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Crab Nebula of Life
Crabs—those sometimes pesky, hard-shelled beachcombers—are a highly diverse animal, with some 7,000 species found in oceans, lakes, and on land, varying in size from
the diminutive pea crab (millimeters) to the giant 4-m wide
Japanese spider crab.
Tsang et al. (2014) have constructed the most complete and extensive data set to date. Their recalibrated
crab gene tree using DNA and mitochondrial sequences
from 140 species and 58 crab families provides some new
important insights into the timing and diversity of crab
evolution.
The research team’s estimates confirm the fossil record of
most living crab families and superfamilies first arising during
the late Cretaceous and early Tertiary (60–100 Ma), at the
same time when dinosaurs ruled the Earth. They also demonstrated that freshwater crabs were derived early in the
evolution of true crabs and are shown to have at least two
independent origins. Molecular methods estimate that
freshwater crabs separated from their closest marine relatives
after the break up of Pangaea (~200 Ma).
The study refines many crab evolutionary issues and provides a new, comprehensive resource for scientists to further
investigate the molecular underpinnings responsible for body
forms, shapes, and functions among the various species.
Reference
Tsang LM, Schubart CD, Ahyong ST, Lai JCY, Au EYC, Chan T-Y, Ng PKL,
Chu KH. 2014. Evolutionary history of true crabs (Crustacea:
Decapoda: Brachyura) and the origins of freshwater crabs. Mol
Biol Evol. 31:1173–1187.
Joseph Caspermeyer*,1
1
MBE Press Office
*Corresponding author: E-mail: [email protected].
doi:10.1093/molbev/msu094
Advance Access publication March 25, 2014
Parallel Evolution of an Enzyme Family in Plants and Animals
May Signal Coevolution of Consumed and Consumer
Animals and plants share a common ancestor about 2 Ga.
Although they still share some of their genes, a major part of
their genomes evolved independently since then.
Currently, Esser et al. (2014) have explored the evolution
of a family of enzymes, called 2-hydroxy acid oxidases, or
2-HAOX, that are involved in breaking down fatty acids in
both plants and animals. They traced the evolution of
2-HAOX back to a common ancestor that once gave rise to
these enzymes. They built a database of all known 2-HAOX
sequences in plants, animals, and bacteria and reconstructed
phylogenetic trees; they also examined and compared the
substrate specificities of different members of this family.
Their data supports the evolution of 2-HAOX from a
common ancestral gene. Strikingly, the evolution of this protein family in animals mirrors that in plants, possibly because
animals have to break down fatty acids ingested from plants.
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This provides an example of how the ancestors of plants and
animals independently found identical solutions to similar
evolutionary challenges.
Reference
Esser C, Kuhn A, Groth G, Lercher MJ, Maurino VG. 2014. Plant and
animal glycolate oxidases have a common eukaryotic ancestor and
convergently duplicated to evolve long-chain 2-hydroxy acid oxidase. Mol Biol Evol. 31:1089–1101.
Joseph Caspermeyer*,1
1
MBE Press Office
*Corresponding author: E-mail: [email protected].
doi:10.1093/molbev/msu095
Advance Access publication March 31, 2014