Echinoderes tchefouensis Lou, 1934

Sørensen, Martin V., Rho, Hyun Soo, Min, Won-Gi, Kim, Dongsung & Chang, Cheon Young, 2012, An exploration of Echinoderes (Kinorhyncha: Cyclorhagida) in Korean and neighboring waters, with the description of four new species and a redescription of E. tchefouensis Lou, 1934 *, Zootaxa 3368 (1), pp. 161-196 : 188-195

publication ID	https://doi.org/ 10.11646/zootaxa.3368.1.8
persistent identifier	https://treatment.plazi.org/id/03E08792-E217-FF8D-FF37-FB5FFB75FE0F
treatment provided by	Felipe
scientific name	Echinoderes tchefouensis Lou, 1934
status

Treatment

Echinoderes tchefouensis Lou, 1934 View in CoL

( Figures 13–15 View FIGURE 13 View FIGURE 14 View FIGURE 15 , Tables 9–10)

Emended diagnosis. Specimens with middorsal spines on segments 4–8; lateroventral tubules on segment 5; lateral accessory spines on segment 8; lateroventral spines on segment 9; laterodorsal tubules on segment 10, being minute in females and of regular size in males. Glandular cell outlets type 2 subdorsal and lateroventral on segment 2 and laterodorsal on segment 8; glandular cell outlets on segment 2 of regular size, outlets on segment 8 extraordinary large.

Type material. Neotype adult male, collected at 28 September 2006, at 79 m depth, from Station MAP-05 (see Table 1) in the East China Sea, 30 o 31’66’’N 125 o 55’86’’E, 400 km south of the Korean Peninsula and east of China ( Fig. 1D View FIGURE 1 ), mounted in Fluoromount G and deposited at the NHMD under accession number ZMUC KIN-468 .

Additional specimens. Mounted in Fluoromount G for LM were found on stations MAP-05 to MAP-08, MAP-15, MAP-23 and MAP-25 to MAP-27, and deposited at NHMD under accession numbers ZMUC KIN- 469 to KIN- 486 and KIN- 554 to KIN- 566, and in the personal collections of the authors. Specimens mounted for SEM were found on stations MAP-02, MAP-05 to MAP-09, MAP-15 to MAP-16, MAP-23, MAP-27 to MAP-29 and MAP-31 to MAP-34. All specimens for SEM are kept in the personal collection of MVS. See Fig. 1D View FIGURE 1 for distribution and Table 1 for further details about the stations.

Distribution. Echinoderes tchefouensis occurred in several samples (see Table 1 and Fig. 1D View FIGURE 1 ), and appears to be rather common in the Korea Strait and the East China Sea. However, it is noteworthy that the species also occurred in samples taken far away from the main study area, inclusive samples from the Malaysian part of Borneo, the Philippines and from Saipan in the Northern Marianas. At the latter locality, E. tchefouensis co-occurs with Triodontoderes anulap Sørensen & Rho, 2009 that otherwise is known from Micronesia only (see Sørensen & Rho, 2009)

Description. Adult specimens consist of a head, a neck and eleven trunk segments ( Figs 13A–B View FIGURE 13 , 15A View FIGURE 15 ). Measurements and dimensions are given in Table 9. A summary of sensory spot, spine, tubule and glandular cell outlet positions is provided in Table 10.

The head consists of an introvert and a mouth cone with 9 outer oral styles, composed of two subunits ( Fig. 15C View FIGURE 15 ). Style bases form a basal plate with folded lateral margins that extend into a pair of anterolateral spikes. The median, external fringe of the style base consists of only two fringe tips, each with bipartite endings ( Fig. 15C View FIGURE 15 ).

Introvert with 10 spinoscalids in Ring 01, followed by 10, 20 and 10 scalids, respectively, in Rings 02 to 04. Ring 05 with 10 scalids, arranged as two scalids in each uneven numbered section; and Ring 06 with 15 scalids, arranged as one scalid in each uneven numbered section and two scalids in each even numbered one. Hence, described section-wise, uneven numbered sections have 7 scalids, whereas even numbered ones have 6 ( Fig. 15B View FIGURE 15 , see also Fig. 8 View FIGURE 8 for an overview of scalid distribution in a species with a corresponding pattern). Additional leaf-like scalids, not following a pentaradial pattern, are present in ring 07. These leaf-like scalids are present as one scalid in sections 1, 5, 6 and 7, and two scalids in sections 3 and 9.

The neck consists of 16 placids, all measuring 9 µm in length and 7 µm in width at bases, except midventral placid that measures 10 µm in width. Placids number 2 and 16 (counting clockwise from midventral placid) with broad trichoscalid plate and attached trichoscalid ( Fig. 14B View FIGURE 14 ). Smaller trichoscalid plates with trichoscalids on placids number 6, 8, 10, and 12 ( Fig. 14A View FIGURE 14 ).

Segment 1 consists of one complete cuticular ring ( Figs 13A–B View FIGURE 13 , 14A–B View FIGURE 14 ). Type 1 glandular cell outlets present in middorsal position ( Figs 13A View FIGURE 13 , 14A View FIGURE 14 ). One pair of minute sensory spots present in ventrolateral position ( Figs 13B View FIGURE 13 , 14B View FIGURE 14 , 15F View FIGURE 15 ); each sensory spot has a single, associated cuticular hair ( Fig. 15F View FIGURE 15 ). Cuticular hairs are otherwise either missing completely or only present sporadically on the dorsal side. Posterior margin with pectinate fringe; fringe tips on dorsal and lateral sides appear short and broad whereas the ventral ones are narrower, but longer and conspicuously stronger.

Segment 2 consists of one complete cuticular ring. Sensory spots are present in middorsal, subdorsal, laterodorsal ( Figs 14A View FIGURE 14 , 15E View FIGURE 15 ) and ventromedial positions; sensory spots on tergal plate with two associated cuticular hairs located anterior to the sensory spots ( Figs 13B View FIGURE 13 , 15E View FIGURE 15 ). Glandular cell outlets of type 2 located in subdorsal and lateroventral positions ( Figs 13A–B View FIGURE 13 , 14A–B View FIGURE 14 , 15E–F View FIGURE 15 ); lateroventral pair is often partly or completely covered by the strong pectinate fringe from the preceding segment. Type 1 glandular cell outlet present in middorsal position, near anterior margin of segment. Cuticular hairs are few and follow almost a straight, transverse line on the dorsal and lateral sides; a few more and longer hairs present on the ventral side. Pectinate fringe as on preceding segment.

Segment 3 and following eight segments consist of one tergal and two sternal plates ( Fig. 13B View FIGURE 13 ). Type 1 glandular cell outlet present in middorsal and ventromedial positions. Paired sensory spots, each with two associated cuticular hairs, located in subdorsal and midlateral positions. Other cuticular hairs are bracteate, scattered on anterior half of the tergal plate and in two large ventrolateral patches on the sternal plates; paraventral positions without hairs and filiform extensions. Well-developed pectinate fringe present along posterior segment margin; posterior margin with middorsal incision in which the middorsal spine of the following segment fits during strong contraction of the trunk segments ( Fig. 13A View FIGURE 13 ).

Segment 4 with long middorsal spine and paired type 1 glandular cell outlets present in paradorsal and ventromedial positions ( Figs 13A View FIGURE 13 ); glandular cell outlets cannot be visualized with SEM, but with LM they appear as three dots on a row (see Fig. 14C View FIGURE 14 for similar structures on following segments). Posterior segment margin with middorsal incision. Cuticular hairs and pectinate fringe as on preceding segment .

Segment 5 with long middorsal spine and pair of lateroventral tubules ( Figs 13A–B View FIGURE 13 , 14C View FIGURE 14 ). Type 1 glandular cell outlets present in paradorsal ( Fig. 14C View FIGURE 14 ) and ventromedial positions. Posterior segment margin with middorsal incision. Cuticular hairs and pectinate fringe as on preceding segment.

Segments 6 and 7 with long middorsal spines ( Figs 13A–B View FIGURE 13 , 14C View FIGURE 14 ). Type 1 glandular cell outlets present in paradorsal ( Fig. 14C View FIGURE 14 ) and ventromedial positions ( Fig. 13B View FIGURE 13 ). Segment 7 furthermore with a pair of ventrolateral sensory spots. Posterior segment margin with middorsal incision. Cuticular hairs and pectinate fringe as on segment 5.

Segment 8 with long middorsal spine and pair of lateral accessory spines ( Figs 13B View FIGURE 13 , 14E View FIGURE 14 ). Type 1 glandular cell outlets present in paradorsal and ventromedial positions ( Fig. 14C View FIGURE 14 ). A pair of very large and conspicuous type 2 glandular cell outlets present in laterodorsal positions ( Figs 13A View FIGURE 13 , 14C–D View FIGURE 14 , 15A, D View FIGURE 15 ). Posterior segment margin without middorsal incision. Cuticular hairs and pectinate fringe as on preceding segments.

Segment 9 without middorsal spine, but with spines in the lateroventral position ( Fig. 13B View FIGURE 13 , 14E View FIGURE 14 ). Type 1 glandular cell outlets present in paradorsal ventromedial positions. Pairs of laterodorsal, ventrolateral and ventromedial sensory spots present. Small, rounded sieve plates present in the lateral accessory position ( Fig. 14E View FIGURE 14 ). Cuticular hairs and pectinate fringe as on preceding segments.

Segment 10 without acicular spines, but with a pair of short, laterodorsal tubules that emerge from a position under the posterior segment margin ( Figs 13C View FIGURE 13 , 15G–H View FIGURE 15 ); the tubules could not be clearly visualized with LM, but from SEM observations the lengths are estimated to ca. 4–8 µm. Two type 1 glandular cell outlets are present in a middorsal position ( Fig. 14F View FIGURE 14 ); one additional pair present in ventromedial positions. Tergal plate with few or no cuticular hairs; sternal plates with bracteate hairs on anterior half of segment. Pectinate fringe weak to moderate on tergal plate, but with long and strongly developed fringe tips on sternal plates ( Fig. 15G–H View FIGURE 15 ). A broad protuberance with fringed end is present middorsally at the intersection between segment 10 and 11 ( Figs 13A View FIGURE 13 , 14F View FIGURE 14 , 15G View FIGURE 15 ). The protuberance appears to be restricted to females only, but this is difficult to determine since it in strongly contracted specimens often is covered by segment 10.

Segment 11 with lateral terminal spines ( Figs 13A–B View FIGURE 13 , 14F–G View FIGURE 14 ). Females furthermore with pair of rather short and somewhat flexible lateral terminal accessory spines, equipped with a row of minute hooks on their external lateral sides. Males with three pairs of penile spines that emerge from the intersegmental joint with the previous segment ( Figs 13C–D View FIGURE 13 , 14G View FIGURE 14 , 15H View FIGURE 15 ); two penile spines are quite short, whereas the third one is long and flexible. Two type 1 glandular cell outlets are present in a middorsal position, underneath the fringed protuberance. Cuticular hairs are present in two laterodorsal clusters only ( Fig. 15G View FIGURE 15 ). Tergal plate terminates into rather short, obliquely truncate extensions equipped with a spinose tip ( Figs 13A–C View FIGURE 13 , 14F–G View FIGURE 14 , 15G View FIGURE 15 ); margin of sternal plates almost straight, with pectinate fringe, but no particular extensions ( Fig. 13B–D View FIGURE 13 ).

Comparison with original description. Echinoderes tchefouensis was originally described from the Yantai area on the Chinese Northeast Coast, about 320 km west of the Korean Peninsula (see Lou 1934). The original description by Lou, 1934 is generally rather poor, and it basically only describes E. tchefouensis as a species with middorsal spines on segments 4 to 8, and lateral spines on some segments that are not specified any further. From this information alone, it would not be possible to identify the species, and it would probably be most correct to consider it a nomen nudum. However, during his numerous collectings in East Asia, Robert P. Higgins sampled specimens of Echinoderes from the coast of Yantai and he considered these to be conspecific with E. tchefouensis . The specimens were never used for an actual redescription of the species, but their existence and putative identity with E. tchefouensis is mentioned by Higgins and Kristensen (1988) under the description of Echinoderes eximus Higgins & Kristensen, 1988 , and it is noted that they have a characteristic spine distribution in the lateral series, with lateral spines on segments 5, 8 and 9 only. Subsequently, it has been broadly accepted that E. tchefouensis is characterized by the presence of middorsal spines on segments 4 to 8, and lateral spines on segments 5, 8 and 9, and the species has been referred under this diagnosis in several studies and keys (e.g. Adrianov and Malakhov 1999; Adrianov et al. 2002a). Since the specimens used in the present study fit this diagnosis, and some of them are collected only 500 km from the Chinese type locality, we consider these specimens conspecific with E. tchefouensis Lou (1934) sensu Higgins.

It would surely have been preferable to have specimens from the exact type locality, but the wide distribution of the specimens collected for present study indicate that the species is very common in the entire region. From this study alone, the species appears to have a distribution that stretches from Malaysia in the south and the Saipan Islands in the West Pacific, to the Korean Peninsula in the north .

Notes on diagnostic features. Echinoderes tchefouensis is easily recognized by its almost unique spine pattern in the lateral series. The combination of having only lateroventral tubules on segment 5, lateral accessory spines on segment 8 and lateroventral spines on segment 9 is solely shared with E. eximus that is known from Greenland only (see Higgins & Kristensen 1988). These two species, however, show great resemblance. Besides having identical spine patterns in the dorsal and lateral series, E. eximus also has subdorsal and lateroventral glandular cell outlets type 2 (gco2) on segment 2. These outlets were reported as “cuticular scars” by Higgins & Kristensen (1988), but are obviously gco2. This was confirmed by re-examinations of two paratypes (ZMUC KIN-27 and 28) that are deposited at the NHMD. Examination of these paratypes furthermore revealed the presence of laterodorsal gco2 on segment 8 as well. These structures are not mentioned by Higgins & Kristensen (1988) and they are positioned so close to the lateral edge of the specimens that it is difficult to get a good view of them. Besides the ‘cuticular scars’ (=gco2) on segment 2, Higgins & Kristensen (1988) reports the presence of two pairs of ‘prominent truncate muscle scars’ on the tergal plate of segment 10. The structures are documented on Figures 48 in Higgins & Kristensen (1988) and are most likely gco2 as well. Such openings are not present on segment 10 in E. tchefouensis .

Besides, the spine formulas and distribution of gco2 on segments 2 and 8, another intriguing similarity between the two species regards the tube-like and terminally fringed protuberance found middorsally in E. tchefouensis at the intersection between segments 10 and 11. A very similar structure appears to be present in E. eximus also, hence this could be one additional character shared by the two species. To our knowledge, such a structure has not previously been reported for any other kinorhynch. However, examinations of the holotype of E. maxwelli Omer-Cooper 1957 revealed that a somewhat similar structure may be present in this species as well.

In general, E. tchefouensis and E. eximus share several similarities, and it may be difficult to distinguish between the two species. The most characteristic differences are probably the putative type 2 glandular cell outlets on the tergal plate of segment 10, present in E. eximus (see Higgins & Kristensen 1988) but absent in E. tchefouensis , the somewhat different shapes of the tergal extensions of the two species, and the presence of short laterodorsal tubules on segment 10 in E. tchefouensis .

Another species that also attracts some interest in relation to E. tchefouensis is Echinoderes caribiensis Kirsteuer, 1964 . In its lateral series, the species has spines on segments 5, 8 and 9, which is the same overall configuration as found in E. tchefouensis and E. eximus . Kirsteuer (1964) does not indicate clearly if the spines on segment 8 are shifted to a lateral accessory position, but knowing the lateral spine formulas in the two latter species, one may speculate if the same pattern is expressed in E. caribiensis . Besides this potential similarity, E. caribiensis is easily distinguished from E. tchefouensis and E. eximus . It has no middorsal spines, and the lateral terminal spines are rather short. Information on gco2 or similar structures is not available.