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''Acrochordonichthys'' is a genus of catfishes (
order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
Siluriformes) of the family
Akysidae The stream catfishes comprise the family Akysidae of catfishes. Distribution and habitat Akysids are known from across a large area in Southeast Asia. They are found in fresh water. Fish of the subfamily Parakysinae are primarily found in the Mal ...
. It includes ten species.


Distribution and habitat

''Acrochordonichthys'' species are generally found at the bottoms of rivers throughout Southeast Asia. Many of the species are only known from Borneo. ''A. guttatus'' is known only from the Barito River drainage in southern Borneo. ''A. mahakamensis'' is known only from the
Mahakam River The Mahakam River (Indonesian: ''Sungai Mahakam'') is third longest and volume discharge river in Borneo after Kapuas River and Barito River, it is located in Kalimantan, Indonesia. It flows from the district of Long Apari in the highlands of ...
drainage in eastern Borneo it is named for. ''A. chamaeleon'' and ''A. strigosus'' are known only from the Kapuas River drainage in western Borneo. ''A. falcifer'' is known only from the
Kinabatangan Kinabatangan ( ms, Pekan Kinabatangan) is the capital of the Kinabatangan District in the Sandakan Division of Sabah, Malaysia. Its population was estimated to be around 10,256 in 2010. Kinabatangan is mostly populated with the Orang Sungai ...
and Segama River drainages, and possibly from the
Kayan River The Kayan River is a river of Borneo island, flowing in the North Kalimantan province of Indonesia, about 1600 km northeast of the capital Jakarta. Tributaries include the Bahau River. Hydrology The Kayan River rises on Mount Ukeng, pa ...
drainage, in north-eastern Borneo. ''A. pachyderma'' is known only from the Kapuas, Mahakam, and Kinabatangan River drainages in western, eastern, and north-eastern Borneo, respectively. ''A. septentrionalis'' is known only from the Mae Klong River drainage in Thailand and the Pahang River drainage in Peninsular Malaysia; it may be found in the
Bernam River The Bernam River ( ms, Sungai Bernam) is located between the Malaysian states of Perak and Selangor, demarcating the border of the two states. The Bernam River flows from Mount Liang Timur (Mount Liang East) in the east on the Titiwangsa Mountain ...
drainage in Peninsular Malaysia. ''A. rugosus'' is known from the Solo,
Ciliwung Ci Liwung (often written as Ciliwung; also as Tjiliwoeng in Dutch, Sundanese: ᮎᮤᮜᮤᮝᮥᮀ) is a 119 km long river in the northwestern region of Java where it flows through two provinces, West Java and the special region of Jakarta. ...
, and Citarum River drainages in Java; the Barito, Kapuas, Mahakam, and Rajang River drainages in Borneo; the Bernam, Terengganu,
Mae Nam Sungai Kolok Mae is an American rock band that formed in Norfolk, Virginia in 2001. The band's name is an acronym for "Multi-sensory Aesthetic Experience", based on a course taken by drummer Jacob Marshall while a student at Old Dominion University. Histor ...
, and
Pattani River Pattani River ( th, แม่น้ำปัตตานี, ; ; ms, Sungai Patani; Jawi: سوڠاي ڤتنا) is a river in southern Thailand, Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailan ...
drainages in Peninsular Malaysia and southern Thailand; and the Musi and Tulangbawan River drainages in
Sumatra Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not including adjacent i ...
. ''A. ischnosoma'' is known from the Citarum River drainage in western Java and the Musi River drainage in southern Sumatra. ''A. gyrinus'', from the Yom River of the Chao Phraya basin in Thailand, represents the northernmost distribution of this genus.


Description

''Acrochordonichthys'' is characterized by a highly rugose skin with tubercles arranged in longitudinal rows along the side of the body, the presence of a long, low adipose fin, and a truncate caudal fin. The tubercles on ''Acrochordonichthys'' may become either greatly hypertrophied or greatly reduced at different stages of the moulting cycle; moulting is known to occur in the related genus ''
Breitensteinia ''Breitensteinia'' is a genus of catfishes ( order Siluriformes) of the family Akysidae. It includes three species. Taxonomy ''B. insignis'' was first described for an unusual akysid by Franz Steindachner in 1881. The genus had been monotypic ...
''. When they are most developed, the tubercles appear more rounded and tightly packed, but are more squamous (flattened) and further apart when least developed. The head is broad and depressed, while the body is moderately compressed. The dorsal profile rises evenly but not steeply from tip of snout to the origin of the dorsal fin, then slopes gently ventrally from there to end of caudal peduncle. The ventral profile is horizontal to origin of the
anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...
, then slopes dorsally to end of the caudal peduncle. The head is covered with small tubercles with poorly demarcated and indistinct margins, and the body with such tubercles arranged in 5–6 longitudinal rows on each side. The dorsal fin origin is nearer the tip of the snout than caudal flexure. The pectoral spine is stout, with or without serrations on the posterior edge. The caudal fin is weakly emarginate. Sexual dimorphism has been reported in ''Acrochordonichthys''. Males have the
anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, d ...
situated immediately in front of a genital papilla, which is located posterior to the
pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...
base. The genital opening is situated at the tip of the papilla, covered by a fleshy flap. In females, the anus is situated more posteriorly and the genital opening is located at the tip of a short genital appendage. In ''A. ischnosoma'', males have a long genital papilla located immediately posterior to anus, while females have a conical genital papilla located immediately posterior to anus.


Species groups

Based on external morphology, two groups of species can be distinguished easily, both of which may be artificial. The first group, the ''A. ischnosoma'' species group, includes ''A. ischnosoma'', ''A. guttatus'', ''A. gyrinus'', ''A. mahakamensis'', ''A. septentrionalis'', and ''A. strigosus''; these species have a narrower head, a more slender caudal peduncle, and 39–41 vertebrae. The second group, the ''A. rugosus'' species group, includes ''A. chameleon'', ''A. falcifer'', ''A. pachyderma'', and ''A. rugosus'', in which the fish have a deeper caudal peduncle, a broader head, and 35–37 vertebrae. ''Acrochordonichthys'' species are cryptically colored. The colouration is extremely variable, particularly in the ''A. rugosus'' group; colouration is less variable in the ''A. ischnosoma'' species group. Most have a light-brown saddle extending for the length of the adipose fin and some have spots on the side of the body in place of the saddle. Variation in colouration may be due to moulting of the skin. However, even though the colouration is highly variable, some general patterns are evident that allows colour to be a useful diagnostic character when variation is taken into account. In the ''A. ischnosoma'' species group, variation in colouration is restricted to the dorsal surface of the head, which ranges from light to chocolate brown. The body colouration is less variable. In ''A. ischnosoma'', a series of longitudinal chocolate brown patches arranged to form a faintly reticulate pattern is present in all specimens observed. ''A. guttatus'' is easily differentiated from other members of the ''A. ischnosoma'' group by a slender (vs. moderately thick) humeral process (maximum width 10.0–11.8% its length vs. 13.2–18.4). ''A. mahakamensis'' is differentiated from other members of its group by a rounded (vs. angular) anterior margin of the anal fin, and a more slender body. ''A. septentrionalis'' can be differentiated by members of the ''A. ischnoma'' group by a smaller dorsal to adipose distance (4.4–5.7% standard length vs. 6.2–9.8), fewer
branchiostegal rays This glossary of ichthyology is a list of definitions of terms and concepts used in ichthyology, the study of fishes. A B C ...
(4 vs. 5–6) and an almost uniformly cream colour pattern with few very small brown spots (vs. a variegated colour pattern with numerous brown patches). ''A. strigosus'' can be differentiated from members of the ''A. ischnosoma'' species group by a rounded (vs. angular) posterior margin of the adipose fin and a more slender body; the genital papilla in male ''A. strigosus'' is also morphologically different from other members of its species group (short and thick vs. long and thin). ''A. ischnosoma'' is distinguished from other members of the ''A. ischnosoma'' group by a greater distance between the dorsal fin and adipose fin (9.0–10.1% SL vs. 4.4–8.7) and a greater exposure of the premaxillary teeth when the mouth is closed (one-third vs. less than one-fifth to none). ''A. gyrinus'' can be distinguished from its congeners by a concave posterior margin of the pectoral fin. ''A. chamaeleon'' can be differentiated from other members of the ''A. rugosus'' species group by shorter nasal barbels (1.0–6.0% length of the head vs. 6.5–23.9), wide-set eyes (distance between eyes 38.9–47·5% length of the head), and a head with gently sloping lateral margins and a broadly rounded snout when viewed dorsally. ''A. falcifer'' can be differentiated from other members of the species group by an adipose fin with a rounded (vs. angular) posterior margin and a longer dorsal-fin base (10.8–13.1% standard length vs. 7.9–10.5); generally the colour pattern of ''A. falcifer'' is also different in having many small blotches (vs. few large blotches) of various shades of brown, with many small dark brown spots (vs. no spots) on the dorsal surfaces of the head. Both ''A. falcifer'' and ''A. pachyderma'' lack serrations on the pectoral spine, but the two species can be separated based on their colouration (cream with numerous small blotches of various shades of brown in ''A. falcifer'' vs. overall cream in ''A. pachyderma'') and the shape of the posterior margin of the adipose fin. ''A. pachyderma'' can be differentiated by its colouration (overall cream vs. generally dark brown with many irregular patches of light brown) and, except for ''A. falcifer'', lack (vs. presence) of serrations on the posterior edge of the pectoral spine. ''A. rugosus'' differs from ''A. chamaeleon'' in having longer nasal barbels (6.5–15.6% head length vs. 1.0–6.0) and a head with steeply sloping (vs. gentlysloping) lateral margins and a convex (vs. broadly rounded) snout when viewed dorsally; from ''A. falcifer'' in having an adipose fin with an angular (vs. rounded) posterior margin; from ''A. pachyderma'' in its colouration (generally dark brown with many irregular patches of light brown vs. overall cream) and the presence (vs. lack) of serrations on the posterior edge of the pectoral spine.


Species

* '' Acrochordonichthys chamaeleon'' ( Vaillant, 1902) * '' Acrochordonichthys falcifer'' Ng & Ng, 2001 * '' Acrochordonichthys guttatus'' Ng & Ng, 2001 * '' Acrochordonichthys gyrinus'' Vidthayanon & Ng, 2003 (Falcate chameleon catfish) * '' Acrochordonichthys ischnosoma''
Bleeker Bleeker is a Dutch occupational surname. Bleeker is an old spelling of ''(linnen)bleker'' ("linen bleacher").Acrochordonichthys mahakamensis'' Ng & Ng, 2001 * '' Acrochordonichthys pachyderma'' Vaillant, 1902 * ''
Acrochordonichthys rugosus ''Acrochordonichthys rugosus'' is a species of catfish of the family Akysidae. It inhabits clear, swiftly flowing forested streams of Thailand, Malaysia and Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southea ...
'' (
Bleeker Bleeker is a Dutch occupational surname. Bleeker is an old spelling of ''(linnen)bleker'' ("linen bleacher").Acrochordonichthys septentrionalis ''Acrochordonichthys septentrionalis'', the Maeklong chameleon catfish, is a species of catfish of the family Akysidae. A detailed discussion of this species's relationship with the other members of its genus can be found on ''Acrochordonichthys'' ...
'' Ng & Ng, 2001 (Maeklong chameleon catfish) * ''
Acrochordonichthys strigosus ''Acrochordonichthys strigosus'' is a species of catfish of the family Akysidae. It is a freshwater fish only known from the Kapuas River drainage in Kalimantan, in the Indonesian part of Borneo. It grows to standard length. A detailed discussi ...
'' Ng & Ng, 2001


Ecology

The axillary pore (or ''porus pectoralis'') lying just below the humeral process in ''Acrochordonichthys'' is unusually large, and produces a milky-white mucus-like secretion when the fish is severely disturbed. The exact function of this secretion is unknown, but it has ichthyocidal properties. This secretion may therefore be defensive in nature.


References

* {{Taxonbar, from=Q3763492 Akysidae Fish of Southeast Asia Fish of Thailand Fish of Indonesia Fish of Malaysia Catfish genera Taxa named by Pieter Bleeker Freshwater fish genera