Sciadonus cryptophthalmus (Zugmayer, 1911)

Nielsen, Jørgen G., 2018, Revision of the cosmopolitan deep-sea genus Sciadonus (Teleostei, Bythitidae) with two new species, Cybium 42 (2), pp. 177-187 : 178

Sciadonus cryptophthalmus (Zugmayer, 1911)

( Tab. I, Figs 1-3 )

Leucochlamys cryptophthalmus Zugmayer, 1911a: 11

(type locality off NW Spain).

Leucochlamys cryptophthalmus : Zugmayer, 1911b: 131;

Roule, 1934: 193; Belloc, 1949: 15; Grey, 1956: 222; Nybelin, 1957: 312; Norman, 1966: 497; Nielsen et al., 1968: 247; Nielsen, 1969: 70.

Sciadonus cryptophthalmus : Cohen and Nielsen, 1978:

62; Nielsen, 1986: 1171; Nielsen et al., 1999: 142.

Material examined (2 specimens, SL 82-100 mm)

Holotype. MOM (no cat. no.), SL 82 mm, male, off northwestern Spain, 44°08’N, 10°44’W, R / V Princesse-Alice , st. 2994, bottom trawl, 5000 m, 19 Aug. 1910.

Non-type. ZMH 120293 , SL 100 mm, female, off Portugal, 41°49’N, 13°55’W , R / V Walther Herwig, st. 16, Agassiz trawl, 5320 m, 6 Jun. 1981 .

Diagnosis

Sciadonus cryptophthalmus is long, rather slender and compressed. Many 1-2 mm black pigment spots seen through transparent skin near dorsal edge of body from above gill cover to caudal fin. Dorsal fin with 80-83 rays, anal fin with 40-46 rays, pectoral fin with 13-16 rays and pelvic fins absent. Precaudal vertebrae 41-42 and total vertebrae 76-78. Origin of anal fin below dorsal fin rays no. 37-39. Anterior gill arch with 14-15 minute rakers on lower branch. No tissue flaps anteriorly on lower jaw.

Description

The principal meristic and morphometric characters are shown in table I. For a thorough description of the holotype see Nielsen (1969: 70). The figure showing the holotype ( Fig. 2 ) is here included to show the coloration, but old photos of the holotype demonstrate that the body proportions are incorrect. Actually it is slender and compressed like the non-type ( Fig. 3 ). Skin loose, transparent and scaleless. Mouth almost horizontal with protruding lower jaw. Tiny, black eyes deep-set. Origin of dorsal fin slightly behind tip of pectoral fins and origin of anal fin well behind midpoint of fish. Pectoral peduncle about three times as long as high. Anterior gill arch with minute rakers each provided with 1-2 small denticles, upper branch with two and lower branch with 14-15 rakers. Gill filaments on anterior arch equal in length to rakers. Holotype with a well-developed urogenital hood partly covering a 1 mm long penis placed close to the tip of the hood. A pair of vestigial claspers placed near base of hood on each side rather similar to those in S. pedicellaris ( Fig. 13 ). Histological examination of the testes showed the presence of spermatophores ( Nielsen et al., 1968: 247). The non-type specimen with ovaries 24 mm long and numerous apparently ripe eggs about 1 mm in diameter. Urogenital hood ends in a pair of 1-2 mm long, fleshy claspers like those in S. pedicellaris ( Fig. 12 )

Figures

Figure 1. – Records of Sciadonus species.

Figure 2. – Sciadonus cryptophthalmus: MOM, holotype, male, SL 82 mm (from Zugmayer, 1911b).

Figure 3. – Sciadonus cryptophthalmus: ZMH 120293, female, SL 100 mm.

Figure 12. – Sciadonus pedicellaris: Female claspers of ZMUC P77456. a: anus (from Nielsen, 1969).

Figure 13. – Sciadonus pedicellaris: Urogenital hood and penis of ZMUC P77457. a: anus, b: vestigial clasper, c: wing-like prolongations (from Nielsen, 1969).