Desmodema polystictum ( Ogilby 1898 )

Martin, Jennifer M. & Hilton, Eric J., 2021, A taxonomic review of the family Trachipteridae (Acanthomorpha: Lampridiformes), with an emphasis on taxa distributed in the western Pacific Ocean, Zootaxa 5039 (3), pp. 301-351 : 343-344

Desmodema polystictum ( Ogilby 1898)

Figures 2C , 23 , 26 , 28

Type species. Trachypterus jacksoniensis polystictus Ogilby 1898

Holotype. lost. 140 mm SL. Beach wash-up, Newcastle, New South Wales, Australia.

Material Examined. AMS I.24154 (Radiograph, 840 mm SL, Pacific, Australia, Nelson Bay); AMS I.24308- 001 (353 mm SL, Pacific, Indonesia, South Java); AMS I.20098-013 (235 mm SL, Pacific, Australia, New South Wales, Broken Bay ) ; BMNH 1982.10 .1.1 (105.9 mm SVL, Indian, off Sumatra ) ; HUMZ 141902 (98.4 mm SL, Pacific, Japan, off Kinkasan Island ) ; HUMZ 199972 (106.9 mm SL, Pacific, East China Sea ) ; MCZ 58907 (cleared and stained, 2 specimens, 11–41 mm SL; Atlantic, western Atlantic , off Brazil) ; MCZ 58909 (3 specimens, 21–29 mm SL, Atlantic, western Central Atlantic ) ; MCZ 58910 (35 mm SL, Atlantic, western Central Atlantic ) ; MCZ 60557 (355 mm SL, Atlantic, northwestern, off Massachusetts ) ; MCZ 96836 (64.5 mm SL, Atlantic , eastern, off Senegal) ; MCZ 164725 (Radiograph, 92 mm; Atlantic, northwestern, off Massachusetts ) ; MCZ 165989 (59 mm, Atlantic, northwestern, Bear Seamount ) ; NMNZ P.16409 (240 mm SL, Pacific, Kermedec Islands, Havre Trough ) ; NSMT-P 57647 (145.1 SVL, Pacific, Japan, Western North Pacific ) ; NSMT-P 63975 (271 mm SL, Pacific, Japan, Sea of Japan, Hyogo Prefecture) ; NSMT-P 65206 (142.4 mm SL, Pacific, Japan, Kagoshima Prefecture) ; NSMT-P 68656 (140.5 mm SVL, Pacific, Japan, Sea of Japan, Hyogo Prefecture) ; NSMT-P 91459 (94.3 SVL, Pacific, Japan, off Kagoshima) ; USNM 287024 (195.4 mm SVL, Pacific, south Pacific Ocean ) ; USNM 215709 (421.17 mm SL, Pacific, Hawaii, off Oahu ) ; USNM 112110 (80 mm SL, Pacific, Philippines, Sulu Sea ) ; USNM 164171 (107.9 mm SL, Pacific, Kiribati, near Washington Island ) ; USNM 16552 (366.6 mm SVL, Atlantic, Florida, off Fort Lauderdale ) ; VIMS 42793 (48 mm SVL; Atlantic, Bear Sea Mount ) ; VIMS 42794 (66.1 mm SL, Atlantic, Straits of Florida ) .

Trachypterus deltoideus (= Desmodema polystictum ); CAS: ICH:5552 (Holotype, radiograph only, Pacific , south Pacific , French Polynesia, Austral Islands, Rurutu Island) .

Diagnosis. Dorsal-fin rays 115–139; in juveniles first 5 or 6 more stout and elongate than more posterior rays; pectoral-fin rays 1+ 11–14; P2 absent in adults, 6–10 elongate rays in juveniles, the posteriormost is branched; caudal 7–10, typically 7 or 8. Snout length less than eye diameter in adults, eye diameter slightly greater than snout length in juveniles. SVL 1.44–2.61 in SL in adults, 1.21–1.43 in juveniles. Vertebrae: 71–74 total, 18–20 precaudal. Scales present in juveniles and adults.

Remarks. Rosenblatt & Butler (1977) listed the lack of scales at all sizes as a diagnostic character for D. polystictum . Although present in both species of Desmodema , scales are not obvious in the genus, and are even less obvious in D. polystictum due to their fragility, simplicity, and what appears to be low frequency of occurrence, at least after preservation. However, scales were detected in nearly all juvenile and adult specimens of D. polystictum examined in this study.

Distribution. Desmodema polystictum is considered circumtropical but large gaps exist in its confirmed distribution. It is currently known as common throughout the western Pacific and the northeastern and tropical Pacific. Also known from the western North Atlantic (Bear Seamount to Guadeloupe), Eastern Atlantic (south of Mauritania-Senegal border) and Indian Ocean ( Oman, India, Pakistan, eastern South Africa, Indonesia). Desmodema polystictum has not been recorded from the northeast Atlantic (north of Senegal) or the Mediterranean ( Palmer 1961, Whitehead et al. 1986) and there are no confirmed collections in those regions known to the authors.

Geographic variation. Juveniles from the Atlantic Basin have five or six pelvic-fin rays and Pacific juveniles have nine or ten. Of the two juveniles reported from the southeastern Indian Ocean ( Heemstra & Kannemeyer 1984), one specimen has nine pelvic-fin rays, and the second has seven on the left and eight on the right.

Taxonomic notes. The synonyms provided in Rosenblatt & Butler (1977), Heemstra & Kannemeyer (1984) and Quéro et al. (1990) are all considered valid. Additionally, Trachypterus trachyurus Poey 1861 from Cuba, a 112 mm SL juvenile specimen that, based on the description, was transitioning from juvenile to adult, is considered a synonym of D. polystictum as outlined below. The Cuban specimen described by Poey has been referenced as a misspelling of Trachipterus trachyurus ( Gmelin 1789) and not an original description. However, after comparison of new material with Poey’s (1861) original description, T. trachyurus Poey 1861 is considered a senior synonym of D. polystictum ( Ogilby 1898) . Rosenblatt & Butler (1977) synonymized Trachipterus trachyurus , not of Poey, as described by Leapley (1953) with D. polystictum . Those authors stated, however, that T. trachyurus Poey 1861 is not D. polystictum for several reasons: 1) number of pelvic-fin rays (6 in T. trachyurus vs. 8 or 9 in D. polystictum ); 2) number of pectoral-fin rays (15 vs. 12–14); and 3) coloration (silvery with a midlateral yellow band vs. polka-dotted). Examination of Atlantic specimens not available to Rosenblatt & Butler reveal that the number of pelvic-fin rays in this region is 5–6 and several Pacific specimens have pectoral-fin ray counts of 15 (1 exceptionally short fin-ray followed by 14 rays). It also appears that Rosenblatt & Butler (1977) translated Poey’s “une band argentée” as “a yellow band” rather than “a silver band”. This midlateral silver band can accompany a ‘spotless’ Desmodema as some specimens do not show spots or lose spots early in development (see Fig. 26 ).

Poey (1861) described several other characters that actually align his specimen with D. polystictum . First, it had a triangular shape to the body, which is the case in juvenile D. polystictum . Second, it had a very large maxilla ( Desmodema has the largest maxilla of the three trachipterid genera). Third, in regards to the caudal fin, Poey stated that the fin was barely detectable but the rays were all dorsal and ran parallel to the body. He essentially described the caudal fin of Desmodema , as there is no ventral caudal lobe present and the caudal fin is easily overlooked, which is not the case in Trachipterus or Zu. Finally, Poey also stated that the post-anal region was rough because the lower processes of the vertebrae pierced through the ventral body margin. This condition has been observed in Desmodema (for example, NMNZ P.016409 240mm SL; see Remarks) and, to a lesser extent, in Trachipterus .

It is for these reasons that we provisionally recognize Trachypterus trachyurus Poey 1861 as a senior synonym of D. polystictum ( Ogilby 1898) . In accordance with Article 23.9 of the International Code of Zoological Nomenclature, the younger name, Desmodema polystictum ( Ogilby 1898) is here provisionally recognized as valid. The junior synonym has been used as the presumed valid name in more than 25 works by at least 10 authors in the immediately preceding 50 years, encompassing the minimum 10 year required span, and therefore satisfies the condition of Article 23.9.1.2 ( Pertseva-Ostroumova & Rass 1973, Rosenblatt & Butler 1977, Bauchot & Bianchi 1984, Heemstra & Kannemeyer 1984, Olney 1984, Whitehead et al. 1986, Quéro et al. 1990, Richards 1990, Amaoka et al. 1992, Charter & Moser 1996, Hutchins 2001, Shinohara et al. 2001, Hayashi 2002, Moore et al. 2003, Nelson et al. 2004, Mundy 2005, Olney & Richards 2006, Fahay 2007, Ji et al. 2009, Zacharia & Kannan 2012, Okiyama 2014, Shinohara et al. 2014, Martin 2015, Deshmukh et al. 2017, Rathnasuriya et al. 2019). However, Trachypterus trachyurus Poey 1861 was used as a valid species name by Leapley (1953). As outlined above, both the description of Poey (1861) and the specimen described by Leapley (1953) fit the concept of Desmodema polystictum . Therefore, because the name has been used after 1899, Article 23.9.1.1 for allowing reversal of precedence is not satisfied. Therefore, an application to the International Commission on Zoological Nomenclature to resolve this issue will be submitted.

Figures

FIGURE 2. Illustrations of representatives of the three genera of Trachipteridae. A, Trachipterus fukuzakii (large juvenile). B, Zu cristatus (large juvenile). C, Desmodema polystictum (juvenile). Illustrations © Val Kells, used with permission.

FIGURE 23. Desmodema polystictum (Ogilby 1898). VIMS 42794; 66.1 mm SL.

FIGURE 26. Desmodema polystictum (Ogilby 1898). Fresh specimen trawled at 1000 m depth, representing the first record from Oman. Photo © Laith Jawad, used with permission.

FIGURE 28. Desmodema polystictum (Ogilby 1898). MCZ 60557; 355 mm SL. A, scales at base of dorsal fin. B, Isolated scale.