The study of diurnal vertical movements of macro-plankton (Russell, 1925) showed that many organisms, including amphipods migrated to the surface of the sea at night. Since this work there have been several papers reporting vertical movements in intertidal waters. Elmhirst (1931), demonstrated that certain species of amphipod swam in the surf zone during the night and that they showed seasonal variations in numbers, with a spring maximum. Subsequently, Watkin (1939, 1941) distinguished between those in-faunal species performing nocturnal vertical migrations into the surf and tidal immigrants carried in from sub-littoral habitats by the tide.
Several authors have studied the rhythmic behaviour of amphipods, including Papi (1955) who demonstrated an endogenous solar time sense in Talitrus saltator which was used for navigation. Talitrids were also investigated by Featherston & Maclntyre (1957) who suggested that changes in light intensity triggered the nocturnal foraging activity. Enright (1961, 1962, 1963) tested the effects of pressure, temperature, light intensity, absence of sand and shaking on rhythmic behaviour of the intertidal and in-faunal amphipod Synchelidium. The activity rhythm of Corophium volutator has been reported by Morgan (1965) in which a peak occurred on the early ebb. Various rocky shore Peracarida including species of Gammarus also perform vertical migrations into the surf at night (Jansson & Källander, 1968); the inhibiting effect of light was proven by experiments with controlled illumination.
Twenty-four hour, lunar-month, and seasonal, samples of amphipods were taken using a light trap from Karaka Wharf, Wellington Harbour, New Zealand (41° 16'S, 174° 51'E). Average number of amphipods for the 31 night samples was 255 per 30-min sample; few amphipods were caught in daylight samples. Algae-dwelling species formed 80.6%, infaunal species 16.6%, and pelagic species 2.8% of the total amphipods caught. Infaunal species appear early in the dark period and numbers decline during the night; numbers of algae-dwelling species build up during the night and reach a peak before dawn. Numbers of infaunal species increase on days 1 and 20 of the lunar month, whereas algae-dwelling species show no lunar rhythmicity but numbers increase in turbulent sea conditions. Seasonal sample numbers were erratic, greatest numbers being taken in early August and small peaks coinciding with spring and autumn sea temperature changes.Peak, swimming activity by adults of the infaunal lysianassid Parawaldeckia stephenseni was on the early ebb tide; juveniles continued to swim until dawn. Ovigerous females were present in the swimming population from days 1 to 12 of the lunar month; non-ovigerous females are mated by day 24 and disappear from the swimming population. Males swim throughout the lunar month. Average number of eggs carried is 12, females mature at 3.6 mm, and numbers of eggs carried increase after each successive moult.
A brief revieh ofthe work on crustacean compound eyes is given. Two main types of eye ha\ e been recognized: apposition and superposition. The ontogeny of the eyes of the common prawn Palaemon .rerratu$ is examined using a variety of methods: photography of live specimens, histological sections, SEM and T E M . In common with other decapod larvae, the common prawn hatches with apposition eyes having circular lenses parked hexagonally. After metamorphosis the gradual squaring of the eye facets, begun during the larval phase, is completed. l h i s is an essential prerequisite h r the functioning of the facultative superposition reflecting optics found in longbodied drcapods (e.g. shrimps, prawns and lobsters) and some Anomura. T h e possible phylogenetical significance of superposition, reflecting optics is also discussed. KEY WORDS: eyes ~ decapod phylogeny. Compound eyesprawn ontogeny ~~ apposition eyesreflecting superposition CONTEXTS 89 0024-4082/84/060089 + 25 $03.00/0 0 1984 The Linnean Socien of London 1
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