Oisi, Y., Ota, K. G., Kuraku, S., Fujimoto, S. & Kuratani, S., 2013: Craniofacial development of hagfishes and the evolution of vertebrates.
–Nature: Vol. 493, #7431, pp. 175-0 [doi: 10.1038/nature11794]
Cyclostomes, the living jawless vertebrates including hagfishes and lampreys, represent the most basal lineage of vertebrates. Although the monophyly of cyclostomes has been supported by recent molecular analyses, the phenotypic traits of hagfishes, especially the lack of some vertebrate-defining features and the reported endodermal origin of the adenohypophysis, have been interpreted as hagfishes exhibiting a more ancestral state than those of all other vertebrates. Furthermore, the adult anatomy of hagfishes cannot be compared easily with that of lampreys. Here we describe the craniofacial development of a series of staged hagfish embryos, which shows that their adenohypophysis arises ectodermally, consistent with the molecular phylogenetic data. This finding also allowed us to identify a pan-cyclostome pattern, one not shared by jawed vertebrates. Comparative analyses indicated that many of the hagfish-specific traits can be explained by changes secondarily introduced into the hagfish lineage. We also propose a possibility that the pan-cyclostome pattern may reflect the ancestral programme for the craniofacial development of all living vertebrates.
Zintzen, V., Roberts, C. D., Anderson, M. J., Stewart, A. L., Struthers, C.
D. & Harvey, E. S., 2011:
Hagfish predatory behaviour and slime defence mechanism.
–Nature Scientific Reports: Vol. 1, #131, [doi: 10.1038/srep00131]
24 August 2011
12 October 2011
27 October 2011
“Hagfishes (Myxinidae), a family of jawless marine pre-vertebrates, hold a
unique evolutionary position, sharing a joint ancestor with the entire
vertebrate lineage. They are thought to fulfil primarily the ecological
niche of scavengers in the deep ocean. However, we present new footage from
baited video cameras that captured images of hagfishes actively preying on
other fish. Video images also revealed that hagfishes are able to choke
their would-be predators with gill-clogging slime. This is the first time
that predatory behaviour has been witnessed in this family, and also
demonstrates the instantaneous effectiveness of hagfish slime to deter fish
predators. These observations suggest that the functional adaptations and
ecological role of hagfishes, past and present, might be far more diverse
than previously assumed. We propose that the enduring success of this oldest
extant family of fishes over 300 million years could largely be due to their
unique combination of functional traits.”
One just started to wonder about conodonts…