The ecology of Euspira pulchellus (Gastropoda: Naticidae)

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Documents

  • Peter Kingsley-Smith

Abstract

Euspira pulchellus is patchily distributed subtidally on muddy sand with significantly higher densities of individuals during summer (700 ha·¹ May to August 2001) than winter (225 ha·¹ November 200 to February 2001 ). Recruitment of Euspira pulchellus occurred over an extended period. Egg collar production in the laboratory occurred in females > 8-9.9 mm and was greatest during July and August. Largest individuals (14-15.9 mm) were most fecund despite ceasing egg collar production in late September. Smaller individuals (8-13.9 mm) laid egg collars until November. Small individuals (4-5.9 mm) grew rapidly during summer (April to September) whilst snails > 9 mm grew slowly. Egg collar wet weight was significantly correlated with the number of larvae released (r = 0.932, p < 0.001). Larvae metamorphosed 6-7 weeks after hatching (19-20° C) when exposed to muddy sand. Juveniles started drilling within 3 days of metamorphosis. Snails were size-selective in their choice of cockles and were cannibalistic. Inner and outer drill hole diameters were significantly (p < 0.001 ) correlated (r = 0.899 and 0.923 respectively) with shell length. Snails drilled cockles in the centre of the shell valve, with no preference for the left or right valve. Feeding rates were highest in July (14.57 cockles snail–¹ month–¹ ) and lowest in March (3.58 cockles snail–¹ month–¹ ) and like growth rates were related to seawater temperature. Statolith diameter and shell length were closely related (R² = 0.972). The larval statolith, settlement ring, first and second annual rings, and weaker rings were observed within the adult statolith. Variation in settlement ring and first ring diameters may reflect time of settlement and consequently time available for growth in the first year. First and second ring diameters were significantly correlated (r = 0.844, p< 0.001 ). Estimates of shell length from first and second ring diameters suggest that the prominent statolith rings are formed annually.

Details

Original languageEnglish
Awarding Institution
  • University of Wales, Bangor
Supervisors/Advisors
Award date2002