Glossary

This glossary defines only those terms that are relevant to fish larvae. For the general body regions and standard measurements recorded in larval fish refer to Figure 1. For spines of the head we follow the terminology of Figure 2.

Abbreviations

These abbreviations are used throughout the larval fish descriptions.

a

anlage
Rudimentary form of an anatomical structure; primordium; a German word the plural of which is anlagen.

b

body depth (BD)
The vertical distance between body margins (exclusive of fins) through the anterior margin of the pectoral‑fin base: not necessarily the greatest body depth.
body length
Size of the larva; corresponds to notochord length in preflexion and flexion larvae and to standard length after flexion.
body width
The transverse distance between body margins at the pectoral‑fin base.

c

choroid fissure
Line of juncture of invaginating borders of the optic cup; apparent in young fish as a trough‑like area below lens.
choroid tissue
An undifferentiated mass of (usually) unpigmented tissue adhering to the ventral surface of the eye (see Moser and Ahlstrom 1970).
cleithrum
Prominent bone of pectoral girdle, clearly visible in many fish larvae.

d

demersal egg
An egg which remains on the bottom either free or attached to the substratum.

e

eye diameter (ED)
The horizontal distance across the midline of the pigmented region of the eye.

f

fin elements
Fin supports; spines and soft rays.
finfold
Medial fold of integument that extends along body of developing fishes and from which medial fins arise.
fin length
Length of the longest soft ray of designated fin.
Flexion
Bending upward of the notochord tip as part of the process of caudal-fin formation.
flexion larva
Development stage beginning with flexion of the notochord and ending with the hypural bones assuming a vertical position.

g

gas bladder
Membranous, gas‑filled organ located between the kidneys and alimentary canal in teleost fishes; air bladder or swim bladder.

h

head length (HL)
The horizontal distance from the tip of snout to posterior‑most part of opercular membrane; prior to development of operculum, measured to the posterior margin of cleithrum.
head width
The transverse distance between margins at the widest area of the head.  Not applicable to larvae with flared opercles.

i

incipient fin‑ray
Early stage in fin-ray development; an unossified thickening in finfold articulating with the fin base.
initially
When used in the Morphology section, meaning in the smallest available specimens.

j

juvenile
Developmental stage from attainment of full external meristic complements and loss of temporary specializations for pelagic life to sexual maturity.

l

lachrymal
The anterior bone of the infraorbital series.  Frequently overlaps the maxilla when the mouth is closed.
larva
Developmental stage between hatching (or birth) and attainment of full external meristic complements (fins and scales) and loss of temporary specializations for pelagic life; yolk‑sac through postflexion stage inclusive.

m

melanin
A black pigment.
melanophores
Melanin‑bearing cells (brown to black); frequently capable of expansions and contractions which change their size and shape.
mouth width
The gape; transverse distance between corners of the mouth.
myomeres
Serial muscle bundles of the body.
myosepta
Connective tissue partitions separating adjacent myomeres.

n

notochord
Longitudinal supporting axis of body which is eventually replaced as a support by the vertebral column in teleostean fishes.
notochord length
Straight line distance from tip of snout to posterior tip of notochord; used prior to and during flexion.

o

olfactory pit
A shallow depression on the snout from which olfactory organ develops.
ossification
Hardening of bony parts through deposition of calcium salts; usually detected by staining with alizarin.
otic capsule
Sensory anlage from which the ear develops; clearly visible during early development.

p

pectoral bud
Swelling at site of future pectoral fin; anlage of pectoral fin.
pelagic
In the water column as distinct from substrate‑associated; neither necessarily planktonic nor oceanic.
pelagic egg
Egg which floats freely in the water column, often slightly positively buoyant.
pelagic juvenile
Pre‑settlement juvenile of a species that is benthic or reef‑associated as an adult.
pelvic bud
Swelling at site of future pelvic (ventral) fin; anlage of pelvic fin.
postanal myomeres
Myomeres posterior to the posterior margin of the anus; includes terminal myomere from which urostyle forms.
postflexion larva
Developmental stage from formation of the caudal fin (hypural elements vertical) to attainment of full external meristic complements (fin rays and scales) and loss of temporary specializations for pelagic life.
preanal length (PAL)
Distance from the tip of the snout along the midline to a vertical line through the posterior edge of the anus.
pre dorsal‑fin length
Distance from the tip of the snout along the midline to a vertical line through the origin of the dorsal fin or dorsal‑fin anlage.
preflexion larva
Developmental stage beginning at hatching and ending at the start of upward flexion of the notochord.
pre gas‑bladder length
Distance from the tip of the snout along the midline to a vertical line through the anterior edge of the gas bladder.
pre pelvic‑fin length
Distance from the tip of the snout along the midline to a vertical line through the origin of the pelvic fin.

s

settlement
Process by which a larva or juvenile leaves the pelagic environment and adopts a substrate‑associated lifestyle; not applicable to species pelagic as adults.
settlement stage
Developmental stage where the pelagic larva or juvenile is morphologically and physiologically ready (competent) to adopt a substrate‑associated life style. Often, but not always, associated with larva to juvenile transition.  Applicable only to species that are not pelagic as adults.
snout length (SnL)
Horizontal distance from the tip of the snout to the anterior margin of the pigmented region of the eye.
soft rays
Bilaterally paired, usually segmented fin supports; often referred to as rays.
spine length
Straight line distance of a fin or body spine from base to tip.
spines
1) Unpaired, unsegmented, unbranched fin supports, usually (but not always) stiff and pungent; may initially form as bilaterally paired structures prior to ossification.  2) Bony, pointed, elongate projections on the body, usually the head, that are often temporary specialisations for pelagic life.
standard length (SL)
Distance from tip of the snout along the midline to a vertical line through the posterior edge of the hypural plate.

t

tail
Portion of body posterior to the anus.
teeth
Larvae of some species develop 'larval teeth' prior to the appearance of definitive teeth.  Larval teeth are little exserted spines on the premaxilla or dentary, and they are lost during the larval phase (Baldwin 1990).  The descriptions herein do not generally distinguish between 'larval teeth' and definitive teeth.
temporary specialisations for pelagic life
Morphological (not pigment) characters such as trailing guts, preopercular spines, or elongate fin spines that are not retained in adults but are present during the pelagic phase.  Often these are lost after settlement, but if present in settled individuals, they are clearly reduced and are disappearing.
total length (TL)
Distance from the tip of the snout along the midline to the posterior edge of the caudal finfold; body length is traditionally expressed as total length in the Japanese literature.
transition
Change from the larval to the juvenile stage. May take place over an extended period of time.  Especially used for pelagic taxa where there is not a change in habitat at or near the end of the larval phase.  Individuals in transition are considered larval. In the text, we avoid the use of the term metamorphosis because of its implications of abrupt and extensive morphological change over a short period.
trunk
Body between head and anus.

u

unspecified length
Undefined measurement of body length derived from the literature.

v

vent to anal‑fin length
Straight line distance from posterior edge of the vent (anus) to the anterior origin of the anal fin or anal‑fin anlage.

y

yolk sac
A bag‑like, ventral extension of the primitive gut containing the yolk.
yolk‑sac larva
Developmental stage beginning with hatching and ending with exhaustion of yolk reserves and characterised by presence of a yolk sac.