varyiug coittlitio~is of' tt:nil)d.rutjirrtb i r l l d food supply, but his figures,
which are c~xpressctl per grit tmii(' tlry weight, are considerably higher
than those for other species where nicwurements have been expressed
in terins of wet weight ('l'al)les I 1 arid 111). The differences between
Croxall's data and those of othrrx an1 tiard to reconcile, but it is clear
from dl of the data that the plilehobrt~nchiate ascidians filter more
slowly than do stolido~)riin(.hiiitc.s and in generitl small animals filter
faster t h n do largo ia~lirnals. ( 'roxall has extended this comparative
approach to show that the o v c d l fheding efficiency of the stolidobranchs is greater thim that of the phlebobrmohs (Table IV). Within
the phlebobranchs, CoreZlrr, with spiral stigmata, is slightly more
efflcient t h n Oionn, atid within t h r stolidobranchs the pyurids arc
more eficieitt t h i b n the Ht*yelids. ?'his is in keeping with the more highly
organizctl iiiLturv of t lit: t)runc.hial x w in pyitrids than ill xt,yclids.
TABLE I v. ()VP;RAlJ, YEEDINO " EFFICIENCY " ICATIOS FOR SIMPLE ASCIDIANS
(Croxa11, 1971)
Ratio of
jiltration rates
Sttmmer
IVdnter
100
I00
I40
14!J
159
I55
I92
186
214
571
217
250
ltalio of
digestive ejiciency
Stmmar
R'inter
Ilatio of food
pas.sage time
-
100
105
137
147
171
I RH
Many of thcb tlifferenres iit the tlirta on filtration ratcs of' i~divitliiril
species rnny bc due to diff(~renws in tc~hi~iquc~. Hcxht ( I 9 I A ) has
pointed O u t that in h c i d i n thiyra it may tihke as h g a x eight holm
for an rminial to recover from handling and to settle tlowir to a urrifiwm
and maximum rate of flow. Furthermore aseidians are capahle of
cutting off the fow of mucus and thereby interrupting the pattern of
particle clearance (Jarrgensen, 1966) and if this occurs during an experiment it will also affect the results. The very low value for Pha1lu.k
maminillutn recorded by Hoyle ( I 953) is probably incorrect and due to a
pressure head of water acting against the animal in the particular
situation (Carlisle, 1966). Tho P I - W S I J ~ C crested by ciliary activitx has
been reported w 2 inni of w t c r in A s d i n ,/iyru (Hecht, 1916) and
Phallusin wznit~rillntn (Hoyle, 1953). However. Goodbody a d Trueman
which are c~xpressctl per grit tmii(' tlry weight, are considerably higher
than those for other species where nicwurements have been expressed
in terins of wet weight ('l'al)les I 1 arid 111). The differences between
Croxall's data and those of othrrx an1 tiard to reconcile, but it is clear
from dl of the data that the plilehobrt~nchiate ascidians filter more
slowly than do stolido~)riin(.hiiitc.s and in generitl small animals filter
faster t h n do largo ia~lirnals. ( 'roxall has extended this comparative
approach to show that the o v c d l fheding efficiency of the stolidobranchs is greater thim that of the phlebobrmohs (Table IV). Within
the phlebobranchs, CoreZlrr, with spiral stigmata, is slightly more
efflcient t h n Oionn, atid within t h r stolidobranchs the pyurids arc
more eficieitt t h i b n the Ht*yelids. ?'his is in keeping with the more highly
organizctl iiiLturv of t lit: t)runc.hial x w in pyitrids than ill xt,yclids.
TABLE I v. ()VP;RAlJ, YEEDINO " EFFICIENCY " ICATIOS FOR SIMPLE ASCIDIANS
(Croxa11, 1971)
Ratio of
jiltration rates
Sttmmer
IVdnter
100
I00
I40
14!J
159
I55
I92
186
214
571
217
250
ltalio of
digestive ejiciency
Stmmar
R'inter
Ilatio of food
pas.sage time
-
100
105
137
147
171
I RH
Many of thcb tlifferenres iit the tlirta on filtration ratcs of' i~divitliiril
species rnny bc due to diff(~renws in tc~hi~iquc~. Hcxht ( I 9 I A ) has
pointed O u t that in h c i d i n thiyra it may tihke as h g a x eight holm
for an rminial to recover from handling and to settle tlowir to a urrifiwm
and maximum rate of flow. Furthermore aseidians are capahle of
cutting off the fow of mucus and thereby interrupting the pattern of
particle clearance (Jarrgensen, 1966) and if this occurs during an experiment it will also affect the results. The very low value for Pha1lu.k
maminillutn recorded by Hoyle ( I 953) is probably incorrect and due to a
pressure head of water acting against the animal in the particular
situation (Carlisle, 1966). Tho P I - W S I J ~ C crested by ciliary activitx has
been reported w 2 inni of w t c r in A s d i n ,/iyru (Hecht, 1916) and
Phallusin wznit~rillntn (Hoyle, 1953). However. Goodbody a d Trueman