7723

• UCREFRP Catalog Number: 7723
• Author: Snyder, D. E. and R. T. Muth
• Title: Editor
• USFW Year: Series
• USFW - Doc Type: 1990
• Copyright Material: NO

metalarva, postflexion mesolarva with yolk,
protolarva without yolk).
The combined terminology is designed to
be relatively simple but comprehensive, pre-
cise in its transition criteria, applicable to
nearly all teleost fishes, and flexible. It can
be utilized in part (essentially as one of its
component terminologies) or its entirety
depending on purposes of the user. For

example, if it is necessary to acknowledge
only that the fish is a larva and whether it
bears yolk, the terms "yolk-sac larva" and
"larva without yolk" are all that is needed.
Biologists who formerly utilized one of its
component terminologies should have no
difficulty in adapting to the combined
terminology -- essential features and terms of
the original terminologies have been retained.

Larva: Period of fish development between hatching or birth and (1)
acquisition of adult complement of fin spines and rays (principal and
rudimentary) in all fins, and (2) loss beyond recognition of all finfold not
retained by the adult.

Protolarva: Phase of larval development characterized by absence of
dorsal, anal, and caudal fm spines and rays. (Standard length measured
to end of notochord.)

Mesolarva: Phase of larval development characterized by presence of at
least one dorsal, anal, or caudal fin spine or ray but either lacking adult
complement of principal soft rays in all median (dorsal, anal, and caudal)
fins or lacking pelvic fm buds or fins (if present in adult). (Standard
length measured to end of notochord or, when sufficiently developed,
axial skeleton.)

PreOexion Mesolarva: Among fishes with homocercal tails, phase
of mesolarval development characterized by absence of caudal fin
rays. (Posterior portion of notochord remains essentially straight
and standard length measured to end of notochord. When first
median fin ray is a caudal ray, as in most fishes, larva progresses
directly from protolarva to flexion mesolarva.)

Flexion Mesolarva: Among fishes with homocercal tails, phase of
mesolarval development characterized by an incomplete adult com-
plement of principal caudal fm rays. (Posterior portion of notochord
flexes upward and standard length measured to end of notochord.)

PostOexion Mesolarva: Among fishes with homocercal tails, phase
of meso larval development characterized by adult complement of
principal caudal fm rays. (Notochord flexion essentially complete
and standard length measured to posterior-most margin of hypural
elements or plates.)

Metalarva: Phase of larval development characterized by presence of (1)
adult complement of principal soft rays in all median fms and (2) pelvic
fin buds or fins (if present in adult). (Standard length measured to
posterior end of axial skeleton, hypural elements or plates in fishes with
homocercal tails.)

Yolk-sac, Yolk-bearing, With Yolk, Without Yolk: Examples of modifiers
used with any of the above period or phase designations to indicate presence
or absence of yolk material, including oil globules.

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