Control of diel vertical migration: Photoresponses of a larval crustacean1

Abstract

The lower threshold for phototaxis of dark-adapted larvae of the crab Rhithropanopeus harrisii is lo-' W *m-2 at 500-nm light. This threshold does not change throughout development. In the Newport River estuary (North Carolina), larvae show a pattern of nocturnal vertical migration in which the distribution of later-stage zoeal larvae centers on the lo-' W .m-2 isolume during the day. The behavioral responses underlying this relationship include a negative geotaxis in darkness which changes to a sinking response in light with a natural underwater distribution. The minimum increase in intensity above the lower threshold which evokes sinking decreases progressively with age. The intensity is well above the phototactic response threshold for stage I zoeae, but within one log unit of threshold for the other three zoeal stages. Thus, during the day larvae are associated with a preferred light level. This association results from a negative geotaxis in darkness that changes to a sinking response upon an increase in light intensity.Light is the dominant environmental factor controlling diel vertical migration of zooplankton (Forward 1976a). There are two main hypotheses concerning the manner in which light acts during vertical migration. Early workers hypothesized that animals were following a particular optimum or preferred light intensity level (preferendum hypothesis: Ewald 19 10; Rose 1925; Russell 1927). The other popular hypothesis is that the cue for initiating vertical movements is the rate and direction of change in light intensity from the ambient level (adaptation intensity), which itself can change over a day (Clarke 1930;Ringelberg 1964;Daan and Ringelberg 1969). The latter hypothesis is now widely accepted (see Kerfoot 1980) and is clearly supported by recent studies of arctic zooplankton (Buchanan and Haney 1980). Nevertheless, there are cases in which zooplankton appear to follow a particular isolume over a day (e.g. Boden and Kampa 1967), which would support the preferendum hypothesis. The main objection to this hypothesis is that behavioral responses which would allow an animal to remain at a particular intensity Cronin ( 1982) determined the vertical distribution of larvae of the estuarine crab Rhithropanopeus harrisii over several days and found that vertical migrations were associated with three environmental factors: currents, salinity, and light. We have measured the diel vertical migration of R. harrisii larvae in relation to light in the field and photoresponses in the laboratory. Our results indicate that the mean depth at which larvae aggregate frequently occurs at a particular light level during the day and that aggregation results from a photoresponse. Materials and methodsDiel vertical distributions of larvae of the crab R. harrisii (Gould) were measured in the Newport River estuary (North Carolina). On four occasions, larval distribution was sampled hourly at four depths: just beneath the surface, 1 m, 2 m, and just above the bottom (2.5-3.5 m). Collections were made with a gasoli...

Population structure and swarm formation of the cyclopoid copepod Dioithona oculata near mangrove cays

“…This threshold light intensity may stimulate a photokinetic response at which the activity of the animals changes to aggregation. This response is similar to that observed to initiate vertical migration of some planktonic crustaceans (Forward et al, 1984).…”

Vertical distribution and migration of planktonic polychaete larvae in Onagawa Bay, north-eastern Japan

“…Although ontogenic migration is not a general feature in polychaete larvae, ontogenic larval migration has been reported in two polychaete species, Pectinaria koreni and Owenia fusiformis (Lagadeuc et al, 1990;Thiebaut et al, 1992), and these ontogenic migrations are believed to be important for larval retention in the estuarine and coastal environments. Larval vertical migration is well known for decapod larvae, bivalve larvae and gastropod larvae (Cronin, 1982;Forward et al, 1984;Forward and Tankersley, 2001;Gibson, 2003;Rawlinson et al, 2004;Lloyd et al, 2012). Meanwhile, many studies assume a passive dispersal of polychaete larvae within the water column (Banse, 1986;Stancyk and Feller, 1986;Levin, 1986;Kingsford et al, 2002).…”

“…Three patterns of diel vertical migration (DVM) have been observed for planktonic invertebrate larvae: (i) nocturnal (normal) DVM, with an ascent to a minimum depth at night and a descent to a maximum depth during the day; (ii) reverse DVM, with the ascent to a minimum depth during the day and the descent to a maximum depth at night; (iii) twilight DVM, with an ascent to the surface at sunset, a descent to deeper water around midnight, a second ascent to the surface in the early morning hours, followed by a final descent to deeper water at sunrise (Forward, 1988;Pearre, 2003). Although the latter two patterns are rare for invertebrate larvae (Young and Chia, 1987;Queiroga and Blanton, 2005), some larvae, particularly decapods, are sensitive to the diel light cycle (Forward et al, 1984). These behaviours occur in a wide range of planktonic animals and are considered to be predator avoidance behaviour because larvae alter their DVM patterns in the presence of predators (Bollens and Frost, 1991;Neill, 1992;Cohen and Forward, 2009).…”

Larval Biology of the CrabRhithropanopeus harrisii(Gould): A Synthesis

“…Kalber and Costlow, 1966;Reisser and Forward, 1991 Characteristics in the water column -Mean Depth Cronin, 1982 Stage I zoea ϭ 1.8 m Stage IV zoea ϭ 2.06 m -Estuarine retention due to tidal vertical migration in all zoeal stages Cronin and Forward, 1979 Swimming speeds -Stage I zoea ϭ 2-9 mm s Ϫ1 Latz and Forward, 1977 -Stage IV zoea ϭ 4-13 mm s Ϫ1 Environmental cues that can be detected -Light Costlow, 1974 Ott and-Temperature Forward, 1990b -Salinity Latz andForward, 1989a -Hydrostatic pressure Wheeler andEpifanio, 1978;Forward and Wellins, 1989 Predator avoidance mechanisms -Shadow response Morgan, 1987b, 1990-Spines Forward et al, 1984Nocturnal diurnal vertical migration Vision -Spectral sensitivity maxima ϭ 420 nm and 500 nm Forward and Costlow, 1974;Cronin and Forward, 1988 -Light intensity threshold ϭ 2.5 x 10 11 photons m Ϫ2 s Ϫ1 Forward et al, 1984 …”