Siphamia cephalotes (Castelnau)

Gon, Ofer & Allen, Gerald R., 2012, 3294, Zootaxa 3294, pp. 1-84 : 26-28

Siphamia cephalotes (Castelnau)

Figure 12

Scopelus cephalotes Castelnau, 1875: 46 (type locality, Adelaide , South Australia; lectotype, MNHN 1877-0569 ).

Apogon roseigaster Ramsay and Ogilby, 1887: 1101 , in part (type locality, Parramatta River , NSW, Australia; 5 paratypes of MCZ 27552).

Adenapogon woodi McCulloch, 1921: 134 , pl. 21, fig. 3 (type locality, Rose Bay , Sydney Harbour, NSW, Australia; holotype, AMS I.15251).

Diagnosis: Dorsal rays VI+I,8 (rarely 7 or 9 soft rays); anal rays II,8–9; pectoral rays 12–14, unbranched and compressed distally; tubed lateral-line scales 22–23; median predorsal scales 4–5; total gill rakers 4–6 + 14–16; developed gill rakers 1–3 + 13–16 = 15–18; gill rakers on ceratobranchial 9–10. Body relatively slender, its depth 3.2–4.8 in SL, and body width 1.6–1.8 in the depth; eye diameter 3.2–3.7 in head length; first dorsal spine 1.1–1.3 in second spine; second dorsal spine 2.6–3.6, spine of second dorsal fin 5.1–6.7, and second anal spine 6.0–7.4, all in head length; pectoral-fin length 5.8–6.7 and pelvic-fin length 5.7–6.1 in SL; caudal-peduncle length 1.05–1.4 in distance between pelvic spine insertion and anal-fin origin. Preopercular edge and ridge smooth, the ventral edge weakly ossified and usually slightly crenulate. Palatines with 1–3 series of small teeth. First infraorbital pore a complex of about 7 small pores. Scales large, mostly ctenoid (see Remarks below); tubed lateral-line scales with vertical series of papillae ( Fig. 4c). Tip of light organ on each side of tongue bound by membrane.

Colour in life (from underwater photo in Kuiter 1993:153): body pale, silvery with greenish or yellowish hue on head and abdomen, peppered with small dark brown dots; dark dots dense on upper part of body from above eye, along dorsal fin bases and on dorsal surfaces of caudal peduncle; fins pale, but faint small dark spots present along anterior spines of first dorsal fin and pelvic spine, and along proximal part of anterior second dorsal- and anal-fin rays; a line of dark brown dots or short dashes along anal-fin base; a round cluster of dark brown dots at base of inner rays of each caudal fin lobe; when joined these clusters form a fairly distinct dark caudal spot; light diffusing organ a silvery stripe along ventral edge of body from pelvic fin base tapering posteriorly and ending at about three quarters of caudal peduncle length; several melanophores of various sizes scattered along its length.

Colour in alcohol: variable, depending on the proportion of expanded melanophores; body brown to dark brown, peppered with darker dots of various sizes, frequently with silvery reflecting areas ventrally and on opercle; dark dots less dense ventrally making that part of body somewhat paler; indistinct, broad stripe along midline of body sometimes present; a line of dark dots along ventral margin of infraorbital bones below eye, and 2–3 series of dark dots from above posterior end of upper jaw to angle of preopercular ridge; fins usually pale; palate sometimes with several dark dots; peritoneum with dense dark dots of various sizes; intestine and stomach with smaller dots, denser near anus.

Smallest specimen examined, CSIRO B2, 12.9 mm, from Flinders Island, Tasmania and largest specimen, AMS I.27063-008, 42.5 mm, from Jervis Bay, New South Wales.

Remarks: See Tables 1–3 for frequency distributions of pectoral rays, lateral-line scales and gill rakers. Variation in the number of second dorsal rays included one specimen (of 36) with 9 rays and one with 7 rays. Three specimens had 9 anal rays. Only one specimen in the material we examined had nearly all its scales. In this individual the last 2 tubed lateral-line scales had rudimentary tubes (included in the count) followed by 3 pitted or perforated scales (excluded from the count). This fish had cycloid scales on the front of the body, becoming increasingly ctenoid posteriorly to middle of caudal peduncle, then cycloid again. In some preserved specimens the anterior 1–3 dorsal spines had dark dots. Scattered dark dots were also present on the second dorsal and anal rays, and on the proximal part of the middle caudal rays. Kuiter (1993) pointed out that the colour of this species depends on the habitat, and noted that in seagrass individuals were greenish, whereas in kelp they were brown.

Siphamia cephalotes is a member of the S. tubulata species group. It is distinguished from all congeners in having the highest number of developed gill rakers (15–18 developed rakers). The closest species is S. roseigaster with 13–15 developed rakers ( Table 3), but the latter is easily separated from S. cephalotes by its higher number of second dorsal- and anal-fin rays (9–11), its higher number of pectoral-fin rays (14) that are mostly branched, its toothless palatines and the free ending of the light organ in its mouth. Siphamia cephalotes also differs from all congeners, except cuneiceps , in having a relatively elongate body (body depth 2.25–3.3 in SL in the others), ctenoid scales (weakly spinoid to cycloid in the others) and a poorly ossified ventral preopercular edge (well ossified in the others). Siphamia cephalotes and S. cuneiceps are modally different in the number of pectoral-fin rays. Moreover, S. cuneiceps has no developed gill rakers on the upper limb of the first gill arch, fewer gill rakers on the ceratobranchial and a smaller total number of developed gill rakers ( Tables 1, 3).

The original description of Scopelus cephalotes ( Castelnau 1875) , though relatively detailed, is problematical, and casts doubt on its placement in Siphamia . We examined the only known type specimen, a syntype (MNHN 1877- 0569), 33.1 mm SL. Bauchot and Desoutter (1986), and Eschmeyer (2009) refer to the same specimen, but provided no information about the fate or whereabouts of the other specimens in the putative type series. However, based on its dorsal and anal fins the MNHN specimen is certainly not the same as the fish that Castelnau described. His description mentions a single dorsal fin on the posterior two thirds of the body and it was specifically stated that he could not “find any vestige of a second dorsal fin.” Although the MNHN syntype is damaged, it clearly has two dorsal fins, a condition also described and shown by Whitley (1933: fig. 3). Castelnau also described the anal fin as having three spines and seven rays in which the first spine was short, “the second longer, and the third much longer still, and almost equal to the rays.” In contrast, the MNHN syntype has two spines and eight rays, although the fin is damaged to the extent that it is impossible to compare lengths of the second spine and first ray. However, in other specimens we examined the first anal ray is about 2.5 times longer than the second anal spine as is also evident from the illustrations of S. cephalotes in McCulloch (1921: plate 21, fig. 3) and Gomon et al. (1994: fig. 502). Lastly, Castelnau made no mention of the silvery light organ (very distinct on the extant syntype) in the colour description of his fish. Clearly the fish that Castelnau described as Scopelus cephalotes is not an apogonid, and its status remains questionable. Although the original description appears to be based on a single specimen he mentions “the specimens are about one inch and a-half long,” clearly indicating that he had more than one fish. Based on the anal-fin count and several other pieces of evidence, we believe that the acropomatid Apogonops anomalus is a distinct possibility.

It occurs in the same area from which Castelnau’s fish came ( Scott et al. 1974); significantly, it has an anal fin with three spines and seven rays, and in which the third spine is exactly as Castelnau described it. He also described scales that are “finely striated.” Apogonops anomalus has several series of slender ctenii that are almost perfectly aligned behind each other ( Fig. 4f) and creating a striated appearance. In contrast the scales of S. cephalotes have only 2–3 series of ctenii ( Fig. 4c) and do not create this impression. Although both species have minute dark dots on the body, young A. anomalus have spots, similar to those described by Castelnau, but these disappear with age ( Scott et al. 1974); S. cephalotes sometimes has a brown stripe along the middle of the body. Specimens of A. anomalus of the size described by Castelnau could be easily confused with S. cephalotes , especially when the dorsal fins are damaged. In both species the head is particularly prominent as implied by the name ‘ cephalotes ,’ and both could be mistaken for a myctophid ( Scopelus is a junior synonym of Myctophum ) if only one dorsal fin was evident. It therefore seems likely that Castelnau’s type series included more than one species. Past authors apparently overlooked the discrepancy between Castelnau’s description and the extant syntype. Whitley’s (1933) comments on the original description were limited to discussing Neoscopelus in the context of myctophids, pointing out the lack of photophores in the description and concluding it could not be a myctophid. He received a drawing and fin counts of the syntype from MNHN but, strangely, did not notice the differences between the fish in the drawing and Castelnau’s description.

In order to resolve the taxonomic problem discussed above and to conclusively fix the name Siphamia cephalotes to the MNHN specimen we designate it as a lectotype for this species. The lectotype (MNHN 1877-0569) is a 33.1 mm SL male with the following counts: D VI + I,8; A II,8; P 13; developed gill rakers 2+14; and 10 gill rakers on the ceratobranchial .

We examined five syntypes of S. roseigaster in the collection of the Museum of Comparative Zoology, Harvard University (MCZ 27522). The counts of dorsal, anal and pectoral fin rays, as well as the number of developed gill rakers of these specimens, all fall within the range given above for S. cephalotes and have therefore re-identified this material. In addition, their palatines clearly bear teeth. McCulloch (1921) described and illustrated Adenapogon woodi from a single specimen. At the end of the description, in a paragraph under the subheading “Localities,” he referred to over fifty specimens collected by D.G. Stead in Rose Bay, Port Jackson and Port Hacking, New South Wales. The AMS fish collection has Stead’s specimens from Rose Bay (AMS I.15251 and I.15252, paratypes) and Port Hacking (I.15253, paratypes). The specimens from Port Jackson (ex-AMS I.15256) were donated to the American Museum of Natural History, New York (AMNH 1738, 2: 42.4–43.2 mm), but they are S. roseigaster .

Siphamia cephalotes occurs in coastal marine and estuarine environments along the southern part of Australia (Munro 1956; Last et al 1983; Hutchins and Swainston 1986), from Exmouth Gulf, Western Australia, through South Australia, Victoria and northern Tasmania to Port Stephens, NSW ( Fig. 7). It was also reported from southern Queensland ( Gomon et al. 1994), but we have not seen material from this area. Scott et al. (1974) stated that S. cephalotes is distributed in all Australian states except Queensland. This species is found usually in schools near kelp or seagrass beds of Zostera or Posidonia , at depths of 1– 10 m. Kuiter (1993) reported it from 30 m. Munro (1956) and Scott et al. (1974) reported males with an egg mass in their mouth.

Material examined: WESTERN AUSTRALIA: Exmouth Gulf , CSIRO A3411 , 34.0 mm. Israelite Bay , CSIRO A782 , 26.0 mm ; CSIRO, B3505 , 35.5 mm . SOUTH AUSTRALIA: Spencer Gulf , NMV A19800 , 26.3 mm. Adelaide , MNHN 1877-0569 , 33.1 mm (syntype of Scopelus cephalotes ) . VICTORIA: Lorne , NMV 14312, 41.4 mm. Port Phillip Bay , NMV 25942-002 , 5 : 30.5–38.9 mm. Phillip Island , NMV A25273-001 , 33.4mm . NEW SOUTH WALES: Port Stephens , AMS I.24168-001, 36.5 mm; Lake Macquarie , CSIRO A1858 , 32.6 mm ; CSIRO A1859 , 27.0 mm ; CSIRO A2072 , 28.0 mm ; CSIRO B1 , 27.8 mm ; CSIRO B3 , 2 : 29.0–30.0 mm ; CSIRO B4 , 24.4 mm. Sydney Harbour , AMS I.15251, 36.7 mm (holotype of Adenapogon woodi ) ; AMS I.15252, 2: 31.4–35.4 mm (paratypes of Adenapogon woodi ) ; MCZ 27522, 5 : 37.0– 41.3 mm (syntypes of Apogon roseigaster ) ; USNM 48831 , 36.1 mm. Botany Bay , AMS IA.6255, 33.5 mm. Port Hacking , AMS I.37939-012, 3: 28.0– 29.2 mm; AMS I.37942-005, 4: 32.9–33.5 mm; AMS I.37943-004, 7: 29.9–36.9 mm; AMS I.37945-006, 6: 30.9 33.8 mm; AMS I.37948-004, 3: 28.8–31.1 mm; AMS I.37959-002, 29.5 mm; CSIRO B5 , 3 : 26.0–27.0 mm ; WAM P.28836-013, 2: 31.9–32.0 mm. Jervis Bay , AMS I.27063-008, 10: 37.5–42.5 mm. TASMANIA: Flinders Island, Lady Barron , CSIRO A785 , 35.8 mm ; CSIRO A786 , 34.7 mm ; CSIRO A787 , 34.5 mm ; CSIRO B2 , 7 : 12.9–14.4 mm. Cape Barren Island , CSIRO H4212-02 , 5 : 35.0–40.0 mm .