Superclass Agnatha

Дата канвертавання24.04.2016
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WFB 232

Taxonomy, Week1 26 Jan 2005

Phylum Chordata

Notochord, Dorsal hollow nerve cord, Gill slits (at some point in life), Deuterostomus (2 openings)

First occurred in Cambrian/pre-Cambrian period (~ 530 MYA)

2 Superclasses: Agnatha, Gnathostomata

Superclass Agnatha

Jawless, fed through sucking mouthparts; Gill openings are pores (not slits); no paired fins.

Silurian/Early Devonian Periods (440-400 MYA)

3 classes

Myxini (hagfishes)

Cephalaspidimorphi (lampreys)

Pteraspidimorphi (extinct)
Class Myxini (Hagfishes) (1 Order)

Order Myxiniformes

Most primitive vertebrates; marine only, no larval stage (that has been found), degenerate eyes, cartilaginous skeleton, no vertebrae, no lateral line, jawless; scavengers; anguilliform shape

Gill openings, no paired fins; vestigial caudal fin; osmoregulation; body fluids at same salinity as ocean; ~ 40 spp. today

Economic importance: Leather and food source in Asia

First fossil evidence: Carboniferous, ~340 – 290 MYA
Class Cephalaspidomorphi (Lampreys)(1 Order)

Order Petromyzontiformes

Developed vertebrae; jawless; oral sucking disk; no paired fins; dorsal fin(s) well developed eyes; lateral gill pouches; long larval stage; anguilliform shape

Anadromous and freshwater species; spawn in tributaries; ~ 30 species

Economic importance: Great Lakes fisheries management; food source (Europe, Asia)

First fossil evidence: Carboniferous, ~340 – 290 MYA
Class Pteraspidomorphi (Extinct)

Oldest known fishes; bony armor, but not true bone (apatite)

No paired fins; tail with reverse heterocercal fins (lobes not equal in size);

not good swimmers; depressiform or compressiform shape

First fossil evidence: Upper Cambrian – Lower Ordovician (~520 MYA)
Good resources:

Tree of Life web:


Hagfish slime recipe:

From: Hagfish at Home,
To start, we prepared a basic scone mix and created two separate portions with everything included except the eggs and slime. Then, we mixed the hagfish slime (about one egg's worth) into one of the portions of the scone mix, using our hands, and we did the same with the egg and the other portion of scone mix. The egg and the slime did not have enough moisture on their own, so we added some water to each of the mixtures. We rolled both portions into balls measuring about 3.5 cm in diameter, slightly less than the size of the palms of our hands. We placed them on an ungreased pan and put them in the oven at 400 degrees Fahrenheit (200 degrees Celsius) for about ten minutes, then we checked on them. They weren't done, so we left them in for another 2.5 minutes, at which point they were finished. Of the two people immediately asked which scone was made with which, they each correctly guessed which ones were made with slime. We theorized that this could be attributed to the fact that the hagfish scones were kneaded more and had more water in them. We also offered a scone to Mike, a Marine Station employee, and he decided that "it was great" and that "it was not icky [sic] at all." He also mentioned that he "could feel the slime pumping through his veins" and that he felt "rejuvenated". Personally, none of us could taste a negative difference, and in fact we agreed that the ones made with hagfish slime tasted better!!

Other suggested uses for the slime of the hagfish are; as a substitute for eggs in other situations, as the colligative agent in raw hamburgers (perhaps Spam?), as an emulsifier or a thickening agent in other cooking, or perhaps in eggnog. There might also be a future for hagfish slime as a flycatcher due to its sticky properties, or as a prop in theatre and film industries requiring slime (ex. Ghostbusters, There's Something About Mary, Alien series).

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