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The viability of an echinostome metacercaria in the American oyster, Crassostrea virginica
JOURNAL
OF
INVJXRTEBRATF,
PATHOLOGY
13, 455-456
(1969)
The Viability of an Echinostome Metacercaria American oyster, Crassostrea virginica J. W. Little, S. H. Hopkins, and F. G. Schlicht (J. Pumsitol., 52, 663, 1966) recently reported the occurrence of Acanthopayphium spinulosum metacercariae in the mantle of Crussostrea &gin&z found near Port Isabel, Texas. The presence of the metacercarial ‘cyst in the oyster, unlike many other parasitic infections, produced little observable tissue reaction (Fig. 1). Furthermore, according lto W. E. Martin and J. E. Adams (J. Parasitol., 47, 777-782, I961), encysted metacercariae of the parasite in Cerithidea californica continue to grow several times the cercarial size. This indicates that A. spinulosum, under natural conditions, is able ,to absorb nutrients from its molluscan host. However, after the encysted parasites att,ain ma certain size, growth apparently ceasesas no organogeny occurred in A. spinulosum while encysted in the Texas oysters. In order to assessthe rate of develop-
FIG.
1.
A. spinubsum
metacercariae
in the
ment, metacercariae from fresh oysters collected December 27, 1965, were fed to baby chicks as previously described (J. W. Little et al., J. Parasitol., 52, 663, 1966). After the infected oysters had remained in ‘aerated aquaria in the shellfish laboratory at Texas A & M University for 2 months, pieces of mantle containing live metacercariae were fed to day-old chicks. Table 1 shows that fewer worms developed from metacercariae that had remained in the oysters kept under laboratory conditions. Although the oysters were not fed, very few ,died in the 2 months between the trematode feeding experiments, which indicated their generally good condition. The loss of infectivity of metacercariae probably resulted from lower glycogen ‘content in the oyster, decreasing the amount of nutrient availabIe to the encysted parasites.
in the made
of C. uirginica.
100x.
456
NOTES TABLE
1
Date
No. of chicks
No. metacercariae in each host
Total metacercariae
No. of worms recovered
Jan. 10 March 3a
16 12
1140 20-10
350 375
92 17
a 1966. b Sig. > .OOl (~2 = 66.49, 1
Recovery rate 26.2% 4.5%”
df).
FIG. 2. A comparison of deteriorated metacercaria losum (arrows) in the mantle of C. uirginica. 100X.
Dead or dying metacercariae could easily be identified ‘as they became cloudy and their outlines became indistinct (Fig. 2). These data were considered worth presenting because of the paucity of information on the influence of normal laboratory conditions on the viability of echinostome metacercariae. It is suggested that time be considered an important factor in
(arrow)
with living
metacercaria
of A. spinu-
investigations when parasites have been kept under these conditions. JOHN W. Lmt~ SEWELL H. HOPKINS J. G. MACKIN
Department of Biology Texas A G M University College Station, Texas 77840 Received January 14, 1969
OF
INVJXRTEBRATF,
PATHOLOGY
13, 455-456
(1969)
The Viability of an Echinostome Metacercaria American oyster, Crassostrea virginica J. W. Little, S. H. Hopkins, and F. G. Schlicht (J. Pumsitol., 52, 663, 1966) recently reported the occurrence of Acanthopayphium spinulosum metacercariae in the mantle of Crussostrea &gin&z found near Port Isabel, Texas. The presence of the metacercarial ‘cyst in the oyster, unlike many other parasitic infections, produced little observable tissue reaction (Fig. 1). Furthermore, according lto W. E. Martin and J. E. Adams (J. Parasitol., 47, 777-782, I961), encysted metacercariae of the parasite in Cerithidea californica continue to grow several times the cercarial size. This indicates that A. spinulosum, under natural conditions, is able ,to absorb nutrients from its molluscan host. However, after the encysted parasites att,ain ma certain size, growth apparently ceasesas no organogeny occurred in A. spinulosum while encysted in the Texas oysters. In order to assessthe rate of develop-
FIG.
1.
A. spinubsum
metacercariae
in the
ment, metacercariae from fresh oysters collected December 27, 1965, were fed to baby chicks as previously described (J. W. Little et al., J. Parasitol., 52, 663, 1966). After the infected oysters had remained in ‘aerated aquaria in the shellfish laboratory at Texas A & M University for 2 months, pieces of mantle containing live metacercariae were fed to day-old chicks. Table 1 shows that fewer worms developed from metacercariae that had remained in the oysters kept under laboratory conditions. Although the oysters were not fed, very few ,died in the 2 months between the trematode feeding experiments, which indicated their generally good condition. The loss of infectivity of metacercariae probably resulted from lower glycogen ‘content in the oyster, decreasing the amount of nutrient availabIe to the encysted parasites.
in the made
of C. uirginica.
100x.
456
NOTES TABLE
1
Date
No. of chicks
No. metacercariae in each host
Total metacercariae
No. of worms recovered
Jan. 10 March 3a
16 12
1140 20-10
350 375
92 17
a 1966. b Sig. > .OOl (~2 = 66.49, 1
Recovery rate 26.2% 4.5%”
df).
FIG. 2. A comparison of deteriorated metacercaria losum (arrows) in the mantle of C. uirginica. 100X.
Dead or dying metacercariae could easily be identified ‘as they became cloudy and their outlines became indistinct (Fig. 2). These data were considered worth presenting because of the paucity of information on the influence of normal laboratory conditions on the viability of echinostome metacercariae. It is suggested that time be considered an important factor in
(arrow)
with living
metacercaria
of A. spinu-
investigations when parasites have been kept under these conditions. JOHN W. Lmt~ SEWELL H. HOPKINS J. G. MACKIN
Department of Biology Texas A G M University College Station, Texas 77840 Received January 14, 1969