244
THE BIOLOGY O F EUPHAUSIIDS
while the second is represented by the bulk of the gland cells (Fig. 86).
Shimomura and Johnson ( 1967) have identified a protein, molecular
weight of 200 000 or more, and another substance that recycles in
the reaction producing luminescence. The oxidative decomposition of
the protein is evidently the major source of energy for the luminescence
and these two types of gland cells may be responsible for the secretion
of these two substances. The secretions are probably discharged into
the striated body whose internal morphology, like a group of spaced
rods, would provide a large reactive surface area immediately behind
the lens in which the light production would take place. Different
species of euphausiids have slightly different shapes of lenses in their
photophores but the shape within any one species is relatively constant.
According to Bassot (1960b) the lens consists of three layers, a cytoplasmic layer, a cortical layer, and a central homogeneous zone. No
information is available on the optical characteristics of the lenses.
Murray (1885), during the voyage of H.M.S. " Challenger '), noticed
that euphausiids luminesce spontaneously but even more so when
stimulated by handling. More anterior photophores light up before
more posterior ones and in many instances the abdominal photophores
do not luminesce but only the ones on the eye stalks and thorax.
Vallentin and Cunningham (1888) noticed that the abdominal and
thoracic photophores are extinguished before those in the eyes. The
duration of any one flash of luminescence is reported in the early
literature to vary from a few seconds to 30 sec. Pierantoni (1921)
states that the developing photophore in the eye of the first calyptopis
of Euphausia krohnii can produce light for longer periods than photophores of the adult. I n recent years, the development of photomultipliers
has allowed quantitative and qualitative investigations of the bioluminescence of these animals to be made without the subjective errors
of the earlier investigators owing to varying degrees of dark adaptation
of their eyes. Thus, the spectral characteristics of euphausiid
luminescence were investigated (Fig. 87) and the maximum emissions
found to be in the blue green range. Nicol (1962) and Boden and
Kampa (1964) have recently reviewed the literature on marine
bioluminescence and recourse should be made to these articles for
information on other luminescent planktonic organisms.
Studies of the flashing of Meganyctiphunes norvegica have been
made in the laboratory to try and determine the mechanisms controlling spontaneous luminescence of this animal. When single animals
are placed in the light for some time, then transferred to a dark container with a photomultiplier, they luminesce (Mauchline, 1960). This
behaviour is referred to as the lightldark reaction and there is a seasonal
THE BIOLOGY O F EUPHAUSIIDS
while the second is represented by the bulk of the gland cells (Fig. 86).
Shimomura and Johnson ( 1967) have identified a protein, molecular
weight of 200 000 or more, and another substance that recycles in
the reaction producing luminescence. The oxidative decomposition of
the protein is evidently the major source of energy for the luminescence
and these two types of gland cells may be responsible for the secretion
of these two substances. The secretions are probably discharged into
the striated body whose internal morphology, like a group of spaced
rods, would provide a large reactive surface area immediately behind
the lens in which the light production would take place. Different
species of euphausiids have slightly different shapes of lenses in their
photophores but the shape within any one species is relatively constant.
According to Bassot (1960b) the lens consists of three layers, a cytoplasmic layer, a cortical layer, and a central homogeneous zone. No
information is available on the optical characteristics of the lenses.
Murray (1885), during the voyage of H.M.S. " Challenger '), noticed
that euphausiids luminesce spontaneously but even more so when
stimulated by handling. More anterior photophores light up before
more posterior ones and in many instances the abdominal photophores
do not luminesce but only the ones on the eye stalks and thorax.
Vallentin and Cunningham (1888) noticed that the abdominal and
thoracic photophores are extinguished before those in the eyes. The
duration of any one flash of luminescence is reported in the early
literature to vary from a few seconds to 30 sec. Pierantoni (1921)
states that the developing photophore in the eye of the first calyptopis
of Euphausia krohnii can produce light for longer periods than photophores of the adult. I n recent years, the development of photomultipliers
has allowed quantitative and qualitative investigations of the bioluminescence of these animals to be made without the subjective errors
of the earlier investigators owing to varying degrees of dark adaptation
of their eyes. Thus, the spectral characteristics of euphausiid
luminescence were investigated (Fig. 87) and the maximum emissions
found to be in the blue green range. Nicol (1962) and Boden and
Kampa (1964) have recently reviewed the literature on marine
bioluminescence and recourse should be made to these articles for
information on other luminescent planktonic organisms.
Studies of the flashing of Meganyctiphunes norvegica have been
made in the laboratory to try and determine the mechanisms controlling spontaneous luminescence of this animal. When single animals
are placed in the light for some time, then transferred to a dark container with a photomultiplier, they luminesce (Mauchline, 1960). This
behaviour is referred to as the lightldark reaction and there is a seasonal