Lepidodasys laeviacus, Lee & Chang, 2011

Lee, Jimin & Chang, Cheon Young, 2011, Two new species of the genus Lepidodasys (Gastrotricha, Lepidodasyidae) from Tsushima Island, Japan, Journal of Natural History 45 (13 - 14), pp. 855-867 : 857-861

Lepidodasys laeviacus sp. nov.

( Figures 2 , 3 )

Type locality

Miuda Beach , Tsushima Island, Japan (34 ◦ 40 ′ 20 ′′ N, 129 ◦ 29 ′ 06 ′′ E) .

Type specimens

Holotype ( DBG1401 ) and eight paratypes ( DBG1402–09 ), mounted in glycerine, 1 October 2009, leg. J.M. Lee and C.Y. Chang. Another two paratypes (NHM reg. nos. NHMUK 2010.1 , 2010.2 ), mounted in glycerine, collection data same as in the holotype.

Additional material examined

Five specimens with the same collection data were mounted on an aluminium stub for observation on a scanning electron microscope.

Diagnosis

Lepidodasys with strap-shaped body; dorsal cuticular armature with herring-bone pattern of scales; scales elongated oval, lacking longitudinal keel; adhesive tubes of four to seven TbA per side forming an arc, six to ten TbD arranged in zigzag in intestinal region, 9–14 TbL per side inserted in intestinal region, round caudum furnished with 8–12 TbP; testes paired, anterior end slightly exceeding middle of body.

Description of the holotype

Body ( Figures 2A, B , 3A, B ). Elongated, vermiform, vaulted dorsally, with indistinct head, Lt 550 µm long; a little swollen at posterior part of intestinal region, then gradually narrowing in caudal region; caudum with simple rounded end; pharynx 100 µm long, PhJIn at U19, pharyngeal pores not seen; widths of anterior head / pharyngeal region / trunk / caudal portion 28 / 40 / 50 / 26 µm at U02 / U16 / U63 / U95, respectively.

Sensory hairs (ca. 6–9 µm long). Scattered sporadically on anterodorsal surface of head at U01–U03; numerous hairs (ca. 12–18 µm long) irregularly implanted on

subdorsal, lateral and ventrolateral surfaces throughout almost whole body length (U06–U95).

Cuticular armature ( Figures 2C–F , 3E ). Body densely covered with elongated oval or wholegrain-shaped scales dorsally, laterally and mid-ventrally; scales smooth, lacking longitudinal keel, with both ends a little protruded; 12–14 slender scales surrounding mouth opening. Dorsal scales 4–6 µm in diameter and 13–15 µm long in middle of trunk region; dorsal and lateral scales arranged in rather irregular herring-bone pattern. Ventral scales situated between ciliary bands, aligned in two columns showing zigzag pattern regularly, anterior ends of scales pointing outward, behind TbA to level of last pair of ventral cilia (at U03–U71); anterior scales small (3 × 7 µm), increasing in size toward end of ciliary bands (5 × 15 µm at U70); ventrolateral scales beside ciliary bands much narrower and elongated (ranging from 2 × 10 µm to 4 × 20 µm) than in scales between ciliary bands; caudum covered densely and irregularly with different size of scales, as in the case of dorsal and lateral scales.

Ventral ciliation. Aligned in a pair of ciliary bands from just behind TbA (U03) to two thirds of trunk region (U71).

Adhesive tubes. TbA of four or five tubes per side, ca. 5–7 µm long, forming an arc behind oral opening at U02–U05, of which three or four tubes gathered ventrally, rearmost one a little apart from others. TbD of nine tubes, ca. 14–18 µm long, irregularly arranged in intestinal region (U29–U84), beside median line; not paired, except for third pair. TbL of nine to ten tubes per side, ranging from 11 to 19 µm long, situated behind PhJIn to posterior trunk region at U23–U89, asymmetrically. TbP of eight tubes ranging ca. 9–16 µm long, inserted along round caudum unevenly.

Reproductive apparatus. Five suboval eggs with different sizes situated dorsally in midintestinal region at U60–U78, of which the anteriormost is largest (ca. 23 × 46 µm) and well-developed, becoming smaller posteriorly. Testes paired, their anterior ends slightly exceeding middle of body (U47); vas deferens not visible. Accessory organs not observed.

Measurements and variability

Among 11 type specimens, only one was immature, 543 µm in length and 42 µm in width. The immature specimen showed two discrepancies from adults, that is, fewer dorsal and posterior adhesive tubes of three TbD and six TbP, respectively, and an absence of reproductive organs.

Body lengths of 10 adult type specimens ranged from 515 to 675 µm (mean 573 µm, SD 43), maximum widths 51–71 µm (08U–13U), when mounted in glycerine.

The number and arrangement of adhesive tubes were somewhat variable, ranging from four to seven TbA per side, 9–14 TbL per side, 7–10 TbD and 7–12 TbP, respectively. Six of 11 type specimens had paired TbD, implanted usually third to sixth, excluding first tube paired in the one specimen. One specimen had two pairs of TbD at fourth and fifth. TbL array was asymmetrical except in one specimen and several of their tubes were located on the ventrolateral trunk near the eggs.

Etymology

The specific name, laeviacus , alludes to smooth (L. laevis) husk (L. acus), which is the characteristic shape of scales of the new species.

Remarks

Since the genus Lepidodasys was first established by Remane (1926), only five species have been recorded: L. martini Remane, 1926 , L. platyurus Remane, 1927 , L. unicarenatus Balsamo, Fregni and Tongiorgi, 1994 , L. arcolepis Clausen, 2004 and L. castoroides Clausen, 2004 . Lepidodasys species have been grouped by two main criteria: whether the scales are arranged in herring-bone or parallel style, and whether the scales bear longitudinal keel(s) or not ( Balsamo et al. 1994; Fregni et al. 1999; Clausen 2000, 2004).

Lepidodasys laeviacus sp. nov. shares the herring-bone disposition of the scales with L. martini . In addition, the new species is closely similar to L. martini in the arrangements of the ventral scales between ciliary bands, the anterior adhesive tubes, and the (ventro-)lateral adhesive tubes.

However, L. martini differs from L. laeviacus sp. nov. by the absence of the dorsal adhesive tubes in the trunk region (six to ten TbD in L. laeviacus sp. nov.). The decisive character discriminating the two species is the shape of scales, that is, smooth scales without any keel in L. laeviacus sp. nov., versus “unicarinated” scales in L. martini .

Lepidodasys martini was originally described as bearing two longitudinal keels on the scales ( Remane 1926). However, later this was corrected and reported as being furnished with only one keel following scanning electron microscopy by Fregni et al. (1999). Clausen (2000) also reported L. martini from Norway and Heligoland under differential interference contrast microscopy, which had “unicarinated” scales. Even in our new species, two faint longitudinal lines were sometimes observed under a light microscope at high magnification (see Figure 3F ). However, as all the scales are evidently smooth without any longitudinal keel when seen in scanning electron micrographs (see Figure 3E ), these lines may result from the inner rib(s) within the scale (not the real keels), or from traces of adherent between scales and body surface, under improper illumination.

Figures

Figure 2. Lepidodasys laeviacus sp. nov. (A) Habitus, dorsal; (B) habitus, ventral; (C) head and pharyngeal region, dorsal; (D) caudal region, dorsal; (E) head and pharyngeal region, ventral; (F) caudal region, ventral. Scale bars: A, B, 100 µm; C–F, 50 µm.

Figure 3. Lepidodasys laeviacus sp. nov. (A–E) Scanning electron micrographs: (A) habitus, dorsal; (B) habitus, ventral; (C) head and pharyngeal region, dorsal; (D) head and pharyngeal region, ventral; (E) dorsal scales in the trunk region; (F) differential interference contrast photograph: dorsal scales in the trunk region. Scale bars: A, B, 100 µm; C, D, 10 µm; E, F, 5 µm.