Rediscovery of rare marine amoeba Rhabdamoeba marina

Figure 1: Rhabdamoeba marina

        A rare marine amoeba, Rhabdamoeba marina, has been rediscovered and successfully cultivated by researchers at the University of Tsukuba. This amoeba has been reported only twice in the last century and was first discovered in England in 1921. However, the original description has been questioned as it was brief and relied on preserved material for observation.
        The amoeboid cells were characterized by their near immobility. Under a limited prey supply, the amoeboid cells of R. marina can generate flagellated cells with two backward-extending flagella through a process called budding. Since only two cases have been documented, the taxonomic classification was unverified despite its distinct characteristics.
        Researchers performed an analysis of the amoeba’s genetic sequence using a culture strain established from seawater that was sourced from the coast of Japan. The comprehensive analysis revealed the phylogenetic position of the R. marina and proposed a new taxonomic classification. Researchers found that the amoeba did not align with the previously assigned taxonomic group and as a result, proposed the reclassification of R. marina into the class Chlorarachnea.
        For the first time, the gene sequence of this rare amoeba was unveiled and its position in the phylogenetic tree has been clarified. This rediscovery highlights the importance of environmental sample observation for rediscovering and understanding the genetic makeup of rarely encountered and scarce unicellular organisms like Rhabdamoeba marina. These studies are essential to understanding microbial diversity, refining our taxonomic classification, and gaining a better understanding of the diversity of life

Links:

https://www.sciencedaily.com/releases/2023/11/231117102454.htm

https://www.the-microbiologist.com/news/rediscovery-of-rare-marine-amoeba-rhabdamoeba-marina/1958.article

https://doi.org/10.2307/3227028

Why is shark DNA so fascinating?

 

Marine scientists all over the world are using new, innovative technology to better understand sharks genetic information that can help us better understand their biology, movement, and evolution. DNA in sharks is rapidly being observed to also show migrating patterns, unique adaptations, and even susceptibility to certain diseases within a species. Marine geneticists have found that the shortfin mako has a genome almost 1.6 times bigger than our own. Other species, such as the great white have also shown a very stable genome, explaining that very little genetic mutations occur. Having a more stable genome leads to being less susceptible to diseases caused by mutations such as cancer. Sharks genomes are also being observed because of their incredible wound-healing ability. Although we have similar genome, our ability to heal isn’t quite as fast, or efficient. Through more studies, we can utilize this information to truly understand them and protect them.

    Sharks have always been so incredibly fascinating to me. Their species, adaptations, movement patterns, etc. Because of external stressors increasing, such as global warming and overfishing, it is so important we study them to learn how we can conserve and understand what makes them up. Diving into their genome could help innovate the idea of genetics itself, and how we could possibly implement that development into human research as well.

Link to article: https://saveourseas.com/worldofsharks/podcast/what-can-we-learn-from-a-sharks-dna#

Pesticide Runoff is affecting Aquatic Mammals due to Lost Genes

Today’s Marine mammals have all evolved from terrestrial mammals that trekked back into aquatic environments and created adaptations to thrive in these new environments. One of the genes they lost in adapting to aquatic life was an enzyme that would aid in defending against pesticides. With this discovery of a missing gene in marine mammals make the issues of pesticide runoff in oceans an even more important issue in our environment. The gene responsible for this defense was labeled as PON1 which was identified to defend against organophosphates, the pesticides used in agriculture. Most marine mammals have pieced together similar enzymes to replicate the results of the PON1 gene with some exceptions being walruses, fur seals, and spotted seals, all of which would be the most vulnerable to organophosphates. Now why did these marine mammals adapt to lose this gene that their terrestrial ancestors once had? The leading theory is that due to the fact that marine mammals take in large amounts of oxygen for deep dives, they evolved to remove oxygen carrying molecules. Molecules such as PON1, that otherwise would be harmful under the pressure of deep dives. (Zimmer, 2018)

These pesticide runoffs have also started to affect coastal avian species as well as the marine mammals. There have been a rise of unidentified diseases and conditions related to issues with the organisms endocrine systems. With an organisms endocrine system being exposed to its surroundings, many believe that these pesticide runoffs are to blame for the unusual mutations and reactions of these organisms. (Tanabe, 2009)

Even though there isn't evidence that directly links the runoff to these mutations and diseases in coastal organisms such as mammals and avians, the consensus of these researchers are that the pesticides have a part to play in this ecological issue. It is impossible to know exactly where runoff from agriculture will wind up but it is a guarantee that it will reach the oceans at once point. This means that we have to be conscious of the volume of pesticides we use on our plants as well as the possible reactions that organisms in the oceans and waterways will have to these chemicals. Although there aren’t direct links to the issues marine mammals are facing, i suspect that in the coming years more information will be discovered on the effects of such pesticides on marine mammals and other ocean going species.

References

Tanabe, S. (2002, 09). Contamination and toxic effects of persistent endocrine disruptors in marine mammals and birds. Marine Pollution Bulletin, 45(1-12), 69-77. doi:10.1016/s0025-326x(02)00175-3

Zimmer, C. (2018, August 09). Marine Mammals Have Lost a Gene That Now They May Desperately Need. Retrieved from https://www.nytimes.com/2018/08/09/science/marine-mammals-pesticides.html

All-female hybrid fish species that 'uses' males for better genetics

A naturally occurring hybrid fish species, Hexagramos octogrammus/H. grampus (Hoc/Hag), composed of all-female members, is thought to have developed a unique method of evolutionary survival by switching matings between two different male species of the same genus.  The (Hoc/Hag) hybrid females are thought to have a competitive advantage because 100% of their species is capable of producing offspring, thus allowing them to quickly replicate and outnumber other species that produce both male and female offspring.  Replication without variation is an evolutionary disadvantage though, and this can be detrimental to the long term survival of the all-female species due to also developing a decreased ability to genetically adapt to environmental pressures.

Researchers from Hokkaido University in Japan have compared the genes of three species: Hexagramos octogrammus/H. agrammus (Hoc/Hag), H. octogrammus/H. otakii (Hoc/Hot), as well as their maternal pure line, H. octogrammus (Hoc).  Their study, published in Ecology and Evolution, found that the hybrid females, (Hoc/Hag), mate with their choice of two hybrid male species: (Hoc/Hot) or (Hoc/Hag).  The result of either mating always produces 100% all-female hybrid offspring in which both maternal and paternal genes influence their development.  The subsequent generation only inherits the maternal genome though, and excludes the paternal genome from gamete formation when they're able to form their own eggs.  In addition, the all female offspring can only mate with (Hoc) males whose sperm activate their eggs to start development.  The resulting (Hoc) offspring undergo normal germ cell development in which genetic recombination can occur between maternal and paternal genomes, resulting in a more diversified genome for their male/female offspring.

“When a female descendant of one of these backcrossed Hocs mates with a Hag male, a new all-female Hoc/Hag hybrid lineage arises. This could be another factor that increases the diversity of Hoc/Hac hybrids, increasing their survivability,” says the paper’s lead author, Hiroyuki Munehara.

The researchers constructed a mtDNA genealogical tree that showed that the (Hot) and (Hag) species diverged from their common ancestor around 1.5 million years ago.  Furthermore, their analysis also revealed that (Hoc/Hot) hybrids originated from hybrid (Hoc/Hag) females switching choice of host; instead of breeding with (Hag) males, they bred with larger (Hot) males that would better protect their eggs.