Streptocephalus sirindhornae Sanoamuang, Murugan, Weekers, and Dumont, 2000

Shu, Shusen, Maeda-Martinez, Alejandro M., Rogers, D. Christopher, Yang, Junxing & Chen, Xiaoyong, 2015, Morphological characterization of Streptocephalus sirindhornae (Branchiopoda: Anostraca) from South East Asia: First record of the Streptocephalidae from China, Zootaxa 3911 (3), pp. 447-450 : 447-449

Streptocephalus sirindhornae Sanoamuang, Murugan, Weekers, and Dumont, 2000

( Figs 1 and 2)

Streptocephalus sirindhornae Sanoamuang, Murugan, Weekers, and Dumont, 2000 ; Sanoamuang et al., 2007; Dararat et al., 2012; Sornsupharp et al., 2013; Rogers et al., 2013; Rogers and Padhye, 2014.

Material examined. China: Yunnan, Luxi County: Laogantang temporary pond, 24 36' 07.05" N, 103 42' 33.88" E, 5 males, 6 females, total body length 23.1 to 30.8 mm, September 2008, S.S. Shu legit. Chongzuo City, Guangxi Zhuang Autonomous Region: Ecology Park, swamp for white-headed langur, 22 16' 22.13" N, 107 30' 54.87" E, 7 males, 6 females, total body length 20.4 to 23.3 mm, August 2009, M. Hou legit. Thailand: Maha Sarakham: aquaculture pond, 16°15’56.50’’ N, 103°08’27.65’’ E, 10 males, 8 females, August 2012, S.S. Shu legit.

Diagnosis. Male. Frontal appendage simple and short. First antenna filiform, second antenna well developed ( Fig. 1 B). Distal antennomere with distinct basomedial outgrowth (wart) ( Fig. 1 C). Proximal antennomere with stout distomedial outgrowth, consisting of a cylindrical, robust, bigeniculated peduncle of the long type (sensu Maeda- Martinez et al. 1995), terminating in a scleroid cheliform structure (hand) ( Fig. 1 B); peduncle without pulvinus, with three to five dorsobasal fleshy processes with their ventral surfaces bearing longitudinal rows of papillae ( Fig. 1 B); peduncle inflexion lateral side with longitudinal row of 9 to 14 slender conical processes ( Fig. 1 B, C); medial side with longitudinal row of triangular protuberances ( Fig. 1 C). Posterior ramus (so called “finger in Maeda-Martinez et al. 1995) biramous and longer than anterior ramus (so called thumb in Maeda-Martinez et al. 1995); posterior ramus with a dorsolateral (lower) sickle-shaped subramus, that is curved dorsally, sharply keeled over most of length, with apical third bearing an undulating free margin; posterior ramus with medial (upper) subramus with small rounded protuberances along dorsal margin, with two apical additional subramium equal in length bearing few small rounded protuberances ( Fig. 1 B; Fig. 2 A, B, C); spur of thumb broad basally, apically subacuminate (Fig. 2E, F). Genitalia with lateral linguiform outgrowths, and tubular gonopods ventrally projected with a spinulated medial appendix ( Fig. 1 D), basal parts not rigid, non-retractile. Cercopods setose.

Female. Ovaries uniramous; brood pouch elongate and fusiform; eggs spherical, ornamented by ribs forming polygonal areas ( Fig. 1 E). Cercopods setose.

Distribution. Streptocephalus sirindhornae is reported from Thailand ( Sanoamuang et al., 2000), southern Laos, and central Cambodia ( Rogers et al., 2013), and now China (this study) ( Fig. 1 A). Streptocephalus sirindhornae occurs in Yunnan, Luxi County, at an altitude of 1,791 ma.s.l; at the time of the field collection in this site water was turbid, temperature 22.8 °C, pH 8.3, and dissolved oxygen 5.5 mg /L. The species also occurs in the Guangxi Zhuang Autonomous Region in an Ecology Park at 169 ma.s.l. The materials from these two locations represent the first records of the family, genus and species in China, and document their northern and easternmost distributional range in South East Asia.

Comments.The Chinese Streptocephalus material corresponds to the description of S. sirindhornae , in having the main diagnostic characters described by Sanoamuang et al. (2000): (1) second antenna proximal antennomere (“basal joint) with a basal projection (“wart) (Fig. 2C); (2) the form of the antennal appendage (peduncle and“hand); the form of the gonopods (Fig.2B); and (3) egg morphology (Fig. 2E).

Conversely, the total body length of the specimens from China (23.1 to 30.8 mm of Yunnan specimens, and 20.4 to 23.3 mm of Guangxi specimens), is longer than those from the type locality (14.2 to 17.7 mm) ( Sanoamuang et al., 2000). The variation range of the number of slender conical processes located at the lateral side of the antennal peduncle inflexion ( Fig. 1 B) were originally reported as from 10 to 12 ( Sanoamuang et al., 2000), whereas in our material they were from 9 to 10 in material from Yunnan, and 12 to 14 in material from Guangxi ( Fig. 1 B). The original description reported the distal antennomere (slender processes) on both sides of the peduncle inflexion ( Sanoamuang et al., 2000), however the specimens we examined from Thailand and China had these processes on the lateral side only. The triangular protuberances located at the medial side of the antennal peduncle ( Fig. 1 C) are present in all specimens from Thailand and China. Their number and size are variable among individuals, even in the same population. Such triangular protuberances were not mentioned in the original description of the species. As in Streptocephalus dichotomus Baird, 1860 , we confirm that the basal lateral side of the thumb in S. sirindhornae has a well developed hollow ( Sanoamuang et al., 2000) ( Fig. 1 B). The fingers of S. dichotomus and S. sirindhornae were shown by Sanoamuang et al. (2000) with a depression on the ventral margin near to the confluence of the two rami. This depression is deeper in the material from Thailand, than in material from Yunnan and Guangxi (Fig. 2 G-I). The two apical subrami of posterior ramus is unequal in the material from Thailand and Guangxi but subequal from Yunnan (Fig. 2 A-C).The spur of the anterior ramus was described as broadly knife shaped, not constricted apically ( Sanoamuang et al., 2000); the spur in specimens from Thailand and Yunnan fits the original description (Fig. 2 D, E), however the Guangxi specimens bear a triangular spur (Fig. 2 F).

Phenotypic plasticity in inter- and intra-populations is an important adaptation in response to variable environments and predators ( Cohen, 2012). Based on the morphological differences, the populations of S. sirindhornae from Maha Sarakham in Thailand, and Yunnan and Guangxi in China show phenotypic plasticity possibly related to environmental differences. The new records extend the known distribution range of S. sirindhornae in altitude (up to 1791 ma.s.l.), and in eastern and northern latitudes, from tropical Thailand, Laos, and Cambodia to temperate zones in China.

The fairy shrimp S. sirindhornae contains high levels of protein ( Dararat et al., 2012), and is widely cultured commercially in aquaculture farms as live food for freshwater ornamental fish and prawns ( Sornsupharp et al., 2013).The species was imported to China in 2011 in Xiamen City, Fujian Province as an ornamental pet named the “Queen Fairy Shrimp(http://konglongxia.ywbb.com). The morphological variation of the Chinese populations here reported may help researchers to distinguish between natural and introduced forms.

FIGURE. 2. Details of the second antenna of Streptocephalus sirindhornae . A, D, G, male from Maha Sarakham, Thailand. B, E, H, male from Yunnan, China. C, F, I, male from Guangxi, China. A, B, C, distal part of medial (upper) subramus of the posterior ramus showing rounded protuberances and the two apical subrami unequal in length. D, E, F, lateral view of the spur of thumb. G, H, I, lateral view of the right posterior ramus showing the depression on the ventral margin near to the confluence of the two rami.

Figures

FIGURE 1. Streptocephalus sirindhornae from China. A, New localities (black circles) in China, and type locality (empty circle) in Thailand. B, lateral view of male right second antenna. C, medial ventral view of male right second antenna. D, ventral view of male genitalia showing the left gonopod with the lateral linguiform outgrowth. E, external morphology of typical egg.