Eustomias (Dinematochirus) dendrobium, Koeda & Ho, 2019

Koeda, Keita & Ho, Hsuan-Ching, 2019, Review of the genus Eustomias (Stomiiformes: Stomiidae: Melanostomiinae) of Taiwan, with descriptions of three new species, Zootaxa 4702 (1), pp. 94-106 : 95-98

publication ID

https://doi.org/ 10.11646/zootaxa.4702.1.14

publication LSID

lsid:zoobank.org:pub:F0FCDD0B-B356-41D0-8848-247BADCA73A2

persistent identifier

https://treatment.plazi.org/id/B1AED941-50BA-4D29-9BD9-BD7E8135A899

taxon LSID

lsid:zoobank.org:act:B1AED941-50BA-4D29-9BD9-BD7E8135A899

treatment provided by

Plazi

scientific name

Eustomias (Dinematochirus) dendrobium
status

sp. nov.

Eustomias (Dinematochirus) dendrobium sp. nov.

Figure 1 View FIGURE 1 ; Tables 1–2 View TABLE 1

Holotype. NMMB-P 30621, 117.8 mm SL, off Dong-gang (ca. 22°39ʹN, 120°24ʹE), Pingtung , South China Sea, Tai- wan, 10 Sept. 2018, obtained at fish-landing ground at Dong-gang, collected by commercial mid-water trawling. GoogleMaps

Diagnosis. A species of subgenus Dinematochirus with a unique barbel structure: barbel short, its length 13.9% SL; three branches arising at distal one-fourth of the barbel stem; distal tip of three branches extend distinctly beyond terminal bulb; medial branch thicker than lateral branches; two long and one very short secondary branches arising from middle of medial branch; two short secondary branches arising from near base of each lateral branch; each branch with 5–14 dendritic appendages comprised 1–15 tiny luminous swellings; terminal bulb simple, lacking terminal filaments; stem and branches solidly pigmented (skin rubbed off in some parts) except for dorsolateral surface of terminal bulb and blotchy unpigmented distal 1/3 of secondary branches of medial branch.

Description. Counts and measurements are given in Tables 1 View TABLE 1 and 2.

Jaws not curved; 7 teeth on premaxilla, 2nd, 4th, and 5th depressible; 8 strongly oblique comb-like teeth on maxilla; 7 teeth on dentary, all depressible, except for 3rd. Postorbital photophore large, its diameter as same as pupil diameter; dorsal third of postorbital photophore covered by black skin.

Etymology. The specific name of the new species, dendrobium , in reference to the diagnostic character of the species, which resembles the flowers of an orchid: branches of barbel with many dendritic appendages of tiny luminous swellings.

Distribution. Eustomias dendrobium sp. nov. is currently only known from southwestern Taiwan. The holotype was collected from shallower than 100 m, by a mid-water trawl targeting Sakura-shrimp ( Lucensosergia lucens ).

Remarks. The species of the genus Eustomias are difficult to identify because most of the species were described based only on structure of the barbel. The present specimen was identified as a species of the subgenus Dinematochirus by the following combination of characters: 3 branches on stem of the barbel; the barbel is uniformly black; photophores of the barbel stem absent; length of the barbel 13.9% SL; pectoral-fin rays 2; pelvic-fin rays 7; number of depressible teeth more than fixed teeth on jaws ( Regan & Trewavas 1930; Prokofiev 2018; only typical characters listed).

Although Prokofiev (2018) indicated that terminal filaments of the bulb present in members of the subgenus Dinematochirus , are actually absent in Eustomias (Dinematochirus) bulbiramis Clarke 2001 and Eustomias (Dinematochirus) triramis Regan & Trewavas 1930 ; they are also absent in our new species. This suggest that a presence of terminal filaments is not diagnostic for the subgenus. Gibbs et al. (1983) re-defined the Dinematochirus and recognized 12 valid species, of which, 10 were described from the Atlantic. Clarke (1998; 1999; 2000; 2001) subsequently described 26 new species and concluded that some of the species occur in both the Atlantic and the Indo-Pacific.

Of the species previously recognized in the subgenus Dinematochirus , the present new species differs in having a distinctly unique structure of the barbel (see Diagnosis). Eustomias dendrobium sp. nov. is most similar to E. bulbiramis and E. triramis in always and usually lacking a terminal filament on the terminal bulb on the barbel, respectively. However, E. dendrobium differs from them in having the structure of median branch with long secondary branches from the lateral branches (vs. similar), distal tip of branches extending distinctly beyond terminal bulb (vs. reached or distinctly shorter), and almost solidly pigmented branches (vs. unpigmented) ( Regan & Trewavas 1930; Clarke 2001). In addition, E. bulbiramis has prominent bulblets at about middle of branches, and E. triramis has a large subovate terminal bulb, whereas E. dendrobium sp. nov. lacks both.

TABLE 1. Meristic data of the specimens of genus Eustomias from Taiwan.

Subgenus Dinematochirus   Haploclonus     Nominostomias  
Species E. dendrobium E. stamen   Eustomias sp.   E. tritentaculatus E. perplexus
Specimen NMMB-P30621 NMMB-P12724 NMMB-P28088 NMMB-P22420 ASIZP64170 NMMB-P22760 NMMB-P30396 NMMB-P12063
Standard length (SL) 117.8 102.8 100.7 126.6 48.6 120.4 130.9 123.1
Counts
Dorsal-fin rays 24 20 damaged 20 22 23 24 N/A
Anal-fin rays 43 32 35 33 36 35 29+ 35
Pectoral-fin rays 2 3 3 3 3 3 3 3
Pelvic-fin rays 7 7 7 7 7 7 7 7
Vertebrae 63 N/A 57 58 N/A 66 68 68
Photophores
IP damaged 8 7 7 8 8   7
PV 30 33   28 31 31 34 34
VAV 17 14 12 12 13 17 18 19
AC 20 20 22 21 18 19 damaged damaged
OV 28 26 26 27 29 33 32 31
VAL 15 13 12 12 14 17 18 19
BR damaged 11 11 11 10 11 10 damaged
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