Corresponding author: Khwanruan Srinui (
Academic editor: D. Defaye
A new species of the calanoid copepod genus
The present new species is a euryhaline species and occurred in brackish waters with salinity ranging from 0.7 to 23.3. Its breeding season may be from June to October, as indicated by the presence of egg-sacs.
We have been intensively investigating the taxonomy, biology and ecology of gelatinous and crustacean zooplankters in Thailand since 1997 (
During our survey in estuaries of Thailand in 2004–2012 a new species of the calanoid copepod genus
The genus
Copepods were collected at 2 stations from the near-bottom of the Prasae River Estuary, Rayong Province, in June 2011 and August 2004, 2012 using a plankton net (0.1 mm in mesh size) and a sledge net (0.3 mm) (
Sampling stations in Prasae River Estuary, Rayong Province.
Prasae River Estuary, the Gulf of Thailand, station1: (
Holotype: 1♀ station 1, 4 June 2011, dissected and mounted on 2 glass slides (BIMS-Z00-0130), allotype: 1♂ station 1, 4 June 2011, dissected and mounted on 5 glass slides (BIMS-Z00-0131); paratypes: 4♀♀, station 1, 13 August 2012, 3 ♂♂ station 2, 23 August 2004 partly dissected and mounted on 3 glass slides (BIMS-Z00-0132).
Antennule (
Antenna (
Mandible (
Maxillule (
Maxilla (
Maxilliped (
Legs 1–4 (
Leg 5 (
Habitus (
Right antennule (
SEM micrograph of ventral side of genital double-somite of female
Leg 5 (
The present new species can be definitely assigned to the
In the
The species was named after the type locality “Siam” (an old name of Thailand).
As mentioned above,
The habitat of the present new species, the Prasae Estuary was euryhaline, where the salinity widely ranged between 0.7 and 23.3 during the present investigation. Dominant copepods that co-occurred with the new species seasonally differed with salinity:
Although our collections of planktonic copepods were intermittently carried out, some information of the breeding of the new species was obtained. The ovigerous and/or spermatopore-bearing females of the new species were found during the wet season (June to October). In addition, the density of immature females reached 139 individuals per cubic meter in August 2004, suggesting it was an active breeding season.
Seventy-eight species of
1 | First urosomite symmetrical without blunt linguiform process on mid-ventral | 2 |
– | First urosomite asymmetrical with blunt linguiform process on mid-ventral |
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2 | First urosomite with pair of anterodorsal spines and posterodorsal cluster of 3 spinules |
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– | First urosomite without pair of anterodorsal spines and posterodorsal cluster of 3 spinules | 3 |
3 | Prosomal ends with one pair of processes dorsally |
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– | Prosomal ends with two pairs of processes dorsally |
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1 | Fifth pair of legs without left endopodal segment |
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– | Fifth pair of legs with left endopodal segment | 2 |
2 | First exopodal segment of fifth right legs with recurved process at distolateral corner |
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– | First exopodal segment of fifth right legs with straight process at distolateral corner | 3 |
3 | Endopod of fifth left leg with outer process tapering distally |
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– | Endopod of fifth left leg with outer process concave at the tip |
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We express our sincere thanks to Mr. Somjai Srinui and Ms. Rujira Kaewking for their help in the field sampling and other members of the Institute of Marine Science, Burapha University. This study was partly supported by a grant from the Asian CORE Program of Japan Society for the Promotion of Science (JSPS) and the RONPAKU Program of JSPS. We also thank to Mr. T. Hirabayashi for his assistance for SEM observations. This study was partially supported by a grant-in-aid from the Japan Society of the Promotion of Science, awarded to SO (No. 25304031).