|Tiger tail seahorse. Hippocampus comes.|
The seahorse is something of a creationist nightmare!
No, not because it's that dreaded 'transitional form' being part fish and part horse - which it isn't of course although many creationists seem to believe 'evolutionists' believe such idiocy is part of mainstream biology, but because its evolution flatly contradicts several creationist articles of faith. These articles include:
- No new information can arise by mutation (or any other way).
- Evolution is about increasing complexity.
- Mutations are always harmful.
- Loss of information is always detrimental.
- The scientific Theory of Evolution is a theory in crisis which is becoming increasingly discarded in favour of the evidence-free creationist notion of intelligent (sic) design.
So, it must be disconcerting when papers like this one on seahorse evolution are published because they simultaneously and quite incidentally refute all of these creationist dogmas and they do so with that other creationist bugbear - evidence.
As the press release announcing the publication of this paper says:
Without a doubt, the seahorse belongs to Darwin's "endless forms most beautiful". Its body form is one of a kind. It has neither a tail nor pelvic fin, it swims vertically, bony plates reinforce its entire body and it has no teeth, a rare feature in fish. Another peculiarity is that male seahorses are the ones to become pregnant. The genome project, comprising six evolutionary biologists from Professor Axel Meyer’s research team from Konstanz and researchers from China and Singapore, sequenced and analyzed the genome of the tiger tail seahorse. They obtained new molecular evolutionary results that are relevant for biodiversity research: the loss and duplication of genes as well as the loss of regulative elements in its genome have both contributed to the rapid evolution of the seahorse.
The international team have sequenced the genome of the tiger tail seahorse (Hippocampus comes) and believe they have explained several things about this seahorse's evolution. None of the findings are good news for creationism.
Seahorses have a specialized morphology that includes a toothless tubular mouth, a body covered with bony plates, a male brood pouch, and the absence of caudal and pelvic fins. Here we report the sequencing and de novo assembly of the genome of the tiger tail seahorse, Hippocampus comes. Comparative genomic analysis identifies higher protein and nucleotide evolutionary rates in H. comes compared with other teleost fish genomes. We identified an astacin metalloprotease gene family that has undergone expansion and is highly expressed in the male brood pouch. We also find that the H. comes genome lacks enamel matrix protein-coding proline/glutamine-rich secretory calcium-binding phosphoprotein genes, which might have led to the loss of mineralized teeth. tbx4, a regulator of hindlimb development, is also not found in H. comes genome. Knockout of tbx4 in zebrafish showed a ‘pelvic fin-loss’ phenotype similar to that of seahorses.
Qiang Lin, et al.
The seahorse genome and the evolution of its specialized morphology.
Nature, 2016; 540 (7633): 395 DOI: 10.1038/nature20595
*Copyright © 2016, Nature Publishing Group. Published open access.
Reprinted under a Creative Commons Attribution 4.0 International Licence (CC-BY 4.0).
The team have shown that:
- The loss of teeth is reflected in the absence of several genes associated with teeth development in many vertebrates including humans. Evolution by loss of information and reduced complexity.
- The loss of the pelvic fin is due to the absence of the gene tbx4, essential for pelvic fin and hindlimb development in many vertebrates including humans. Additionally, the team showed that by switching off this gene in zebra fish, they too would have missing pelvic fins. Loss of information and reduced complexity again.
- The ability of male seahorses to become 'pregnant' is due to a modified gene which originally arose by duplication of a gene used for an entirely unrelated process. New information by mutation and mutation not being detrimental but beneficial.
The University of Konstanz press release again:
According to this study in "Nature", evolution does not only act through changing major roles of genes, but it also influences regulatory elements (genetic switches) during evolution. Regulatory elements are DNA segments that control the function of genes. Some of them barely change during the course of evolution since they have important regulatory functions. But several such unchanging and seemingly crucial elements are missing in sea-horses. This is also and especially the case for elements that are responsible for the typical development of the skeleton in fish, but also in humans. This is probably one of the reasons why the seahorse's skeleton has been so greatly modified. It lacks ribs, for example. Instead, its body is armoured with bony plates that add strength and better protection from predators. Additionally, its prehensile curly tail allows seahorses to be camouflaged and remain motionless by holding on to seaweed or corals. The genome sequences suggest that the loss of the corresponding regulatory sequence led to this ossification.
Due to its special morphology, the seahorse superbly demonstrates how genetic changes can lead to evolutionary changes in distinguishing traits – and therefore to a better understanding of the genetic basis for the evolution of bizarre and beautiful organisms such as seahorses.
So there we have several examples of a loss of information being responsible for evolution. Not only is a loss of information not detrimental to the tiger tail seahorse but in the context of the environment in which the seahorse lives, it provided evolutionary advantages.
And a mutation in the form of a gene duplication not only failed to be detrimental but actually proved to be essential for male 'pregnancy' in the seahorse style.
And lastly we see the Theory of Evolution not only being taken for granted as offering the best (or only) answer to how the seahorse got to be the way it is, but there is never a hint that it might not be up to the task and the team should be including magic and Bronze Age superstitions in their explanation of reality.
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