PIETSCH and VAN DUZER: SYSTEMATICS AND DISTRIBUTION OF ANGLERFISHES 



Melanocetus polyactis Regan 1925 

 Figures 21-24, 26, 30 



Females 



Melanocetus polyactis Regan 1925:565 (original 

 description, 3 specimens, lectotype designated 

 by Bertelsen 1951, ZMUC P9260, 61 mm, Dana 

 stn. 1206(3), Gulf of Panama, 6°40' N, 80°47' W, 

 3,500 m wire, 1845 h, 14 January 1922); Regan 

 1926:34, pi. 8, fig. 2 (description after Regan 

 1925); Regan and Trewavas 1932:53, fig. 78 

 (listed, after Regan 1925, 1926); Bertelsen 

 1951:44, 54-55, tables 4, 7, 8 (description, addi- 

 tional material, 2 males, 6 larvae, comparison 

 with all known material, in key); Grey 1956:238 

 (synonymy, distribution). 



Melanocetus niger Regan 1925:565 (in part, 3 of 11 

 cotypes [see Comments, p. 79], all Gulf of 

 Panama); Regan 1926:33, pi. 8, fig. 1 (in part, 

 description, 4 additional specimens); Regan and 

 Trewavas 1932:53, fig. 76B (in part, listed, after 

 Regan 1925, 1926); Bertelsen 1951:44, 53, table 

 4 (in part, description, comparison with all 

 known material, in key); Grey 1956:237 (in 

 part, synonymy, distribution). 



Melanocetus ferox, Regan and Trewavas 1932:49, 

 52, fig. 75 (in part, nontype material only, in 

 key); Bertelsen 1951:44, 53, table 4 (in part, 

 nontype material only, comparison with all 

 known material, in key); Grey 1956:237 (in part, 

 after Bertelsen 1951, synonymy, distribution). 



Males 



Rhynchoceratias rostratus, Regan 1926:44 (in part, 

 misidentification). 



Rhynchoceratias leucorhinus, Regan 1926:44 (in 

 part, misidentification). 



Material. — Metamorphosed females, 15 (16.5-61 

 mm): BMNH 1925.8.11.30, 26 mm; BMNH 

 1925.8.11.32, 42 mm (paralectotype); BMNH 

 1932.5.3.6, 42 mm; lOAN uncatalogued, 33 mm; 

 LACM 33603-4, 2 (16.5 and 30 mm); LACM 

 33574-5, 17 mm; LACM 33624-1, 33 mm; LACM 

 33629-3, 35 mm; ZMUC P92155, 25 mm (paralec- 

 totype); ZMUC P921974, 26 mm; ZMUC P9251, 29 

 mm; ZMUC P92210, 30.5 mm; ZMUC P9253, 47 

 mm; ZMUC P9260, 61 mm (lectotype). 



The following adolescent females, all collected 

 from the eastern tropical Pacific, are only tenta- 



tively referred to M. polyactis: LACM 33618-2, 16 

 mm; LACM 31119-2, 2 (17 and 18 mm); LACM 

 31109-2, 18 mm; LACM 31120-20, 2 (18 and 19 

 mm); LACM 31126-29, 2 (19.5 and 20 mm). 



Metamorphosed males, 2: ZMUC P92460, 16 

 mm (22 mm total length (TL)); ZMUC P92459, 

 19.5 mm (30 mm TL). 



Larvae, 6 (2 males, 4 females, 3-9 mm TL): 

 ZMUC P92461; ZMUC P92462. 



Diagnosis. — A species of Melanocetus unique in 

 having the following combination of characters: 

 anterior margin of vomer nearly straight; least 

 outside width between frontals 18.0-26.0% SL; 

 number of lower jaw teeth 58-90 (Figure 22); 

 length of longest lower jaw tooth 9.3-13.1% SL 

 (Figure 21); width of pectoral fin lobe 10.9-16.0% 

 SL; escal bulb width 5.2-8.5% SL (Figure 23); 

 illicium length 34.6-56.0% SL (Figure 24); esca 

 with a conical, distal prolongation, crests absent 

 (Figure 26); integument relatively thick. 



Description. — Escal bulb not compressed, with 

 conical distal prolongation nearly always slightly 

 constricted at base, and usually as long as or 

 longer than length of escal bulb, pigmented on tip 

 in some specimens, posterior and anterior crests 

 absent (Figure 26); integument as in M.johnsoni. 

 Number of upper jaw teeth 42-120; dorsal fin 

 rays 14-17; pectoral fin rays 17-21 (rarely 22 and 

 23) (Table 2). 



Distribution. — Melanocetus polyactis appears to 

 be restricted to the eastern tropical Pacific Ocean 

 where 15 specimens have been collected between 

 lat. 10° N and 13° S as far west as long. 88° W (see 

 Distribution, p. 83). Approximately 67% of the 

 material was captured by open nets fished at max- 

 imum depths of 1,000 m or below. 



Comments. — Melanocetus polyactis is most easily 

 confused with M. niger. Both forms are similar in 

 having exceptionally short lower jaw teeth (Fig- 

 ure 21). They differ significantly, however, in the 

 number of lower jaw teeth, escal bulb width, and 

 illicial length (see Key, Figures 22-24). 



Part of the material originally listed as M. niger 

 has been reallocated to M. polyactis (see Com- 

 ments, p. 79). Also included with the material of M. 

 polyactis are two specimens (ZMUC P92210, 30.5 

 mm; BMNH 1932.5.3.6, 42 mm) previously iden- 

 tified as M. ferox by Regan and Trewavas (1932). 



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