Owstonia Tanaka 1908

Smith-Vaniz, William F. & Johnson, David, 2016, Hidden diversity in deep-water bandfishes: review of Owstonia with descriptions of twenty-one new species (Teleostei: Cepolidae: Owstoniinae), Zootaxa 4187 (1), pp. 1-103 : 27-32

Genus Owstonia Tanaka 1908

Owstonia Tanaka, 1908:46 (type species Owstonia totomiensis Tanaka 1908 by monotypy).

Sphenanthias Weber, 1913:210 (type species Sphenanthias sibogae Weber 1913 by monotypy). Parasphenanthias Gilchrist, 1922:69 (type species Parasphenianthias weberi Gilchrist 1922 by monotypy). Loxopseudochromis Fowler, 1934a:354 (type species Loxopseudochromis dorypterus Fowler 1934 by monotypy). Opsipseudochromis Fowler, 1934a:355 (type species Opsipseudochromis grammodon Fowler 1934 by monotypy). Pseudocepola Kamohara, 1935:135 (type species Pseudocepola taeniosoma Kamohara 1935 by original designation and

monotypy.

Diagnosis. Owstonia differs from all other cepolids in having the dorsal and anal fins not connected to the caudal peduncle by a membrane. It also has fewer dorsal- and anal-fin ray counts, dorsal fin III-IV, 1 9‒26 (vs. 0-III; 54‒89), anal fin I-II, 11‒19 (vs. 0‒I, 50‒101); and fewer caudal and total vertebrae 16‒18 and 27‒33 (vs. 40‒67 and 48‒79).

Description. Cepolids ranging in size as adults from about 70 ( O. sarmiento ) to 408 mm SL ( O. kamoharai ) with dorsal and anal fins not connected to caudal peduncle by a membrane; dorsal fin III-IV (2 supernumerary), 19‒26; anal fin I-II (typically 1 supernumerary ( Fig. 16 A), except 2 in O. sarmiento ( Fig. 16 B); dorsal- and anal-fin spines and soft rays relatively thin and flexible and in some species difficult to distinguish; pectoral-fin rays 17‒23; caudal fin unforked with middle rays longest and notably elongate in most species, 1.3‒3.6 times in SL; principal caudal-fin rays 17 (9+8 = branched rays plus one dorsal and ventral unbranched ray); procurrent caudal-fin rays ( Johnson, 1980) 2–4+2–3; procurrent spur absent ( Johnson, 1975); vertebrae 11‒15 precaudal, 16‒18 caudal, total 27‒33; supraneurals absent; first dorsal-fin pterygiophore inserted between first and second neural spines; a single postcleithrum on each side; pelvic fin I,5 without an axillary scale and the first (outermost) soft ray unbranched or only weakly branched distally; scales cycloid, variously crenulate or scalloped ( Fig. 11 ); dorsal and anal fins without scales; cheeks naked or scaly (most species); oblique body scale rows in mid-lateral series 27‒108; mouth large, oblique and terminal; maxilla exposed, without a supramaxilla, and usually with a darkly pigmented premaxillary stripe or “moustache” (absent in O. hawaiiensis and O. ignota and in most specimens of O. psilos ); adults with 30‒60 total gill rakers; branchiostegals six, branchiostegal membranes separated from each other, free from isthmus; lower limb of preopercle smooth or with weak to strong spines ( Fig. 8 ); palatine and vomer without teeth; infraorbitals 5, including dermosphenotic, with moderate to well-developed suborbital shelf; swim bladder well developed.

Larvae. ( Figs. 17–20 ) The eggs of the cepolid subfamily Cepolinae were first described and illustrated by Holt (1891, pl. XLVIII, fig. 2) based on a female Cepola macrophthalma (= C. rubescens ) found in the stomach of a skate. Fage (1918, fig. 26), described and illustrated a 6 mm preflexion larva of this species from specimens collected from the Western Mediterranean and the Sea of Marmara. Clark (1920, fig. 8) described and illustrated a 7 mm preflexion specimen from off Plymouth, England, and Russell (1976, fig. 48) illustrated three early preflexion specimens, also from off Plymouth, and noted the gradual diminution of head spination in larger specimens. The most complete developmental series of cepolines, again based on C. macrophthalma , is the classic Italian monograph of Montalenti (1956),which was published in four parts between 1931 and 1956 (see Ahlstrom 1962). Montalenti on plate XXXIII included 14 figures, most of which were hand-colored. Cepoline larvae are characterized by distinctive features that appear early in postflexion and persist, though gradually diminishing, through transformation ( Leis & Carson-Ewart 2000, fig. 67). All cepoline larvae have a prominent, median, serrate supraoccipital ridge that extends posteriorly as an elongate spine and bears a smaller spine anterior to the divergence of the former, an elongate, median, serrate spine at the angle of the preopercle with several smaller serrate spines on either side, a variously developed supracleithral spine, serrate supraocular and dentary ridges, and rugose frontals and opercles ( Figs. 17‒20 ). These features are reminiscent, to varying extents, of those seen in priacanthid and holocentrid larvae, among others (see Leis & Carson-Ewart 2000:191).

Larvae of the Owstoniinae (= Owstonia ) are much less common in collections and were not recognized until Fourmanoir (1976) described and illustrated ( Fig. 90 ) a 13.2 mm transforming postflexion specimen. Postflexion Owstonia bear no resemblance to pre- or postflexion cepolines and actually more closely resemble the larvae of uranoscopids (see Leis & Carson-Ewart 2000, fig. 156), as first noted by Mundy (1990) or chaetodontids (see Micklich et al. 2009, fig. 7), because of the plate-like expansion of several of the head bones. On the other hand preflexion/flexion Owstonia are strikingly similar to larval cepolines, and exhibit all the features described above for the latter ( Figs. 17 , 18 ). The serrate spine at the angle of the preopercle is longer than the other peopercular spines, but not as distinctly elongate as it is in cepolines. The similarity to cepoline larvae begins to diminish at flexion, as the supraoccipital, preopercular and supracleithral spines recede and several head bones begin to expand to form plate-like structures. This distinctive transformation appears to occur over a very short size range ( Fig. 19 ). We have seen very few preflexion Owstonia larvae, but all of those, illustrated here for the first time ( Fig. 17 ), have the well developed, pungent supraoccipital and preopercular spines that characterize cepoline larvae at all stages. On the other hand all postflexion Owstonia larvae ( Fig. 20 ) lack the pungent spines of preflexion cepoline larvae and exhibit instead the extensive plate-like expansions of the posttemporal and preopercle that characterize these larvae until transformation. Thus, larval cepolids are very similar in early ontogeny, but the morphological trajectory of owstoniines changes drastically postflexion. The largest untransformed Owstonia specimen we have seen is 57.6 mm ( O. lepiota ), the next largest, only 17 mm. The smallest fully transformed specimen we have seen is 26 mm ( O. taeniosoma ), so we presume that transformation typically occurs between 17‒26 mm.

Etymology. The genus Owstonia was named for Alan Owston (1853‒1915), amateur naturalist, yachtsman ( Fig. 21), and collector of Asian wildlife, notably fishes from Japan and China; see Wikipedia for more details of Owston's extraordinary life. A collection of 1364 of Owston’s Asian fishes was donated to the Carnegie Museum of Natural History, Pittsburgh (transferred to the FMNH in 1952).

Distribution. Most species of Owstonia have been collected only from relatively deep water (155–550 m) on hard bottom substrata, where many localities have not been sampled with appropriate trawl gear, and are therefore poorly represented in natural history collections. Accordingly, our knowledge of the distributions of the 36 species we recognize is partly a reflection of collection effort, and we are certain that more undescribed species remain to be discovered. However, a few generalizations about Owstonia distributions can be made from examination of the maps ( Figs. 22‒27 ). Five species, O. lepiota , O. raredonae , O. similis , O. simotera and O. weberi , appear to be restricted to the western Indian Ocean from South Africa to Kenya and Madagascar ( Fig. 27 ) (not counting one apparently undescribed species based on a small individual from Madagascar), and O. whiteheadi known only from near the southern tip of India. No species occurs on both sides of the Indian Ocean, and no species has been collected from both the western and eastern sides of Australia. Two species, O. psilos and O. scottensis , are restricted to Western Australia ( Owstonia sp 1, based on two small individuals, probably is a third such species); two others, O. kamoharai and O. tosaensis , have ranges that extend from Japan to Western Australia, but there are no collections of them from between these two localities, and they are also absent from eastern Australia. Four species are known only from eastern Australia, O. ainonaka , O. hastata , O. maccullochii , and O. merensis from Torres Strait; two others, O. fallax and O. taeniosoma , also occur in eastern Australia but are more widely distributed. Ten species occur in the Philippine Archipelago, including Owstonia sp. (based on two specimens, not treated by us, that are being described elsewhere by Y.-C. Liao), with four of these species, O. doryptera , O. macrophthalma , O. melanoptera , O. nigromarginata , known only from their original type localities. As the result of collecting effort during multiple French expeditions, six species have been collected off New Caledonia, although none of them is restricted to the immediate vicinity of that island. The absence of any Owstonia species from off New Guinea is most likely a collecting artifact.

Figures

FIGURE 8. Margins of preopercle lower limb (not drawn to scale), showing relative spine development in selected species of Owstonia: A, O. contodon, USNM 438013, 162 mm SL; B, O. elongata, USNM 432454, 110 mm SL; C, O. geminata, ASIZP 68128, 79 mm SL; D, O. maccullochi, holotype (right side reversed), AMS IA. 5815, 156 mm SL; E, O. maccullochi, NTM S. 11765 − 001, 146 mm SL; F, O. rhamma, holotype, MNHN 1995 – 0005, 102 mm SL; G, O. sarmiento, ANSP 165126, 82 mm SL; H., O. scottensis, CSIRO H. 7136 − 04, 103 mm SL; I, O. sibogae, ANSP 152035, 113 mm SL; J, O. taeniosoma, CAS 133928, 126 mm SL; K, O. tosaensis, ANSP 153169, 100 mm SL; L, O. weberi, ZMUC P. 531552, 127 mm SL.

FIGURE 11. Body scale removed from left side just posterior to pectoral fin in selected species of Owstonia: A, O. maccullochi, AMS I. 37598 – 007; B, O. melanoptera, AMS I. 36454; C, O. taeniosoma, CAS 133928; D, O. weberi, AMS I. 28137 – 003.

FIGURE 16. Anal-fin spines on first pterygiophore: A, Owstonia sibogae, ANSP 152035 (1 supernumerary spine); B, O. sarmiento, ANSP 165126 (2 supernumerary spines).

FIGURE 17. Preflexion larval cepolids: A, Cepolinae, LACM 36040 ‒ 13, 4.7 mm NL; B, Acanthocepola, 4.7 mm NL, from Leis and Carson-Ewart (2000, fig. 67); C, Owstonia, LACM 45149 ‒ 20, 2.8 mm NL; D, drawing of C by Rick Feeney, LACM.

FIGURE 18. Flexion larval cepolids: A, Acanthocepola, 5.9 mm SL; B, Owstonia, 6.9 mm SL. From Leis and Carson-Ewart (2000), figs. 66, 67.

FIGURE 19. Postflexion larval Owstonia, lateral view left, dorsal view right: A, AMS I. 36418 ‒ 0025, 4.9 mm SL; B, AMS I. 19742 ‒ 032, 6.9 mm SL.

FIGURE 20. Heads of postflexion larval cepolids, A – B Acanthocepola Dana Sta. 3881, 9 mm SL (B cleared and stained); C, Owstonia, LACM 45967, 13.3 mm SL; D, Owstonia, USNM 307399, 13.2 mm SL, cleared and stained. Abbreviations: Pop = preopercle; Pt = posttemporal; Scl = supracleithrum; Soc = supraoccipital.

FIGURE 22. Distributions of selected species of Owstonia based on specimens examined.

FIGURE 23. Distributions of selected species of Owstonia based on specimens examined.

FIGURE 24. Distributions of selected species of Owstonia based on specimens examined, except records of O. mundyi from Kingman Reef based solely on submersible videos, and possibly could have been misidentifications of O. hawaiiensis.

FIGURE 25. Distributions of selected species of Owstonia based on specimens examined.

FIGURE 26. Distributions of selected species of Owstonia based on specimens examined.

FIGURE 27. Distributions of selected species of Owstonia based on specimens examined.

FIGURE 90. Owstonia sp. 3, USNM 307399, 13.2 mm SL, Lifou Island. After Fourmanoir 1976, fig. 8. See also Fig. 20 D.