26
THE BIOLOQY OF EUPHAUSIIDS
morphology of species in the genus ThysanoGsa. He studied, in
particular, the number of articulations on the antennular flagellum, the
relative proportions of the carapace and of the rostrum, the position
of the lateral denticle, the shape and size of the eyes, the mouthparts,
stomach, and petasma. No such detailed information is available for
other genera but once this becomes available and is compared to
Nemoto’s data then some very interesting information on variation
and constancy of characters within the euphausiids as a whole will be
available. Nemoto has shown that within the genus Thysanoessa, some
species show sexual dimorphism in characters such as the eyes,
antennular flagella, and the form of the preanal spine.
The synonymy and general distribution of each species of euphausiid
is detailed in the next chapter. The key presented in this chapter allows
identification of species but the identification should be checked by
reference to original descriptions. Boden (1954), Boden et al. (1955),
Einarsson (1945), and John (1936) are references of particular value for
identifications. Other references are mentioned in the key. One of the
best methods of using the key is to identify the unknown euphausiid
with it and then, if no special reference is given in the key, to turn to
the next chapter and examine the references given under the synonymy
of that species ; original descriptions are referred to there.
Several species mentioned in the literature are now considered to be
invalid, usually because the descriptions are not detailed enough to
refer them to one of the valid species. Colosi (1916) described
Euphausia messanensis from the Straits of Messina and Torelli (1934)
recorded it in the Red Sea ; no other records of this species are available
and it is probably not a valid species but a variant form of some other
species. Boone (1935) found E. alvae in the East Indian Archipelago
but no euphausiid corresponding to this species has been found since.
Euphausia pellucida Dana (1850) is referred to by several authors but
is, according to Hansen (1 905b), unrecognizable from Dana’s description.
Two species, Thysanoessa armata Marukawa (1928) (now
T . longipes) and T . mansui Marukawa (1928) were wrongly included by
Sheard (1942) in the genus Thysanopoda (Sheard, 1953), although
Ponomareva (1963) places T . mansui as a species synonymous with
Th.ysanopoda monacantha. Thysanopoda spinula Macdonald (1 929) has
not been recognized by other workers. According to Sheard (1953)
Stylocheiron armatum was distinguished from S. carinaturn by Colosi
(1917b) on the basis of small differences in the petasma and in the
elongated thoracic limb and, bearing in mind the variation found in the
petasma of S. maximum by Banner (1950), it is possible that S. armatum
is synonymous with S. carinaturn.
THE BIOLOQY OF EUPHAUSIIDS
morphology of species in the genus ThysanoGsa. He studied, in
particular, the number of articulations on the antennular flagellum, the
relative proportions of the carapace and of the rostrum, the position
of the lateral denticle, the shape and size of the eyes, the mouthparts,
stomach, and petasma. No such detailed information is available for
other genera but once this becomes available and is compared to
Nemoto’s data then some very interesting information on variation
and constancy of characters within the euphausiids as a whole will be
available. Nemoto has shown that within the genus Thysanoessa, some
species show sexual dimorphism in characters such as the eyes,
antennular flagella, and the form of the preanal spine.
The synonymy and general distribution of each species of euphausiid
is detailed in the next chapter. The key presented in this chapter allows
identification of species but the identification should be checked by
reference to original descriptions. Boden (1954), Boden et al. (1955),
Einarsson (1945), and John (1936) are references of particular value for
identifications. Other references are mentioned in the key. One of the
best methods of using the key is to identify the unknown euphausiid
with it and then, if no special reference is given in the key, to turn to
the next chapter and examine the references given under the synonymy
of that species ; original descriptions are referred to there.
Several species mentioned in the literature are now considered to be
invalid, usually because the descriptions are not detailed enough to
refer them to one of the valid species. Colosi (1916) described
Euphausia messanensis from the Straits of Messina and Torelli (1934)
recorded it in the Red Sea ; no other records of this species are available
and it is probably not a valid species but a variant form of some other
species. Boone (1935) found E. alvae in the East Indian Archipelago
but no euphausiid corresponding to this species has been found since.
Euphausia pellucida Dana (1850) is referred to by several authors but
is, according to Hansen (1 905b), unrecognizable from Dana’s description.
Two species, Thysanoessa armata Marukawa (1928) (now
T . longipes) and T . mansui Marukawa (1928) were wrongly included by
Sheard (1942) in the genus Thysanopoda (Sheard, 1953), although
Ponomareva (1963) places T . mansui as a species synonymous with
Th.ysanopoda monacantha. Thysanopoda spinula Macdonald (1 929) has
not been recognized by other workers. According to Sheard (1953)
Stylocheiron armatum was distinguished from S. carinaturn by Colosi
(1917b) on the basis of small differences in the petasma and in the
elongated thoracic limb and, bearing in mind the variation found in the
petasma of S. maximum by Banner (1950), it is possible that S. armatum
is synonymous with S. carinaturn.