External Morphology Gross Anatomy: Fins Dorsal & Taxonomy Caudal

Lab 1 Anal Pectoral Pelvic

1. Median fins (dorsal, anal, adipose, caudal) 2. Paired fins (pectoral and pelvic) – abdominal vs. thoracic placement 3. Fish use different fins for locomotion (wrasses use pectorals, triggerfish use median fins, tunas use caudal fins) 4. Fins are constructed of either radial cartilage (sharks) or bony rays (most fishes)

Caudal Fin Shape Body Shape body shape can predict ecology: • fusiform tend to be fast swimming and inhabit the upper portions of the water column • compressed tend to be good maneuvers • elongate tend to be good accelerators Caudal fin shape can predict fish ecology (ambush • anguilliform and globiform tend to be poor swimmers and benthic predator, continuous swimmer, burst swimmer, benthic dweller, etc.) • depressed tend to be benthic

Mouth Morphology Eyes Mouth morphology can be used to infer what types of prey are eaten (piscivores, planktivores, invertebrate eaters, herbivores, etc.) and where in the water column the prey are consumed

Inferior Subterminal 1. placement and size may indicate something about the ecology of the fish 2. some fish (e.g., mudskippers) are adapted to see both in and outside of water 3. stalked eyes in deepwater fish are one adaptation to gather light Terminal Superior

1 Countershading Lateral Line

• countershading is a feature common to most fish, especially those that inhabit the surface and midwater • fish are dark on the dorsal region and light on the ventral region • functions as camouflage in open water

1. lateral line extends along the midsection of the fish 2. can be continuous or broken 3. used in the detection of predators/prey (near touch sense) and for schooling

Scales Scales

Ø Placoid scales Ø Ctenoid/Cycloid scales • sharks • teleosts (more advanced bony fishes) • developmentally similar to teeth • ctenoid have ctenii (teeth Placoid (Chondrichthyes) on posterior margin) – Ganoid (Chondrostei) • reduces drag - increases breaks up turbulence at swimming efficiency high speeds Ø Ganoid scales • both lack hard enamel • sturgeon and gars • light weight, promote • outer layer of ganoine – flexibility similar to an enamel coating • hard protective plates… but heavy Ctenoid (Teleostei) Cycloid (Teleostei)

Morphological features commonly used in Spines & Rays taxonomy Spines Soft Rays Counts (“meristics”) • spines and rays – dorsal (D), anal (A), pectoral (P1), pelvic (P2) • lateral line scales – LLs Branched and • lateral line pores – LLp segmented • gill rakers – GR rays 1. Spines: roman numerals Measurements 2. Rays: numbered • length measurements – TL, FL, SL, HL, etc. 3. example: China Rockfish dorsal fin = D XII + 7-9 (12 spines, 7-9 rays)

2 Lateral Line Gills: gill arches & gill rakers 1. Lateral line scales designated as LLs 2. Lateral line pores designated as LLp 3. Some fishes have secondary branches of LL

1. use anterior-most, left gill arch 2. upper and lower gill raker count 3. GRt = total gill raker count (upper + lower)

Length Other Measurements & Features

1. head length: 1. total length (TL): snout to end of tail snout to end of opercle 2. standard length (SL): snout to end of 2. snout length: tip hypural bone of snout to eye

3. fork length (FL): snout to start of fork

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