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- 23 - :L)IATO1.`IS AS FOOD OF OYSTERS by Thurlow C. Nel son Rutgers (Tniversity Modern knowledge of the food of the oyster is due madly to three ~- vestigators: Martin t23 who emphasized the importance of nannoplankton formerly overlooked; Savage '25 who shorted the importance of diatoms in fattening the English oyster' while Yonge i26 disproved the contention of Danish investigators that Zostera_tritus was the main food of the European oyster. Yonge considers :Lamellibrano~;to be Unspecialized herbivores capable of the extracellu~ar digestion only of starch or g;lycogenon Yo~n<~;e emphasized the importance of ~artints ~f~nd:urlgs extent to which digestion in the oyster is intracellular. t hat the oyster is unable to utiliz e zoOplankt on who in :1921 and in 1933. showed that both in the by shoveling the very large his conclusion was questioned by Nelson, European and in the Arneri- can oyster copepods, nauplii, snail veligers, and nematodes are Rag rented and dissolved. to elson ~ 71 dem~nstra~ ed the importance of diatoms living on the shells of oysters andin this year end again in 1941 and '42 emphasized the outstanding qualities of Skeletonema in but 1G~ ng :;lycogen reserves and superior flavor in oysters. Savage gives chief credit for t'fatter~ng" of oysters in Eng:Lisl~ waters to 2iit:zschiella lon`~ssima f. larva. The ~r,por- tance of this and of other littoral diatoms for American and Atlantic Coast oysters was confinned by Nelson in 'fly and f42. The verge long or sp5nous diatoms such as Chaetoceros, ~hizosolenia' and Thalasscothr~x were designated in 1942 as "weeds of tile sea" since they are eaten in finch smaller proportion by the oyster than are the smooth spine:tess and shorter forms. That diatoms have long played a major role in the food of lamel~ibranchs Is indicated first by the rapid accumulation of glycogen reserves by the m.olluscs ashen diatoms are abundant, and by the de~.onstration of Berkeley '33 that in Saxido.rnus the au(ox disable component of the oxidase system of the . crystals ne sty e is strongest activated by some substance contused ~ n diatoms while the style extract alone is Quite inactive. this would indicate _ gL very long period of association between ~Saxidomus and the diatoms Schick. comprise its food. Artificial culturing of diatoms in the laboratory has bee~carr~ed on for many years while recent efforts to increase the plankton and the fish of fishponds through a~,pClicatior~s of fertilizer appear to be unusually suc~ cessful. As yet, however, Little is known regarding the factors which rake for the abundance or the scarcity of the littoral and pelagic diatoms of brackish Waters. Gran t31 showed the importance of soil extract and specifica:Lly of iron to growth and reproduction in Skeletonema cost`atu~. Thins has just been confirmed for Delaware Bay mater by Johnstone (~pub- Jished). In this element may lie the explanation of the stimulating effect of heavy run off from the land upon the abundance of this diatom. Exper- ience also shows that a heavy door occurring at 101N tide with exposed

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- 24 - ouster bars and flats usually stimulates the growth or- lit,-~oral diatoms. Tlie most probable explanation is the Co2 brought do-,~n lay the rain from the air. ~per:~ments have been in progress on the Delaware I3av~ shore of Cape May County, N.~., to determine the possib~.litey of enrich: the su-~.<'ace of art oyster bed and thereb,,r increasing; the nur~;be-r of diatoms thereon. Con~r,~ercial ~'er-tiJizer, Lone meal, soybean and cottonseed meal, fish meal, arid iron salts have been mixed witl: peat, with peat and clay, with and 'without sand and Blade into pellets which are there sunbathed. These are hard enough to stand even rough handling without breaking, =~d Allen thrown overboard sink quickly to the surface of the oyster bed where they retain their form for at least a month. Plenary experiments reveal two difficulties dot Present in fresh water. Soluble ~no-.~ganic phosphates are quickly precipitated at the pit S.4-~3.6 of -the bay floater. T``r~hen applied in organic Born in the various meals, decomposition of the meal causes local deple-uJon of anger with deposition of sulphides by the action of suiphate bacteria in sea rater. FI:cTrogen suiphide is deleterious to oysters reducible, Their rate and extent of ;,-iaterpumpin,~;. If abundant end persistent wholesale death of oyster occurs bone mea] is t.,he Recast objectionable on this score but to date has not proven succ e ssf ul . Simple r~tu-res of cor'~mercia:l fertilizers and peat will Live gd diatom ,~owths oil the surface of the pellets in the laLcratory and in an enclosed basis but to date hairs faiicd to do so on the oyster beets. Successful solution o~ the problem would result ~ a Tremor large financia:L return to the oyster growers Echo fr~a,uently arc prevented i--rorn har~resting thousands of bushels of oysters by the poor quality of lathe ~eats. The greats abund~cc of Skeletonema in D'-~la~are Bay in 1940-4] added app-ro~nately half a million dollars to the value of the cyst- crop :~om Chat area in this one season. i It is felt that the facts necessary- to a successful solution off This problem probably are known today but that they a^re widely scattered th-rou,:~,h the literature or are unpub]Lished. The wailer feels tone Bleed of exert advice from a number of quarters and eagerly seeks it;. R~-~:'~NC;SS Berkeley, C. ' 33. The oxidase and dehydrogenase systems of the crystal 1 i ice style of l`.Iof usca. Biochem. Jour. 27: 1357-1365. Gran, H. H. 131. On the conditions for the production of plankton in the sea. Con. Per. Int. p. Lex. d.1. men 3= du Ba.p et Proverb, 75: Martin, ~ ;. :.~i. Food of -the oyster. Bot ~Gaz . 75: 143-169 ~

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25 - T7el=`on' T. C O ~ 2:~ ~ ~. ~ P:^oc . Repo rt 1;t . J O Agr @ Empty . ,Sta ~ f or 1 920: 3i7-3L~9 . t33. On the digestion of arenas ionns by tile oyster Soc. hap. Biol. & trek. 30: 1237-l290 ~ 3Lr . Report ~ . ~J O or . Sxpt ~S' a . for 1934 0 13-21 . 'L~2. C~ the ro~e of diatoms in the fa.ttening of o::sters. E,~] l. Ct~ster I:~st. ~ . hmerica S., l`To. 30, 5-S, Was'r!in~,ton. Sa-~ag~, ;;~. =~.. '250 The foocl of the oyster. Fisher~ Invest. Vo] . 8, ii0. 13 l-5C. i.~"inO Ag~o ~ T'iSh. I,onr2.o:r~. rc\,]ge ~ C O L\'t.... ~ 26 . a,~cl di~,e j6~on Ser. 2, ;:t/r: cttlre ~nd pl~l~,rsiolo{~y of t'ne orgarls of ir ()~t;~ea edil:~ i~ `Ic);lr. 5~!ra^~ S:i c:1 9 i1'\,8<~' Lr feed5.~= ]~ ~ a 2; S ~) 63