BIOTIC Species Information for Neomysis integer
|Researched by||Georgina Budd||Data supplied by||MarLIN|
|Refereed by||This information is not refereed.|
||Feeding method||Active suspension feeder
|Typical food types||Detritus, diatoms, filamentous algae and small crustaceans.||Habit||Free living|
|Bioturbator||Not relevant||Flexibility||High (>45 degrees)|
|Height||Not relevant||Growth Rate||1-2 mm/month|
|Adult dispersal potential||100-1000m||Dependency||Independent|
|General Biology Additional Information||Growth rate
In mature adults from the Ythan Estuary, Scotland, growth rate was recorded to be 1-2 mm per month in the field, which followed a rapid period of growth, of 4-5 mm per month in the summer juveniles (Astthorsson, 1980). The winter generation had a growth rate of 3-4 mm monthly for juveniles and about 1 mm per month for mature adults. During the winter there was a period of about 3 months when growth ceased (Astthorsson & Ralph, 1984).
Neomysis integer performs a diel vertical migration, rising towards the surface waters during the night and returning to the deeper waters at daylight where it remains throughout the day (Hough & Naylor, 1992). Normal diurnal light levels are inhibitory and produce a negatively phototactic response in most species; the 24 hour cycle of change in ambient light intensity is the dominant factor controlling the diel vertical migration of mysids, such as Neomysis integer (Mauchline, 1980).
Maintenance of position
As a pelagic organism, Neomysis integer faces the problem of retaining its position within the estuarine environment, against conditions of net seaward transport (Hough & Naylor, 1992). In general, there are three main controls of the positioning of pelagic invertebrate populations in estuarine systems: reproductive compensation of seaward losses (a relatively large number of juveniles are produced per brood, behavioural adaptations (alterations in swimming activity at different tidal phases) and hydrodynamic process (distribution directly related to patterns of water circulation) (Schlacher & Wooldridge, 1994).
In laboratory experiments, Hough & Naylor (1992) found Neomysis integer to have an endogenously controlled circa-tidal swimming activity, with peak swimming activity expressed during the ebb tide. In the investigation of the significance of its endogenously controlled ebb tide swimming, Hough & Naylor (1992) observed Neomysis integer to demonstrate rheotaxic behaviour. Typically on the ebb tide in the Conway Estuary, shallow pools of isolated water are left as the tide ebbs. Aggregations of Neomysis integer in imminent risk of stranding initially headed into the current, but as the water level dropped, and before a pool was completely cut off, the species swam with the current draining from the pool and entered the stream before finally re-orientating and swimming into the current. Hough & Naylor (1992) suggested that such rheotaxic behaviour coupled a continuous ebb-phased swimming rhythm, may be of importance in the avoidance of stranding on the shore at low tide.
Maximum swimming speed by the mysid is also important, since it dictates in which flow velocities the species can maintain its position. Specimens studied by Roast et al. (1998b) from the East Looe River Estuary (Cornwall) tolerated current velocities of 6 and 9 cm s-1, a few could swim at speeds of up to 27cm s-1, but was not sustainable for more than a few seconds. Roast et al. (1998b) found the swimming speeds of Neomysis integer correlated well with the distribution of the species in the East Looe River Estuary, where mysids were found consistently in slower moving water (<15 cm s-1) and were absent in faster flowing water (>20 cm s-1). Roast et al. (1998b) stated that if swimming speed is an important factor in the position maintenance of the species, it is likely to be beneficial for the mysid to utilize any available shelter in order to conserve energy. In experimental conditions, Roast et al. (1998b) observed Neomysis integer to attach themselves to the substratum, thereby entering the boundary layer where lower velocity flows are experienced. This corresponds with field studies, for instance in the Conway Estuary, North Wales, Neomysis integer was always caught in greatest abundance in near-bottom plankton samples (Hough & Naylor, 1992). On the ebb tide, during flood and high-tide periods in the Ythan Estuary, Scotland, the species was concentrated in a band toward the moving tide edge where flows were typically lower. Also on the ebb tide and at low tide the species aggregated in shallower water and in the lee of rocks and macroalgal clumps where water flow rates were less than 10 cm/sec (Lawrie et al.,1999). Shallow burrowing into the sediment is also a common means of position maintenance in moving waters, and is a common behaviour of mysids inhabiting areas subject to tidal disturbance (Roast et al., 1998b).
|Biology References||Makings, 1977, Mauchline, 1980, Tattersall & Tattersall, 1951, Mauchline, 1971, Astthorsson, 1980, Hough & Naylor, 1992, Lawrie et al., 1999, Barnes et al., 1979, Astthorsson & Ralph, 1984, Schlacher & Wooldridge, 1994, Roast et al., 1998b,|