Streblocerus cf. serricaudatus (Fischer 1849)
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publication ID |
https://doi.org/ 10.11646/zootaxa.4780.2.3 |
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publication LSID |
lsid:zoobank.org:pub:7735402E-CD9B-4127-A3E4-D8EA04F6623F |
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DOI |
https://doi.org/10.5281/zenodo.3854351 |
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persistent identifier |
https://treatment.plazi.org/id/03F987D7-FFE6-5250-FF45-518270E799DB |
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treatment provided by |
Plazi |
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scientific name |
Streblocerus cf. serricaudatus (Fischer 1849) |
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Streblocerus cf. serricaudatus (Fischer 1849) View in CoL
( Figs. 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 )
Studied material: 3 parthenogenetic females from Lake Kud-Thing (localities 2 and 7; 20 parthenogenetic females from Ban Na-thong Reservoir , Bueng Kan Province, 18°08᾿26.28᾿᾿ N, 103°53᾿38.83᾿᾿ E, 166 m a.s.l.
Description. Parthenogenetic female. General. Length of adult parthenogenetic females is 0.34–0.45 mm. Body sub-oval in lateral view ( Figs. 2A View FIGURE 2 , 3 View FIGURE 3 A–B, 4A), maximum height after the middle of body. Dorsal margin convex, postero-dorsal angle well-defined with rounded tip, postero-ventral angle not defined, ventral margin convex with about 15 setae. Valves and head covered with distinctive polygonal sculpture ( Fig. 3C View FIGURE 3 ). Head relatively large, two times shorter than valves with evenly curved antero-dorsal margin. Major head pore small, round ( Fig. 4B View FIGURE 4 ). Labrum large, with a distinct keel covered by polygonal sculpture, anterior margin of the keel convex, apex broadly rounded ( Figs. 3G View FIGURE 3 , 5D View FIGURE 5 ). Compound eye large, ocellus much smaller than an eye.
Antennule ( Figs. 3H View FIGURE 3 , 4C View FIGURE 4 ) long, strongly curved with four long lateral setae in distal portion. Seven terminal aestetascs, of about 1/3 length of antennule.
Antenna ( Fig. 3I View FIGURE 3 ) with antennal formula; setae 0-0-1-3/1-1-3, spines 0-1-0-1/0-0-1. The first segment of exopod much smaller than others. Setae of the first and second segment of endopod larger than other setae.
Trunk limb I. Outer distal lobe with one curved seta ( Figs. 3J View FIGURE 3 , 4F View FIGURE 4 ). Inner distal lobe with 3 curved setae long and curved unequal in size, the largest one with long spines in distal portion ( Figs. 3K View FIGURE 3 , 4F View FIGURE 4 ).
Postabdomen ( Figs. 2B View FIGURE 2 , 3 View FIGURE 3 D–F, 4E) short, with preanal portion 2 times longer than distal (anal+postanal). Ventral margin straight. Dorsal margin bilobed with incursion (but no cleft) between preanal and anal margins. Preanal margin strongly convex with single row of 6–7 large saw-like teeth, increasing in size proximally ( Figs. 2B View FIGURE 2 , 3F View FIGURE 3 , 4E View FIGURE 4 ). Preanal portion of postabdomen with polygonal sculpture. Postanal angle not defined, distal part of dorsal margin convex. Distal portion of postabdomen without sculpture and about 8 clusters of short setulae. Postabdominal claw as long as distal portion of postabdomen. Basal spine very small. Swimming seta longer than postabdomen with basal and distal portions of similar length, distal portion armed with short setulae.
Taxonomic notes. Streblocerus cf. serricaudatus from Thailand clearly differs from the more common species of SE Asia, S. spinulatus Smirnov 1992 , in presence of well-developed saw-like teeth on preanal margin of postabdomen (earlier records of S. spinulatus in Thailand were attributed to S. pygmaeus Sars, 1901 (Maiphae 2008) , but it is a South American species ( Smirnov 1992). It is obviously different from the African S. inexpectatus Dumont 1981 in the absence of cleft between preanal and anal margins.
Streblocerus serricaudatus s. str. was first described in the vicinity of St. Petersburg, Russia. According to Smirnov (1992), the species was recorded in the Holarctic region, Greenland, Australia, New Zealand and Argentina. Such situation suggests the presence of a species complex, and in our opinion S. cf. serricaudatus from Thailand could be an independent species. Holarctic populations of S. serricaudatus are confined to acid sphagnum bogs with pH 5 or less, but we found S. cf. serricaudatus in neutral or slightly alkaline waters, with pH 6.85–8.58.
Distribution and ecology. In Thailand, S. cf. serricaudatus is a rare species found in only two localities, Lake Kud-Thing and Ban Na-thong Reservoir, Bueng Kan Province. The distance between the localities is about 30 kilometers. Water variables of localities where S. cf. serricaudatus occurred were, temperature 27.1-28.3°C, pH 6.85- 8.58, electric conductivity, 14-19 μS cm-1, total dissolved solid 7-9 mg L-1, and dissolved oxygen 3.15-4.89 mg L-1.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.