120
THE BIOLOGY OF EUPHAUSIIDS
each other in size and this character alone can often be used to identify
them. The ranges in size and/or the mean size of nauplii, metanauplius
and the three calyptopes of several species are shown in Table I.
Several authors have found that the sizes of the calyptopes of the same
species are different in different sea areas, and Einarsson's (1945)
results for Thysanoessa raschii and T . longicaudata illustrate this point
quite clearly (Fig. 45). The calyptopes of T . longicaudata in the top
graph were taken in 1925 and they differ markedly in size from those
in the rest of the figure which have the same corresponding sizes.
A
5k 5
1.0
59" 21", 37"56'W
60"16'N, 14"26'W
I .5
2.0
2 5
Total lei igth
2 .
c
&
a-"
t
L
2
5
Z
Clyde
8-1 1°C
8 5- I I.5"C
30
5
W.Greenland
1-0
1-5
2.0
2.5
F I ~ .
45. Size distributions of calyptopos of A, Thysanoessa longicaudata and B, T. raschii.
(A, after Einarsson, 1945; B, after Mauchline, 1965%)
Similar differences in sizes of these larvae are evident in the case of
T . raschii (Fig. 45) and it will be seen that even greater differences are
found when older larval stages are examined.
Calyptopes of different species of euphausiids sometimes look very
different (Fig. 44). The edge of the carapace frequently has small spines
along all or parts of its length, the detailed distribution of these spines
being characteristic of a species. The form of the telson and its distal
and lateral spines also vary from species to species. Larvae of some
species, for example Thysanoessa species (Fig. 44, T. macrura), are thin
while other species have much more robust larvae, e.g. Meganyctiphanes
norvegica (Fig. 44). The median dorsal region of the carapace may be
developed as a spinous process (Fig. 44) or may be quite simple in form.
Live larvae can have chromatophores which are distributed throughout
the body in a pattern characteristic of a species. It is, however, in
practice usually extremely difficult to identify the species to which any
THE BIOLOGY OF EUPHAUSIIDS
each other in size and this character alone can often be used to identify
them. The ranges in size and/or the mean size of nauplii, metanauplius
and the three calyptopes of several species are shown in Table I.
Several authors have found that the sizes of the calyptopes of the same
species are different in different sea areas, and Einarsson's (1945)
results for Thysanoessa raschii and T . longicaudata illustrate this point
quite clearly (Fig. 45). The calyptopes of T . longicaudata in the top
graph were taken in 1925 and they differ markedly in size from those
in the rest of the figure which have the same corresponding sizes.
A
5k 5
1.0
59" 21", 37"56'W
60"16'N, 14"26'W
I .5
2.0
2 5
Total lei igth
2 .
c
&
a-"
t
L
2
5
Z
Clyde
8-1 1°C
8 5- I I.5"C
30
5
W.Greenland
1-0
1-5
2.0
2.5
F I ~ .
45. Size distributions of calyptopos of A, Thysanoessa longicaudata and B, T. raschii.
(A, after Einarsson, 1945; B, after Mauchline, 1965%)
Similar differences in sizes of these larvae are evident in the case of
T . raschii (Fig. 45) and it will be seen that even greater differences are
found when older larval stages are examined.
Calyptopes of different species of euphausiids sometimes look very
different (Fig. 44). The edge of the carapace frequently has small spines
along all or parts of its length, the detailed distribution of these spines
being characteristic of a species. The form of the telson and its distal
and lateral spines also vary from species to species. Larvae of some
species, for example Thysanoessa species (Fig. 44, T. macrura), are thin
while other species have much more robust larvae, e.g. Meganyctiphanes
norvegica (Fig. 44). The median dorsal region of the carapace may be
developed as a spinous process (Fig. 44) or may be quite simple in form.
Live larvae can have chromatophores which are distributed throughout
the body in a pattern characteristic of a species. It is, however, in
practice usually extremely difficult to identify the species to which any