Crustacea: Branchiopoda) from the Island of Olkhon (Lake Baikal, Russia) and the Zoogeography of East Asian Spinicaudata

Jpn. J. Limnol., 60 : 585-606, 1999

A New Spinicaudatan (Crustacea: Branchiopoda) from the Island of Olkhon (Lake Baikal, Russia) and the Zoogeography of East Asian Spinicaudata

Hidetoshi NAGANAWA

ABSTRACT A spinicaudatan branchiopod crustacean, Baikalolkhonia tatianae gen. et sp. nov., is described from the Baikal region in Russia. The genus is assigned to the family Cyzicidae STEBBING,1910, based on the absence of a frontal organ on the head, the absence of triangular epipodal laminae on the thoracopods, and the presence of a pair of large frontal spines on the telson. The main distinguishing characteristic is that the epipodal upper corners of many anterior thoracopods (including even the first pair) are transformed into "sausage-like organs." Since such epipodal processes have been until now unknown in the Cyzicidae, the diagnosis of the family is emended, and 2 newly defined subfamilies, Baikalolkhoniinae and Cyzicinae, are proposed. Up to the present, 11 species belonging to 7 genera in 4 families of Spinicaudata (Cyclestheriidae, Cyzicidae, Leptestheriidae, and Lim- nadiidae) are known from the neighboring regions of East Asia, including the Russian Far East, Mongolia, China, Korea, and Japan. The list of species and the key to the species are provided. Their distribution defines 4 zoogeographical provinces, and the species diversity clearly shows a latitudinal gradient in a similar pattern to the European fauna.

Key words : Baikalolkhoniinae, Lake Baikal, Spinicaudata, zoogeography

INTRODUCTION

The "Large Branchiopods" of the order Spinicaudata of the freshwater fauna of Asia were partly treated by HU (1989). In total, 19 nominal species are known from China (UENO, 1927b, 1940; ZHANG et al., 1976; HU, 1985- 1993 ; SHEN and DAI, 1987 ; SHU et al., 1990), including several synonymic taxa (more details are given below in the section List of East Asian Spinicaudata). Additional records are available from the rest of East Asia (e.g., Japan: ISHIKAWA,1895; UENO, 1927a; Mongolia: SARS, 1901 ; BRTEK et al., 1984; Korea : YOON and KIM, 1992 ; Russian Far East : NAGANAWA et al., 1996). According to the latest studies, the currently known spinicaudatan fauna of East Asia consist of 11 valid species belonging to 7 genera in 4 families : Cyclestheriidae, Cyzicidae, Leptestheriidae, and Limnadiidae. 586 NAGANAWA

The Cyzicidae STEBBING,1910 is characterized by the absence of a frontal organ on the head, the absence of a triangular epipodal lamina on the thoracopods, and the presence of a pair of large frontal spines on the telson. In addition, STEBBING(1910) based his family diagnosis on the absence of a terminal spine on the rostrum and the unsegmented nature of the antennules, but there is considerable diversity in the morphology of these struc- tures within the Cyzicidae, and now a reassessment of the original diagnosis is in order. Since the Baikal specimens described below have no frontal organ on the head, thoracopods without a triangular epipodal lamina, and a pair of large frontal spines on the telson, they are therefore assigned to the Cyzicidae ; moreover, the present species possesses a unique feature concerning epipodal processes of the thoracopods, which warrants establishment of a new genus. This genus is furthermore separated at the level of subfamily from the other 2 closely related, currently recognized genera : Cyzicus AUDOUIN,1837 and Eocyzicus DADAY, 1913.

Order Spinicaudata LINDER,1945 Family Cyzicidae STEBBING, 1910 Baikalolkhonia gen. nov.

Diagnosis. - Female : Head with rounded occipital angle. Rostrum with a spine-like process. Body formed of 20-23 limb-bearing trunk segments, the number inconstant. Some posterior trunk segments provided dorsally with well developed hooks bearing spines. Epipodal upper corners of several anterior thoracopods, or almost all thoracopods, and always including the first pair, transformed into "sausage-like organs." Exopodal upper corners of the thoracopods not modified for bearing eggs. Telsonal spines unequally- sized, very low in number. Male : Unknown.

Type species. - Baikalolkhonia tatianae gen. et sp. nov.

Etymology. - The genus name is a latinized combination referring to the type locality ("Baikal" + "Olkhon"). Gender feminine.

Baikalolkhonia tatianae gen. et sp. nov. (Figs. 1-3)

Type Material. - Holotype •Š (960803-1) (3.4 mm carapace length), deposited in the Zoological Museum at Irkutsk State University, Irkutsk, Russia ; collected by H. NAGANAWA from a freshwater ephemeral pool on the Island of Olkhon in Lake Baikal, Russia (53•‹04'N, 107•‹01'E), 3 August 1996. Paratypes 4•Š•Š(2.9•}0.1 mm) from type locality, in author's collec- tion. Specimens are preserved in 80% ethanol with 1/10 volume of glycer- ol. New Prospect of East Asian Clam Shrimp Fauna 587

Fig.1. Baikalolkhonia tatianae gen. et sp. nov. (holotype female). (A) Carapace (left side) ; (B) Same (dorsal view) ; (C) Whole animal (left side with left valve removed, arrow [a] indicating flagella of biramous antenna ; see text for further explanation); (D) Two of the dorsal processes of the trunk (left side).

Description.- Female : Carapace laterally compressed, oval quadrangular in lateral view ; height about 3/5 of length ; dorsal margin nearly straight (Fig.1A) ; ventral margin gently curved, anterior extremity bluntly truncated, posterior one considerably expanded and broadly rounded (Fig. 1C) ; umbo very small and placed far to front (Figs.1A, B). Valve thin and pellucid, with 8-10 regularly arranged growth lines ; surface between lines irregularly reticulated ; margins with minute hairs. Body composed of 25 somites in holotype, distinctly divided into a head (usually 2-segmented in Spinicaudata), 21 limb-bearing similar and 1 limbless trunk segments, and telson ; 6th to 19th trunk segments armed dorsally with conical hooks, latter longer than width at base (Fig. 1C. Last 588 NAGANAWA

22nd trunk segment confluent with telson. Dorsal terga of anterior 5 trunk segments without spines;dorsal processes of posterior trunk segments large, with backwardly-directed long, strong spines (Fig. 1D), giving dorsal face an imbricate appearance;left armature of spines in holotype : Head 0.0.0.0.0. 3.3.5.5.6. 8.7.5.3.3. 3.3.3.2.1. 1.0. Telson. A pair of dorsal processes per segment, with 1-8 spines per process. Head narrowly rounded distally and with obtuse occipital prominence (Fig.2A [b]) ; rostrum triangular and somewhat recurved, with some spinules on the front and a well-marked apical terminal process (Figs.2A, C). Two closely placed, sessile compound eyes located some distance from ventral margin of head in lateral view (Figs. 2A-C). Ocellus, ventral to eyes, triangular in lateral view and variable in shape (Figs.2A, C). Labrum

Fig. 2. Baikalolkhonia tatianae gen. et sp. nov. Holotype female : (A) Head (left side, antennae omitted, arrows [b, c, d, and e] indicating occipital prominence, spine-like rostral process, labrum (upper lip), and antennule, respectively ; see text for further explanation) ; (B) Same (anterior) ; Paratype females : (C) Head shape of two individuals (left side). New Prospect of East Asian Clam Shrimp Fauna 589

(upper lip) developed, elongate backward, with setae confined to tip (Fig. 2A [d]). Antennule arising from posterolateral surface of rostrum, distinctly segmented, with several sensilla-bearing lobes (Fig.2A [e]). Antenna large, well developed, biramous (Fig.1C). Peduncle with short spines on anterior edge, divided into 2 poorly demarcated cylindrical segments ; proximal segment without distal setae ; distal segment wrinkled, with a few short spines on anterior edge. Each biramous flagellum 9-segmented (Fig.1C [a]) ; each segment bearing 1-4 short spines along anterior edge and 3-4 longer, simple, distal setae on posterior edge.

Fig. 3. Baikalolkhonia tatianae gen. et sp. nov. (holotype female). (A) Left thoracopod of 1st pair (outer side, arrow [f] indicating sausage-like epipodal organ) ; (B) Left thoracopod of 7th pair (outer side, arrow [g] indicating sausage-like epipodal organ) ; (C) Telson with caudal rami (left side, arrow [h] indicating the large frontal spine, arrows [i, j] indicating larger telsonal spines, arrow [k] indicating the left furcal spine) ; (D) Posterior part of trunk with caudal rami (ventral view, arrows [1, m] indicating long, acute, bifid furcal spines on medial surfaces of caudal rami ; [m] is identical with [k]). See text for further explanation. 590 NAGANAWA

Twenty-one pairs of similar thoracopods in holotype, range among paratypes is 20-23, decreasing in size posteriorly (Fig.1C). Epipodal upper corners of first 7 thoracopods (in holotype) each with sausage-like, cylindrical process (Figs.1C, 3A [f] , B [g]). In paratypes, however, number of such pairs varying (up to 20) among specimens of the same state of maturity, always beginning with anteriormost pair. Telson with a pair of long filaments and 7 pairs of spinulose, unequally- sized spines, including a pair of large frontal spines (Fig. 3C [h], left frontal spine); dorsal profile concave and leading to terminal projection ; telsonal filaments long, plumose, arising from vicinity of second most anterior spine . Caudal rami well developed ; distal half with a row of identical denticules, fewer toward tip (Fig.3C) ; a long, acute, bifid spine on medial side (Figs. 3C [k], D [1, m] ; [m] is identical with [k]) . Live specimens translucent, dominant color of valves yellow pale tending toward orange. Male : Unknown.

Etymology. -The species is named after the author's co-worker, Ms. Tatiana I. ORGILJANOVA, who contributed greatly to the finding of this new form.

Remarks. -The Baikal specimens may possibly not be fully mature ; however, I believe enough key characters are present to differentiate the taxon as a valid species (see NOTES ON TAXONOMY).

Ecological notes. -Up to the present, this species is known only from its type locality, approximately 5 km from the island's Lake Baikal shoreline . The pool had a surface area of about 400 m2 with an average depth of 30 cm . The fresh water was pH 7.7 and remained constant around 25 •Ž in the daytime in August. The accompanying fauna included several species of branchiopods : an undescribed anostracan species (Chirocephalus sp .), an unidentified notostracan Triops sp ., and some cladocerans. Olkhon is the largest of 22 islands in Lake Baikal . It is 71.7 km long and 15 km wide, with an area of about 720 km2 . As recounted by GALAZIY (1984), AFANASEV (1967) distinguished 5 climatic districts in the Baikal region according to the annual precipitation : (1) North Baikal district (north of Pokoyniki and Turka Rivers) -700 mm, (2) "Hamar-Daban" district - 1145 mm, (3) Cisbaikal southwest district (between Angara and Pokoyniki Rivers) - 475 mm , (4) Chikoysk taiga district - 555 mm, and (5) "Selenga -Dauriya" district (the Selenga basin , excluding the Chikoysk taiga) - 420 mm (GALAZIY, 1984). Exceptionally , on the Island of Olkhon the annual precipitation is less than 200 mm . Because of the very low precipitation and the many fine-weather days on the island (on average only 62.2 rainy days per year (GALAZIY, 1984)), there is usually very little or no surface water, and even in winter the snow cover sometimes evaporates entirely. The southern and southwestern parts of Olkhon (including the type New Prospect of East Asian Clam Shrimp Fauna 591 locality of this species) are steppes, and they are the most arid places in the Baikal region. This is the first record of a spinicaudatan species from shallow aquatic biotopes in the Baikal region.

NOTES ON TAXONOMY Family taxon of Baikalolkhonia According to the current system of spinicaudatan classification (STEBBING, 1910 ; DADAY,1913, 1923 ; STRASKRABA,1965a, 1965b, 1966 ; BELK, 1982 ; FRYER, 1987; HU, 1989; BRTEKand THIERY, 1995), the new species Baikalolkhonia tatianae is an intermediate form between the families Cyzicidae STEBBING,1910 and Leptestheriidae DADAY,1923. Until now, the sausage-like, cylindrical epipodal organs on the thoracopods in females, which are usually adapted for bearing eggs, have been considered as a unique, typical characteristic of leptestheriids, and they are unknown among the other 3 spinicaudatan families (the Cyclestheriidae, Cyzicidae, and Limnadiidae), with the single exception of the present species. How- ever, there is an analogous feature common to these latter 3 families : the exopodal upper corners of the thoracopods, including the 10th and some vicinal pairs in females, are partly produced upward as elongate filaments (not as lobes) adapted for bearing eggs. In the Leptestheriidae the modified epipodal lobes start at the 10th pair of thoracopods and continue to the 11th pair and beyond. In contrast, in Baikalolkhonia tatianae the modified thoracopods begin more anteriorly, including even the first pair without exception (Figs. 1C, 3A [f] , B [g]) , and sometimes all pairs are involved (not shown in illustration). STEBBING(1910) established the family Cyzicidae with Cyzicus AUDOUIN, 1837 as the proper type genus (based on Decision 54 of the International Commission on Zoological Nomenclature, taken at the 14th International Congress of Zoology at Copenhagen, 1953). The family characters as stated by STEBBING(1910) were (a) "conchostracans" (now divided into two independent orders : Spinicaudata and Laevicaudata ; FRYER, 1987) enveloped by a bivalved carapace marked by numerous growth lines, (b) the first and second post-cephalic appendages of the male modified into claspers, (c) no frontal organ on the head, (d) unsegmented antennules, (e) no terminal spine on rostrum, and (f) with a conspicuous, truncated telson (* now a reassessment is in order ; more on this below). Baikalolkhonia tatianae has a spine-like rostral process (Figs.2A [c] , B, C) ; because the same process has also been observed in cyzicid females (e. g., STRASKRABA,1965b), it is not a valid character to separate the new species from the Cyzicidae. In addition, a segmented type of antennule (Fig. 2A[e]) has also been drawn in some cyzicids, e.g., Cyzicus gifuensis (ISHIKAWA,1895) (syn. Caenestheriella gifuensis (ISHIKAWA)),Eocyzicus davidi (SIMON,1886), E. propinquus (SARS,1901), and E. sahlbergi (SIMON, 1886). The large spine on the medial surface of each caudal ramus of the 592 NAGANAWA

Baikal specimens (Fig. 3C [k], D [l, m]) is similar to those of some cyzicids, e.g., Cyzicus gifuensis, C. tetracerus (KRYNICKI,1830) (in southern Slova- kian specimens ; STRASKRABA,1965b), and Eocyzicus orientalis DADAY, 1915 ; and the rounded occipital angle in the Baikal specimens (Fig. 2A [b] ) is also reminiscent of another genus, Eocyzicus, of the same family. The large frontal spine on the telson (Fig. 3C [h]) and the unequally-sized telsonal spines (Fig. 3C [i, j]) are characteristics common to many cyzicids. Thus, while Baikalolkhonia tatianae is considered a member of the cyzicids because it shares certain general characteristics with them ; it is a form that seems to be related to leptestheriids because of the modified epipods of thoracopods in the female.

Family Cyzicidae with proposal of 2 new subfamilies The present species may be a "living fossil" close to the common ancestor of the Cyzicidae and Leptestheriidae. We may assume two different lines of evolution within the cyzicid group, namely one represented by the monotypic new genus Baikalolkhonia, and the other represented by the closely related genera Cyzicus and Eocyzicus. This can be indicated by considering the group as a family with two subfamilies, defined as follows :

Family Cyzicidae STEBBING, 1910

Estheriidae SARS, 1900: 10 (invalid name). Cyzicidae STEBBING, 1910: 486 ; BARNARD, 1929: 253-254 ; MATTOX, 1957a : 370 ; BELK, 1982: 178 ; HU, 1989: 4 ; BRTEK and THIERY, 1995: 265-266. Caenestheriidae DADAY,1913: 66 ; 1915: 49 ; UENO, 1927a : 267 ; FORROand BRTEK, 1984: 79, 85.

Diagnosis. - Carapace with numerous growth lines ; umbo distinct but small. Head with prominent or rounded occipital angle ; a frontal organ lacking. Fornices (a pair of anatomical folds on both sides of the head) distinctly developed. Compound eyes divided, closely placed. Rostrum usually without terminal spine, but in some females with a spine-like process. Segmented type of antennules with several sensilla-bearing lobes. Body formed of 15-26 limb-bearing trunk segments. Some posterior trunk segments provided dorsally with rows of denticles, or with processes bearing rows of setae and/or spines. Thoracopods without triangular epipodal lamina. Telsonal spines various in size and number among species, a pair of frontal spines developed. First two pairs of thoracopods modified as claspers in male. The family contains 2 subfamilies : Baikalolkhoniinae and Cyzicinae, each newly defined as follows based on the presence or absence of epipodal "sausage -like organs."

Baikalolkhoniinae subfam. nov. New Prospect of East Asian Clam Shrimp Fauna 593

Diagnosis. -Female : Head with rounded occipital angle. Rostrum with a spine-like process. Body formed of 20-23 limb-bearing trunk segments. Some posterior trunk segments provided dorsally with developed processes bearing spines. Epipodal upper corners of several anterior thoracopods, or almost all thoracopods, and always including the first pair, transformed into "sausage -like organs." Exopodal upper corners of the thoracopods in female unadapted for bearing eggs. Telsonal spines unequally-sized, very low in number. Male : Unknown.

The subfamily contains only genus : Baikalolkhonia gen. nov. Distribution. -Baikal subregion (Island of Olkhon).

Cyzicinae subfam. nov.

Diagnosis. -Head with prominent or rounded occipital angle. Rostrum without terminal spine, in some females with a spine-like process. Body formed of 15-26 limb-bearing trunk segments, the number inconstant. Some posterior trunk segments provided dorsally with rows of denticles, or with hooks bearing setae and spines. All epipods of thoracopods without "sausage -like organs." Exopodal upper corners of 9th and 10-11th thoracopods in female elongate, adapted for bearing eggs. Telsonal spines unequally-sized, various in number depending on species. The subfamily contains 2 genera : Cyzicus (syn. Estheria RUPPELL,1837 [in part], Caenestheriella DADAY,1913 [in part]), and Eocyzicus (syn. Caenestheria DADAY,1913 [in part]). The genera are not adequately distinguished from each other. The only character currently judged to be valid is the prominent (Cyzicus) or rounded (Eocyzicus) occipital angle of the head. Distribution.- Worldwide (except for Antarctica). Both genera are known from East Asia.

List of East Asian Spinicaudata Order Spinicaudata Conchostraca SARS, 1867: 5-6; DADAY, 1913: 61 ; 1915: 39-47 ; 1923: 255 ; 1925 : 143 ; 1926: 1 ; 1927: 1 ; BARNARD,1929: 242 ; MATTOX, 1957a : 367 ; 1959: 577- 580 ; ZHANG et al., 1976: 4-19 ; BELK, 1982: 178 ; HU, 1989: 1. Spinicaudata LINDER, 1945: 1-28 ; FRYER, 1987: 368-374 ; BRTEK and THIERY, 1995 : 265-266.

Family Cyclestheriidae (1 species in East Asia) Limnadiidae : SARS,1888: 24 (in part). Cyclestheriidae DADAY,1913: 66-88 ; BARNARD,1929: 248 ; BELK, 1982: 178 ; SHEN and DAI, 1987: 353 ; HU, 1989: 2-3.

Paracyclestheria SHEN and DAI, 1987 594 NAGANAWA

Paracyclestheria SHEN and DAI, 1987: 353 ; HU, 1989: 3.

Paracyclestheria sinensis SHEN and DAI, 1987 Paracyclestheria sinensis SHEN and DAI, 1987: 353-356, figs. 1-9 ; HU, 1989: 3, figs. 8- 11.

Family Cyzicidae (5 species in East Asia) Subfamily Baikalolkhoniinae subfam. nov.

Baikalolkhonia gen. nov. Baikalolkhonia tatianae gen. et sp. nov.

Subfamily Cyzicinae subfam. nov.

Cyzicus AUDOUIN, 1837 Estheria RUPPELL, 1837 (in part) (invalid name) . Cyzicus AUDOUIN, 1837: 9 ; DADAY, 1915: 232-235 ; MATTOX, 1957b : 206-209 ; 1958: 123 ; 1959: 583 ; STRASKRABA,1965b : 210-212 ; UENO, 1967: 252 ; FORRO and BRTEK, 1984: 89 ; HU, 1989: 5 ; BRTEK and THIERY, 1995: 265-266. Caenestheriella DADAY, 1913 (in part).

Cyzicus gifuensis (ISHIKAWA,1895) [Japanese name : Kaiebil Estheria gifuensisISHIKAWA, 1895: 10-12, pl. 4, figs.1-12. Caenestheriellagifuensis : DADAY,1915: 124, fig. 22; UENO,1927a: 267 ; YOONand KIM,1992: 474-479, figs.2-4. Cyzicussinensis HU, 1988a: 52-58, figs.1-13. Syn. nov. Cyzicusgifuensis : SASSAMAN,1995: 48.

Eocyzicus DADAY, 1913 Eocyzicus DADAY,1913: 67-74 ; 1915: 190 ; BARNARD,1929: 260 ; UENO, 1935: 15 ; DURGAPRASAD et al., 1981: 195-203 ; BRTEK et al., 1984: 94-95 ; HU, 1985: 357 ; 1989: 4 ; 1992: 274; BRTEK and THIERY, 1995: 266. Caenestheria DADAY, 1913 (in part) ; HU, 1989: 5 ; 1991: 111-114.

Eocyzicus davidi (SIMON, 1886) Estheria davidi SIMON,1886: 452 ; SARS,1901: 152-153, pl. 6, figs. 1-14. Caenestheria davidi : DADAY,1915: 73-77, fig. 7 ; UENO, 1940: 98; ZHANGet al., 1976: 24 ; HU, 1988b : 77 ; 1989: 5, pl. 1, figs. 54-60 ; 1991 : 111-112, pl. 2, figs. 23-27. Caenestheriella kawamurai UENO, 1927a: 267-269, pl. 30, figs. 35, 35a-35i. Eocyzicus mongolianus UENO, 1927b : 157-160, fig. 1 ; 1935: 15-16, pl. 4 ; ZHANG et al., 1976: 24 ; BRTEK et al., 1984: 94-96 ; HU, 1985: 360; 1988b : 73, figs. 29-35 ; 1989: 4, figs. 29-35 ; 1991a: 69, fig. 1 ; 1993b: 55-56, figs. 6-14. Syn. nov. Eocyzicus davidi : BRTEK et al., 1984: 94, figs. 17-25 ; HU, 1993b: 56-57, figs. 15-23. Eocyzicus laiyangensis HU, 1985: 357-362, figs. 1-16; 1986: 24-25, figs. 1-8 ; 1988b: 73-74, figs. 36-42 ; 1989: 4-5, figs. 36-42 ; 1991a: 69, fig. 8 ; 1993b: 57-58, figs. 24- New Prospect of East Asian Clam Shrimp Fauna 595

31. Syn. nov. Caenestheria kawamurai : HU, 1989: 5, figs. 61-66 ; 1991b: 111-112, figs. 1-5. Syn. nov. Caenestheria shiquanica HU, 1991b : 111-118, figs. 6-18 ; 1993a: 181-184, figs. 1-14. Syn. nov.

Eocyzicus orientalis DADAY, 1915 Eocyzicus orientalis DADAY, 1915: 205-210, figs. 45, 46 ; UENO, 1927b : 158-160 ; DURGAPRASAD et al., 1981: 199 ; FORROand BRTEK, 1984: 79 ; HU, 1985: 357 ; 1988b: 72, figs. 21-28 ; 1989: 4 ; 1991a: 69 ; 1993b: 54-55, figs. 1-5 ; DOBRYNINA and BRATNIK,1989a : 49-51, fig. 2 ; 1989b : 144-150 ; BRTEK and THIERY, 1995: 266. Eocyzicus yanzhouensis HU, 1992: 274-277, figs. 1-11 ; 1993b: 58-59, figs. 32-42. Syn. nov. Eocyzicus paralaiyangensis HU, 1992: 277-280, figs. 12-23 ; 1993b : 59-64, figs. 43-54. Syn. nov.

Eocyzicus propinquus (SARS, 1901) Estheria propinqua SARS,1901 : 155-157, pl. 8, figs. 1-8. Caenestheria propinqua : DADAY,1915; HU, 1991b: 111-113, figs. 48-50. Eocyzicus propinquus : BRTEKand THIERY,1995: 266.

Family Leptestheriidae (3 species in East Asia) Leptestheriidae DADAY,1923: 255-258 ; UENO, 1927a: 267 ; BARNARD,1929: 263- 264; MATTOX,1959: 583; STRASKRABA,1966: 571-589 ; ZHANGet al., 1976: 24 ; BELK, 1982: 178-179; HU, 1986: 25; 1987:357; 1989: 5-6; BRTEKand THIERY, 1995: 266.

Eoleptestheria DADAY, 1923 Eoleptestheria DADAY,1923: 258-260 ; ZHANGet al., 1976: 24 ; HU, 1986: 25 ; 1987 : 357; 1989: 7 ; BRTEK and THIERY, 1995: 266.

Eoleptestheria ticinensis (BALSAMO-CRIVELLI,1859) Isaura ticinensis BALSAMO-CRIVELLI,1859: 115, pl. 1. Eoleptestheria ticinensis : DADAY,1913: 95, fig. 8a-o ; 1923: 263, fig. 82a-q ; STRAS KRABA,1966: 578-584, figs. 4-7 ; BRTEKand THIERY,1995: 266. Eoleptestheria inopinata DADAY,1923: 262, fig. 81a-i. Eoleptestheria chinensis DADAY,1923: 269-273, fig. 83a-q; UENO,1940: 99-100, figs. 21-28 ; ROEN,1952: 212, fig. 19; ZHANGet al., 1976: 24 ; HU, 1989: 7, figs. 92-98. Eoleptestheria variabilis BOTNARIUC,1947: 82, pls. 1, 2, 4, 5, figs. 2, 3. Eoleptestheria spinosa MARINCEK,1978: 103-118. Eoleptestheria spinosa tenuis MARINCEKand VALVAJTER,1979: 155-167. Eoleptestheria spinosa magna MARINCEKand VALVAJTER,1982: 63-72. Eoleptestheria spinosa mira MARINCEKand PETROV,1983: 89-103. Eoleptestheria dongpingensis HU, 1986: 25-27, figs. 9-23 ; 1987: 341-347, figs. 1-15 ; 1989: 7, figs. 99-109. Syn. nov. Eoleptestheria yanchowensis SHU et al., 1990: 410-416, figs. 1-21. Syn. nov. 596 NAGANAWA

Leptestheria SARS, 1898 Leptestheria SARS, 1898: 23 ; 1900: 10; STEBBING, 1910: 488 ; DADAY, 1913: 80 ; 1923: 273-276 ; UENO, 1927a: 269 ; BARNARD,1929: 264; MATTOX, 1959: 583 ; ZHANGet al., 1976: 24 ; HU, 1987: 357 ; 1989: 6 ; BRTEK and THIERY, 1995: 266. Leptestheriella DADAY, 1923 (in part).

Leptestheria dahalacensis (RUPPELL, 1837) Estheria dahalacensis RUPPELL,1837: 119, pl. 7a, b. Isaura dahalacensis : JOLY, 1842: 341. Estheria pesthinensis BRUHL,1860 ; CHYZER,1861: 115, pl. 3, figs. 1-4. Leptestheria tenuis SARS,1901: 157-158, pl. 8, figs. 9-17 ; DADAY,1923: 319-324, fig. 95 ; UENO, 1940: 98-99 ; 1967: 24 ; HU, 1989: 6, figs. 67-72. Leptestheria dahalacensis : KEILHACK,1909: 182 ; DADAY,1913: 106, figs. 10a-m, 11a-1; 1923: 337, figs. 99a-m, 100a-o; STRASKRABA,1966: 571-578, figs. 1-4. Leptestheria rotundirostris DADAY,1913: 102, fig. 9a-p ; 1923: 329, fig. 97a-p. Leptestheria lybica COLOSI,1920: 120 ; 1923: 292. Leptestheria aegyptiaca DADAY,1923: 333, fig. 98a-o. Leptestheria dives DADAY,1923: 345, figs. 101a-h, 102a-i. Leptestheria intermedia BOTNARIUC,1947: 88, pl. 1, figs. 5-6, p1. 2, figs. 3, 4, pl. 6a-p. Leptestheria dives var. securiformis BOTNARIUC,1947: 90, pl. 7a-n. Leptestheria xinjiangensis HU, 1987: 357-361, figs. 1-15 ; 1989: 6, figs. 83-91. Syn.

nov.

Leptestheria kawachiensis UENO,1927 [Japanese name: Togekaiebi] Leptestheria kawachiensis UENO, 1927a: 269-270, pl. 31, figs. 36, 36a-n; HU, 1989: 6, figs. 73-77. Leptestheria nanjingensis ZHANG et al., 1976: 25-26, fig. 30; HU, 1989: 6, figs. 78-82 . Syn. nov.

Family Limnadiidae (3 species in East Asia) Limnadiidae BURMEISTER,1843 (in part) ; SARS, 1896: 84; DADAY, 1913: 66-84; 1915: 113 ; 1925: 143 ; UENO, 1927a : 270 ; BARNARD,1929: 250 ; STRASKRABA, 1965a : 263 ; BELK, 1982: 179 ; HU, 1989: 3-4 ; BRTEKand THIERY,1995: 266.

Subfamily Limnadiinae BURMEISTER, 1843 Limnadiinae : STRASKRABA,1965a: 269.

Eulimnadia PACKARD, 1874 Eulimnadia PACKARD,1874; ISHIKAWA, 1895: 15-20; SARS, 1896: 8 ; DADAY, 1913: 84-85 ; UENO ; 1927a : 270-271 ; MATTOX, 1937: 249 ; 1939: 642 ; 1953: 57 ; 1954: 3 ; 1959: 581 ; STRASKRABA,1965a: 271 ; HU, 1986: 27; 1989: 3-4; BELK, 1989: 115-125.

Eulimnadia braueriana ISHIKAWA,1895 [Japanese name : Hime- kaiebil Eulimnadia braueriana ISHIKAwA , 1895: 15-19, p1.8, figs. 1-9; DADAY, 1926: 27-30, New Prospect of East Asian Clam Shrimp Fauna 597

figs. 132a-o ; UENO, 1927a: 271. Eulimandia packardiana ISHIKAWA, 1895: 19-20, pl. 7, figs. 1-5 ; DADAY, 1926: 20-22, figs. 130a-c; UENO, 1927a: 271. Syn. nov. Eulimandia taoluoensis HU, 1986: 27-28, figs. 24-30 ; 1989: 4, figs. 17-20. Syn. nov.

Eulimnadia kobai UENO, 1940 Eulimnadia kobai UENO, 1940: 97, figs. 16-20; HU, 1989: 3, figs. 12-16.

Limnadia BRONGNIART, 1820 Limnadia BRONGNIART,1820: 84.

Limnadia lenticularis (LINNAEUS,1761) [Japanese name : Usuhime- kaiebi] Monoculus lenticularis LINNAEUS, 1761 : 499. Daphnia gigas HERMANN, 1804: 134, p1. 5, figs. 4, 5. Limnadia hermanni BRONGNIART, 1820: 84, pl. 13. Limnadia gigas : GRUBE, 1853: 154, pl. 8, figs. 9-11. Limnadia lenticularis : SAHLBERG, 1875: 317 ; SARS, 1896: 85, pls. 14-17 ; DADAY, 1925: 158, fig. 117; STRASKRABA, 1965a: 263-266, figs. 1-4; BRTEK and THIERY , 1995: 266. Limnadia americana MORSE, 1866-1868: 404. Limnadia nipponica ISHIKAWA, 1895: 13-15, pl. 7, figs. 6-10; DADAY, 1925: 155, fig. 116.

Key to East Asian Spinicaudata *. Carapace bilaterally compressed, enclosing the head and trunk , usually with growth lines. Posterior trunk segments with rows of denticles dorsally, or with a pair of rows of processes, bearing setae and/or spines. Telson massive, armed dorsally with spines or denticles, and with a pair of caudal rami. More than 12 pairs of thoracopods (up to 32) •c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c Order Spinicaudata

1. Head with frontal organ, carapace partly with growth lines . Umbo lacking. Head with rounded occipital angle ...... Family Limnadiida

e Subfamily Limnadiinae•c•c4 •\ Head lacking frontal organ •c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c2

2. Carapace with rudimentary growth lines antero-dorsolaterally . Fornices undeveloped. Compound eyes fused into one structure. Antennules

bar-shaped, unsegmented, lacking sensilla-bearing lobes. Only first pair

of thoracopods modified as claspers in male. Body with 13-14 pairs of thoracopods•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•cFamily Cyclestheriidae Genus Paracyclestheria Paracyclestheria sinensis

•\ Carapace with numerous growth lines. Fornices distinctly developed . Compound eyes divided, closely placed. Segmented type of antennules

with several sensilla-bearing lobes. First two pairs of thoracopods 598 NAGANAWA

modified as claspers in male•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c3 3. Rostrum armed with permanent terminal spine in both sexes. All thoracopods with triangular epipodal lamina. Frontal spine on telson undeveloped •c•c•c•c•c•c•c•c•c•c•c•c•c•c•cFamily Leptestheriidae•c•c6 •\ Rostrum lacking terminal spine. Thoracopods without triangular epipodal lamina. Frontal spine on telson highly developed •c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c Family Cyzicidae •c•c•c8 4. Telsonal hind-corner prominent•c•c•c•c•c•c•c•c•cGenus Eulimnadia•c•c5 •\ Telsonal hind-corner rounded •c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•cGenus Limnadia Limnadia lenticularis

5. Frontal organ pyriform. Rostrum truncated. Antennal flagella 7-8 segmented •c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•cEulimnadia braueriana

•\ Frontal organ very large, fan-shaped in lateral view. Rostrum promi-

nent. Antennal flagella about 17 segments •c•c•c•c•c•c•c Eulimnadia kobai 6. Head with rounded occipital angle•c•c•c•c•c•c•c•c•c•cGenus Eoleptestheria Eoleptestheria ticinensis•\ Head with prominent occipital angle Genus Leptestheria•c•c7

7. Posterior trunk segments dorsally with rows of short denticles

•c•c•c•c•c•c•c Leptestheria dahalacensis•\ Posterior trunk segments dorsally with developed processes bearing 1-2

spines on top•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•cLeptestheria kawachiensis 8. Epipodal upper corners of anterior thoracopods in female with "sausage- like organs" •c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•cSubfamily Baikalolkhoniinae Genus Baikalolkhonia gen. nov. Baikalolkhonia tatianae gen. et sp. nov. •\ Epipodal upper corners in female without "sausage-like organs" •c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c Subfamily Cyzicinae •c•c•c9 9. Head with prominent occipital angle •c•c•c•c•c•c•c•c•c•c•c•c•c•c Genus Cyzicus Cyzicus gifuensis•\ Head with rounded occipital angle•c•c•c•c•c•c•c•c•cGenus Eocyzicus•c•c•c•c•c•c10 10. Body with about 15 pairs of thoracopods•c•c•c•c•cEocyzicus propinquus •\ Body with 20-26 pairs of thoracopods •c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c11

11. Posterior trunk segments dorsally with developed processes bearing

many unequally-sized setae and spines •c•c•c•c•c•c•c•c•c•cEocyzicus davidi •\ Posterior trunk segments dorsally with rows of 1-5 acute, similar spines

posteriorly •c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•c•cEocyzicus orientalis

Zoogeographical aspects of East Asian Spinicaudata I follow basically BELK's (1982) synopsis and classification , FRYER'S (1987) new classification system, and BRTEK and THIERY's (1995) checklist, with 2 additional valid genera (Cyclestheriidae : Paracyclestheria SHEN and DAI, 1987 and Cyzicidae : Baikalolkhonia gen . nov.). From East Asia 12 species listed above, belonging to 8 genera in 4 families , are valid. The geographic distribution of the species is mapped in Figure 4. Species diversity was measured by counting the species occurring in intervals of 5 degrees of north latitude (after BRTEK and THIERY'S (1995) method), and is illus- New Prospect of East Asian Clam Shrimp Fauna 599

Fig.4. Distribution patterns of East Asian spinicaudatan species : Cyclestheriidae (diamond), Cyzicidae (triangles), Leptestheriidae (squares), and Limnadiidae (circles). X, Y, and Z indicating endemic species ; broken lines are zoogeographical boundaries : (1) "Baikal-Olkhon" elements, (2) Palaearctic elements, (3) Oriental elements, (4) "Far Eastern" elements ; compare the two dis- tributional densities of spinicaudatans on the Asian Continent and in the Japanese Islands. See text for further explanation.

Fig. 5. Relationship between species diversity and latitude for Spinicaudata of East Asia and Europe. The spinicaudatans of East Asia show a clear diversity gradient (striped) similar to the pattern of European fauna (open) (the graphic method and data on the European fauna after BRTEK and THIERY, 1995). 600 NAGANAWA trated in Figure 5, compared with that of the European fauna. In the East Asian fauna (12 spp.) (Fig.4) the following 4 elements may be recognized (# endemic species in East Asia) :

1. "Baikal-Olkhon" elements (1 sp.) : # Baikalolkhonia tatianae. 2. Palaearctic elements (7 spp.) : Eocyzicus davidi, Eocyzicus orientalis, Eocyzicus propinquus, Eoleptestheria ticinensis, Leptestheria dahalacensis, # Eulimnadia kobai, and (Holarctic) Limnadia lenticularis. 3. Oriental elements (1 sp.) : # Paracyclestheria sinensis. 4. "Far Eastern" elements (3 spp.) : Cyzicus gifuensis, Leptestheria kawachiensis, and Eulimnadia braueriana.

Baikalolkhonia tatianae is known only from its type locality. Most palaearctic elements of the East Asian fauna are wide-ranging species ; for Eocyzicus orientalis, Eocyzicus propinquus, Eoleptestheria ticinensis, and Leptestheria dahalacensis, the westernmost limits reach Central Asia, Asia Minor, and even Europe. The range of Eocyzicus davidi is restricted to East Asia. The origin of the point-endemic species Eulim- nadia kobai deserves further consideration. Holarctic Limnadia lenticularis is considered a northern component of the European and North American faunas (40-60•‹N). In the basins of the Yellow and Yangtze Rivers, the Far Eastern elements are partly coexistent with some palaearctic species. Until now most Japanese freshwater biologists seem to have held the idea for many years only from old literature (e.g., UENO, 1927a) that Japan has a completely endemic, yet diverse, clam shrimp fauna. A Czechoslovakian clam shrimp researcher STRASKRABA (1965a) for the first time discredited that long-held idea. In recent years Chinese and Korean workers have made an additional valuable contribution to clam shrimp studies (e.g., ZHANG et al., 1976 ; HU, 1985-1993 ; YOON and KIM, 1992), and many taxonomic and biogeographical questions are nearing a solution. Thus, all Japanese spinicaudatan species are obviously not endemic to Japan, but are common to East Asia. A further study by our group on taxonomic and biogeographical aspects of the East Asian fairy shrimp (Branchiopoda : Anostraca) fauna is in progress.

ACKNOWLEDGMENTS Special thanks are due to my colleagues Prof. B. I. PISARSKYand Dr. A. I. ORGILJANOV(Institute of the Earth's Crust, Siberian Division of Russian Academy of Sciences [SD RAS]), to Mrs. L. V. ORGILJANOVAand G. I. NAGORNAYA(Irkutsk, Russia), to Drs. N. A. BONDARENKOand N. G. MELNIK (Limnological Institute SD RAS), and to my late father K. NAGANAWAfor their support. I also express my gratitude to Prof. HU WEIXING(Ocean University of Qingdao, China) for providing useful information on Chinese spinicaudatans. New Prospect of East Asian Clam Shrimp Fauna 601

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Hidetoshi NAGANAWA: c/o Prof. Dr. Boris I. Pisarsky, Institute of the Earth's Crust, Siberian Division of Russian Academy of Sciences, Irkutsk 664033, Russia ; Domestic address (for correspondence), Daifukucho 5-13-442, Gifu-shi,Gifu 502-0934,Japan(長縄秀俊:ロシア科学アカデミー(シベリア支部)地殻研究所客員研究員;〔国内連絡先〕〒502-0934岐阜市大福町5-13- 442)

(Received : 19 October 1998 ; Accepted : 29 July 1999) 606 NAGANAWA

ロシア・バイカル湖オリホン島から初めて見いだされた大型鰓脚甲殻類(カイエビ目)および東アジア産カイエビ目の動物地理学

長縄秀俊

摘要

バイカル湖オリホン島の小水域から得られた大型鰓脚甲殻類(カイエビ目)の1種を

Baikalolkhonia tatianae gen. et sp. nov.(バイカロルホニア・タチヤニ新属・新種)として記載した。本属は,前額部に付属器官および全鰓脚に上肢三角板をそれぞれ欠き,尾節に1対の顕著な前棘が存在する点に基づき,科Cyzicidae STEBBING,1910(カイエビ科) に属すると判断された。本属固有の主な分類学的特徴は,第1脚対を含む前寄りの鰓脚上肢上角の多数が「円筒器官」へと変形していることである。この一連の上肢付属器官の特異な体制は,カイエビ科としては全く未知のものであり,かつ異例の形質でもあるため, カイエビ科の標徴を再評価し,同科において新たに定義された2亜科(バイカルカイエビ亜科Baikalolkhoniinaeおよびカイエビ亜科Cyzicinae)を提示した。本種以外のカイエビ目として,今日までに東アジア(極東ロシア,モンゴル,中国,韓国および日本)の隣接地域からは,4科(マルカイエビ科Cyclestheriidae,カイエビ科Cyzicidae,トゲカイエビ科Leptestheriidaeおよびヒメカイエビ科Limnadiidae)に分類される7属11種が知られている。これらの分布は,4つの動物地理学的な要素によってほぼ説明され,種の多様性については,ヨーロッパのカイエビ相と同様な,緯度に伴う明確な勾配が認められた。東アジアのカイエビ類について,種レベル・タクサまでのリストと検索表を付した。