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FEEDING RADIUS, BURYING DEPTH AND SIPHON SIZE
June; FIELD DATA siphon length (cm)=0.365mm+0.5 Oct. LABORATORY siphon lengih (cm)=0.216mm*5.9
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shell length (mm)
shell length (mm)
Kin- I. Burying depth (cm) and feeding radius (cm) in Scmbicularia. as a function of shell length, measured A. in the field In = 751 and B. in
Ihe laboratory In = 261; dala were pooled per mm shell lengih. All regressions shown are highly significant. The regression equations for siphon
lengih are based on the sum of feeding radius and bury ing depth.
between burying depth and feeding radius in Fig. I
shows lhat siphon length increased with shell size. The
longest siphon measured 17 cm in a Scrobicularia 37
mm long. Green (1967) recorded a siphon length of 28
cm in an individual of 40 mm.
The feeding radius of individual Macoma varied
between 0.2 and 4 cm and was related to shell si/e
(Fig. 2). ln contrast, no. or hardly any. increase of feeding
radius with shell si/e was found in Abra nirida and
A. longicallus (Wikander 1980) and Macoma secta
ilevinton 1991). Brafield & Newell (1961), Gilbert
(1977) and Kamermans & Huitema (1994) recorded
for Macoma a maximal feeding radius of 4, 6 and 5
cm, respectively, close to present values. Lin & Hines
(1994) mentioned a maximal radius of 10cm. but their
dala referred to the larger American Macoma up to 39
mm long. Reid & Keid (1969) reported for seven
species of Macoma a feeding radius of 1.5 to 3 cm.
The variation in burying depth of Macoma (0 to 6 cm)
was similar to values found in the field (Reading &
McGrorty 1978, Zwarts & Wanink 1989). Contrary to
the normal situation in the field, where depth was independent
of size in Macoma larger than 10 mm
(Zwarts & Wanink 1989. 1993). small animals buried
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more deeply than large ones. There was a weak, nonsignificant
increase in siphon lengih (i.e. ihe sum of
feeding radius and burying depth) with shell size for
Macoma greater than 10 mm (Fig. 2). The longest
35
Oct: LABORATORY siphon length (cm)=0.089mm.3.3
14 16 18
shell length (mm)
Fig. 2. Burying depth (cm) and feeding radius (cm) in Macoma. as
a function of shell lengih measured in Ihe laboratory