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INTRODUCTION
Freshwater oligochaetes live in a broad range of aquatic environments worldwide and include about 1,100 species of 13 families (Martin et al. 2008). The family Naididae is a large group of freshwater oligochaete (Milbrink 1987; Chapman 2001; Smutná et al. 2008). Of these the subfamily Naidinae appears in a wide range of habitats, ranging from rivers, pools, and estuaries (Timm and Martin 2015). These worms are generally smaller than other aquatic oligochaete families and they have a very soft body, pale body color and unique chaetae from other oligochaetes. Naidinae comprises 238 freshwater species (Martin et al. 2008) of which about 26 species belong to the genus Nais. Thirty-two species of Naididae have been reported from Korea with only 3 species from the genus Nais: N. communis, N. variabilis, N. pardalis (Jung 2011; Jung 2012; Park et al. 2013a, b; Lee and Jung 2014a, b). Key characteristics for identification of Nais species are the chaetae shape and number per bundle (Envall et al. 2012). Most species of Nais have ventral bundles with bifid and sigmoid crotchets. Some species have giant chaetae in the ventral bundles of some segments. The dorsal chaetae begin in segment VI and include long, thin hair chaetae, as well as short, bifid or single pointed needle chaetae (Brinkhurst and Jamieson 1971). In this study, we newly found 6 Nais species living in Korea.
MATERIALS AND METHODS
We collected Nais specimens from fine sand and muddy sediment with high organic material at the waterside of 4 locations in Korea (Jungrang-gu; Namyangju; Paju; Yangyang) using a plankton hand net or hand shovel from April 2013 to September 2014. Samples have been brought to the laboratory while they were alive. Then, they were sorted under the stereomicroscope (Motic, SMZ-168, Hong Kong). For detailed observation, specimens were fixed in 5% formaldehyde or 80% ethanol solution and mounted in Canada balsam according to the protocol described by Erséus in 1994. BX41 research microscope (Olympus, Tokyo, Japan) attached with 650D digital camera (Canon, Tokyo, Japan) was used for pictures. Measurements on pictures were performed by using the image analyzing software, InnerViewTM- i series (Innerview Co. Ltd, Gyeonggi-do, Korea).
RESULTS AND DISCUSSION
Phylum Annelida Linnaeus, 1758 환형동물문
Class Clitellata Linnaeus, 1740 환대강
Order Haplotaxida Grube, 1850 지렁이목
Family Naididae Ehrenberg, 1828 물지렁이과
Subfamily Naidinae Ehrenberg, 1828 물지렁이아과
Genus Nais Muller, 1773 물지렁이속
1.N ais behningi Michaelsen, 1923 큰낫물지렁이 (신칭) (Fig. 1A, B)
Synonyms: Nais behningi Michaelsen, 1923: 34.
Material examined: Korea: 1, Toegyewon-myeon, Namyangju- si, Gyeonggi-do, 37°38′33.01″N, 127°9′1.65″E, 22 Sep 2013, collected by Lee JH.
Diagnosis: Length 0.18 mm, width at V 0.14 mm, number of segments 22.
Eyes present. Dorsal chaetae with hair and needle chaetae 1~2 per bundle, needles thin and hair-like distally. Ventral chaetae of II-V, 5~10 per bundle, with long, strong curved with sickle-shaped upper tooth; enormously as long as the lower (Fig. 1A, B). Stomach beginning from VII.
Remarks: N. behningi have a specific anterior ventral chaetae resembles (or looks like) sickle-shaped not appeared from other species.
Habitat: The sample was collected along the edges of stream. Bottom of this site consists of sandy and gravel bottom with some water plants.
World distribution: Holarctic.
Deposition: NIBR No. KOSPIV0000193710.
Identifiers: Jeounghee Lee, Jongwoo Jung.
2.N ais pseudobtusaPiguet, 1906 머리털물지렁이 (신칭) (Fig. 2A-D)
Synonyms: Nais obtuse (Gervais) var. pseudobtusa Piguet. Piguet, 1906: 238.
Nais pseudobtusa Piguet. Piguet, 1909: 193.
Material examined: Korea: 1, Geumchon-dong, Paju-si, Gyeonggi-do, 37°45′59.37″N, 126°46′27.01″E, 27 Aug 2013, collected by Lee JH.
Diagnosis: Length 0.28 mm, width at V 0.03 mm, number of segments 37.
Eyes present. Dorsal bundles with 1~3 straight, long hairs and long needle chaetae bearing distinct nodulus (Fig. 2A). Ventral chaetae by 2~5, upper tooth thinner than lower tooth and up to 1.5 times as long as lower (Fig. 2B, D); slightly thicker from VI (Fig. 2C).
Remarks: N. pseudobtusa is hard to distinguish from Nais simplex, N. barbata, N. alpine (Van Haaren T and J Soors, 2012). All worms have simple point needle tips. Dorsal needles in N. pseudobtusa are thinner, sharper tipped, and normally hair-like, as compared to other species.
Habitat: This species from the roots of waterweeds at the edge of streams covered with sand or organic matter.
World distribution: Common, Asia, Africa, America, Europe, Africa, Afghanistan.
Deposition: NIBR No. KOSPIV0000193709.
Identifiers: Jeounghee Lee, Jongwoo Jung.
3.N ais simplex Piguet, 1906 둥근털물지렁이 (신칭) (Fig. 3A-C)
Synonyms: Nais variabilis var. simplex Piguet, 1906: 260. Nais simplex Piguet. Piguet, 1909: 202.
Material examined: Korea: 1, Myeonmok-dong, Jungranggu, Seoul, 37°34′52.87″N, 127°4′41.74″E, 22 Sep 2013, collected by Lee JH.
Diagnosis: Length 0.28 mm, and width at V 0.067 mm, number of segments 29.
Dorsal hair chaetae and needles 1~2 per bundle, needles simple pointed (Fig. 3A). Ventral chaetae of II-V, 2~6 per bundle, longer, straighter and thinner, with nodulus proximal and upper tooth nearly twice the length of the lower one (Fig. 3B, C). Dorsal vessel to the left of the middle line. Swims with spiral movements.
Remarks: Nais simplex is very difficult to distinguish from N. pseudobtusa, N. barbata, N. alpina (Van Haaren and Soors 2012). N. simplex have round end tips, as compared with N. pseudobtusa.
Habitat: Bottom of collected site is sludge such as soft mud and organic matter.
World distribution: Europe, Asia, North America, South America.
Deposition: NIBR No. KOSPIV0000206591.
Identifiers: Jeounghee Lee, Jongwoo Jung.
4.N ais bretscheriMichaelsen, 1899 큰손물지렁이 (신칭) (Fig. 4A-D)
Synonyms: Nais bretscheriMichaelsen, 1899: 121.
Material examined: Korea: 1, Beopsuchi-ri, Hyeonbukmyeon, Yangyang-gun, Gangwon-do, 37°53′57.89″N, 128° 36′51.57″E, 9 Sep 2014, collected by Lee JH.
Diagnosis: Length 0.14 mm, width at V 0.019 mm, number of segments 14.
Eyes present. Dorsal chaetae and needles 1~2 per bundle; hair chaetae single, short, 1~2 needle, with quite long parallel teeth (Fig. 4A, D). Ventral chaetae of II-V, 4~6 per bundle, thin and straight, with upper tooth about double the length of lower; those of the following segments 1~6 per bundle (Fig. 4C). Giant chaetae beginning from VII, 2 per bundle, thick, straight, and very short (Fig. 4B).
Remarks: N. bretscheri has giant ventral chaetae from VII. Shape of upper teeth is very thick and straight, while lower tooth is very short or reduced. This worm is often confused with N. pardalis which have giant chaetae from VI, whereas those in N. bretscheri start from VII.
Habitat: This site is up the river which is clear, cool and shallow water. The streambed consists of various types of sand with some organic matter.
World distribution: Cosmopolitan.
Deposition: NIBR No. KOSPIV0000216560.
Identifiers: Jeounghee Lee, Jongwoo Jung.
5.Nais stolciHrabe, 1981 작은손물지렁이 (신칭) (Fig. 5A-C)
Synonyms: Nais stolci Hrabe, 1981: 33.
Material examined: Korea: 1, Beopsuchi-ri, Hyeonbukmyeon, Yangyang-gun, Gangwon-do, 37°53′57.89″N, 128°36′51.57″E, 9 Sep 2014, collected by Lee JH.
Diagnosis: Length 0.162 mm, width at V 0.043 mm, number of segments 24.
In II-V ventral chaetae by 3~5 with upper tooth twice as long. From VI on, 3~4 enlarged chaetae per bundle, upper tooth up to 4 times longer (Fig. 5A, B). Dorsal chaetae beginning in VI, including 1 hair, 1~2 needle with long parallel teeth (Fig. 5C).
Remarks: Specimens of posterior ventral chaetae shape looked similar to N. pardalis or N. bretsheri. They have giant chaetae. N. bretsheri have giant chaetae from VII, while N. pardalis and N. stolci beginning from VI. Hair chaetae of N. stolci are longer than N. pardalis. So, these chaetae shapes correspond with those of N. stolci. This is the first report on this species from Asia.
Habitat: This site is up the river which is clear, cool and shallow water. The streambed consists of various types of sand with some organic matter.
World distribution: Europe.
Deposition: NIBR No. KOSPIV0000216600.
Identifiers: Jeounghee Lee, Jongwoo Jung.
6.Nais pardalis Piguet, 1906 시골물지렁이
Synonyms: Nais pardalis Piguet, 1906: 253.
Nais pardalis Park et al., 2013a: 511.
7.N ais elinguisMüller, 1773 하천물지렁이 (신칭) (Fig. 6A-C)
Synonyms: Nais elinguisMüller, 1773: 22.
Material examined: Korea: 1, Toegyewon-myeon, Namyangju- si, Gyeonggi-do, 37°38′33.01″N, 127°9′1.65″E, 22 Sep 2013, collected by Lee JH.
Diagnosis: Length 0.10 mm, width at V 0.013 mm, number of segments 12.
Dorsal chaetae 1~2 hairs and needles 1~3 per bundle, long parallel teeth (Fig. 6A, B). Ventral chaetae 2~5 per bundle, with upper tooth 1.5~2 longer and thinner than lower (Fig. 6C, D). Swims with lateral movements.
Remarks: Previous studies, this species is frequently found in brackish water, abundant in organically enriched sediment. But this specimen collected in relatively clean water with some organic sediment.
Habitat: The sample was collected along the edges of stream. Bottom of this site consists of sandy and gravel bottom with some water plants.
World distribution: Cosmopolitan.
Deposition: NIBR No. KOSPIV0000216623.
Identifiers: Jeounghee Lee, Jongwoo Jung.
8.Nais communisPiguet, 1906 보통물지렁이 Synonyms: Nais communisPiguet, 1906: 247.
Nais communis Park et al., 2013a: 511.
9.Nais variabilils Piguet, 1906 물지렁이 Synonyms: Nais variabilisPiguet, 1906: 253.
Nais variabilisJung, 2011: 408.
Key to the Korean species of the Genus Nais
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Eye present. Needles simple-pointed······························2 - Eye present. Needles bifid···············································4
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Ventral chaetae 5~10 per bundle with long and thin teeth, enormously long upper teeth strongly curved over the short lower teeth·····································N. behningi*
2′. Ventral chaetae, long and thin, with very long upper teeth strongly curved over the short lower teeth·············3
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Ventral chaetae with upper teeth thinner and longer than the lower. Needle chaetae hair-like with a thin tip············ ································································N. pseudobtusa* - Ventral chaetae with upper tooth twice longer than the lower. Dorsal chaetae with 1~2 hair, 1~2 broad tipped simple pointed needles···································N. simplex*
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Giant chaetae present······················································5 - Giant chaetae absent························································7
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Ventral chaetae of II-V, with upper tooth about double the length of lower. Giant chaetae beginning from VII with 2 per bundle, thick, straight, with very short············ ····································································N. bretscheri*
5′. Giant chaetae beginning from VI, without any significant difference between VI and VII································6
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Ventral chaetae with upper teeth thinner, up to 2 times as long as lower. Chaetae of VI on slightly thicker··············· ··········································································· N. stolci* - Ventral of VI on thicker, more curved, upper tooth slightly longer and thinner, sometime single giant chaetae per bundle······························································N. pardalis
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Ventral chaetae with all upper teeth longer than lower. Needle with long parallel teeth····················· N. elinguis* 7′. Needle chaetae short, with distinct diverging teeth·········8
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Oesophagus gradually leading into mid-gut····················· ······································································N. communis - Oesophagus abruptly leading into mid-gut······················· ······································································N. variabilils * Species of present study.
