The fin rays are soft and may number up to 400 or more. At the head of the fish, the rays are lengthened forming a distinctive red crest. Its pectoral and pelvic fins are nearly adjacent. The pectoral fins are stubby while the pelvic fins are long, single-rayed, and reminiscent of an oar in shape, widening at the tip. Its head is small with the protrusible jaw typical of lampriformes; it has 40 to 58 gill rakers, and no teeth. The organs of the giant oarfish are concentrated toward the head end of the body, possibly enabling it to survive losing large portions of its tail. It has no swim bladder. The liver of "R. glesne" is orange or red, the likely result of astaxanthin in its diet. The lateral line begins above and behind the eye then, descending to the lower third of the body, extends to the caudal tip. The skin of "R. glesne" is scaleless but covered with tubercles. The skin color is silver with streaks, spots or splotches of black or dark gray, and a bluish or brownish tinge on the head. Its fins, including its long dorsal fin and crest, are red, again probably resulting from its diet. Little is known about oarfish behavior. It has been observed swimming by means of its dorsal fin, and also swimming in a vertical position. In 2010, scientists filmed a giant oarfish in the Gulf of Mexico swimming in the mesopelagic layer, the first footage of a reliably identified "R. glesne" in its natural setting. The footage was caught during a survey, using an ROV in the vicinity of Thunder Horse PDQ, and shows the fish swimming in a columnar orientation, tail downward. It feeds on krill and other small crustaceans, as well as small fish and squid. It is known to spawn from July to December. The eggs are large, and float near the surface until hatching. Its larvae are also observed near the surface during this season. As an adult, it is believed to be solitary. "R. glesne" is not fished commercially, but is an occasional bycatch in commercial nets, and as such it has been marketed. Because they are not often seen and because of their size, elongated bodies, and appearance, giant oarfish are presumed to be responsible for some sea serpent sightings. Formerly considered rare, the species is now suspected to be comparatively common, although sightings of healthy specimens in their natural habitat are unusual.