Hagfish, Lamprey, Coelacanth

by on February 1st, 2011
Share Button

If a molecular biologist were to analyze the genome of the ancient hagfish (Myxine glutanalis model), coelacanth or lamprey (Lampetra fluviatilis model), they would find differences in genotype despite limited obvious change in phenotype. The morphology of the jawless fish is likely unchanged, but variance in immunity has been reported (Rast and Buckley 2013).

Lamprey and hagfish have exceptional predatory capabilities, and the latter has a defense system akin to “slime” production. Both an latch onto medium-sized predators (such as acanthopterygians) until the host is no longer living, eating up to 18 kilograms of fish per year. The hagfish has a propensity to eat dead fish as well, a factor dependent on geography, species and saline content. These cyclostomes did not adapt armored scales, or have not had the required amount of evolutionary time to do so. It has clearly caused them limited detriment (NOAA 2013).

The lamprey and hagfish are both considered roughly cyclostomes, but differ in morphology and taxonomic conditions. Combined they have over 100 distinct species. Both possess cartilage and single nostrils. The lamprey has a more defined circulatory system (Helfman et al. 2009) and is more similar to the vertebrate body plan. Additional differences are voluminous and ubiquitous throughout the body plan, the most salient of which is enhanced cranial and ocular development in lampreys (Cohn 2002).

It is the opinion of the author that acanthopterygians are not required to compete with jawless fish for a food source. A lamprey or hagfish attaches to an apex or middling predator and ignores the smaller fish that a medium-sized fish attacks.

Equally important to note: the hagfish also has the defense mechanism of mucous (hence myxine ), which makes their taste unappealing to predators. This unique capability

makes them less likely to be eaten along with having exquisite predation capability. This

combination of traits seems uncommon in the animal kingdom (Fudge et al. 2005). When the mucin is released with seawater, its purpose is to clog the gills of the attacker (Lim et al. 2006). The hagfish and lamprey do not have traditional gills, but rather specialized inlets allowing mucous to inundate their respiratory system without suffocation.

Depending on the source of the interpretation of the hox genes, coelacanths are either evolving quickly or very slowly. The dissonance may be contributed to bias in the hypotheses, particularly confirmation bias.

Furthermore, almost every aspect of the coelacanth’s internal organs has undergone significant change, including olfaction and jaw structure. Another assumption is coelacanths may have a perfect predation niche with limited predators (like the deep sea shark), due to their hunting and hiding habits. Recent fossil discoveries have indicated they approach 200 pounds and have an extraordinarily small brain size compared to teleost fish, and observations indicate vast resources used for reproduction (NOAA 2013). Ray finned fish such as guppy have larger brains compared to their body size, which has considerable evolutionary cost (Kotrschal et al. 2013).

The lamprey may be used as a positive evolutionary example according to evidence in the stratigraphy. Based on the current data, gnathostomes evolved from a process referred to as heterotopy (differentiation) in the upper jaw and neural crest cells, leading to diversity in nasal passages and the pituitary gland (Kuratani 2004). The cause of this diversity is believed to be a sequence named ‘dlx’ present in comparative embryology, possibly responsible for many of synapomorphies defining the taxa (Neidert et al. 2001).

All three sea-dwelling creatures are part of the evolution debate from a creationist perspective. Not only is the alleged genomic stability untrue, it may be used against the theory of evolution as a whole. It’s imperative to understand the bottom of the ocean has not changed as dramatically as land susceptible to an ice age, so what natural selection would apply? Darwin himself is to blame for this living fossil idea, like Quintis “Horace” Flaccus is to blame for the phrase “you only live once”.

The frequency of stasis in the record is generally explained by punctuated equilibrium or phyletic gradualism, but all subsets rely on millions of years being a long time. Suppose Refuting creationist teleost arguments is like shooting bulletproof fish in a barrel, if you have enough time to stand there.


Prev Article: »
Next Article: «

Related Articles