New mullet described

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Scientists from the USA, Venezuela and Brazil have described a new species of mullet from the coastal waters of Venezuela.

The new species is named Mugil rubrioculus in a paper by Ian Harrison, Mauro Nirchio, Claudio Oliveira, Ernesto Ron and Juan Gaviria published in the latest issue of the Journal of Fish Biology.

Mugil rubrioculus is easily distinguished from other mullet species found in the Western Central Atlantic in having a red eye in life (the specific name comes from the Latin ruber, meaning red, and oculus, meaning eye), and was previously identified as M. gaimardianus.

However, the original description of M. gaimardianus is not detailed enough to permit exact determination of which Western Central Atlantic mullet species the name should be used for.

For this reason, many specimens in museums identified as M. gaimardianus have turned out to be misidentifications of other mullet species found in the region, frequently M. curema.

Because of the confusion surrounding the name M. gaimardianus, a successful application to suppress the name was made to the International Commission on Zoological Nomenclature.

Besides the red eye, M. rubrioculus can be distinguished from other mullet species in the region by the combination of the presence of three spines and nine soft rays in the anal fins of adults, 15"16 pectoral-fin rays, less than 43 scales in the longitudinal series, depth of body at anal-fin base 23.8"25.5 %SL and pectoral-fin length 17.3"18.9% SL.

Mugil rubrioculus is very similar to M. curema, but has a smaller goldish opercular spot, paler pigmentation on the flanks without longitudinal bands, paler anal fin, smaller spot at the base of the pectoral fin, the anterordorsal tip of the second dorsal fin darker than the rest of the fin, and a different chromosome structure (all acrocentric chromosomes vs. metacentric and either submetacentric or subtelocentric+acrocentric chromosomes).

The study also revealed the presence of two slightly different morphotypes of M. rubrioculus: a wide-jawed form with a thinner body, longer anal-fin base, usually a longer snout and sometimes a shallower caudal peduncle and a narrow-jawed form.

However, these differences are not significant and the two morphotypes are considered to be the same species.

In addition, a small number of specimens from Panama very similar to M. rubrioculus have slightly longer pectoral fins, more scales in the longitudinal series, longer head and a thinner body.

Pending a more detailed study to determine their status, these are identified as M. aff. rubrioculus.

For more information, see the paper: Harrison, IJ, M Nirchio, C Oliveira, E Ron and J Gaviria (2007) A new species of mullet (Teleostei: Mugilidae) from Venezuela, with a discussion on the taxonomy of Mugil gaimardianus. Journal of Fish Biology 71(a), 76"97.