Lecture 4 – Teleostean radiation
1. Mobile premaxilla - (not mobile maxilla) Jaw protrusion. Evolved at least 3 times w/in teleosts a) Ostariophysi–Cypriniformes; b) Atherinomorpha and c) Percomorpha
2. Unpaired basibranchial tooth plates (part of an overall trend of consolidation of dermal tooth patches in pharynx.)
3. Internal carotid foramen in parasphenoid - functional role?
4. Well developed Mauthner system (specialized nerve cells)
5. MOST IMPORTANT - Structure of caudal fin.
Halecomorphs/ginglymodes = caudal rays articulate with posterior edge of haemal spines and hypurals (modified haemal spines). Fin is heterocercal (inside and out).
Chondrostean hinge – at base of upper lobe - zone of weakness
Teleosts - ural neural arches elongated into uroneurals. Pre-urals carry normal or little modified haemal arches and spines - while ural centra carry hypurals. Ural neural arches modified into uroneurals - stiffen upper lobe and insertion site for dorsal fin rays. Hypurals are expanded - into a broad plate.
Internally asymmetrical but externally symmetrical tail fin.
SYSTEMATICS - Four major groups.
1) Osteoglossomorpha – Bony tongues, phylogenetically primitive but extreme modifications, Parasphenoid bite, bone of palate toothed;
2) Elopomorpha –
Lecture 5 - Teleostei. Review features that make teleost a teleost - emphasize enhanced locomotory prowess of homocercal tail w/ reinforcing uroneural structures and functional implications of attaining symmetrical thrust.
Elopocephala - 2 elopocephalan lineages: Elopomorpha & Clupeomorpha
Elopomorpha - Leptocephalus larva; example = eels
Clupeomorpha - five families, about 300 species but in terms of biomass and importance for fisheries statistics unsurpassed. Largest taxon of non-domesticated vertebrates harvested by man. Unique otophysic connection between swim bladder and inner ear.
Lecture 6 = Lower euteleostean fishes
Ostariophysi - four major clades; Share a Weberian apparatus ‑ Chain of bony ossicles (derived from vertebral process) link swimbladder with inner ear ‑ change in swimbladder volume as sound waves pass through the fish ‑ rock the tripus and movement transferred through the intercalium and schaphium to the claustrum which abuts onto the perilymphatic sinus impar ‑ this in turn is linked to an endolymphatic transverse duct joining saculii of either side ‑ unusually wide range of frequencies and also seems capable of directional hearing.
Gonorynchiforms may be sister group to. Interesting feature uniting these with the otophysans ‑ so‑called "fright reaction" and production of "alarm substance" (shcreckstoff), a pheromone produced by specially modified epidermal club cells – found only in otophysans and gonorynichiforms.
Cypriniformes 2422 (6 families 256 genera)
Characiformes 1335 (10 families 253 genera)
Gymnotoids 55 (6 families 23 genera)
Siloroids 2211 (30 plus families 400 genera)
Cyprinid jaw protrusion mechanism radically different from Acanthomorphs (Atherinomorph and Percomorph). Functions same way ‑ high-speed inertial suction.
All three systems have analogous features:
1. Median rostral cartilage
2. Each overlain by premaxillary process
3. Head of maxilla bears a condyle that articulates via a meniscus with the ethmoid
4. A superficial layer of the adductor mass insert on maxilla