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Vol. 61, 2022
(update: 2022.5.5)
Predation of Oysters Using an
Autonomic Pharynx in the Oyster Leech Cryptostylochus
sp. (Polycladida: Stylochidae)
Ching-Jung Teng1, Ying-Jung Su1, Chih-Yu Yeh1, and Wei-Ban Jie1,*
doi:10.6620/ZS.2022.61-07
1National
Experimental High School at Hsinchu Science Park, No.300, Jieshou Rd,
East Dist., Hsinchu City 300, Taiwan. *Correspondence: E-mail:
wbjie@nehs.hc.edu.tw (Jie).
E-mail: ally901119@gmail.com (Teng); h611119@nehs.hc.edu.tw (Su);
rubyyehmail@gmail.com (Yeh)
Received 27 May 2021 / Accepted 28
January 2021
Communicated by Benny K.K. Chan
Oyster
farming has been threatened by marine flatworms for over 40 years, but
few studies have been done to address this issue. Here, we examine the
predatory behavior of the polyclad flatworm Cryptostylochus
sp. from Penghu, Taiwan. Its predation process consists of three parts:
the attack, invasion, and ingestion period. During the attack period,
which begins 4 or more hours before the invasion, protruding pharynges
form fragments that we call “autonomic pharynges”. The autonomic
pharynx is translucent white, membrane-like, and variable in length.
Using time-lapse photography, we show that the pharynx moves around
slowly and independently for roughly 10 hours before losing mobility.
The autonomic pharynx moved toward the edge of the oyster shell and
increases the frequency at which the oyster or clam opens and closes
compared to the control group. The passageway demonstrates negative
phototactic behavior in petri dishes. Linear regression showed a
positive correlation between the number of autonomic pharynges and the
clam mortality rate. Histological dissections showed that clam mantle
tissue is externally digested by the autonomic pharynx. The fragments
of multi-branched ruffled pharynxfrom polyclad flatworms slowly detach and play a critical role during the period of the attack on bivalves.
Key words: Stylochid flatworms,
Polyclad, Predatory behavior, External digestion, Oyster farming.
Citation: Teng CJ, Su YJ, Yeh CY, Jie WB.
2022. Predation of oysters using an autonomic pharynx in the oyster
leech Cryptostylochus sp.
(Polycladida: Stylochidae). Zool Stud 61:7. doi:10.6620/ZS.2022.61-07
Supplementary
Materials: Video S1
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