Nekogigi (Pseudobagrus ichikawai)

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Nekogigi with lateral line sensory system visible along flank
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Nekogigi fact file

Nekogigi description

KingdomAnimalia
PhylumChordata
ClassActinopterygii
OrderSiluriformes
FamilyBagridae
GenusPseudobagrus (1)

The rare nekogigi catfish (Pseudobagrus ichikawai) is endemic to Japan (3), where it has been designated a national monument (4). The nekogigi has four pairs of well developed whisker like appendages called ‘barbels’ around its mouth and it is from these whiskers that catfish get their name (5). The dominant colouration on the back and sides of the nekogigi is yellow-brown with brown-grey patches, and the underside is predominantly white (6).

The nekogigi can be distinguished from other catfish by the numbers of rays and spines in its fins. Rays and spines give the fins structural support and may be soft and flexible, or spiny and stiff. The dorsal fin, on the back of the nekogigi, has 1 spiny ray and 6 to 7 soft rays and the anal fin has 0 spiny rays and 14 to 16 soft rays (2). The adipose fin is relatively large, and the tail fin is less forked compared to other Pseudobagrus species (7).

A scale less fish, the nekogigi protects itself by using a potent toxic protein, excreted from a hollow ray located on the dorsal or pectoral fin (8).

Size
Length: 10.8 cm (2)
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Nekogigi biology

The majority of catfish, including the nekogigi are nocturnal, emerging at night to feed (9). The barbels of catfish contain taste buds, and these sensory organs are used to detect their surrounding environment and potential prey. The nekogigi preys mainly on crustaceans, but may also feed on plankton, small fish, insect larvae and tadpoles (2).

Like the majority of fish the nekogigi is oviparous, with fertilisation occurring externally (10). Mating occurs in the spring, when the male will find and defend a nest site to attract a female (10). No parental care has been seen in this species, but the male guards the nest during egg development and after hatching (10).

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Nekogigi range

The nekogigi is found only in rivers which flow into the Ise and Mikawa Bays in Honshu, Japan (3).

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Nekogigi habitat

The nekogigi inhabits freshwater rivers, where it is found in crevices and under boulders on the riverbed during the day (9).

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Nekogigi status

Classified as Vulnerable (VU) on the IUCN Red List (1).

IUCN Red List species status – Vulnerable

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Nekogigi threats

The biggest threats to the nekogigi are man-made changes to its habitat and water pollution due to surface run-off (4). Poaching may also be a threat, but its significance in causing nekogigi population declines is currently unclear (4).

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Nekogigi conservation

Conservation efforts currently focus on reducing the effects of habitat change in the nekogigi’s river environment, as well as monitoring the nekogigi population size (4).

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

This species information was authored as part of the ARKive and Universities Scheme.
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Glossary

Adipose fin
In some fish, a second dorsal fin consisting of a flap of fatty tissue, which lacks supporting rays.
Anal fin
In fish, an unpaired fin on the under surface of the fish, behind the anus.
Barbels
Fleshy projections near the mouth of some aquatic vertebrates.
Crustaceans
Diverse group of animals with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
Dorsal fin
The unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans (whales, dolphins and porpoises).
Endemic
A species or taxonomic group that is only found in one particular country or geographic area.
Fertilisation
The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.
Larval
Of the stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Nocturnal
Active at night.
Order
A category used in taxonomy, which is below ‘class’ and above ‘family’. All members of an order have characteristics in common.
Oviparous
An animal that reproduces by laying eggs, which hatch outside the mother’s body.
Pectoral fin
In fish, the pair of fins that are found on either side of the body just behind the gills. They are generally used for balancing and braking.
Plankton
Aquatic organisms, usually tiny, that drift passively with water movements; includes phytoplankton (plants), zooplankton (animals), or other organisms such as bacteria.
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References

  1. IUCN Red List (November, 2010)
    http://www.iucnredlist.org/
  2. FishBase - Nekogigi Pseudobagrus ichikawai (November, 2010)
    http://www.fishbase.org/
  3. Watanabe, K. (1998) Meristic variation in the endangered bagrid catfish. Pseudobagrus ichikawai. Ichthyological Research, 45(1):99-104.
  4. Watanabe, K. (2009) Sudden crash of a local population of the endangered bagrid catfish Pseudobagrus ichikawai. Icthylogical Research, 56(3): 219-321.
  5. Okada, Y. and Kubota, S. (1957) Description of a new fresh water cat-fish Coreobagrus ichikawai, with an emendation of the genus Coreobagrus Mori. Japanese Journal of Ichthyology, 5:143-145.
  6. Hildyard, A. (2001) Endangered Wildlife and Plants of the World. Marshal Cavendish Corporation, New York.
  7. Watanabe, K., Mori, S., Nagoshi, M., Jeon, S. and Shimizu, Y. (1992) Morphological differences between two bagrid catfishes, Coreobagrus ichikawai and C. brevicorpus. Ichthyological Research, 39(2): 157-162.
  8. Nelson, J.S. (2006) Fishes of the World Fourth Edition. John Wiley & Sons, New Jersey.
  9. Watanabe, K. (2008) Diel activity and reproductive territory of the Japanese bagrid catfish, Pseudobagrus ichikawai. Environmental Biology of Fishes, 81(1): 77-86.
  10. Watanabe, K. (1994) Mating behaviour and larval development of Pseudobagrus ichikawai (Siluriformes: Bagridae). Ichthylogical Research, 41(3): 243-251.
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Image credit

Nekogigi with lateral line sensory system visible along flank  
Nekogigi with lateral line sensory system visible along flank

© Dr. Yuichi Kano

Dr. Yuichi Kano
kano@species.jp

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