Gieysztoria guangdongensis, Lu, Yan-Hong, Wu, Cheng-Chen, Xia, Xiao-Jie & Wang, An-Tai, 2013

Lu, Yan-Hong, Wu, Cheng-Chen, Xia, Xiao-Jie & Wang, An-Tai, 2013, Two new species of Gieysztoria (Platyhelminthes, Rhabdocoela, Dalyelliidae) from a Freshwater Artificial Lake in Shenzhen, China, Zootaxa 3745 (5), pp. 569-578 : 573-577

Gieysztoria guangdongensis n. sp. Wang & Xia

( Figs. 3–4 )

Locality. Constructed wetland system (pH=6.78, 27.5?) in an artificial lake in Shenzhen University campus, Shenzhen, Guangdong province, China (22° 31' 44"N, 113° 55' 52"E).

Material. Holotype (PLA–G0021) permanent slides of specimen strained by H.E. Method. Paratype (PLA– G0022–PLA0025). PLA–G0022–24: permanent slides of specimens strained by H.E. Method. PLA–G0025: permanent slides of stylet in polyvinyl-lactophenol.

Etymology. The species was discovered in Guangdong province, China.

Description. Animals are up to 1140–1160µm long and 275µm wide, with a truncated head and tapering posterior region ( Fig. 3 A). Dorsally, eyes (e) are situated at the blunt front end above the brain (br). Pharynx (ph), 1/4 of the entire body length long, is 284µm in length and 220µm in width in a barrel-shape tightly connecting to the intestine (i) ( Fig. 3 A).

The female reproductive system comprises a rod-shaped ovary (ov), 624µm in length and 169µm in width, located dorsally on the left side of the body and posterior end of the intestine ( Fig. 3 D). Compactly, the ovary (ov) continues into a muscular oviduct (od) and distally connects to a separate seminal receptacle (rs) filled with allosperms. Entering a variable-shaped female duct (fd), the oviduct (od) and the seminal receptacle (rs) associate to the uterus ( Fig. 3 D & E). The uterus consists of thick muscular walls, with an opening entering the genital atrium. Oval eggs (e) are 163µm long and 85µm wide. Two feather-like vitellaria (vi), 303µm long, begin in the region of the posterior end of the pharynx (ph) and lead to the ovary (ov). Entering into a common female duct (fd), vitellaria (vi) have numerous finger-like papillae (110µm long) ( Fig. 3 D). Gonopore lies ventro-caudally and can be closed by the strong sphincter.

The male reproductive system comprises a pair of oval testes (t) ( Fig. 3 F), 41µm in length and 21µm in width, located under both ventro-caudal sides of the intestine (i). Vasa deferentia arise from the middle of each testis and enters into a double-bulb shaped seminal vesicle (vs) subapically (98µm in length and 60µm in width). Seminal vesicle (vs) ( Fig. 3 F) connects to the columnar prostate vesicle (pv) (71µm in height and diameter 71µm), then becomes tightly associates to the sclerotic stylet (st) ( Figs. 3 B1, B2, B3 & C; Fig. 4 ).

The stylet (st) ( Figs. 3 B1, B2, B3 & C; Fig. 4 ) is formed by a proximal belt-like girdle and 18 distal spines in similar shape and size. The total length of the stylet (st) is 61µm. With a circumference ca.117µm, the proximal girdle is 23µm high, and curves into a crescent shape. The 18 distal blade-shaped spines, each 42µm long, are hollow and fine with a ca.1µm thick wall. Spines are 5µm (n=6) wide tubes in the middle portion and taper rapidly at both ends.

Remarks. Due to the paucity of available specimens, the description of G. guangdongensis n. sp. is based mainly on the sclerotic stylet construction. G. guangdongensis n. sp. has a sclerotic stylet with 18 distal spines. The construction of sclerotic stylet firmly shows that G. guangdongensis n. sp. is an “Aequales” species of Gieysztoria . Based mainly on the stylet morphology and configuration, G. guangdongensis n. sp. can be compared to the following species: G. bellis (Marcus, 1946) ; G. foreli (Hofsten 1911) ; G. lugubris (Reisinger 1924) ; G. lugubris wigrensis (Gieysztor 1938) ; G. ornata (Hofsten 1907) ; and G. oryzae (Nasonov 1929) . The species above have a sclerotic stylet with ca.18 distal spines (see Table 2 ). G. oryzae is the species most similar to G. guangdongensis n. sp. The sclerotic stylet of G. oryzae comprises a 14µm fibrous girdle and 18~19 distal spines which are 20µm long. The spines of G. oryzae are dagger-shaped, with distinct “U” shaped muscle attachment concave at the basal portion. Nevertheless, the sclerotic stylet of G. guangdongensis n. sp. comprises a 23µm fibrous girdle and 18 distal spines that are 42µm long. The spines of the new species are blade-shaped and straight with fine tips. Thus, the new species differs from G. oryzae by the girdle height and spine configuration. G. italica has a stylet (39µm total length) with 18 straight spines that are 21µm long. Although the girdle height is similar, the length of the distal spines is different from the new species. G. foreli has a prominent concave girdle and dagger-shaped spines, much shorter than the new species, which are 22.5µm long. G. lugubris and G. lugubris wigrensis have a small stylet with extremely short girdle (5µm) and straight spines (16µm) tapering rapidly. The girdle construction of G. ornate is a complex hollow portion distinct from the fibrous girdle of the new species. Furthermore, spines of G. ornata are much shorter than G. guangdongensis n. sp. (spines are 42µm long). G. bellis , with 19 spines (16µm) that are obconical in the pointed end, shows less similarity to the new species either in shape and length.

Discussion. The two new species described in this study belong to the “Aequales” group according to Luther’s criteria (1955), and they are also represent the first discovery of “Aequales” species in China. As for biogeography, the location of the collecting spot is in the Oriental realm.

The sclerotic stylets of “Aequales” species always have a proximal girdle bearing distal spines in similar shape and size (Luther 1955; Van Steenkiste et al. 2012). The morphology of the sclerotic stylet is the main basis of species classification (Luther 1955). In this study, G. bimaculata n. sp. was collected from 3 locations and bred in laboratory conditions. More than 100 stylets were dissected out of the fixed specimens and noted for variation in both size and number of distal spines. The total number of distal spines and their individual lengths do not appear to increase during the maturation of the animal. The height of the belt-like girdle remarkably increases along with the animal’s development (21–45µm; 35±5.2µm; n=13).

As reported previously, descriptions of the reproductive system of Gieysztoria are mainly focused on mature adults (Hochberg & Cannon 2001; Van Steenkiste et al. 2011; Van Steenkiste et al. 2012). In this study, careful observation was conducted during the maturation of G. bimaculata n. sp. Based on our observation, the female reproductive system develops prior to the male reproductive system, i.e., protogyny. With a soft and weak stylet, i.e., not fully sclerotized, and the lack of the ability to copulate, young individuals begin to lay eggs 4d after incubation. The stylet becomes comparatively more sclerotic approximately 14d into the lifecycle and adults are able to copulate. Besides, the stylet sclerotizes gradually, and then becomes friable in the old specimen.

Detailed research on the maturation of the sclerotic stylet in Microdalyellia ( Microdalyellia and Gieysztoria belong to Dalyelliidae ) was performed in 2008 (Yu et al. 2008). The study shows that shape and size of the distal branches of the stylet are stable, but the proximal shafts expand during maturation (Yu et al. 2008). The above results are in accordance with the observations in our study. The number of distal spines of G. bimaculata n. sp. is relatively stable at 44–46 spines/individual, while the proximal girdle continues growing during its life cycle. G. guangdongensis n. sp. has 18 distal blade-shaped spines. Therefore, this study suggests that the number and size of the distal spines are stable, but the height of the proximal girdle is variable. Nevertheless, in the description of some species, the number of the distal spines is more variable, such as in the stylet of G. expedita (Hofsten 1907) with 19–24 distal spines and G. expeditoides (Luther 1955) with 20–24 distal spines. Consequently, further detailed research should be conducted to improve the “Aequales” species classification.

Acknowledgements

This study was supported by University Student Innovation Project of Guangdong Province, China (Grant No. 1059013016), Opening Fund of Laboratory of Shenzhen University (Grant No. 2012720), Scientific and Technological Planning Project of Shenzhen, China (Grant No. CXB201104210005A) and the National Natural Science Foundation of China (Grant No. 41176106).

Figures

FIGURE 3. Gieysztoria guangdongensis Wang & Xia n. sp. (A) Photographed in life. (B) Sclerotic stylet in whole-mounted specimen (1, 2, 3 represent different depth of microscope view). (C) Dissection of sclerotic stylet. (D) Permanent slide stained by H. E. method. (E) Detail of reproductive system stained by H. E. method. (F) Ventral view of the male copulatory organ stained by H. E. method.

FIGURE 4. Gieysztoria guangdongensis Wang & Xia n. sp. Reconstruction of the sclerotic stylet.

Tables

TABLE 2. Comparison of the stylets between Gieysztoria guangdongensis n. sp. and other 7 similar species in genus Gieysztoria.

	Length of total stylet (µm)	The amount of distal spines	The length of distal spines (µm)	Distribution
G. guangdongensis n. sp.	61	18	42	China
G. bellis Marcus, 1946	40	19	16	Brazil
G. foreli Hofsten N, 1911	37.5	18–20	22.5	Switzerland
G. lugubris Reisinger, 1924	30–36.5	18	20.5–33	Austria
G. lugubris wigrensis Gieysztor, 1938	19–20	17–20	15–16	Poland
G. ornata Hofsten N, 1907	42–44	17–18 or 20–22	9	Switzerland
G. oryzae Nasonov, 1929 G. italica Luther,1955	34 39	18–19 18	20 21	Brazil Italy