Escal bulb rounded, not compressed, bearing a 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; integument as in M. johnsonii; vomerine teeth 0–10; dorsal-fin rays 14–17; anal-fin rays 4 (very rarely 5); pectoral-fin rays 17–21 (rarely 22 or 23). Additional description as given for the genus and family.
Metamorphosed females of Melanocetus polyactis differ from those of all other described species of the genus in having the following combination of characters states: anterior margin of vomer nearly straight; least outside width between frontals 18.0–26.0% SL; number of teeth in upper jaw 62–120, in lower jaw 58–90; length of longest tooth in lower jaw 9.3–13.1% SL; width of pectoral-fin lobe 10.9–16.0% SL; width of escal bulb 5.2–8.5% SL; length of illicium 34.6–56.0% SL; esca with a conical distal prolongation, crests absent; integument relatively thick.
Metamorphosed males of Melanocetus polyactis are distinguished from those of all other described species of the genus in having upper denticular with 19 ventrally directed anterior teeth and a postero-medial series of 6 teeth; lower denticular with 22 teeth; posterior nostril contiguous to eye; olfactory lamellae 16; skin with a few dermal spinules.
Larvae of Melanocetus polyactis differ from those of all other described species of the genus in having skin with scattered melanophores; caudal peduncle unpigmented in smaller specimens, dorsal pigment spreading to dorsal half of peduncle in larger specimens; branchiostegal pigment well developed; cephalic, sphenotic, and branchial pigmentation usually present.
Melanocetus polyactis appears to be restricted to the Eastern Tropical Pacific Ocean where 15 (plus another eight specimens tentatively identified specimens) have been collected between 10°N and 13°S and as far west as 88°W. Approximately 67% of the material was captured by open nets fished at maximum depths of 1000 m or below.
Meso- to bathypelagic
Pietsch TW. 2009. Oceanic Anglerfishes: Extraordinary Diversity in the Deep Sea. Berkley: University of California Press. 638 p.
The body of metamorphosed females is short and deep, globular, the depth 60–75% SL (but often appearing highly compressed due apparently to deformation following capture). The head is short, the mouth large, its opening oblique to nearly vertical and the cleft not extending past the eye. The jaws are equal anteriorly. The oral valves are only weakly developed. There are two nostrils on each side of the snout, situated on the distal surface of a rounded papilla. The eye is small and subcutaneous, appearing through a circular translucent area of the integument, within a shallow orbital pit formed between the sphenotic and frontal bones. The teeth are slender, recurved, and depressible, some slightly hooked distally, those in the lower jaw less numerous (except in some small specimens, less than approximately 20 mm) but slightly longer than those in the upper jaw. There are 29–178 teeth in upper jaw and 32–142 in lower jaw. The longest tooth in the lower jaw measures 6.9–25.0% SL. There are 0–12 vomerine teeth. The first epibranchial and the proximal one-half of the first ceratobranchial are bound to the wall of the pharynx by connective tissue. All four epibranchials are closely bound together. The fourth epibranchial and ceratobranchial are bound to the wall of the pharynx, leaving no opening behind the fourth arch. The proximal one-half of the first ceratobranchial is bound to the wall of the pharynx, while the distal half is free, not bound by connective tissue to the adjacent second ceratobranchial. The proximal one-quarter to one-half of ceratobranchials II–IV are not bound together by connective tissue. Gill filaments are absent on the epibranchials, but present on the proximal tip of ceratobranchial I and the full length of ceratobranchials II–IV. A pseudobranch is absent. The length of illicium is 23.1–60.8% SL. The anterior-most tip of the pterygiophore of the illicium is exposed, emerging on the snout between the eyes, the posterior end concealed under the skin. The escal bulb is simple, usually with a rounded or conical distal prolongation, and often with posterior and anterior crests. Elongate cylindrical escal appendages and filaments are absent. The neuromasts of the acoustico-lateralis system are located at the tips of low cutaneous papillae, the pattern of placement as described for other ceratioids.
Until very recently, the only evidence of sexual parasitism in this family was an anomalous case of a 20-mm male Melanocetus johnsonii attached to the upper lip of a 168-mm female Centrophryne spinulosa (LACM 30843-1). However, the attachment did not involve fusion of male-female tissue and is therefore not considered to be a parasitic association. Two similar couplings in Melanocetus, but between sexes of the same taxon, have recently been discovered. One of these, a 23.5-mm male attached to a 75-mm female Melanocetus johnsonii (BMNH 2004.6.3.2-3), was collected in the eastern North Atlantic off Ireland in 1999 by the RRS Discovery in a cruise partially funded by the British Broadcasting Corporation for the celebrated “Blue Planet” video series. The second example is part of collections made by Hiromitsu Endo, aboard the R/V Tansei-Maru, west of Okinawa, in April 2002: a 15-mm male attached to a 73-mm female Melanocetus murrayi (BSKU 57842). Both males are only loosely attached, with tissue of the female pinched by the tightly closed denticular jaws of the male, the BMNH example hanging from the middle of the belly of the female, the BSKU specimen attached to the right side of the head of the female, just beneath the sphenotic bone. In both cases, it does not appear that any fusion of male and female tissue has taken place. Either the connections of the two were so recent that the tissues did not have time to fuse, or, more likely, these are the first and only known examples of a non-parasitic coupling—male ceratioids caught in the act of temporary attachment.
Known from 32 females (10–82 mm; including nine tentatively referred to this species), three metamorphosed males (9.0–19.5 mm), and seven larvae (3–9 mm TL).
DANA station 1206(3), Gulf of Panama, 6°40'N, 80°47'W, 3500 m wire, 1845 hr, 14 January 1922.
Lectotype of Melanocetus polyactis: ZMUC P9260, 61 mm.
Melanocetus polyactis is a species of black seadevil, a type of anglerfish. The fish is bathypelagic and has been found at depths ranging from 1,000 to 2,200 metres (3,300 to 7,200 ft). It is endemic to the Gulf of Panama.[1]
Melanocetus polyactis is a species of black seadevil, a type of anglerfish. The fish is bathypelagic and has been found at depths ranging from 1,000 to 2,200 metres (3,300 to 7,200 ft). It is endemic to the Gulf of Panama.
