200-220 u. A few remained planktonic until 280 u. At 5°C larvae failed 

 to grow. At temps from 10°C to 22.5°C larvae behaved normally. Mortality 

 was low at these temps but high at 5° and 26°C. Growth rates increased 

 with temp increase from 5° to 16 °C. Maximum growth rate appeared to be at 

 about 18°C and growth was retarded above 20°C. In nature, spat grew to 

 0.1 to 0.3 mm before the first winter, then growth slowed or stopped. 

 Noticeable growth was restricted to May-Aug inclusive, and reached a max 

 in July. More or less well-defined rings on the shell are formed annually, 

 and can be used to estimate age. The 1955 set grew faster than clams born 

 earlier despite the larger population. About 15% of the clams in their 

 first year of life were bored by Natica alderi , 5% in their 2nd, and 1-2% 

 in their third year. An additional 25% of the population died from unknown 

 causes. Experiments showed that mortality was not a function of population 

 density between 300 clams/m 2 and 10,000/m2. Clams of the 1955 set grew 

 from a mean of about 9 mm on 23 Oct 1956 to 17.9 mm on 18 Feb 1959. - J.L.M. 



)4 



Ansell, Alan D. 1961. 



The functional morphology of the British species of Veneracea (Eulamelli- 

 branchia) . J. Mar. Biol. Assn. U.K. 41(2): 489-517. 



Venus casina, V. ovata, and V. fasciata were taken off the British coast 

 (exact location not cited) in stony or coarse gravel bottom. V. striatula 

 was obtained from Karnes Bay and Hunterston Sands, Ayrshire. Some species 

 of Venus have short, fused siphons, which may be regarded as primitive in 

 the Veneracea. The genus contains shallow-burrowing forms. The ability 

 to move horizontally as well as ventrally in a soft substrate is retained. 

 Venus (= Meraenaria) meraenaria is not mentioned. (Abstracter's note: 

 Hillman (1963) says this paper also contains information on a 4th fold in 

 the mantle of other Venus species.) - J.L.M. and M.W.S. 



!5 



Ansell, Alan D. 1962. 



Observations on burrowing in the Veneridae (Eulamellibranchia) . Biol. Bull. 

 123(3) : 521-530. 



Recordings were made of time sequence of movements of Meraenaria meraenaria 

 and 4 other bivalve species. All observations were on animals burrowing in 

 clean sand. The sequence is essentially as follows: 1) valves separate; 2) 

 foot is protruded, pointed with a probing motion; back and forth searching 

 motion continues until foot fully extended; tip of foot may extend to a 

 length equal to that of the whole animal; degree of vertical penetration 

 may vary considerably, depending partly on type of substrate; 3) heel of 

 foot is protruded vertically; 4) heel expands laterally and posteriorly so 

 that an anchor is formed; if substrate is firm enough, foot maintains this 

 position and shell moves; 5) valves open slightly; 6) siphonal apertures 

 close, and adductor muscles contract, reducing volume of mantle cavity; 

 excess water is forced out in a stream from anterior end just below 

 adductor muscle; presumably the pallial curtain (velum) maintains a seal 

 around foot and remainder of mantle edge during the operation; almost 

 immediately anterior pedal retractors contract and posterior retractors 

 relax, causing anterior end of shell to dip and posterior end to rise; it 

 is probable that contraction of anterior retractors is confined to that 

 part near its insertion into the shell; final movement takes place as shell 

 moves forward and down; foot remains in position of anchorage and more 

 distal portion of anterior retractors acts to draw body forward; at same 

 time elements of posterior retractors running downward and forward to base 

 of foot contract, assisting movement. At all times during the whole of the 

 digging period tips of siphons maintain contact with surface of substrate. 

 If contact is lost by disturbance or some other cause the sequence of 

 movements is broken. After completion of downward movement siphonal 

 apertures reopen. A short time later, if shell is completely buried, 

 apertures close again and siphons are slightly withdrawn then "stretched." 

 Apertures then reopen. Relaxation of retractor muscles and changes in 



22 



