the siluriformes & gymnotiformes
Post on 07-Jan-2016
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Ostariophysii
Auditory specialization of ear Weberian complex Gas bladder Alarm substances Almost entirely freshwater fishes
25% of fish, 68% of fw spp.
Weberian Complex
Chain of bones- Weberian ossicles Connect swim bladder to ear canal Transmit vibrations
Siluriformes 3000 species, monophyletic group
Synapomorphies: Live everywhere and include hypogean and
trilobictic species Benthic- heavy bony head, reduced gas
bladder Most lack scales (naked), have barbels Eat everything: fish scales, blood, wood Fertilization: internal, external, sperm drinking Parental care in some species: mouth brooding
Ictaluridae
Only family in Illinois 14 species in IL Have bony pectoral and dorsal fins to
reduce predation
Giant Mekong Catfish
•646 pounds
•9 feet long
•Endangered due to dam construction
•Locals used to catch up to 50 per year, now only 2
Gymnotiformes
Electric eels and knifefishes 173 species Can generate electrical fields from
muscle/nerve cells to stun prey and deter predators
Also used for navigation and communication Range: fw streams in Neotropics Lack pelvic, dorsal, and commonly caudal
fins, very long anal fin (>140 fin rays) from pectoral girdle to end of body
Restricted gill openings
Gymnotiformes cont.
No maxillary teeth No schreckstoff or fright response Anus located anterior to mid-length
Review Questions1. Is the group Siluriformes a monophyletic
group or a paraphyletic group?2. Do you consider Siluriformes and
Gymnotiformes to be sister groups?3. How do facial phenotypes explain
feeding behaviors of the Siluriformes?4. Why are the Mekong catfish so
susceptible to over exploitation?5. What is the most important thing to not
do when swimming in central or south America?
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