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Journal of Experimental Marine Biology and Ecology 246 2000 85–101
www.elsevier.nl locate jembe
Eye function of Mysidacea Crustacea in the northern Baltic Sea
¨ Magnus Lindstrom
¨ Tvarminne Zoological Station
, University of Helsinki, FIN-10900 Hanko, Finland Received 5 August 1999; received in revised form 20 October 1999; accepted 28 November 1999
Abstract
Eye spectral sensitivity, [S l], was measured in seven northern Baltic mysid species using an
electroretinogram technique. Their S l curves were compared with the spectral distribution of
underwater light at their normal habitats. In the littoral species Neomysis integer, Praunus flexuosus and Praunus inermis, the S
l maxima, [Sl ], were in the wavelength-bands of
max
525–535, 505–515 and 520–530 nm respectively. The neoimmigrant species Hemimysis anomala had a S
l around 500 nm and high sensitivity at 393 nm, possibly indicating UV-sensitivity.
max
S l of the pelagic species Mysis mixta and Mysis relicta sp. II was at about 505–520 nm. M.
¨ ¨ ¨ relicta sp. I from Pojoviken Bay and fresh water humic Lake Paajarvi had S
l at ¯ 550 nm
max
and 570 nm respectively. This is in accordance with a similar long-wavelength shift in light transmittance of the respective waters. The eyes of the latter population were also damaged by
strong light. The pontocaspian neoimmigrant H . anomala is clearly adapted to waters transmitting
more blue light.
2000 Elsevier Science B.V. All rights reserved.
Keywords : Adaptation to UWL; Baltic Sea; ERG; Mysidacea; Light damage; Spectral sensitivity
1. Introduction
Traditionally five mysid species have been attributed to the northern Baltic Sea, ´
namely the pelagic glacial relict species Mysis relicta Loven, the pelagic Mysis mixta Lilljeborg, the benthic opportunist Neomysis integer Leach, and the phytal species
¨ ˚
¨ ¨
Praunus flexuosus Muller and Praunus inermis Rathke Segerstrale, 1945; Jarvekulg ¨
¨ ¨ and Veldre, 1963; Salemaa et al. 1986. Vainola 1986 however split M
. relicta into two separate species, M
. relicta I and M. relicta II, on the basis of electrophoretic findings. A
Tel.: 1358-19-280-148; fax: 1358-19-280-122. ¨
E-mail address : magnus.lindstromhelsinki.fi M. Lindstrom
0022-0981 00 – see front matter
2000 Elsevier Science B.V. All rights reserved. P I I : S 0 0 2 2 - 0 9 8 1 9 9 0 0 1 7 8 - 1
¨ 86
M . Lindstrom J. Exp. Mar. Biol. Ecol. 246 2000 85 –101
few years later the pontocaspian sublittoral immigrant Hemimysis anomala was first found by Salemaa and Hietalahti 1993.
The mysids have an important role as predators and prey in the Baltic ecosystem Gorokhova and Hansson, 1997; Viitasalo and Rautio, 1998 as well as in other seas
Mauchline, 1980, 1982. Their schooling behaviour and choice of specific habitats, their diurnal migrations and feeding behaviour point to extensive use of vision. M
. relicta has been shown to use vision in prey catching Ramcharan and Sprules, 1986. Also the big
eyes with hundreds of ommatidia indicate the importance of light and light fluctuations in their lives. M
. mixta, however, feeds more efficiently in darkness Rudstam et al., 1989 but obviously also uses vision in low light conditions own observations.
The prerequisite for vision is that the visual pigment of an eye is able to absorb radiation within the spectrum of available light. The light spectrum becomes narrower
with depth [Tyler, 1959, colour picture in Levine and MacNichol 1982]. The narrower the spectrum and the lower the light intensity, the more important it is for the animal that
the eye visual pigment absorbs as much as possible of the available light. This implicates tuning of the pigment’s absorption maximum towards the wavelengths of maximal light
transmission. This concept may also be applied to mysids, inhabiting a wide range of habitats in the Baltic sea and in lakes with waters of different spectral properties.
Relatively few measurements have been conducted on mysid spectral sensitivity [S
l]. Beeton 1959 used the activity spectrum of M. relicta to calculate its Sl, and so did Herman 1962 with Neomysis americana. S
l and light tolerance of M. relicta ¨
were investigated by Lindstrom and Nilsson 1984, 1988, S l of N. integer, P.
¨ flexuosus and M
. mixta by Lindstrom 1992 and light damage in M. relicta caused by ¨
¨ excessive light by Lindstrom et al. 1988, and Meyer-Rochow and Lindstrom 1997.
Spectrophotometric measurements of the M . relicta visual pigment has been performed
by Gal et al. 1999 and of visual and screening pigments by Dontsov et al. 1999. An adaptation of the visual system to the photic environment has been demonstrated
in fish by comparing the absorbance spectrum of visual pigments in solution with the available light spectrum Munz and McFarland, 1973; Levine and MacNichol, 1982.
The absorbance maximum of the pigment is frequently shifted to shorter wavelengths for species living in oceanic waters, with maximum transmittance in the blue, whereas the
pigments of species living in fresh waters, with maximum transmittance in the red, usually have absorbance maxima at longer wavelengths Lythgoe, 1972, 1979, although
Govardovskii 1976 doubted the significance of this sensitivity hypothesis for fishes. Animals without colour vision have only one visual pigment. The S
l of the eye is not always exactly the same as the absorbance spectrum of the visual pigment. Different
structures in the eye may alter the light spectrum reaching the rhabdom Goldsmith, 1978. In crabs Forward et al. 1988 also rejected the sensitivity hypothesis, basing
their opinion on microspectrophotometrically measured visual pigment spectra from 27 species of crabs. Donner 1971, however, showed an almost perfect correspondence
between S
l maxima [Sl ] of the amphipod Monoporeia
[Pontoporeia] affinis as
max
well as Pontoporeia femorata and the spectral distribution of light in the Baltic Sea. In ¨
the isopods Cirolana borealis and Saduria entomon, Lindstrom and Nilsson 1983 and ¨
Lindstrom et al. 1991 found good correspondence between S l
and spectral
max
distribution of underwater light UWL in the animals’ habitats in the North Sea and the Baltic Sea, respectively.
¨ M
. Lindstrom J. Exp. Mar. Biol. Ecol. 246 2000 85 –101 87
During the last years there has been extensive research on mysid ecology in the northern Baltic Sea Rudstam and Hansson, 1990; Salemaa et al., 1990; Kauppila, 1994;
¨ Nordstrom, 1997; Viherluoto, 1998; Viitasalo and Rautio, 1998; Gorokhova, 1999. This
called for a review on what is known about mysid vision in this area, with the two species of M
. relicta separated, and the newcomer of the nineties, the pontocaspian neoimmigrant H
. anomala included. The aim of this review is to show to what extent the eyes of mysids from the Finnish
coastal area are adapted to the light conditions prevailing in their normal habitats. The S
l recorded from the eyes of the different species are compared with the spectrum of downwelling light in their respective habitats.
2. Material and methods
