there is a limited number of resources available in caves compared to the surface? Well, that seems to be exactly the reason.

Sinocyclocheilus microphthalmus, one of the cave-dwelling species used in this study. Photo extracted from the Cool Goby Blog.

As I mentioned, species of Sinocyclocheilus are omnivores. On the surface, they have plenty of food available and can have the luxury of choosing a preferred food type. As a result, their gut microbiome is composed mainly by species that aid in the digestions of that specific type of food. In caves, on the other hand, food is so scarce that one cannot chose and must eat whatever is available. This includes feeding on small amounts of many different food types, including other animals that live in the cave and many different types of animal and plant debris that reach the cave through the water. Thus, a much more diverse community of gut microorganisms is necessary for digestion to be efficient.

Look how the number of different genera of bacteria is much larger in the cave group (right) than in two groups of surface species (left and center). Image extracted from Chen et al. (2019).

More than only an increased diversity by itself, the gut community of cave fish also showed a larger number of bacteria that are able to neutralize toxic compounds of several types. The reason for this is not clear yet but there are two possible explanations that are not necessarily mutually exclusive. The first states that water in caves is renewed in a much lower rate than surface waters, which promotes the accumulation of all sort of substances, including metabolic residues of the cave species themselves that can be toxic. The second hypothesis is of greater concern and suggests that this increased number of bacteria that are able to degrade harmful substances is a recent phenomenon caused by an increase in water pollutants coming from human activities, which is promoting a selective pressure on cave organisms.

The diverse gut microbiome of cave fish is, therefore, a desperate but clever strategy to survive in such a harsh environment. Nature always finds a way.

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More on cave species:

Think of the worms, not only of the wales, or: how a planarian saved an ecosystem

Don’t let the web bugs bite

Friday Fellow: Hitler’s beetle

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Reference:

Chen H, Li C, Liu T, Chen S, Xiao H (2019) A Metagenomic Study of Intestinal Microbial Diversity in Relation to Feeding Habits of Surface and Cave-Dwelling Sinocyclocheilus Species. Microbial Ecology. doi: 10.1007/s00248-019-01409-4

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Filed under Bacteria, Ecology, Evolution, Fish

Hundreds of lionfish were released in the Atlantic out of pity

by Piter Kehoma Boll

The red lionfish, Pterois volitans, is a beautiful and venomou coral fish native from the Indo-Pacific region. Due to its great beauty, it is a very popular in fish tanks all around the world.

799px-red_lionfish_near_gilli_banta_island

A red lionfish in its natural and native habitat in Indonesia. Photo by Alexander Vasenin.*

Since the 1980s, the lionfish started to be found in the waters of the Atlantic ocean around Florida. How did they get there? Certainly humans had something to do with it, but the exact way is yet unknow. Originally a small population, the species spread quickly by the beginning of the 21th century and in 2010 had colonized the Caribbean and the Gulf of Mexico.

Some original studies on the genetic diversity of the Atlantic population estimated that the minimum number of introduced specimens was around 10. If that was true, the established population may have been the result of an accident, like, for example, the fish of a single aquarium accidentally ending up in the sea.

800px-caribbean_lionfish3f_28519689049529

A red lionfish photographed in Curaçao, Caribbean. Photo by Laszlo Ilyes.**

A recently published study (see reference), however, reestimated this number using new models and additional data. The conclusions are that the number of fish that colonized the Atlantic was much bigger, around 272 individuals. Such a large introduction would unlikely occur by accident. Introductions by fish being transported from the Indo-Pacific region in the ballast water of ships is unlikely, as they would hardly survive the transport. The most likely answer is that these fish were introduced through several small releases that happened in Miami. How and why? Well, many people like to have fish in beautiful fish tanks at home, and when they get tired of managing the animals or cannot afford continuing to have them, they decide to simply release them in the ocean out of pity, because the alternative would be to kill them.

Now can you see what are the consequences of thinking this way? You care too much for a single specimen, has no ecological knowledge, and simply decide to release them in the wild. Years later, they have depleted whole ecosystems and caused a large-scale disaster. That’s what humans do. As they say, the road to hell is paved with good intentions.

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References:

Selwyn JD, Johnson JE, Downey-Wall AM, Bynum AM, Hamner RM, Hogan JD, Bird CE. (2017Simulations indicate that scores of lionfish (Pterois volitans) colonized the Atlantic OceanPeerJ 5:e3996 https://doi.org/10.7717/peerj.3996

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Filed under Conservation, Fish, Zoology

New Species: February 11 to 20, 2017

by Piter Kehoma Boll

Here is a list of species described from February 11 to February 20. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa, International Journal of Systematic and Evolutionary Microbiology, and Systematic and Applied Microbiology, as well as journals restricted to certain taxa.

pseudomacrochenus_wusuae

Pseudomacrochenus wusuae is a new longhorn beetle described in the past 10 days.

SARs

Plants

Fungi

Nematodes

Arachnids

Myriapods

Crustaceans

Hexapods

Tunicates

Ray-finned  fishes

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Filed under Systematics, taxonomy

New Species: December 1 to 10

by Piter Kehoma Boll

Here is a list of species described from December 1 to December 10. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa, International Journal of Systematic and Evolutionary Microbiology, and Systematic and Applied Microbiology, as well as journals restricted to certain taxa.

brunfelsia_cabiesesiana

Brunfelsia cabiesesiana is a new flowering plant from Peru described in the past 10 days.

SARs

Plants

Fungi

Mollusks

Nematodes

Arachnids

Crustaceans

Hexapods

Cartilaginous fishes

Ray-finned fishes

Reptiles

Mammals

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Filed under Systematics, taxonomy

New Species: October 21 to 31

by Piter Kehoma Boll

gelanoglanis_varii

The picture shows the cleared and stained head of Gelanoglanis varii, a recently described catfish from the Tocantins River Basin in Brazil.

Here is a list of species described from October 21 to October 31. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa, International Journal of Systematic and Evolutionary Microbiology, and Systematic and Applied Microbiology, as well as journals restricted to certain taxa.

Archaeans

Bacteria

SARs

Plants

Fungi

Sponges

Cnidarians

Flatworms

Mollusks

Annelids

Nematodes

Arachnids

Myriapods

Crustaceans

Insects

Ray-finned fishes

Lissamphibians

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Filed under taxonomy

Friday Fellow: Flounder Glugea

by Piter Kehoma Boll

While looking for flatfish you may eventually find one with some grotesque growth on the body, like the one in the picture below:

glugea_stephani_xenoma

A xenoma caused by Glugea stephani on a flatfish Limanda limanda. Photo by Hans Hillewaert.*

This sort of tumor is called xenoma and, in flatfish, is caused by a microscopical and parasitic fungus named Glugea stephani, or the flounder glugea.

The flounder glugea is part of a group of fungi called Microsporidia that until recently were classified as protists. They are unicellular and parasite other organisms, especially crustaceans and fish.

Once inside a flatfish, the flounder glugea enters an intestinal cell and starts to develop. They induce the host cell to increase in size and may give rise to the xenomas, which are the most extreme stage in the development of the disease. The proliferating and active stage of the glugea are free in the cytoplasm of the host cell, but they may change into a spore-like form called sporoblast that remains inside a vacuole.

glugea_stephani

Image of electron microscopy of an intestinal cell of winter flounder (Pseudopleuronectes americanus) infected by flounder glugea (Glugea stephani). The S indicates sporoblasts inside the vacuole (SV) and the P the proliferating organisms inside the host cytoplasm (H). Image extracted from Takvorian & Cali (1983).

Fortunately most infections are mild and do not compromise the fish health, at least not very much…

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References:

Takvorian, P. M.; Cali, A. (1983). Appendages associated with Glugea stephani, a microscporidian found in flounder. Journal of Protozoology, 30(2): 251-256.

Wikipedia. Xenoma. Available at: < https://en.wikipedia.org/wiki/Xenoma >. Access on September 17, 2016.

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Filed under Disease, Fish, Friday Fellow, Fungi

Friday Fellow: Winter Flounder

by Piter Kehoma Boll

Can you spot the two fish in the photo bellow?

pseudopleuronectes_americanus

Perfect camouflage. Two winter flounders, Pseudopleuronectes americanus. Photo by Brent Wilson.*

Belonging to the species Pseudopleuronectes americanus, commonly known as winter flounder or black back, it is a flatfish native to the North Atlantic coast of Canada and the United States. It may reach up to 70 cm in length and 3,6 kg in weight, although in most areas it is smaller.

As with other flatfish, the winter flounder is asymetrical. It lives on the substrate, lying on one of its sides (in this case, on the left side) and its left eye has migrated to the right side, so that both point upwards.

pseudopleuronectes_americanus_2

Condemned to lie on its left side.

Living in very cold waters, the winter flounder suffers the risk of freezing during winter. As a result, its blod has a set of proteins that have the ability to reduce the freezing point of water, allowing it to remain liquid below 0°C.

The winter flounder is an important commercial fish in the USA and regarded as having a delicious meat. It has been overfished in the past decades and some populations have been depleted. Despite a recent large reduction in fishing pressure, many populations are recovering very slowly due to other factors, such as habitat degradation and low genetic variability. Furthermore, there are still some areas where overfishing may still be happening.

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References:

Duman, J. G.; DeVries, A. L. (1976) Isolation, characterization, and physical properties of protein antifreezes from the winter flounder, Pseudopleuronectes americanusComparative Biochemistry and Physiology Part B: Comparative Biochemistry, 54(3): 375-380.

Wikipedia. Winter flounder. Available at: < https://en.wikipedia.org/wiki/Winter_flounder >. Access on September 17, 2016.

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