Population biology of the sand dollar, Peronella lesueuri, in Cockburn Sound, southwest Australia

摘要: Peronella lesueuri, commonly known as the pink sand dollar, is an irregular echinoid that can be found in sandy sediment substrates of Cockburn Sound, southwest Australia. The numbers which they are indicate likely to ecologically significant species. This first study biology and ecology this species. A survey current spatial distribution abundances lesueuri populations at a range sites within Sound shows presence dollars on shallower, sills surround Sound. P. was notably absent from deeper central basin where silt major component sediment. population densities ranged 0.3 2.5 individuals m-2 no than ten metres. Mean test lengths were larger less five metres depth. Sediment grain size preference food availability factors determined Detailed monthly sampling for demographics conducted Jervoise Bay over 23-month period temporal variations recorded. Two spikes December 2010 January 2011 indicative clear annual recruitment events. spike caused by recruitment, however, quick return what appeared stable density 0.13 – m-2. showed reproductive cycle annual, with peak spawning summer. Gametogenesis recorded spring, summer, spent gonads autumn recovered during winter. gametogenic underwent distinct morphological stages; Recovery, Growth, Mature, Partially Spawned Spent, similar those described other echinoderm cycles. In recovery stage, nutritive phagocytes filled lumen both testes ovaries. Primary gametocytes (Stage 1 gametes) present large numbers. Growing contained increasing secondary gametocytes. Mature gametes some while decreased volume. fully mature male gonads, lumens densely packed spermatozoa. variants stage observed ovaries; one full ova few oocytes, oocytes all stages development. Some female produced only cohort spawned out once released, others produce several cohorts throughout period. although spaces left observed. Lumens mostly empty, unspawned various degeneration occasionally present. Unspawned eventually broke down incorporated into phagocytes. highly synchronous between sexes. Juveniles attained sexual maturity half two years age. Size frequency distributions well variation indicated recruits annually. adult around May/June, six months after start Annual strength variable juvenile mortality high. Up 88% measured year alone. Pooled length-at-age data derived 2009 combined “adult” obtained growth zone counts construct scatter plot fit curve. Growth sigmoidal best Richards’ Curve. Juvenile grow quickly, maximum rate 60 mm yr-1 Intermediate-sized scarcely encountered. rapid intermediate predicted curve coupled high provides explanation scarcity 50 100 mm. slowed close zero approximately age, may associated attainment maturity. Maximum studied 182 life expectancy years. has diurnal seasonal patterns activity year, greater movement rates summer (mean 5.3 cm hr-1, day; 3.9 night) winter 2.7 2.0 night). Seasonal changes temperature physiological requirements dollar most reason differences; however reasons unclear. Direction random times year. Based rates, estimate 0.5 per m-2, it estimated rework entire area sediments habitats occupy 20 days. This provided histological description established annual. also determined. bioturbator. While further research required assess biological ecological significance shallow bottoms imply have potentially important role agent mediating biogeochemical processes surface sediments.