Barbere Best 1
Feeding Activities
Tegula funebgelis
b
Barösta f Best
Intredustien
The intertidel regions st Chins Feist provide an abum-
danee ef merine plente for a dense pepulation of the prinarily
herbivorous gastroped Tegala funebralig (1. Adoms, 1894).
sith the varisty of plant foods avsilable, I. funebrells
sculd be expsetsd to display preferenees. Foeding aetivity
of the large snail population (400/*) could certainly effost
Leighten
the algal erop within the I. fumebralis sone.
(in press) has ustablished food preferanses for several gub¬
litterel benthie gresers and his extensive field observatiens
have choun the profound effeet of grezing setivities on tas
stending algal erop.
The pessible fosd seurees of Tagula funebralls fell
into three estegoriess rock enerusting sigse, Baeroscepie
383-310
plant forme, end organie detritus (seo Fen, 1957) on th
predominantly granite surfacee.
10

testasa Dest 2
Ia edditien to the food onurese, praferenses, and iho annl'e
effect en the littaral algal orep, à quenti tative cetinate
ef the fecd camomed by the snail unday laboratory ensditiens
ras ebtained. Light was investigetel as a jossible fagtaf.
lla nA hi
1) Foad owuree determisstien. One to 3 grans ef an dige
fer etonde evregud vith an engrusting fora) vore plased in
rlestie diches containing 2 andmals (3 to 10 groms cach,
vot weight, with chall). The diches, legsted in a grocchauge,
vere contimususly supplied with rumming sorwoter at 10 0.
Aag ingestien ef the food uas noted aftey 34 Mure. Agifiom
reight less ef the alga, fragaaatation, evidenop of radulas
resping, of idestifiestien of the feod in the gat og foonl
geterial vas used to determins chether er sot ingeotien has
ossurred. All enimals and fosts usod voro taken froch fron
the field. To piants listed in Table 1 were Ingecdcd zu
verving angante and ere therofere osasiderod feod sourede.
4 eimplifisstien ef the erganie carben dstersinatica in
(Srick sond, Josl, aud Patsons, T.R., 1960, pp 117-121
was used to seazure
Analreis
the Maulft
the erganie detritus, er leptepel, om tho gramite gurfagss,
and therefere the availebility of leptopel as a ford sougen.
Sameles vere collested by placing a plestie eylinder uprigja
egeinst the grenite zurfaces, aesled at tho base wich plastil.
sane medeling elay. Five mi of 1.0 f. Hoh aud 3 - 3 m
Sietilled water unchings vore sussessively pedred into us
Sestese Best
lisg elnder. The as epaed ty ligt r
es the rock euffese with a glass rod to simalate ihn raspiag
ef Fe fabralis. Cne ni of 70 phosphorie seid vas addes to
te sasple and hasted far 2 simtes in e beiling mater bath,
fellewed by 10 ni of petasslum dichreuste in sulfurie scie
seltties asd 60 mimtes of additienal heating, Atar ng
ue to 2 si velume with distilled vater, the sasple was roaa
es the Hett celerisster, uupplied with a blus filter. The
reswit is given in ug ef earbon, taken fren a standard carve
ef glucdee sarbon. The sumplee vore token fron barran rocka,
3te 4 foot abero ILd.
Beinz the sans techmigse, the ergenie carben content er
a esndstoss sample (sarfacs serapings dova t0 2 u) uns
femd. The stene was taken fros the intertidal on the norta
side of Pusta Banda naar enponsds, Baja California, ana 1a
prebably a food soures fes the leeal Lemia milina (Forbeg
18) peyalatiea. Thie warn water region has an simpge auelusivaly
sandstene eubstrate with a fou petches ef broun, filenenteus
elgse. Enaminsties ef the fesal naterial from cevral f.
malling ehoved apprentntely 004 sandstene ky velune. ne
teneining 20f scntsinsd fragneste ef the filemestous eiges,
The ergasie content ef foud grenito cusfage cenplos
eeraged  pa Ge raaging fres 2 t9 67 pa 0/. Te
fou n  ave 10  O, i ta a 0 e
22 20/2 renge.
Sarbara Best
2) Feod preferense determinstien. Preferenee experimenta
vere restricted to the meerossopis elgas. Plastie diahee vere
again used in the greenbouse. Three sots of algee were effered
en alternate days to the sams animals, which had bean collestel
ene day before starting the series. The four species of
algee in each set were plased, in combinatiens of three, in the
dishes with 10 animals (range 1 to 4 grams) or 3 (range 6 te
12 grams). Wet weight differenees of the algae to the nearest
O.l gram were taken after 24 hours. Control dishes showed
ne appreeiable change in wet weight of any alga (maximum of
0.03 grams). Results are shoun in Cable II.
3) Feeding rates. Maeroexstie integrifolia blades were
selested for the feeding rate detormination because of the
sccessibility of its large blade area and its apparent appeal
to T. funebralis. Andmals collected in the field were fod M.
integrifolia for 36 hours before beginning. The wet weight of
the alge conzumed vas weasured 6 times at intervals of Ste
23 hours for a tetal of 82 hours. Two size ranges of the
snail vere again selested (3 to 5 and 7 to 9 grams) vith
four enimals in each dieh. Rezults are eenverted to graus
of the algs sonsumed per dey per gram wet weight (with shell)
ef 1. funchralis (Table III). Ihe contrel algae chowed a
naximm wet weight change of 6.02 graus.
4) Effeet ef grazing en the litteral algal crop. Fer this
Darbarn Best 9
shert peried etudy (17 daye), vire nech eagee, 30 x 20 n 30
a, were fastened over the subatrate vith the basse fluah to
the rocks. Four cages vare placad adjasantly (2 in each of
2 erese). Togala funebralig vae eneluded from one oege and
20 to 200 anisale vere enelosed in the adjadant sage of esoh
Arse. At the and of the study, tho only apprecieble changes
tut occurred wares a) neticable grazing on Rederlogsun
afing, Gelidiun 2p., and iridsna flessideg b) the appearende
of Mvs s2. in one of the seges withest anisele (the alge
vas feund novhere else vithin a radius of over 3 matore)
Diequssion
Though Regule funebrelig vill ingest almost any opanen
elge, it displeys dafinits preforengse among the Eseroscopie
forma, i.e. Maerooystie integrifolie, Hersogystig Lustkane,
Rodoglessug affing, and Cigartine sanaliggleta. in saan
esse, the preferred elga is a eflechy" form. It ia non-
salearious, noo-filenentous, and has a tender thallus sontrastal
to the lasthery testure of Gigartima Aghardii and Pelyetia
fastigistg. The proferenses are consietent in the two eire
groupe of T. funabgalle.
sinee the highly preferred gient brovn sigae are normaliy
aveileble to the snail populstion only as drift paterial, the
food sourecs of the enimals inelude plante groving outside the
f. fumebrelig sone. Thie is supported by a fleld altustien
Berbara Best
et a site of organie detritus sampling. The T. funebralie
population at this leestion dvells en extremely barren rocke
and is apparently nourished by the considerable quantities of
drift seavseds thet secumulste.
The enerusting algse, partieularly the abundant green algs
and Balfeis pacifies, are undoubtedly inportant in the diet
of the animal. As Figure 1 illustrates, the width of tho
resping pattern on a glass plete thinly costed with distoms
greatly exeeeds that found en a thick Hacroeystis intsgrifelie
blade, sheving en effisient nechanies for oovering a lerge
aurfase area then necsssary: Thie may be inportant in keeping
larger algee free of diatos grovth.
Organie detritus on granite surfacee is probably enly an
sccidental food sourse at best. The detritus does contain
90 2-
digestible compounds, bowever (see Nigrelli, 1963). Tegala
gellina undeubtedly utilizes the orgenie contsnt of its candotone
substrate in s menner sisilar to Littorina planazig (Thilippi
1847) and L. seutulata (Oould 1849) as shown by North, 1934.
In esrlier work, North (umpublished data) meszured the erceite
setivitiee of T. funebralis en sandstone. Re colleeted 1.109)
ams of eroded (ingested) sandstone from the fecal seterial
of 11 sneils (total weight 58.4 grams) in 24 hours. Orgenie
detritus, as found in sandstone, may therefore be inoleded se
a foed couree of T. funebralis as vell as T. gellins, though
sendstone is not found in the Chins Point area.
Barbarn Best7
Table III eleerly shavs that the larger snimals heve a levee
fesding rate then the eæaller snails. The overall differenee
ef 17% in feeding rate found between sunlicht and constant
darknecs is toe small to support the possibility of a photo-
kinetie reeponze in feeding sctivity. The mean feeding rute
in light (0.012 gne/ge of animal/day) probably represents the
meximum found in the field, einee the feed was evsileble in
exesse and shown to be highly preferred.
The cenditien of the algse in the esgee at the end of the
17 dey perlod (in experiment 4) verifies the preferenecs
determined in the laboratory. Lach of the species of algae
effected could be called a "fleshy" form. A definite
relationship between the Tegula funsbralis populatien and the
marine plants in ite envirenment is certeinly indiseted.
Sery
1) Teguls funebralis vill ingest nearly any alge groving in
er out of the litteral zone. Both seeroscopie and anerusting
forms constitute importent food sources; the grenite surfeces
contsin s negligible smount of erganic detritus end contribute
littie to the diet of the anisel. Karlier wosk on I. fumebralig
and observations of I. gallina show that the animals will ingest
ergenie detritus when it is aveileble.
2) The snail profers a 'fleshy9 alga azong mecroscopie foras
(e.g. Macrocystiz int grifolie, Jereoeystis Luetkenne, and
Sigertina sapalioolete).
O
Barters Best
2) Feeding rates per gren ars gretter in the smeller anisale
atkot
and ere apparently not affected by sunlight.
er auggestzthe importanee of the feeding
4) A short field st
setivitios of T. funabralig on the local slgal erops,
C
Bebang de
Ladle 1
Flamt foots ingested by Tegula fusebgalis
Chsetemerpha ep.
Pelvetia fastigista
Cledephora ep.
Peystennelia paeifies"

Oerellina ep.
Fhylleepadiz Seeuler!
Mater)
Prienitie lanosolata
Egregis Menziesii
Ralfeia pacifiea
Endocladia muriesta
Rbedeglessun affine
Castroelonium Goulteri
Ulra ep.
Celidius sp.
Unidentified untsellujer green)
alga grewing on reeks
Cigertins /Oghardii
1
Gigertine esneliculate
lEnerusting alge
Irideee fleceidm
Atale far tlsn
Lithothennion sp.
kaus ale aer lu
Hecroeystie integrifolis
Rereocystis Luetkeana
Siutt (1744
Table 11
Feod preferences ef Tegula funetgalis
Experizent
Aneber ef andmale0D  1 3 k l.
10 0.3 0. 2 „ 0.0 2.0 0.1 n 0,0 2.3 0.1 = 0.1
1 0.3 2 0.1 0.0 » 0,1 0,1 0.1 „ 0,0 0,0 6.0
10 0.3 0.2 0.2 u 2.1 0.0 0.0 2 2.3 0.2 0,0 a
29 3 0.3 0. 1 0.8 | 2. 1 a 0.0 0.0 | 2.6 | 2 0.0 0.1
Ftal ceten 1.3 0.7 0.4 C.g 6,2 0.2 0,1 0.1 7,6 0.3 0.0 0.2
Hamber of anizals
3 0.2 0.1 2 0.0 | 2.2 0.1 | 2 0.0 3.0 | 0. 1 1 6.0
3 0.7 2 0.1 0.1  0.0 0.2 0.0  0.1 0.1 0.0
9 0.3 0. 2 0.1 „ 2.7 0.1 0.0 2 2.7 0.0 0.0 1
3 1 0.3 0.1 0.0 | 2. 2 2 0.0 0.0 | 2.6 | 2 0.0 0.0
Tetal enten 1.4 0.6 0.3 0.1 7.1 0.2 0,2 0.0 8.3 0.2 0.1 6.9
8 Pelvetie fastigiete
A Cigartina eenaliculata
n Sigartina agtardii
B Rhodegloszum affind
1 Herescyetis lastkeam
0 Endoeladis wuricsta
3 Gladepbera 29.
D Iridace flescidum
K Flyllospediz Seouleri
I Haereeystis integrifelia
L Prienitis 2p.
P Orallina s.
olant ohilld tiom 8pt
Embers represent trase of the plant consumed afteg 24 houge
Barben Et
Bler .
Table 111
Feeding retes of Ieguls funehrelis
Sunlight
heurs in tezt perieis eseumt conzumed
animal weight
total rango 8.3 25.3 12.5 12,6 12,3 11,3 total gus
day
E
4221 7-9 6.18 0.14 0.35 0.16 0.18 0.12 1.13 0.33 0,010
34.9 7-9 0.06 0.2 0.64 0.13 0.12 0,05 1.30 0.38 0.611
15.5  0.06 0.Z 0.3 0.00 0.11 0.10 0.90 0.2 0.017
14,9 35 0.17 0.2 0.10 0.12 0.12 0,07 0.78 0.23 0.013
Ceastant Derkness
32,1 7-9 0,03 0.26 0.4 0,02 0,01 0.2 1.07 6. 0.010
35.7 7-9 0.14 0.00 0.00 0.2 0.01 0,12 0.47 0.14 0.004
13.1 35 0.00 0.19 0.2 o.11 0.07 0.07 0.69 o.20 0.013
16.3 33 0.0 0.38 0.02 0.06 0.28 0.13 0.92 0.27 0.017
Numbers represent the grass ef Maaroerstiz intsgrifelis conzuned in the
given time period. Horisontal rows give data fog å saimals, with total
weights and weicht ranges.
(in vet weicht of animals, with chell)
0
B1
Figure 1
Legend
a, Rasping pattern on glass plate, thinly coated with diatomsX
tattern on Macrocystis int grifolia blade X
B
..
/