Three new species of Panaque described

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Three new species of the large wood-eating plecs in the genus Panaque have been described.

The revision of the Panaque nigrolineatus group by ichthyologists Nathan Lujan, Max Hidalgo and Donald Stewart is published in the most recent issue of the journal Copeia, and recognises three valid species: P. cochliodon, P. nigrolineatus and P. suttonorum, as well as describing P. armbrusteri, P. schaeferi and P. titan as new species.

Panaque armbrusteri (pictured above)
This is the species known in the aquarium trade as the Tapajos or Golden line royal plec, or more simply as L27b. 

It is distinguished from the other members of the P. nigrolineatus group in the adults having a larger angle between the left and right tooth rows on the upper and lower jaws (typically greater than 100°); more teeth at equivalent body sizes; from all but P. suttonorum in having the pelvic-fin spine terminating between the anterior and posterior insertions of the anal fin when pressed against the body (vs. terminating at or beyond the posterior insertion of the anal fin); from all but P. titan by having the dorsal half of the sixth infraorbital strongly flared laterally (vs. sixth infraorbital vertical and straight or only slightly flared laterally at its dorsalmost margin); from all but P. cochliodon in having the supraoccipital raised as a hump (vs. smoothly rounded); from P. nigrolineatus, P. schaeferi, and P. titan in having the pectoral-fin spine terminating between pelvic-fin insertion and anus when pressed against the ventral surface of the body (vs. pectoral-fin spine terminating around the anus); from P. cochliodon, P. nigrolineatus, and P. suttonorum by adults having a truncate (vs. lunate or forked) caudal fin; from P. cochliodon, P. suttonorum, and P. schaeferi by having a colour pattern consisting of alternating dark brown to black and light brown to grey longitudinal stripes (vs. body uniformly dark grey to black or pale grey to brown with dark or faded black spots); from P. cochliodon and P. suttonorum in having red to brown (vs. blue or bluish) eyes, and in juveniles up to approximately 11 cm standard length having a hyaline anterior caudal-fin window (vs. uniformly opaque); from P. nigrolineatus in having dark longitudinal body stripes frequently wider (vs. frequently narrower) than light stripes; from P. schaeferi in reaching a maximum size of approximately 35 cm (vs. 60 cm) standard length; and from P. titan in having the postorbital pterotic region being flush with (vs. bulging beyond) the ventral pterotic margin.

Named for loricariid expert Jonathan Armbruster, P. armbrusteri is known only from the Tapajós River drainage, although the authors state that some very similar forms from the Xingú, Tocantins, and Araguaia rivers to the east may also belong to this species.

Panaque schaeferi
This species is known in the aquarium trade as the Titanic plec (not to be confused with P. titan), L203, or L65, and is named after American ichthyologist Scott Schaefer.

It is distinguished from the other members of the P. nigrolineatus group in having black spots distributed evenly on a pale grey to brown body (vs. body uniformly dark grey to brown or with alternating dark and light grey, brown, or black longitudinal stripes), and in reaching to a maximum size of approximately 60 cm standard length (vs. no greater than approximately 40 cm); from all but P. nigrolineatus in having the pelvic-fin spine terminating at (vs. anterior or posterior to) the posterior insertion of anal fin; from P. armbrusteri, P. cochliodon, and P. suttonorum in having the pectoral-fin spine terminating around the anus (vs. approximately halfway between the pelvic-fin base and the anus); from P. cochliodon and P. suttonorum by having brown to grey (vs. blue or bluish) eyes, and in juveniles up to approximately 13 cm standard length having a hyaline, anterior caudal-fin window (vs. uniformly opaque); from P. armbrusteri and P. cochliodon in having a smoothly rounded supraoccipital (vs. raised as a hump, Fig. 5); from P. armbrusteri and P. titan in having the sixth infraorbital vertical and straight (vs. its dorsal strongly flared laterally); from P. cochliodon in having the enlarged odontodes on the trunk plates arranged in rows (vs. as a cluster); from P. armbrusteri by having fewer teeth at equivalent body sizes and a smaller angle between the left and right tooth rows; and from P. titan in having a postorbital pterotic region flush with (vs. bulging beyond) the ventral pterotic margin.

Panaque schaeferi is widespread in the main river channels of the Upper Amazon, where it appears to be restricted to white- and clearwater rivers.

Panaque titan
This species is known in the aquarium trade as the Gold trim or Shampupa plec, or more simply as L418.

It is distinguished from the other members of the P. nigrolineatus group in having the postorbital region of the pterotic bulged beyond (vs. flush with) the ventral pterotic region; from all but P. armbrusteri in having a strongly flared (vs. straight or slightly flared) dorsal half of the sixth infraorbital, and a truncate (vs. lunate or forked) caudal fin in adults; from P. armbrusteri, P. cochliodon, and P. suttonorum in having the pectoral-fin spine terminating around the anus (vs. between the posteriormost pelvic-fin insertion and the anus) when pressed ventral to the pelvic fin; from P. cochliodon, P. nigrolineatus, and P. suttonorum in reaching about 40 cm (vs. no larger than 30 cm) standard length; from P. cochliodon, P. schaeferi, and P. suttonorum by having a colour pattern of irregular and widely spaced dark grey to brown stripes and spots on a light brown to tan body (vs. uniformly dark gray to black or with black spots on a pale grey to brown body); from P. armbrusteri and P. cochliodon in having a smoothly rounded supraoccipital (vs. raised as a hump); from P. cochliodon and P. suttonorum by juveniles up to approximately 14.5 cm standard length having a hyaline, anterior caudal-fin window (vs. uniformly opaque), and in having brown (vs. blue or bluish) eyes; from P. cochliodon in having the enlarged odontodes on the trunk plates arranged in rows (vs. as a cluster); and from P. armbrusteri by having fewer teeth at equivalent body sizes and a smaller angle between the left and right tooth rows.

This species is only known from the Napo River drainage in Ecuador, where it inhabits deep, fast-flowing rivers.

For more information, see the paper: Lujan, NK, M Hidalgo and DJ Stewart (2010) Revision of Panaque (Panaque), with descriptions of three new species from the Amazon Basin (Siluriformes, Loricariidae). Copeia 2010, pp. 676–704.