Sciency Thoughts: Trout

Showing posts with label Trout. Show all posts

Saturday, 19 August 2017

Neovahlkampfia nana: A new species of Heterolobosean Amoeba from the Czech Republic.

Heteroloboseans are flagellated Amoebas closely related to Slime Molds, and generally though to be the most primitive group of flagellated Eukaryotes (i.e. the group closest to the first such organisms to have appeared. They typically have a life-cycle which includes both flagellated and non-flagellated stages, as well as an inert cyst stage that can survive periods of hostile conditions, such as a cold, or dry season.

In a paper published in The Journal of Eukaryotic Microbiology on 13 July 2017, Tomáš Tyml of the Faculty of Science at the University of South Bohemia and the Faculty of Science at Masaryk University, Luis Lares-Jim énez, also of the Faculty of Science at Masaryk University, Martin Kostka, also of the Faculty of Science at the University of South Bohemia, and Iva Dykov á, again of the Faculty of Science at Masaryk University, describe a new species of Heterolobosean Amoeba from the gills of Rainbow Trout, Oncorhynchus mykiss, infected with an unknown nodular gill disease in the Czech Republic.

The new species is place in the genus Neovahlkampfia, which currently only contains a single species, Neovahlkampfia damariscottae, a marine Amoeba from an estuary in Maine, which was formerly placed in the genus Vahlkampfia until a genetic analysis sugested that it should be excluded from this group. It is given the specific name Neovahlkampfia nana, in reference to the small size of this species, which reached 8–15 μm in length.

Globular form of Neovahlkampfia nanawith nucleus (n), mitochondria (m), electron-dense structure (es), and dense bodies (db) in cytoplasm. Tymel et al. (2017).

Neovahlkampfia nana was identified as a a member of the Heterolobosea and a close relative of Neovahlkampfia damariscottae by genetic analysis (morphological comparisons of Amoebae are close to worthless). The species adopted a number of forms in response to changes in conditions, but these were essentially behavioural, rather than true metamorphoses, and the Amoebas were not observed to produce a flagellated or cyst stage (though this does not necessarily mean that they cannot do this).

Wednesday, 31 December 2014

The effect of non-lethal Carbosulfan exposure on Rainbow Trout.

Carbosulfan, 2,3-dihydro-2,2-dimethyl-7-benzofuranyl (di-n-butylaminosulfenyl) methyl carbamate, is a carbamate pesticide which was banned in for use the European Union in 2007, but is still manufactured for export, and is widely used in countries such as Mexico, Brazil, India and Sri Lanka. It is used on a wide variety of crops, particularly Citrus fruits, Corn, Soya beans and Rice. Carbamate pesticides, like organophosphates, act by inhibiting the enzyme acetylcholinesterase by reacting with its active sites, i.e. they are neurotoxins which halt synaptic transmission in the nervous system. Such toxins readily enter the aquatic ecosystem, where they are harmful to Fish and aquatic invertebrates, but break down rapidly in the environment, which can make them hard to detect by analysis of water samples.

In a paper published in the Turkish Journal of Fisheries and AquaticSciences on 24 September 2014, Erol Capkin of the Department of Marine Sciences andTechnology Engineering at Karadeniz Technical University, Halis Boran of the Department of Fisheries and Aquatic Sciences at Recep Tayyip Erdoğan University and Ilhan Altinok, also of the Department of Marine Sciences and Technology Engineering at Karadeniz Technical University, discuss the results of an experiment in which Rainbow Trout, Oncorhynchus mykiss, were exposed to sub-lethal levels of Carbosulfan exposure over a period of 60 days, with enzyme activity in the blood and liver monitored during this period and a 24 day recovery period.

A commercially availble brand of Carbosulfan. Juanco SPS Ltd.

The exposure of the Fish to the toxin was gauged at levels known to be sublethal, and none of the Fish died during the procedure. Fish exposed to Carbosulfan showed a number of abnormalities compared to Fish in a control group, including loss of balance, darkening in colour and reduced feeding. There was some improvement during the second week of exposure, suggesting that the Fish were able to adapt to Carbosulfan exposure to some extent. The exposed showed a much reduced growth rate compared to the control group, gaining only 3% bodyweight over the course of the experiment, compared to 39% in the unexposed Fish.

The exposed Fish showed reduced protein levels in the liver, a symptom of metabolic degradation (the liver is the principle organ used for the removal of toxins from the body by vertebrates). They also showed reduced levels of acetylcholinesterase activity in the blood and liver, with the liver affected more than the blood. The level of enzyme activity in the blood had returned to normal 18 days after exposure ceased, while that in the liver recovered after 21 days.

A Rainbow Trout, Oncorhynchus mykiss. Wikimedia Commons.

From this Capkinet al. conclude that freshwater Fish are useful biomarkers for the presence of the toxin in aquatic ecosystems, even if it is not present at levels high enough to be lethal. They suggest that it should be possible to monitor for the presence of Carbosulfan by taking blood samples from wild Fish, a relatively simple procedure which can be carried out in the field.

Tuesday, 30 December 2014

A new species of Trout from southwest Anatolia.

The Swedish naturalist Carolus Linnaeus originally described a single Trout species, Salmo trutta, to deascribe small Samonid Fish across Europe, western Asia and North Africa in 1758. Over the next two centuries, as the diversity of these fish was recognised, this species was split into a large number of sub-species, and with the event of genetic classification techniques in the late twentieth century, many of these upgraded to full species, with some species being formed from the spitting or merging of the former subspecies based upon genetic data. There are currently eleven species of trout recognized from northern and eastern Anatolia, with the taxonomic status of populations in the south and west of the country under review.

In a paper published in the journal ZooKeys on 10 December 2014, Davut Turan, Esra Doğan and Cüneyt Kaya of the Faculty of Fisheries and Aquatic Sciences at Recep Tayyip Erdogan University and Mahir Kanyılmaz of the Mediterranean Fisheries Research, Production and Training Institute, describe a new species of Trout from Alakır Stream in southwest Anatolia.

The new species is named Salmo kottelati, in honour of the ichthyologist Maurice Kottelat, for his studies of the Fish of Europe and Asia. The fish are greenish to silvery in colour, with brown on the back and flanks, darker towards the dorsal (upper) surface. The males are slightly larger than the females, with adult male Fish measured at 122–210 mm and adult females at 98–208 mm. The males have longer heads and jaws and a greater mouth gape than the females.

Salmokottelati, (b) male and (c) female. Turan et al. (2014).