30
THE BIOLOGY OF EUPHAUSIIDS
Genus Meganyctiphanes
Antennular peduncles of males and females are similar ; first segment
possesses backwardly projecting membranous lappet. Eighth pair of
thoracic limbs rudimentary ; endopodite of seventh pair consists of only
two elongated segments. Both terminal and proximal processes of
petasma developed. No ovisacs.
Only one species M . norvegica
Genus Nyctiphanes
There are four species in this genus. The antennular peduncle is
elongate and stronger in the male than in the female ; the third segment
in males is of peculiar shape. The basal segment carries a reflexed,
membranous lappet which shows sexual differences. Eggs are carried
by the females. For more detailed descriptions see Einarsson (1945),
Sheard (1953), Boden (1954), Boden et al. (1955).
la. Lappet on first antennular segment somewhat small, broader than long,
triangular with the acute end situated above the inner margin of the
ant ennule .
2a. Second antennular segment of female with rather large, oblong plate
terminating anteriorly in spine, frequently digitate along its upper
margin, and situated at the upper, inner end of the segment near its
end. The second antennular segment in males with a close row of
generally 3 (3-5) spiniform, strong, partly plumose setae on the
inner side of the segment near its base. Median lobe of copulatory
organs reaching rather near its base. Median lobe of copulatory
organs reaching near the end of the lateral process. Length
14-17mm . . .. .. . . .. . . . . couchii
2b. Second antennular segment of female with the upper inner edge
terminating in a minute spine, but without raised plate. Second
antennular segment of male with a low, raised plate projecting from
the inner upper edge near its distal end ; third segment without any
spiniform setae but with some minute setae distributed along the
inner side. Median lobe of copulatory organs reaching fully the end
of the lateral process
. . .. .. .. . . australis
2c. Second antennular segment of female with the upper inner margin
terminating in a minute or quite rudimentary spine, but without any
protruding plate. Second antennular segment of male without any
plate at the end of the upper inner edge; third segment with the
close row of nearly spiniform setae placed somewhat from the base or
at the middle of the inner side of the segment. Median lobe of the
copulatory organs reaching scarcely the middle of the lateral process.
Length of the largest male 12.3 mm
, ,
.. , , capensis
THE BIOLOGY OF EUPHAUSIIDS
Genus Meganyctiphanes
Antennular peduncles of males and females are similar ; first segment
possesses backwardly projecting membranous lappet. Eighth pair of
thoracic limbs rudimentary ; endopodite of seventh pair consists of only
two elongated segments. Both terminal and proximal processes of
petasma developed. No ovisacs.
Only one species M . norvegica
Genus Nyctiphanes
There are four species in this genus. The antennular peduncle is
elongate and stronger in the male than in the female ; the third segment
in males is of peculiar shape. The basal segment carries a reflexed,
membranous lappet which shows sexual differences. Eggs are carried
by the females. For more detailed descriptions see Einarsson (1945),
Sheard (1953), Boden (1954), Boden et al. (1955).
la. Lappet on first antennular segment somewhat small, broader than long,
triangular with the acute end situated above the inner margin of the
ant ennule .
2a. Second antennular segment of female with rather large, oblong plate
terminating anteriorly in spine, frequently digitate along its upper
margin, and situated at the upper, inner end of the segment near its
end. The second antennular segment in males with a close row of
generally 3 (3-5) spiniform, strong, partly plumose setae on the
inner side of the segment near its base. Median lobe of copulatory
organs reaching rather near its base. Median lobe of copulatory
organs reaching near the end of the lateral process. Length
14-17mm . . .. .. . . .. . . . . couchii
2b. Second antennular segment of female with the upper inner edge
terminating in a minute spine, but without raised plate. Second
antennular segment of male with a low, raised plate projecting from
the inner upper edge near its distal end ; third segment without any
spiniform setae but with some minute setae distributed along the
inner side. Median lobe of copulatory organs reaching fully the end
of the lateral process
. . .. .. .. . . australis
2c. Second antennular segment of female with the upper inner margin
terminating in a minute or quite rudimentary spine, but without any
protruding plate. Second antennular segment of male without any
plate at the end of the upper inner edge; third segment with the
close row of nearly spiniform setae placed somewhat from the base or
at the middle of the inner side of the segment. Median lobe of the
copulatory organs reaching scarcely the middle of the lateral process.
Length of the largest male 12.3 mm
, ,
.. , , capensis