Melanocetus johnsonii

Melanocetus johnsonii Günther, 1864

Common Names

Johnson's black anglerfish (English), Negro (Castilian)

Languages: English

Overview

Description

Escal bulb slightly compressed, with a low rounded or conical distal prolongation nearly always darkly pigmented on tip; a compressed posterior crest usually darkly pigmented, becoming larger and more conspicuous with growth; a considerably smaller compressed anterior crest present in some specimens; integument relatively thick (cross sections measuring 1.55 mm in thickness), not easily torn, usually retaining heavy pigmentation during fixation and preservation; vomerine teeth 2–12; dorsal-fin rays 13–15 (rarely 16); anal-fin rays 4 (very rarely 3 or 5); pectoral-fin rays 17–22 (rarely 23).

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

Type Information

Type specimen(s)

Holotype of Melanocetus johnsonii: BMNH 1864.7.18.6, female, 64 mm.

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

Type locality

Off Madeira, 24 December 1863.

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

Synonymy

Data on Catalog of Fishes

View data on Catalog of Fishes here.

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

Description

Diagnostic Description

Metamorphosed females of Melanocetus johnsonii are distinguished from those of all other described species of the genus in having the anterior margin of the vomer nearly straight; least outside width between frontals 13.5–28.6% SL; number of teeth in upper jaw 48–134, in lower jaw 32–78; length of longest tooth in lower jaw 8.4–25.0% SL; width of pectoral-fin lobe 10.7–17.8% SL; width of escal bulb 4.3–8.6% SL; length of illicium 32.4–60.8% SL; esca with posterior and usually anterior crests; skin with minute spinules over most of body; integument relatively thick (1.55 mm).

Metamorphosed males of Melanocetus johnsonii differ from those of all other described species of the genus in having upper denticular with 9–13 ventrally directed anterior teeth and a postero-medial series of 8–11 teeth; lower denticular with 12–24 teeth; posterior nostril contiguous with eye; as many as 24 olfactory lamellae; skin naked or spinulose.

Larvae of Melanocetus johnsonii are distinguished from those of all other described species of the genus in having anterior body musculature unpigmented; dorsal pigment extending posteriorly to beneath middle of base of dorsal fin; a separate lateral group of peduncular pigment in smaller specimens, connecting in larger specimens with dorsal pigmentation; branchial pigmentation strong; branchiostegal, cephalic, sphenotic, preopercular, and pectoral pigment usually present.

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

Morphology

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.

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

Size

Known from 852 metamorphosed females (10–154 mm), eight metamorphosed males (15.5–28 mm), and 329 larvae (2.5–17.5 mm TL).

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

Ecology and Distribution

Distribution

Melanocetus johnsonii has a wide horizontal distribution in tropical and subtropical waters of all three major oceans of the world between approximately 55°N and 45°S. Compared to its congener M. murrayi, it appears to occupy relatively shallow depths: about 62% of the material (for which data are available) was captured by open nets fished at maximum depths of 1000 m; 82% of the material can be accounted for by gear fished above 1500 m, and 98% by gear fished above 2100 m.

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

Habitat

Meso- to bathypelagic.

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

Reproduction

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.

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

References

Main Reference

Pietsch TW. 2009. Oceanic Anglerfishes: Extraordinary Diversity in the Deep Sea. Berkley: University of California Press. 638 p.

Author(s): Kenaley, Christopher
Rights holder(s): Kenaley, Christopher

Taxonomy

  • Melanocetus johnsoni Günther, 1864 (synonym)