130 
R.J. Tregonning, D.J. Gaughan, W.J. Fletchei 
The selected eggs were placed in four glass 
containers of seawater, two lightly aerated and two 
non-aerated, and maintained at ambient 
temperature (15.2 - 24.0°C, mean = 17°C). The eggs 
survived well under these conditions and nearly 
all them hatched. Forty larvae obtained from these 
hatched eggs were transferred to a constant 
temperature tank (18°C). Algae and enriched 
rotifers were added to the water as a potential food 
source for the developing larvae. 
Samples of eggs and larvae were taken daily and 
preserved in 5% formalin. The first few reared 
larvae were identified as being those of H. vittatus, 
thereby confirming that the eggs chosen for 
culturing were of this species. Hypertophus vittatus 
eggs were thus also able to be identified. Whilst 
the sample of eggs collected for rearing did not 
contain any early embryonic stages, these were 
described using material collected from previous 
plankton tows in Warnbro Sound. These earlier 
stages of whitebait eggs were identified by their 
size, the presence of a segmented yolk and the 
relative size of the yolk, as determined from the 
reared eggs of known identity. 
Measurements of eggs and larvae were made 
using an eyepiece micrometer fitted in a compound 
microscope. The measured lengths of the larvae 
refers to body length (BL, tip of snout to tip of the 
notochord; Leis and Tmski 1989). Descriptions of 
pigment refers to black pigment (melanin) unless 
stated otherwise. Because future identification of 
eggs and early larvae will most likely involve 
formalin-preserved samples, the illustrations and 
measurements were done with formalin-preserved 
material. The illustrations were made with the aid 
of camera lucida. 
RESULTS 
Development time of eggs 
Most (> 95%) of the reared H. vittatus eggs 
hatched within 48 hours of capture. The seven, 
least developed eggs had embryonic keels (see 
Figure Id) at the time the live sample was sorted 
(1400 hours, 2 hours after capture). Five of these 
eggs were allowed to develop through to hatching, 
which occurred 50 - 51 hours post-capture. 
General description of eggs 
Hyperlophus vittatus eggs are planktonic and 
spherical. The eggs have a thin chorion that 
appears smooth under low magnification. Under 
high magnification, however, evenly spaced 
corrugations can be seen. The diameter of 
formalin-preserved eggs ranges from 0.83 to 0.95 
mm, with a mode of 0.93 mm. 
Each egg contains one oil globule ranging in 
diameter from 0.025 to 0.075 mm, with a mode of 
0.048 mm. The oil globule is not pigmented. 
The yolk is spherical to ovoid, depending on the 
angle of view (Figure la,aa), with a diameter 
ranging from 0.50 to 0.87 mm (mode = 0.83 mm). 
In live eggs, the yolk appeared nearly transparent, 
but became opaque when preserved in formalin 
and is semi-translucent both under bright 
transmitted and reflected light. The yolk is coarsely 
and completely segmented with a 'frothy' or 
'bubbly' appearance which is readily apparent 
during all stages of development. 
The perivitelline space occupies 8.6 - 30.9% of 
the eggs diameter (mode = 14.5%). 
Description of various stages during 
development of the eggs 
Initially, the segmented yolk is the most 
prominent feature of the egg (Figure la,aa). Cell 
growth becomes obvious at the pole opposite to 
that containing the oil globule, i.e. the vegetative 
pole (Figure 1 b). This cap of cells appears to bulge 
slightly over the yolk. The cell-cap flattens out as 
cells multiply and spread in a thinner layer over 
the yolk towards the opposite pole (Figure lc). In 
contrast to the opacity of the relatively thick cell- 
cap, the yolk is visible beneath this thin layer of 
cells. 
The anterior end of the embryo becomes visible 
at the vegetative pole as a slightly raised strip (i.e., 
embryonic keel), with a flatter layer of cells lying at 
either side (Figure Id). The embryo is less distinct 
towards the posterior end and the thin layer of 
cells, although difficult to observe, is much wider 
than at the anterior end. 
The embryo then becomes more distinct, with the 
eye and some somites visible (Figure le). The tip of 
the tail lies beyond the oil globule. Divisions of the 
brain are visible from dorsal view of the head, 
which lies flat against the yolk, hi the majority of 
the eggs, at this and later stages, the yolk-sac lying 
beneath the head is concave, but with a central 
bulge (Figure If). However, the yolk remained 
rounded in a few of the eggs examined (cf. Figures 
lf,ff). The concavity may be due to absorption of 
the yolk by the developing embryo. 
With further development, the tail lifts away 
from the yolk, develops finfolds at the tip and 
begins to curve to the right. The tail also becomes 
more pointed and increases in length, while the 
finfold extends anteriorly almost to the head 
(Figure If). The anterior end of the embryo begins 
to lift away from the yolk. The gut which is present 
along the ventral surface of the embryo is difficult 
to distinguish and has therefore not been shown in 
Figure If. 
As development continues, the tail lengthens, the 
finfold widens and the hindgut becomes more 
obvious (Figure lg). At the time of hatching, the 
dorsoventrally flattened head of the embryo still 
