Geminofilum thailandica, Plathong & Plathong & Capa, 2020
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publication ID |
https://doi.org/ 10.11646/zootaxa.4790.1.3 |
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publication LSID |
lsid:zoobank.org:pub:9C0BB652-39A7-444C-9BA5-89C116C6256A |
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persistent identifier |
https://treatment.plazi.org/id/0A4AC5C2-EB2D-4FA1-9704-CE7E3BAF8A04 |
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taxon LSID |
lsid:zoobank.org:act:0A4AC5C2-EB2D-4FA1-9704-CE7E3BAF8A04 |
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treatment provided by |
Plazi |
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scientific name |
Geminofilum thailandica |
| status |
sp. nov. |
Geminofilum thailandica View in CoL sp. nov.
Figs 1A View FIGURE 1 , 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 , 5 View FIGURE 5 A–D
Material examined. Two specimens, collected from Songkhla Sea , the Gulf of Thailand, Western Pacific. Coll. MEM (Marine Ecosearch Management Co., Ltd.), mud mixed with sand and shells. Holotype: PSUZC-POL-0020 (1 spec.), S21 (7°33’17” N, 100°46’43” E), 21 Aug. 2013, 24.0 m, complete specimen, female. Paratype: PSUZC- POL-0057 (1 spec. on SEM stub), S08 (7°29’10” N, 100°47’06” E), 14 Oct. 2015, 25.0 m, complete specimen, female GoogleMaps .
Type locality. Songkhla Sea , Gulf of Thailand ( Fig. 1A View FIGURE 1 ) .
Diagnosis. Body eight times longer than wide, cylindrical, up to 2.9 mm long and 350 µm wide. Prostomial appendages smooth, lacking spurs or basal papillae. Dorsal macrotubercles sessile, ellipsoid, arranged in two transverse rows per segment, with eight and seven macrotubercles each, from segment 3. Dorsum without additional papillae. Ventrum with ca. 12 ellipsoid papillae per segment, arranged in three transverse rows. Parapodia with a spherical papilla on the base of anterior side from chaetiger 3. Acicular lobe from chaetiger 2. Compound chaetae in all parapodia, 5–7, with blades 4–6 times as long as wide, and with variation in the length of the serration along the edge within fascicles.
Description. Holotype cylindrical, complete with 2.9 mm long and 0.47 mm wide, up to 21 chaetigers, in poor conditions. Dorsum convex, ventrum flattened. Segmentation inconspicuous. Preserved specimen without pigmentation. One pair of sub-epithelial eyes in head, black in preserved holotype ( Fig. 2 View FIGURE 2 A–B); muscular pharynx not seen. Anterior end bluntly rounded; prostomium and peristomium indistinct ( Figs 2 View FIGURE 2 A–B, 3A). Appendages digitiform, about twice as long as wide, smooth, without basal spurs. Some scattered additional papillae behind lateral and median antennae. Tentacular cirri not clearly distinct. Dorsal macrotubercles arranged in two transverse rows per segment ( Figs 3A View FIGURE 3 , 5A View FIGURE 5 ). Macrotubercles sessile, hemi-ellipsoid, longer than wide (but collapsed in SEM photographs, Fig. 3 View FIGURE 3 A–B, D). First chaetiger with five macrotubercles in anterior row, lateral and middle tubercles smaller, and posterior row with seven larger macrotubercles ( Fig. 3B View FIGURE 3 ). Second chaetiger with seven and eight tubercles on each anterior and posterior rows, arranged in zig-zag pattern; tubercles enlarging in size from lateral to mid-dorsal position ( Fig. 3B View FIGURE 3 ). Following chaetigers with eight macrotubercles between parapodia and seven in posterior transversal row ( Fig. 5A View FIGURE 5 ). Additional dorsal papillae absent ( Figs 3A View FIGURE 3 , 5A View FIGURE 5 ). Ventrum with ca. 12 spherical papillae per segment arranged in three transverse rows ( Figs 3D View FIGURE 3 , 5B View FIGURE 5 ). Additional large and spherical ventral papilla at the base of each parapodia from chaetiger 3 ( Fig. 3A, D View FIGURE 3 ). Parapodia about twice as long as wide, with digitiform acicular lobe, from chaetiger 2; ventral cirri digitiform, enlarged at the base on mid-body chaetigers from chaetiger 3. Parapodia with at least one papilla on the base of the anterior side ( Figs 3A View FIGURE 3 , 4D View FIGURE 4 , 5 View FIGURE 5 C–D). Compound chaetae present in all chaetigers, arranged in curved row posterior to acicular lobe, numbering 5–7 per fascicle ( Figs 4 View FIGURE 4 A–D, 5C–D). Shaft with slen- der distal end; blades slender, ranging 4–6 times longer than maximum width, with fine serration along all their edge ( Fig. 4 View FIGURE 4 E–G). A few spines on distal side of opposite edge ( Fig. 4G View FIGURE 4 ). Pygidium blunt with ventral pygidial cirrus and a pair of rounded terminal papillae, similar in shape but smaller than dorsal macrotubercles ( Fig. 3E View FIGURE 3 ).
Female with oblong eggs scattered in coelomic cavity ( Fig. 2A View FIGURE 2 ). Genital openings or sexual structures not observed.
Methyl green staining: only heavily stained on macrotubercles ( Fig. 2B View FIGURE 2 ).
Variation. Paratype 2.1 mm long, 0.3 mm wide, female; 20 chaetigers. Anterior end invaginated as in holotype, anterior appendages as described (tentacular cirri not observed). Other morphological traits such as the number and arrangement of dorsal and ventral tubercles, the parapodial and chaetal morphology does not vary with respect to that described for the holotype.
Remarks. Geminofilum thailandica sp. nov. is characterised by the presence of dorsal macrotubercles arranged in double transverse rows of, being elongated and ellipsoid in shape, the absence of additional dorsal epithelial papillae, the arrangement of transverse rows of spherical ventral papillae, being those near the base of parapodia much larger, and the presence of chaetae with blades 4–6 times as long as wide. Intraspecific variation could not be assessed in G. thailandica sp. nov. due to low number of specimens found, and some details are awkward to see in the type material given its size and not optimal conditions. Some of the features mentioned in the description (e.g., the number, arrangement and relative size of head appendages in a contracted anterior end and the number of macrotubercles in the first chaetiger) should be verified when additional material is found.
There are 15 species currently accepted within the genus Geminofilum ( Capa et al. 2019). They are mostly characterised by the arrangement of dorsal and sessile macrotubercles in double transverse rows per segment. Most species bear spherical or hemispherical macrotubercles, but macrotubercles in G. thailandica sp. nov. are elongated, longer than wide, especially in mid-body segments, such as those described for G. megatuberculata (Capa & Bakken, 2015) from Bass Strait, Australia. Both species also share the number and arrangement of these dorsal tubercles (8+ 7 in mid-body segments), compound chaetae serrated along all blade length, with some spines on opposite edge, and a pair of black subepithelial eyes. Geminofilum thailandica sp. nov. is distinguished from G. megatuberculata in the absence of dorsal papillae between macrotubercles, unlike the latter species that bears 2–3 transverse rows of small spherical papillae per segment. In addition, G. thailandica sp. nov. bears only one parapodial papilla, while G. megatuberculata bears two. The new species also has longer blades than the Australian congener, being between 4–6 times as long as wide in G. thailandica sp. nov. and 2–3 times as long as wide in G. megatuberculata . Sexual features have not been clearly identified in G. thailandica sp. nov., but both specimens studied are females and bear large spherical ventral papillae, near the base of parapodia from chaetiger 4 to at least 9, a feature that if related to pseudocopulation. In G. megatuberculata porous tubercles between chaetigers 5 and 6, were observed.
Other species of Geminofilum with similar number of dorsal macrotubercles seemingly presenting two more macrotubercles in one of the dorsal trasverse rows (8+7, instead of 6+7) are G. arctowskiensis ( Hartmann-Schröder & Rosenfeldt, 1988) , from South Shetland Islands; G. bisphaeroserialis ( Hartmann-Schröder, 1974) from South Africa; G. garciaalvarezi (Moreira; Cacabelos & Troncoso, 2004), from the NW of Spain ( Hartmann-Schröder 1974; Hartmann-Schröder & Rosenfeldt 1988; Moreira et al. 2004). Geminofilum thailandica sp. nov. is distinguished from all these species, from distant world localities, in the apparent complete absence of additional dorsal papillae in our species, while G. arctowskiensis , G. bisphaeroserialis and G. garciaalvarezi bear some scattered spherical papillae along with the macrotubercles. Moreover, chaetal blades are shorter in G. arctowskiensis , G. bisphaeroserialis and G. garciaalvarezi than in the new species.
Etymology. The species is named after Thailand, the country in which it was collected.
Distribution. Only known from type locality, the Songkhla Sea, Gulf of Thailand ( Fig. 1A View FIGURE 1 ).
Habitat. Found at 24–25 m deep, in muddy mixed with sand and biogenic soft bottoms.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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