Argyropelecus affinis

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Argyropelecus affinis
FMIB 53392 Argyropelecus alfinis Brauer (Valdivia).jpeg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Stomiiformes
Family: Sternoptychidae
Genus: Argyropelecus
Species:
A. affinis
Binomial name
Argyropelecus affinis
Garman, 1899 [2]
Synonyms
  • Argyropelachus affinis Garman, 1899
  • Argyropelecus pacificus Schultz, 1961

Argyropelecus affinis is a species of ray-finned fish in the family Sternoptychidae, described by Garman in 1899, found in the tropical and subtropical Atlantic, Indian and Pacific Oceans. Common names for this fish include Pacific hatchetfish, deepsea hatchetfish and slender hatchetfish. It inhabits the upper mesopelagic zone between 350 and 600m during the day, and between 100m and 350m during the night and is either non-migratory or performs short daily vertical migrations. They are distributed widely throughout all tropical and temperate seas. They are known for its laterally compressed body and characteristic photophores, which aid in bioluminescence. Argyropelecus affinis is closely related to Argyropelecus gigas. [3]

Contents

Figure 1. Horizontal Distribution of A. affinis (Baird 1971) Horizontal Distribution of Argyropelecus affinis.png
Figure 1. Horizontal Distribution of A. affinis (Baird 1971)

Description

Argyropelecus affinis is a small laterally compressed fish with a standard length of up to 70 millimetres (2.8 in). It has a vertical mouth and tubular eyes that are directed upwards. [4] There is a short spine in front of the operculum but no spine behind the eye. The dorsal fin has 9 short soft rays and there is also a dorsal adipose fin. The pectoral fin has 11 or 12 soft rays, the pelvic fin 6 and the anal fin 13. There are several short post-abdominal spines. The swim bladder is gas-filled and well-developed. This fish has a dark-coloured back and silvery sides, with darker pigment along the lateral line. The scales have a tendency to detach, and adult fish have rows of photophores on the underside. [4]

Taxonomy and classification

Argyropelecus affinis was first described by Samuel German in 1899. Its taxonomy has been relatively stable, though Schultz (1961) introduced A. pacificus based on variations in supination and morphological traits. [3] This classification was later synonymized with A. affinis by Baird (1972), who recognized the variation as insufficient for distinguishing a separate species. Despite some historical confusion regarding its classification, modern revisions support the inclusion of A. pacificus as a junior synonym of A. affinis.

Figure 2. Cladogram depicting phylogenetic relationships among the seven recognized species of Argyropelecus and four outgroups (Harold 1993) Cladogram depicting phylogenetic relationships among the seven recognized species of Argyropelecus and four outgroups.png
Figure 2. Cladogram depicting phylogenetic relationships among the seven recognized species of Argyropelecus and four outgroups (Harold 1993)

Phylogeny

In phylogenetic studies, Argyropelecus affinis is placed within the affinis species complex, along with A. gigas. This complex is considered the sister group to the remaining species of the genus Argyropelecus. The analysis of morphological traits suggests that A. affinis and A. gigas retain some primitive features relative to other members of the genus, placing them as a basal in the phylogeny of Argyropelecus. Derived characteristics present in other Argyropelecus species are absent in A. affinis, supporting its placement in a separate, more primitive clade. [5]

Morphology

Argyropelecus affinis displays a number of distinctive morphological traits [5] including:

Additionally, A. affinis possesses some unique traits, such as an acute spine-like angle on the anterodorsal surface of the ventral section of the cleithrum and specific pitting patterns on the cleithrum’s surfaces.

Distribution and habitat

Argyropelecus affinis lives in deep-sea environments, typically found in midwater oceanic regions. This species is circum-global and is found in the warmer parts of the Atlantic, Indian and Pacific Oceans. It is plentiful off the coast of West Africa from about 10°S northwards, and is present as far south as 15°S near Madagascar. It is usually found in the mesopelagic zone. [6] During the day, trawls at depths between 350 and 600 m (1,100 and 2,000 ft) produce the highest catches and at night the greatest abundance of fish is in the depth range 170 and 400 m (600 and 1,300 ft); this indicates that some, but not necessarily all, fish make short daily vertical migrations. [1] As with other members of the genus, it has photophores along its body, which are used for counter-illumination, a form of camouflage against predators in the deep sea. [7]

Evolutionary significance

The placement of A. affinis and A. gigas as a distinct clade within the genus Argyropelecus is supported by five derived traits, though some aspects of their evolutionary relationships remain ambiguous. Baird’s (1972) assessment suggested that A. affinis was one of the more primitive members of the genus, a hypothesis that has been further refined in subsequent phylogenetic studies. The genus’s evolution is characterized by changes in the structure of the pelvic girdle, photophore arrangement, and ossification patterns. Here, ossification pattern refers to the pattern that the bones form in the body of a fish. This is important because it shows the evolution, growth, and development of the fish. [8]

Relationship with other species

Argyropelecus affinis is part of the broader affinis species complex, which is distinct from the lychnus complex, comprising species such as A. lychnus, A. aculeatus, A. olfersi, and A. sladeni. The lychnus complex is considered more derived and is characterized by modifications such as reduced number of hypurals and distinct photophore arrangements. In contrast, A. affinis retains traits like three hypurals in the lower caudal lobe and a continuous series of posterior ventral photophores, suggesting a closer resemblance to ancestral forms within the genus. [9]

Diet

Argyropelecus affinis diet [10] is composed of unidentified Teleostei (32% weight percentage), Teleostei larvae (24% weight percentage), Gonostomatidae (13% weight percentage), and Euphausia spp. (9% weight percentage). [11]

Structure of the eye

The eyes of Argyropelecus affinis are large, and oriented dorsally. They are tubular or telescopic which are one of the specific characteristics of oceanic deepsea fishes. The larger vertical (ventro-dorsal) diameter of the tubular eye constitutes 10 to 15% of the fish’s standard length. Lens and pupil are very large, but the lens muscle is much reduced compared with that of shallow water fishes. The retina of the eye consists of the main and the accessory retinas. The visual cells of retina are composed of rods, and no cones. [12]

Main retina and accessory retina

Figure 3. Main Retina of A. affinis Main Retina of A. affinis.png
Figure 3. Main Retina of A. affinis

The main retina (Figure 3) forms the ventral and temporal walls of the retinal eye cup. [13] Histologically, the retina is composed of 10-layer elements as seen in the retina of shallow water fishes. The greatest thickness of the retina, about 200 micrometer, occurs ventrally, where rod’s outer segment is long (about 50 micrometer).

Figure 4. Accessory Retina of A. affinis Accessory Retina of A. affinis.png
Figure 4. Accessory Retina of A. affinis

The position of the accessory retina is shown in Figure 4. The outer segments of these rods are short (15 micrometers). Pigment epithelium, visual cells and outer nuclear layer were identified, but the other layers could not be distinguished. [13]

Eye pigmentation

Eye lens pigmentation in the deep-sea hatchetfish is characterized by 1) an abrupt onset and steady increase in concentration during the life history of the fish; 2) restriction to the outer layers of the lenses of adult fishes; 3) a complex absorption profile in the near UV and blue-violet wavelengths; and 4) a chromophore that is tightly bound to a single, specific soluble lens protein, alpha crystallin. No other visual systems with lens pigmentation yet described have these four characteristics. The distribution of pigment within the A. affinis lens suggests that, beginning at a specific age, the pigment is incorporated into new lens fiber cells as they are laid down over preexisting cells. [14]

Figure 5. Yellow Lens of Argyropelecus affinis Yellow Lens of Argyropelecus affinis.png
Figure 5. Yellow Lens of Argyropelecus affinis

Ecology

Adult Argyropelecus affinis feed on planktonic organisms, salps, krill, arrow worms, copepods and ostracods. [15] Smaller fish consume mainly copepods and ostracods, and their adult arrangement of photophores develop when they are about 14 mm (0.6 in) long. [4] [16]

The lenses of the eyes of A. affinis contains yellow pigments that absorb short-wave radiation; the proportions of the two carotenoid-like pigments present change as the fish grows older. [17] It is not clear what precise function is served by the pigments, but with some of the incident illumination being absorbed, the fish's absolute sensitivity to light must be reduced. [18]

Conservation

Argyropelecus affinis is a common fish and is abundant in many parts of its wide range. No specific threats [19] have been identified especially to humans and the International Union for Conservation of Nature has rated its conservation status as being of "least concern". [1]

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Stomiiformes is an order of deep-sea ray-finned fishes of very diverse morphology. It includes, for example, dragonfishes, lightfishes, loosejaws, marine hatchetfishes and viperfishes. The order contains 4 families with more than 50 genera and at least 410 species. As usual for deep-sea fishes, there are few common names for species of the order, but the Stomiiformes as a whole are often called dragonfishes and allies or simply stomiiforms.

<span class="mw-page-title-main">Marine hatchetfish</span> Subfamily of fishes

Marine hatchetfishes or deep-sea hatchetfishes are small deep-sea mesopelagic ray-finned fish of the stomiiform subfamily Sternoptychinae. They should not be confused with the freshwater hatchetfishes, which are not particularly closely related Teleostei in the characiform family Gasteropelecidae.

<span class="mw-page-title-main">Sternoptychidae</span> Family of fishes

The marine hatchetfishes or deep-sea hatchetfishes as well as the related bottlelights, pearlsides and constellationfishes are small deep-sea ray-finned fish of the stomiiform family Sternoptychidae. They are not closely related to and should not be confused with the freshwater hatchetfishes, which are teleosts in the characiform family Gasteropelecidae. The Sternoptychidae have 10 genera and about 70 species altogether.

<i>Argyropelecus</i> Genus of deep sea hatchetfishes

Argyropelecus is an oceanic ray-finned fish genus in the deep sea hatchetfish family Sternoptychidae. A collective name is "silver hatchetfishes", but this can also refer to a species of the freshwater hatchetfishes which are not particularly closely related to this. The large pupils of these marine hatchetfishes enable them to see dim objects in the deep sea, where light barely penetrates.

<i>Polyipnus</i> Genus of fishes

Polyipnus is a genus of oceanic ray-finned fish in the family Sternoptychidae. This is the largest genus of the marine hatchetfishes subfamily Sternoptychinae and indeed of the entire Sternoptychidae. It is not quite as apomorphic as their relatives; it may be that the genus is actually a paraphyletic assemblage of less advanced Sternoptychinae and would need to be split.

<i>Sternoptyx</i> Genus of fishes

Sternoptyx is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. This is the type genus of the Sternoptychidae, as well as the marine hatchetfish subfamily Sternoptychinae.

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<span class="mw-page-title-main">Viperfish</span> Genus of fishes

A viperfish is any species of marine fish in the genus Chauliodus. Viperfishes are mostly found in the mesopelagic zone and are characterized by long, needle-like teeth and hinged lower jaws. A typical viperfish grows to lengths of 30 cm (12 in). Viperfishes undergo diel vertical migration and are found all around the world in tropical and temperate oceans. Viperfishes are capable of bioluminescence and possess photophores along the ventral side of their body, likely used to camouflage them by blending in with the less than 1% of light that reaches to below 200 meters depth.

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<i>Argyropelecus hemigymnus</i> Species of fish

Argyropelecus hemigymnus, the half-naked hatchetfish, short silver hatchetfish or spurred hatchetfish, is a deep-sea hatchetfish of the genus Argyropelecus found mesopelagically in the Atlantic, Indian, and Pacific Oceans as well as in the Mediterranean Sea. It is a small species rarely exceeding 38 millimetres (1.5 in) standard length. It feeds on zooplankton, particularly ostracods and copepods. Sexual maturation occurs at length of about 22 mm, and adult males have more developed olfactory organs than females, i.e. the species is sexually dimorphic.

<i>Argyropelecus gigas</i> Species of fish

Argyropelecus gigas, the giant hatchetfish or greater silver hatchetfish, is a marine fish of the genus Argyropelecus. It is found in every ocean except the north Pacific in the mesopelagic zone of tropical and subtropical waters. "Giant" in relative terms only, this is the largest species of marine hatchetfishes, often exceeding 110 millimetres (4.3 in) standard length.

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Maurolicus muelleri, commonly referred to as Mueller's pearlside,Mueller's bristle-mouth fish, or the silvery lightfish, is a marine hatchetfish in the genus Maurolicus, found in deep tropical, subtropical and temperate waters of the Pacific Ocean and the Atlantic Ocean, from the surface to depths of 1,500 metres (4,900 ft). It can grow to a maximum total length of 8 centimetres (3.1 in).

<i>Argyropelecus aculeatus</i> Species of fish

Argyropelecus aculeatus, the lovely hatchetfish or Atlantic silver hatchetfish, is a species of fish in the family Sternoptychidae. It may exceed 70 millimetres (2.8 in) standard length (SL). It lives in the mesopelagic zone of all oceans and performs diel vertical migration. A. aculeatus feeds on a large range of prey items; in the Gulf of Mexico ostracods and copepods dominated the diet of small individuals and euphausiids, molluscs, and fish the diet of larger ones. The silvery coloration and bioluminescence of the lovely hatchetfish allows it to hide from predators and prey in the down-welling light of the twilight zone.

<i>Opisthoproctus</i> Species of fish

Opisthoproctus soleatus is a species of fish in the family Opisthoproctidae. It was first described in 1888 by Léon Vaillant. The species lives in most tropical seas, but is more common in the eastern Atlantic, from western Ireland to Mauritania and from Sierra Leone to Angola, and also in the South China Sea. O. soleatus can grow to a standard length of 10.5 centimetres (4.1 in) and usually live from about 500 to 700 metres deep.

<i>Argyropelecus sladeni</i> Species of fish

Argyropelecus sladeni, or Sladen's hatchetfish, is a species of ray-finned fish in the family Sternoptychidae, found in the tropical and subtropical Atlantic, Indian and Pacific Oceans. This small fish lives in the mesopelagic zone by day and makes a daily vertical migration to the epipelagic zone at night.

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Polyipnus clarus, commonly known as the stareye hatchetfish or slope hatchetfish, is a species of ray-finned fish in the family Sternoptychidae. It occurs in deep water in the western Atlantic Ocean from the Gulf of Maine southward to the Caribbean Sea and the Gulf of Mexico. It most commonly occurs between 300 and 400 metres but can range from 40 and 830 metres.

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<i>Argyropelecus olfersii</i> Species of fish

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References

  1. 1 2 3 Harold, A. (2015). "Argyropelecus affinis". IUCN Red List of Threatened Species . 2015: e.T190118A21913659. doi: 10.2305/IUCN.UK.2015-4.RLTS.T190118A21913659.en . Retrieved 12 November 2021.
  2. ↑ Bailly, Nicolas (2015). "Argyropelecus affinis Garman, 1899". WoRMS. World Register of Marine Species . Retrieved 17 February 2016.
  3. 1 2 Haruta, C. (1975). "Taxonomy and geographycal distribution of the genus Argyropelecus (Family Sternoptychidae) from the Western North Pacific Ocean". Jap. G. Ichthyol. 22 (2): 83–96.
  4. 1 2 3 "Argyropelecus affinis". Fishes of the NE Atlantic and the Mediterranean. Marine Species Information Portal. Retrieved 17 February 2016.
  5. 1 2 Harold, A. S. (1993). "Phylogenetic Relationships of the Sternoptychid Argyropelecus (Teleostei: Stomiiformes)". Copeia. 1993 (1): 123–133. doi:10.2307/1446303. JSTOR   1446303.
  6. ↑ Smith, Margaret M.; Heemstra, Phillip C. (2012). Smiths' Sea Fishes. Springer Science & Business Media. p. 256. ISBN   978-3-642-82858-4.
  7. ↑ Baird, R. Clay (1971). "The systematics, distribution, and zoogeography of the marine hatchetfishes (family Sternoptychidae)". Bulletin of the Museum of Comparative Zoology at Harvard College. 142: 1–128.
  8. ↑ Baird, R. C.; M. J. Eckardt (1972). "Divergence and Relationship in Deep-Sea Hatchetfishes (Sternoptychidae)". Systematic Zoology. 21 (1): 80. doi:10.2307/2412260. JSTOR   2412260.
  9. ↑ Schultz, L. P. (1961). "Revision of the Marine Silver Hatchetfishes (Family Sternoptychidae)". Proceedings of the United States National Museum. 112 (3449): 587–649. doi:10.5479/si.00963801.112-3449.587.
  10. ↑ Hopkins, T. L.; R. C. Baird (1973). "Diet of the hatchetfish Sternoptyx diaphana". Marine Biology. 21 (1): 34–46. doi:10.1007/BF00351190.
  11. ↑ Eduardo, L. N.; A. Bertrand; M. M. Mincarone; L. V. Santos; T. Frédou; R. V. Assunção; A. Silva; F. Ménard; R. Schwamborn; F. Le Loc’h; F. Lucena-Frédou (2020). "Hatchetfishes (Stomiiformes: Sternoptychidae) biodiversity, trophic ecology, vertical niche partitioning and functional roles in the western Tropical Atlantic" (PDF). Progress in Oceanography. 187 (102389). doi:10.1016/j.pocean.2020.102389.
  12. ↑ McFall-Ngai, M.; F. Crescitelli; J. Childress; J. Horwitz (1986). "Patterns of pigmentation in the eye lens of the deep-sea hatchetfish, Argyropelecus affinis Garman". Journal of Comparative Physiology A. 159 (6): 791–800. doi:10.1007/BF00603732. PMID   3806437.
  13. 1 2 Somiya, H. (1976). "Functional significance of the yellow lens in the eyes of Argyropelecus affinis". Marine Biology. 34 (2): 93–99. doi:10.1007/BF00390750.
  14. ↑ McFall-Ngai, M. (1984). Biochemical-Analysis of The Age-Related Lens Pigmentation of The Deep-Sea Hatchetfish, Argyropelecus affinis (3rd ed.). American Society of Zoologists. p. A59.
  15. ↑ Kinzer, J.; Schulz, K. (1988). "Vertical distribution and feeding patterns of midwater fish in the central equatorial Atlantic II. Sternoptychidae". Marine Biology. 99 (2): 261–269. doi:10.1007/BF00391989.
  16. ↑ Drazen, J. C.; T. T. Sutton (2017). "Dining in the Deep: The Feeding Ecology of Deep-Sea Fishes". Annual Review of Marine Science. 9 (1): 337–366. doi:10.1146/annurev-marine-010816-060543. PMID   27814034.
  17. ↑ Douglas, R.H.; Thorpe, A. (1992). "Short-wave absorbing pigments in the ocular lenses of deep-sea teleosts". Journal of the Marine Biological Association of the United Kingdom. 72 (1): 93–112. doi:10.1017/S0025315400048815.
  18. ↑ Muntz, W.R.A. (1976). "On yellow lenses in mesopelagic animals". Journal of the Marine Biological Association of the United Kingdom. 56 (4): 963–976. doi:10.1017/S0025315400021019.
  19. ↑ Prokofiev, A. M. (2017). "Argyripnus boreopacificus sp. nova, a new species of hatchetfishes (Sternoptychidae) from the subtropical Northwestern Pacific". Journal of Ichthyology. 57 (2): 325–328. doi:10.1134/S0032945217020151.
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