Southeast Asian Fisheries Development Center Aquaculture Department
SEAFDEC/AQD Institutional Repository http://repository.seafdec.org.ph
Institutional Reports Quarterly Research Reports
1979
Studies on the fungal diseases in
crustaceans I. Lagenidum scyllae sp.
nov. isolated from cultivated ova and
larvae of the mangrove crab (Scylla serrata)
Bian, Bo Zhong
Aquaculture Department, Southeast Asian Fisheries Development Center
Bian, B. Z., Hatai, K., Po, G., & Egusa, S. (1979). Studies on the fungal diseases in crustaceans I. Lagenidum scyllae sp. nov. isolated from cultivated ova and larvae of the mangrove crab (Scylla serrata). SEAFDEC Aquaculture Department Quarterly Research Report, 3(3), 10–13.
http://hdl.handle.net/10862/2353
Downloaded from http://repository.seafdec.org.ph, SEAFDEC/AQD's Institutional Repository
Studies on the fungal diseases in crustaceans
I.
L a g e n id u m scylla esp. nov. isolated from cultivated ova and larvae o f the mangrove crab
(S cylla serrata)Bo Zhong Bian1, Kishio H atai2, G ilda Po and Syuzo Egusa1
In 1978, a highly lethal and fungal disease fre q u e n tly occurred in ova and larvae o f the mangrove crab, S c y lla s e rra ta , at the w et laboratory o f SEAFDEC. A causative organism o f the disease is described and compared w ith the previous members o f L a g e n id iu m know n to be parasitic on th e crustacean ova and larvae. F o r the grow th in th e liquid culture, the effects o f tem perature, NaCI concentration and pH are also shown.
In the shaking cu ltu re , vegetative th a lli appeared as spherical colonies. The fungus on PYGS agar plate inoculated w ith these colonies appeared w h itish and filam entous, and attained a diam eter o f 2 cm in a week at 25°C . From the m orphological observations o f these and other cultures in PYGS b ro th , the f o llo w in g descriptions were made.
Hyphae stout, branched, sparingly septate, infecting the ova or bodies o f both zoea and megalopa o f the crab, holocarpic. In pure cultures, the hyphae is at firs t somewhat u n ifo rm w ith a diam eter o f 7.5-17 µ m , generally vacuolate, w ith numerous m inute cytoplasm ic oil droplets, then becoming qu ite irregular and swollen up to 4 0 µm th ic k in age, coarsely granular ju s t before spore fo rm a tio n . Vesicle form ed at the end o f the discharge tube measuring 37-500 x 4-10 µ m , 25-72.5 µ m in diam eter, contains a sphere o f protoplasm ic material measuring 2 2 .5 -6 5 um diam.
Zoospores m onoplanetic, laterally biflagellate, irregular in shape and size, p y rifo rm , globose or elongate, 8-17.5 x 7 .5 -1 5 µm , m ostly 12.5 x 10 µm, d iffe re n tia te d fro m the protoplasm ic material in the vesicle, discharged sim ultaneously by rapid deliquescence o f the vesicle, or liberated one b y one through th e opening o f the vesicle; collapsed vesicles n o t persistent. When the discharge failed, zoospores swarming w ith in the discharge tube and vesicle, com ing to rest and converted to cystospores w hich may germinate in situ . Encysted zoospores were spherical, 7.5-15 µ m in diam, averaging 10 µm , w ith walls up to 1 .5 µm th ic k . Sexual reproduction not observed.
1 L a b o r a t o r y o f A q u a c u l t u r e B i o l o g y , D e p a r t m e n t o f F is h e r ie s , F a c u l t y o f A g r i c u l t u r e , t h e U n i v e r s i t y o f T o k y o , 1 -1 -1 Y a y o i , B u n k y o - k u , T o k y o 1 1 3 .
2 C e n t r a l R e s e a r c h L a b o r a t o r y , S a n k y o C o . , L t d . , H ir o m a c h i 1 - c h o m e , S in a g a w a - k u , T o k y o 1 4 0 . ( P r e s e n t a d d r e s s : A q u a c u l t u r e R e s e a r c h L a b o r a t o r y , N a g a s a k i P r e f e c t u r a l I n s t i t u t e o f F is h e r ie s , N o m o s a k i, N a g a s a k i 8 5 1 - 0 5 . )
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The effects o f tem perature on grow th are summarized in Table 1. The fungus tolerated a w ide range o f tem perature (16 to 42°C ) b u t grew w ith the o p tim u m at 22.5-31.8°C . For earlier stages o f grow th, higher tem perature seems to be required. The fungus did not grow at 11-13°C, b u t at least survived beyond 7 days when cultured.
Table 1. E ffe ct o f tem perature on g ro w th o f Lagenidium scyllae in PYGS b ro th
Temperature (C)
G row th-rate at day after in cu b atio n *
Survival * *
1 3 7
9.5 _ _ _ _
11.0 - - - +
13.0 - - - +
14.2 - - ±
16.0 - + +
17.4 - ± ++
19.0 - + +++
20.5 - + +++
22.5 ± ++ +++
30.0 ± ++ +++
31.8 + ++ +++
33.8 + ++ ++
36.0 ++ ++ ++
37.6 ++ ++ ++
39.0 + ++ ++
42.0 ± ± ±
44.0 — — —
* Symbols, — : no growth; + : barely visible growth;+ , ++, +++ : increasing amounts of growth from slight to excellent.
** Viability of inoculated spores was checked by re-incubation of the culture after 7 days, at 25 C for more 3 days.
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As seen in Table 2, the fungus was also to le ra n t to relatively high concentrations o f NaCl . Its grow th occurred over a w ide range o f NaCI concentrations (0-7% NaCI-PYG b ro th ). M axim um grow th was obtained at 2-3% NaCI. E xcept fo r a few cases, there was no difference o f grow th between cultures w ith 8.0 x 104 spores and those w ith 8.0 x 103 spores. A t higher NaCI concen
trations, such as 8 o r 9%, larger amounts (8.0 x 104 ) o f the inoculum supported slight grow th o f the fungus. Smaller amounts o f the inoculum had no apparent grow th.
The fungus grew well b u t slow ly in the PYG b ro th . I t did n o t grow in the PYG broth containing 2.5% KCI. The sim ilar grow th in KCL-PYG broth was described on Lagenidium sp.
(N ilson e t al., 1976).
A lth o u g h grow th occurred over a wide range o f pH (5-11), the greatest yield was obtained at an in itia l pH o f 7 o r 8 (Table 3). There was no difference o f grow th between cultures w ith 6.8 x 104 spores and those w ith 6.8 x 103 spores.
Table 2. E ffe c t o f NaCI concentration on grow th o f Lagenidium scyllae in PYG b ro th
Concentration o f N a C I***
(%)
Experim ent 1 * Experim ent 2 *
G row th-rate at day after incubation
S u rviva l** G row th-rate at day after incubation
S u rviva l**
1 3 7 1 3 7
0 — + + — + +
1 - + + - + +
2 - + +++ - + +++
3 - + +++ - + +++
4 - + ++ - + ++
5 - + ++ - + ++
6 - + + - - +
7 - + + - - +
8 - - ± - - - -
9 - - ± - - - -
10 — — — — — — - —
* Exp. 1: inoculated with 8.0 x 10 spores; Exp. 2: inoculated with 8.0 x 10 spores.
** Viability of inoculated spores was checked by re-incubation that 1 ml of the cultures after 7 days inocu
lated into 10 ml of newly prepared PYGS broth and then incubated at 25 C for 3 days.
*** Each culture contained very small excess NaCI which was brought from 1 ml of sea water as inoculum.
1 2
Table 3. E ffe ct o f pH on grow th o f Lagenidium scyllae in PYGS broth
pH
Experim ent 1 * E xperim ent 2 *
G row th-rate at day after incubation
S u rviva l** G row th-rate at day after incubation
S u rviva l**
1 3 7 1 3 7
4 — — — — _ _ _ _
5 ± + ++ — — ++
6 ± + ++ — + ++
7 + + +++ ± + +++
8 + ++ +++ + + ++
9 + + ++ + + ++
10 ± ± ++ ± ± ++
11 — — + — — + -
12 — — — — — — —
* Exp. 1: inoculated w ith 6.8 X 104 spores; Exp. 2: inoculated w ith 6.8 X 103 spores.
* * V ia b ility o f inoculated spores was checked by re-incubation th a t 1 ml o f the cultures a fte r 7 days inoculated into 10 ml o f newly prepared PYGS broth and then incubated at 25 C fo r 3 days.
The fungus could be assigned to a member o f the genus Lagenidium on th e basis o f its parasitic, endobiotic and holocarpic th a lli and laterally flagellate, m onoplanetic zoospores in a vesicle at the end o f discharge tube. W hile the fungus is very sim ilar to L. callinectes (Couch, 1942; Bland and Amerson, 1973), there are, however, some differences between the tw o . In this fungus it needs o n ly 3 h and 15 m in fo r the in itia tio n o f spore fo rm a tio n fro m the transfer o f hyphae in to sea w ater; both long and short discharge tubes are fo u n d in the fungus; the gela
tinous envelope fo u n d in L. callinectes is not seen and the protoplasm ic material nearly fills in the whole inside; and all the spores are simultaneously discharged b y the rapid deliquescence o f the vesicle o r the spores are liberated one by one through the opening o f vesicle. From all the other members o f Lagenidium know n to attack animals, this fungus d iffe rs in having the non-segmented hyphae. Thus the fungus is proposed as a new species o f Lagenidium , L. scyllae Bian, Hatai, Po & Egusa.
L IT E R A T U R E C IT E D
B la n d , C .E . a n d H .V . A m e r s o n , 1 9 7 3 . O b s e rv a tio n s o n L a g e n id iu m c a llin e c te s is o la tio n a n d s p o ra n g ia l d e v e lo p m e n t. M y c o lo g ia 6 5 : 3 1 0 -3 2 0 .
C o u c h , J .N . , 1 9 3 5 . A n e w s a p r o p h y tic spe cie s o f L a g e n id iu m . w i t h n o te s o n o t h e r fo r m s . M y c o lo g ia 2 7 :3 7 6 - 3 8 7 .
N ils o n , E .H ., W .S . F is h e r a n d R .A . S h le s e r, 1 9 7 6 . A n e w species m y c o s is o f la rv a l lo b s t e r ( H o m a ru s a m e ric a n u s ).
J . In v e rte b r. P a th o l. 2 2 :9 4 - 9 9 .
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