14
THE BIOLOGY OF EUPHAUSIIDS
Nematobrachion
with 3 species
Thysanoessa
with 9 species
Tessarabrachion
with 1 species
Nematoscelis
with 6 species
Stylocheiron
with 11 species
How are euphausiids related to other crustaceans? Earlier in this
chapter we mentioned that Milne-Edwards grouped the euphausiids
and mysids together as the Schizopoda and that Bell went even further
and placed Thysanopoda as a family of Mysidae. It was Boas who, in
1883, first stated the fundamental differences between euphausiids and
mysids, placing them in the orders Euphausiacea and Mysidacea
respectively and abandoning the use of the name Schizopoda. Nevertheless, G. 0. Sars two years later published his report on the Schizopoda
collected by H.M.S. “ Challenger ’’ and the discredited but convenient
grouping together of euphausiids and mysids persisted for many years
and indeed was used by H. J. Hansen in a report published in 1927 on
the mysids and euphausiids collected during the cruises of the
“ Travailleur )’ and the “ Talisman ” in 1880-83. He did, however,
agree with the views of Boas and excused his use of the artificial
grouping on grounds of convenience, recognizing that the two orders
should be separated not only by structural details but also by their mode
of development; the mysids do not have nauplius, etc., larvae but
emerge from the marsupium as miniature adults. The report of Boone
(1930) on the material collected during the cruises of the yachts
‘( Eagle ” and (‘Ara ’) shows that confusion had not entirely been
dispelled. He listed Schizopoda, in the title of his paper, as distinct
from, but equivalent to, Mysidacea and then, in his text, he included
Meganyctiphanes norvegica in the family Lophogastridae of the order
Mysidacea. The practice of taxonomy would appear to classify not
only animals but, a t times, also zoologists.
So far we have concerned ourselves with the grouping together of
the Euphausiacea with the Mysidacea to which they are not closely
related. To attain a more positive approach we must go back to a paper
by Calman (1904) on the classification of Crustacea Malacostraca. He
compared the features given by Sars in his ( ( Challenger ” Report for
the euphausiids with those for the mysids and pointed out that the two
groups did not agree in any character, except one which they did not
share with the lower Decapoda or, for the most part, with the
Stomatopoda and Leptostraca. The characters stated by Calman to be
shared by all these groups of crustaceans were a carapace, movable
eyes, a scale-like exopodite or branch on the antenna, an elongated and
THE BIOLOGY OF EUPHAUSIIDS
Nematobrachion
with 3 species
Thysanoessa
with 9 species
Tessarabrachion
with 1 species
Nematoscelis
with 6 species
Stylocheiron
with 11 species
How are euphausiids related to other crustaceans? Earlier in this
chapter we mentioned that Milne-Edwards grouped the euphausiids
and mysids together as the Schizopoda and that Bell went even further
and placed Thysanopoda as a family of Mysidae. It was Boas who, in
1883, first stated the fundamental differences between euphausiids and
mysids, placing them in the orders Euphausiacea and Mysidacea
respectively and abandoning the use of the name Schizopoda. Nevertheless, G. 0. Sars two years later published his report on the Schizopoda
collected by H.M.S. “ Challenger ’’ and the discredited but convenient
grouping together of euphausiids and mysids persisted for many years
and indeed was used by H. J. Hansen in a report published in 1927 on
the mysids and euphausiids collected during the cruises of the
“ Travailleur )’ and the “ Talisman ” in 1880-83. He did, however,
agree with the views of Boas and excused his use of the artificial
grouping on grounds of convenience, recognizing that the two orders
should be separated not only by structural details but also by their mode
of development; the mysids do not have nauplius, etc., larvae but
emerge from the marsupium as miniature adults. The report of Boone
(1930) on the material collected during the cruises of the yachts
‘( Eagle ” and (‘Ara ’) shows that confusion had not entirely been
dispelled. He listed Schizopoda, in the title of his paper, as distinct
from, but equivalent to, Mysidacea and then, in his text, he included
Meganyctiphanes norvegica in the family Lophogastridae of the order
Mysidacea. The practice of taxonomy would appear to classify not
only animals but, a t times, also zoologists.
So far we have concerned ourselves with the grouping together of
the Euphausiacea with the Mysidacea to which they are not closely
related. To attain a more positive approach we must go back to a paper
by Calman (1904) on the classification of Crustacea Malacostraca. He
compared the features given by Sars in his ( ( Challenger ” Report for
the euphausiids with those for the mysids and pointed out that the two
groups did not agree in any character, except one which they did not
share with the lower Decapoda or, for the most part, with the
Stomatopoda and Leptostraca. The characters stated by Calman to be
shared by all these groups of crustaceans were a carapace, movable
eyes, a scale-like exopodite or branch on the antenna, an elongated and