12
T H E BIOLOGY OF EUPHAUSIIDS
Messina, including a new euphausiid species, Euphausia intermedia.
When he made this identification, Meganyctiphanes norvegica had not
been reported from the Mediterranean, but just before his own paper
was published, he saw that of Lo Bianco (1904) in which Nyctiphanes
norvegica was identified from the vicinity of Capri. Riggio, therefore,
added a note to the end of his report confirming the synonymy of
Euphausia intermedia and Meganyctiphanes norvegica as he now knew
it to be from the work of Holt and Tattersall (1905a).
Another controversial species in the history of Meganyctiphanes
norvegica has been Meganyctiphanes calmani, first described from
Mediterranean specimens by Colosi (1918), the two species being said
to differ in the forms of the petasma and the thelycum. As has been
already mentioned, the petasma is the complex clasping organ on each
of the first pair of pleopods in the males and the thelycum is the copulatory organ in the female. Ruud (1936), reporting on the Euphausiacea
collected during the Danish oceanographic expedition to the Mediterranean and adjacent seas in 1908-10, pointed out that these characters
vary greatly according to the state of maturity of the animals and that
he, therefore, did not consider Meganyctiphanes calmani a valid species
and suggested that all the specimens belonged to the species Meganyctiphanes norvegica. Einarsson (1 945) supports Ruud’s views ; he
recognized the differences in the shape of the thelycum as being typical
of different degrees of maturity in Meganyctiphanes norvegica. Colosi
found some small additional processes a t the bases of the proximal,
terminal and lateral processes of the petasma but Einarsson, who
examined very many specimens of Meganyctiphanes norvegica, never saw
variations in these processes and considered that Colosi must have
mistaken the successors of the processes mentioned above, which had
already formed under the cuticle prior to moulting, as additional
processes. I n these circumstances too much weight should perhaps not
be placed on the form of the petasma as an additional specific character
for the genus Meganyctiphanes as was earlier suggested by Hansen
(1908a). Zimmer and Griiner (1956), although noting that Ruud did
not recognize Meganyctiphanes calmani as a valid species, list it as a
Mediterranean neritic species, on no very definite grounds. Colosi’s
material was apparently not examined by later workers and so the
matter remains inconclusive but it is perhaps significant that no further
specimens of Meganyctiphanes calmani have ever been reported from
the Mediterranean or other seas.
It is quite evident from this brief history of the species that
Meganyctiphanes norvegica (M. Sars) is now a well identified and firmly
established species of euphausiid. Similar stories of confusion in
T H E BIOLOGY OF EUPHAUSIIDS
Messina, including a new euphausiid species, Euphausia intermedia.
When he made this identification, Meganyctiphanes norvegica had not
been reported from the Mediterranean, but just before his own paper
was published, he saw that of Lo Bianco (1904) in which Nyctiphanes
norvegica was identified from the vicinity of Capri. Riggio, therefore,
added a note to the end of his report confirming the synonymy of
Euphausia intermedia and Meganyctiphanes norvegica as he now knew
it to be from the work of Holt and Tattersall (1905a).
Another controversial species in the history of Meganyctiphanes
norvegica has been Meganyctiphanes calmani, first described from
Mediterranean specimens by Colosi (1918), the two species being said
to differ in the forms of the petasma and the thelycum. As has been
already mentioned, the petasma is the complex clasping organ on each
of the first pair of pleopods in the males and the thelycum is the copulatory organ in the female. Ruud (1936), reporting on the Euphausiacea
collected during the Danish oceanographic expedition to the Mediterranean and adjacent seas in 1908-10, pointed out that these characters
vary greatly according to the state of maturity of the animals and that
he, therefore, did not consider Meganyctiphanes calmani a valid species
and suggested that all the specimens belonged to the species Meganyctiphanes norvegica. Einarsson (1 945) supports Ruud’s views ; he
recognized the differences in the shape of the thelycum as being typical
of different degrees of maturity in Meganyctiphanes norvegica. Colosi
found some small additional processes a t the bases of the proximal,
terminal and lateral processes of the petasma but Einarsson, who
examined very many specimens of Meganyctiphanes norvegica, never saw
variations in these processes and considered that Colosi must have
mistaken the successors of the processes mentioned above, which had
already formed under the cuticle prior to moulting, as additional
processes. I n these circumstances too much weight should perhaps not
be placed on the form of the petasma as an additional specific character
for the genus Meganyctiphanes as was earlier suggested by Hansen
(1908a). Zimmer and Griiner (1956), although noting that Ruud did
not recognize Meganyctiphanes calmani as a valid species, list it as a
Mediterranean neritic species, on no very definite grounds. Colosi’s
material was apparently not examined by later workers and so the
matter remains inconclusive but it is perhaps significant that no further
specimens of Meganyctiphanes calmani have ever been reported from
the Mediterranean or other seas.
It is quite evident from this brief history of the species that
Meganyctiphanes norvegica (M. Sars) is now a well identified and firmly
established species of euphausiid. Similar stories of confusion in