Izuzuki Diver, Satoshi Yamamoto, Japan
Info
The body of Regalecus russellii is silver-gray with amorphous, oblique dark stripes and spots scattered across the body.
These dark stripes and spots are clearly pronounced in the first third of the body.
The forehead, mouth, preoperculum, operculum (except for the upper front corner), and the lower edge of the head are grayish black, covering almost 16% of the body length.
The upper and lower edges of the body have a purple-red sheen, especially in the first half of the body.
The pupil is dark and the iris is light.
The dorsal and ventral fins are purple-red, the pectoral fins are less strongly colored (the dorsal fin crest and ventral fins are completely dark purple-red).
The head and body are silvery, dark near the base of the dorsal fins; the dorsal fin rays are reddish; there are small dark spots on the body.
This species has a unique adaptation in the form of self-amputation (autotomy) of the rear part of the body behind the cloaca, which can extend only to the tail fin (or one or more small adjacent vertebrae) or to just before the abdomen.
This apparently occurs several times during the course of its life (serial autotomy), but does not damage any vital organs and is usually survived, except in cases of stranding.
All specimens longer than 1.5 m have bodies shortened by autotomy and may have a healed stump or “terminus.”
Nevertheless, many specimens are found with fresh (with a jagged appearance that differs greatly from a healed terminus) incomplete self-amputations of the rear part of the body, which in particular do not correspond to shark bites. The front part of the body is never regenerated.
This species is often sighted vertically with its head pointing upwards in clear marine or coastal waters; it is believed that this is a feeding posture that allows the fish to see the silhouette of its potential prey against the sky.
Regalecus russellii is toothless, its protruding jaws suck krill-containing water into the mouth-gill cavity and hold it in the throat with long, spiny and bristly gill rakers.
The mouth can be extended to catch prey.
This species occasionally lives in pairs (sex not documented), but there are no reports of groups of more than three animals or of shoaling behavior.
Spawning occurs between July and December, with larvae occurring near the surface.
Regalecus russellii spawns in the North Pacific, west of the Mariana Islands, and may also spawn in South Africa near Durban.
Large adult animals sometimes kill themselves by swimming out of the water onto beaches.
The occurrence of such strandings may be related to specific areas, seasons, or months and often occurs in bursts.
Predators: Sharks
Etymology: Regalecus: Latin, regalis = belonging to a king
Synonyms:
Gymnetrus hawkenii Bloch, 1795 · unaccepted (synonym)
Gymnetrus hawkinsii Bloch, 1795 · unaccepted > misspelling - incorrect subsequent spelling
Gymnetrus russelii Cuvier, 1816 · unaccepted
Gymnetrus russellii Cuvier, 1816 · unaccepted (senior synonym)
Regalecus caudatus Zugmayer, 1914 · unaccepted
Regalecus glesne pacificus Wood-Jones, 1929 · unaccepted (other)
Regalecus kinoi Castro-Aguirre, Arvizu-Martinez & Alarcón-Gonzalez, 1991 · unaccepted (synonym)
Regalecus russelii (Cuvier, 1816) · unaccepted
Regalecus woodjonesi Whitley, 1933 · unaccepted (synonym)
These dark stripes and spots are clearly pronounced in the first third of the body.
The forehead, mouth, preoperculum, operculum (except for the upper front corner), and the lower edge of the head are grayish black, covering almost 16% of the body length.
The upper and lower edges of the body have a purple-red sheen, especially in the first half of the body.
The pupil is dark and the iris is light.
The dorsal and ventral fins are purple-red, the pectoral fins are less strongly colored (the dorsal fin crest and ventral fins are completely dark purple-red).
The head and body are silvery, dark near the base of the dorsal fins; the dorsal fin rays are reddish; there are small dark spots on the body.
This species has a unique adaptation in the form of self-amputation (autotomy) of the rear part of the body behind the cloaca, which can extend only to the tail fin (or one or more small adjacent vertebrae) or to just before the abdomen.
This apparently occurs several times during the course of its life (serial autotomy), but does not damage any vital organs and is usually survived, except in cases of stranding.
All specimens longer than 1.5 m have bodies shortened by autotomy and may have a healed stump or “terminus.”
Nevertheless, many specimens are found with fresh (with a jagged appearance that differs greatly from a healed terminus) incomplete self-amputations of the rear part of the body, which in particular do not correspond to shark bites. The front part of the body is never regenerated.
This species is often sighted vertically with its head pointing upwards in clear marine or coastal waters; it is believed that this is a feeding posture that allows the fish to see the silhouette of its potential prey against the sky.
Regalecus russellii is toothless, its protruding jaws suck krill-containing water into the mouth-gill cavity and hold it in the throat with long, spiny and bristly gill rakers.
The mouth can be extended to catch prey.
This species occasionally lives in pairs (sex not documented), but there are no reports of groups of more than three animals or of shoaling behavior.
Spawning occurs between July and December, with larvae occurring near the surface.
Regalecus russellii spawns in the North Pacific, west of the Mariana Islands, and may also spawn in South Africa near Durban.
Large adult animals sometimes kill themselves by swimming out of the water onto beaches.
The occurrence of such strandings may be related to specific areas, seasons, or months and often occurs in bursts.
Predators: Sharks
Etymology: Regalecus: Latin, regalis = belonging to a king
Synonyms:
Gymnetrus hawkenii Bloch, 1795 · unaccepted (synonym)
Gymnetrus hawkinsii Bloch, 1795 · unaccepted > misspelling - incorrect subsequent spelling
Gymnetrus russelii Cuvier, 1816 · unaccepted
Gymnetrus russellii Cuvier, 1816 · unaccepted (senior synonym)
Regalecus caudatus Zugmayer, 1914 · unaccepted
Regalecus glesne pacificus Wood-Jones, 1929 · unaccepted (other)
Regalecus kinoi Castro-Aguirre, Arvizu-Martinez & Alarcón-Gonzalez, 1991 · unaccepted (synonym)
Regalecus russelii (Cuvier, 1816) · unaccepted
Regalecus woodjonesi Whitley, 1933 · unaccepted (synonym)
