Slender Snaggletooth

While there is little known about the communication and perception of Rhadinesthes decimus, several sources state in the physical description of this animal that it has a line of luminous material on its body as well as luminous material at the stem of the barbel near its mouth. Though no sources make an effort to explain these luminous structures, we presume that they are used to communicate, perhaps to lure prey, confuse predators, or signal other individuals of R. decimus.

The species has fairly large eyes, so we can presume that vision is important, and all fish use chemical senses to some extent, but further details on sensory information in this species are not documented.

Communication Channels: visual

Other Communication Modes: photic/bioluminescent

Perception Channels: visual ; tactile ; chemical

Rhadinesthes decimus is known primarily as a mesopelagic ocean fish living at depths around 500 m. According to Gibbs (1990), it is characteristic of members from this family (Stomiidae) to live at depths deeper than 500 m during the day and to migrate closer to the ocean surface during the night.

Rhadinesthes decimus has been found in both tropical waters (i.e. the Indian Ocean) and temperate waters (i.e. the northern and southern Atlantic and Pacific Oceans).

Range depth: 100 to 600 m.

Average depth: 500 m.

Habitat Regions: temperate ; tropical ; saltwater or marine

Aquatic Biomes: pelagic

Specimens of Rhadinesthes decimus have been collected in the tropical Indian Ocean, the southern Atlantic Ocean, the eastern and western south Pacific Ocean, and the central north Pacific Ocean. In the south Atlantic Ocean, the range of Rhadinesthes decimus seems to stop around 27 degrees south of the equator. In the North Pacific, the range of this animal seems to be to the east of 21 degrees west and to the north of 20 degrees north.

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

According to Gibbs, the feeding habits of Rhadinesthes decimus are still poorly known, but it is assumed that they feed on midwater fishes and crustaceans (1984).

Animal Foods: fish; aquatic crustaceans

Foraging Behavior: stores or caches food

Primary Diet: carnivore (Piscivore , Eats non-insect arthropods)

Rhadinesthes decimus is an intermediate predator. It's relations with other species in the deep-water pelagic ecosystems have not been studied.

There is currently little or no information about this topic regarding Rhadinesthes decimus.

There is currently little or no information about this topic regarding Rhadinesthes decimus.

We have no information about the development of Rhadinesthes decimus.

The wide distribution of occurrences of this species suggest that it may occur in large populations, but there are no studies determining the actual population size of Rhadinesthes decimus, much less its conservation status. Given this absence of information, it is not surprising that the species is not listed on any major lists of threatened or endangered species.

US Federal List: no special status

CITES: no special status

Rhadinesthes decimus was first formally described in 1911 by Erich Zugmayer.

Many classification systems put Rhadinesthes decimus in the family Astronesthidae. However, according to Fink, the most appropriate classification scheme puts Rhadinesthes decimus in the Stomiidae family (1985). Furthermore, common synonyms for Rhadinesthes decimus are Rhadinesthes jacobssoni, Rhadinesthes lucberti, and Astronesthes decimus. All of these synonyms describe the same species Rhadinesthes decimus (Bigelow et al., 1964 and Gibbs, 1984).

There is currently little or no information about this topic regarding Rhadinesthes decimus.

The body of Rhadinesthes decimus is described as long and slender, reaching lengths of up to 410 mm (Gibbs, 1990). This species is distinguished from other closely related members of the family Stomiidae by the line of luminous material that begins behind the post-orbital organ and continues along the side of the body for most of its length. Rhadinesthes decimus also has a barbel that extends about half the length of the head and has photophores and luminous material near the stem.

The dorsal fin on this fish has 11 to 13 rays. The fin's origin is relatively far behind the pelvic fin insertion. There is no dorsal adipose fin present on Rhadinesthes decimus (Bigelow et al., 1964). The ventral adipose fin is long and low, extending from the back of the pelvic bone to the anus. The lower caudal rays are also greatly elongated. The color of Rhadinesthes decimus tends to be black except for the line of luminous material.

There are no fangs present in the mouth of this fish. Rather, the teeth of Rhadinesthes decimus tend to be relatively small. On the upper jaw, these teeth are widely spaced and some are slightly curved. There are usually between 10 and 12 teeth on the premaxillary and between 14 and 30 teeth on the maxillary. Rhadinesthes decimus also has small gill teeth.

Range length: 79 to 410 mm.

Other Physical Features: ectothermic ; bilateral symmetry

There is currently no published information about predators of Rhadinesthes decimus. It's possible that the bioluminescent structures on these fish are used to confuse or distract predators.

We have no information about mating behavior in Rhadinesthes decimus.

We have very little information about reproduction in this species. One source (FishBase 2004) classifies this species has having low reproductive resilience, meaning that the time it would take for a population of these fish to double is between 4.5 and 14 years. There is little additional information available.

We have no information about parental investment by Rhadinesthes decimus.

View data on Catalog of Fishes here.

Body long and slender, compressed, its depth more than 10 times in SL; no enlarged teeth in jaws; posterior of maxilla with widely spaced, slightly curved, short teeth; gill arches bearing well seperated spines along length. Postorbital photophore single. Ventral (IC) and lateral (OA) rows of photophores with gap in area between pelvic-fin insertion and anal-fin orgin. Dorsal-fin origin less than 60% of SL, considerable behind pelvic-fin insertion; dorsal adipose fin absent.

Body long, slender. Teeth in jaws all relatively small, none enlarged as fangs, with widely spaced, slightly curved short teeth on posterior part of upper jaw; well separated short spines on gill arches. Gaps present in lateral and ventral photophore rows in area between pelvic insertion and anal-fin origin. Dorsal-fin origin considerably behind pelvic-fin insertion; no dorsal adipose fin. Head and body black; line of luminous material extening from opercle to caudal peduncle, glowing red and green in life.

Prabably worldwide in subtropical and temperate oceanic waters.

Gibbs RH, Jr. 1984. Astronesthidae. In: Whitehead PJP, Bauchot M-L, Hureau J-C, Nielsen J, Tortonese E, editors. Fishes of the North-eastern Atlantic and the Mediterranean. Paris: UNESCO. p 325–335.

Teeth on upper jaw slender, all short, widely spaced; 10 to 12 on premaxillary, 14 to 30 teeth on maxillary. No well-developed canines in jaws. Pelvic insertion nearer to tip of snout than to caudal base. Dorsal origin well behind pelvic insertion. Dorsal adipose fin absent.

Dorsal spines (total): 0; Dorsal soft rays (total): 11 - 13; Analspines: 0; Analsoft rays: 18 - 21

An oceanic (Ref. 2802) and meso-bathypelagic species (Ref. 4465). Usually found deeper than 500 m during the day (Ref. 2802). Feeds on midwater fishes and crustaceans.

An oceanic (Ref. 2802) and mesopelagic-bathypelagic species (Ref. 4465). Usually found deeper than 500 m during the day (Ref. 2802). Feeds on midwater fishes and crustaceans (Ref. 2802).

廣泛分布於印度-太平洋及大西洋。台灣海域記錄深度約400公尺。

胸鰭條數：8(6-8); 腹鰭軟條數：7; 背鰭軟條數：9(11-13); 臀鰭軟條數：18(18-21); 鰓耙數：上枝 5+下枝12; 發光器排列：IP 9(9-10); PV 27(26-31); VAV (23-25); AC (12-14); IC (72-76); OA (50-52); BR 14-17; 身體細長，體高大於頭長；上頷齒及前上頷齒短小，彼此分離，上頷齒數14-30，前上頷齒數10-12；下頷鬚長度大於頭長；背部脂鰭缺如。

Rhadinesthes decimus, the slender snaggletooth, is a species of barbeled dragonfish found in the ocean depths reaching to 4,900 metres (16,100 ft). This species grows to a length of 41.0 centimetres (16.1 in) SL. This species is the only known species in its genus.

63.1°N to 44°N

bathypelagic

nektonic

Known from seamounts and knolls