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Vol. 58, 2019
(update: 2020.05.12; 06.15)
Latitudinal Difference in the
Species Richness of Photosymbiotic Ascidians Along the East Coast of
Taiwan
Euichi
Hirose1,* and Yoko Nozawa2
doi:-
1Department
of Chemistry, Biology and Marine Science, Faculty of Science,
University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan.
*Correspondence: E-mail: euichi@sci.u-ryukyu.ac.jp (Hirose)
2Biodiversity Research Center, No. 128, Academia Road
Sec. 2, Nankang, Taipei 115, Taiwan. E-mail: nozaway@gate.sinica.edu.tw
(Nozawa)
(Received 29 January 2020 / Accepted 5
May 2020)
Communicated by Benny K.K. Chan
Some didemnid ascidians harbor
cyanobacterial symbionts, and this is the only obligate photosymbiosis
system known in chordates. These photosymbiotic ascidians are found
only in tropical and subtropical waters, probably because the
photosymbionts are vulnerable to low temperatures. We surveyed the
photosymbiotic ascidian fauna along the east coast of Taiwan. The
present and previous reports recorded 13 species in Taiwan, and the
species richness and composition is different in five areas along the
east coast. Along the middle-east, southeast, and south coasts, five or
more species have been recorded, whereas only one species has been
found along the northeast coast, and no species have been recorded on
the north coast. This gap in the species richness is probably related
to the Kuroshio Current, which travels from south to north along the
east coast of Taiwan but changes to an easterly direction off the
northeast coast. Increases in water temperature due to global warming
could cause northward expansion of the distribution ranges of these
ascidians in the future. Hence, the photosymbiotic ascidian fauna could
be an environmental indicator in subtropical, shallow water, and the
present study provides a basic dataset that illustrates the current
status of photosymbiotic ascidians in Taiwan.
Key words: Biogeography, Coral
reef, Didemnid ascidians, Cyanobacterial symbiosis, Latitude, Species
diversity.
Citation:
Hirose E, Nozawa Y. 2020. Latitudinal difference in the species
richness of photosymbiotic ascidians along the east coast of Taiwan.
Zool Stud 59:19.
doi:10.6620/ZS.2020.59-19.
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