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Esca with a single elongate internally pigmented (except for distal tip) anterior appendage (distal tip bifurcated in some specimens), less than one-fourth to nearly one-third length of escal bulb; medial escal appendages absent; a posterior escal appendage consisting of a swollen basal portion and a somewhat compressed distal crest, with a posterior filament or filaments and a pair of anterior lobes each bearing numerous filaments; a filamentous anterolateral escal appendage on each side; basal series of filaments absent; subcutaneous, internally pigmented, descending escal appendage well developed, often extending full length of illicium.
Illicium length 20.1–41.3% SL; escal bulb width 2.1–6.3% SL; total number of teeth in upper jaw 21–45, in lower jaw 26–42; ratio between number of teeth in upper jaw to number of teeth in lower jaw 0.78–1.30; vomerine teeth 4–7; dorsal-fin rays 6–8 (of 19 specimens counted only one had dorsal-fin rays 8); anal-fin rays 5 or 6; pectoral-fin rays 16–18.
Metamorphosed females of C. melanorhabdus are easily separate from those of all other species of Chaenophryne by unique features of the esca. In addition, the ratio between the number of upper and lower jaw teeth is less than that of C. draco but significantly greater than that of C. longiceps and C. ramifera. The illicium of C. melanorhabdus is shorter than that of its congeners. Finally, fewer pectoral-fin rays, and fewer dorsal-fin and anal-fin rays, help to distinguish C. melanorhabdus from C. longiceps and C. ramifera, respectively.
Chaenophryne melanorhabdus appears to be restricted to the western continental slope of North and Central America, ranging from approximately 46°N, 125°W in Pacific Subarctic Water, through the mixed Transition Zone of the California Current (18 specimens), and into the Eastern Pacific Equatorial waters of the Gulf of Panama (type locality).
Based on maximum depths reached by fishing gear, metamorphosed female specimens of C. melanorhabdus are vertically distributed between approximately 200 m and an unknown lower limit. Eighty-three percent of the known material (19 individuals), including the largest known specimens (35 mm and larger) was collected by gear fished below 450 m. Material from the Transition Zone of the California Current permits an analysis of vertical data and indicate a concentration between 300 and 1000 m.
Mesopelagic.
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 globular. The mouth is large, its cleft extending past the eye. The illicium length is 20.1–47.4% SL, becoming longer proportionately with growth.
The anterior end of the pterygiophore of preserved specimens is usually concealed under the skin, within the illicial trough, but apparently capable of considerable forward extension (as in Oneirodes and ceratiids). The esca bears a single, conical to elongate, anterior escal appendage or appendages, internally pigmented, with one or three round translucent windows at its tip. Filamentous medial escal appendages are absent. A posterior escal appendage, consisting of a swollen basal portion and a compressed distal crest, is present, bearing none to numerous filaments anteriorly or distally, with a pair of fringed anterior lobes. A subcutaneous internally pigmented appendage emerges from the base of the esca and descends along the anterior margin of the illicial bone.
The teeth are slender, recurved, and all depressible, arranged in overlapping sets as described for other oneirodids. The teeth in the lower jaw are larger and slightly more numerous than those in the upper jaw. There are 21–51 teeth in the upper jaw and 26–57 in the lower jaw. Jaw teeth are few and rudimentary in specimens smaller than approximately 18 mm. The vomer bears 4–8 teeth, the longest tooth outermost. The second and third pharyngobranchials are well developed and toothed. Epibranchial and ceratobranchial teeth are absent.
Known from 49 metamorphosed females (11–102 mm).
As with most oneirodid taxa, males of the genus Chaenophryne are free-living and presumed non-parasitic.
DANA station 1203(14), Gulf of Panama, 7°30'N, 79°19'W, 2500 m wire, 2030 hr, 11 January 1922.
Holotype of Chaenophryne melanorhabdus: ZMUC P92117, 40 mm.
