A small new species of Crenicichla Heckel, 1840 from middle rio Xingu, Brazil (Teleostei: Cichlidae)

A new species of Crenicichla is described from the middle rio Xingu and tributaries, upstream from Volta Grande do Xingu. The largest specimen measured 47.8 mm SL. The new species can be distinguished from all other Crenicichla species by the combination of the following character states: presence of serrae on supracleithrum (diagnostic of Crenicichla wallacii species group), large caudal blotch centrally located on caudal lateral line (shared with C. urosema and C. virgatula), vertical dark stripes on the caudal fin and up to three series of teeth on premaxilla and maxilla (vs. more than four series of teeth). The new species described herein is the eleventh species of Crenicichla listed from the rio Xingu basin. Similarities of color pattern among small species of Crenicichla is discussed.


Introduction
Crenicichla Heckel, 1840 is currently recognized as the most species-rich among cichlids (Varella et al., 2012), with more than 85 valid species (Mattos et al., 2014), compared to 87 species of Apistogramma (Eschmeyer, 2015).Phylogenetic relationships within Crenicichla are still controversial.Based on a mitochondrial cytochrome b gene analysis, Kullander et al. (2010) reported the monophyly of some previously defined Crenicichla species groups that were recognized based on morphology.Kullander (1990) presented a discussion on small species of Crenicichla from the Amazon basin.He remarked that, besides length (≤ 75 mm SL), all Crenicichla species of reduced size should be grouped by the presence of serrations on the margin of the supracleithrum (vs.absence in other Crenicichla).Ploeg (1991) informally grouped these small species in the Crenicichla wallacii group.Currently, the C. wallacii group comprises the following species: C. wallacii Regan, 1905; C. notophthalmus Regan, 1913;C. compressiceps Ploeg, 1986; C. heckeli Ploeg, 1989;C. regani Ploeg, 1989; C. urosema Kullander, 1990;and C. virgatula Ploeg, 1991.The rio Xingu is a wide, clear water and fast-running river, stretching over large areas of rocks, and with its origins on the Brazilian Shield.During the dry season, large sandy beaches arise on the shores and clear water pools are easily seen.Kullander (1991) pointed out that many of the cichlids actually known to occur in the rio Xingu drainage actually also appear to occur in the rio Tocantins drainage.From the eleven valid species of Crenicichla registered for rio Xingu, three appear to be endemic.
Recent expeditions, some involved with the monitoring activities of the construction of the Belo Monte dam, a huge hydroelectic power facility in rio Xingu, yielded specimens of a new species being revised by the first author (PMI) as part of a larger revision of the C. wallacii group.This new species has been firstly noticed, but not formally named, by Kullander (1990Kullander ( , 1991)), who pointed out the similarities shared between some small specimens of Crenicichla with C. urosema and C. virgatula but with a divergent color pattern.In the present paper, we formally describe this new species and discuss the overall similarities between the small Crenicichla species from rio Xingu.Measurements, counts and color features were based on Kullander (1979Kullander ( , 1986Kullander ( , 1988)).Body measurements were taken point to point with a digital caliper with 0.1 mm of precision, summarized in Table 1, and presented as percentages of Standard Length (SL) (except for SL which is presented as absolute numbers).In the text, counts from the holotype are indicated by an asterisk (*).Color markings terminology follows Kullander (1986) and Kullander & Nijssen (1989).

All
For studies of internal anatomy, some specimens were cleared and double stained, following the protocol of Taylor & Van Dyke (1985).Vertebrae counts were made on digital x-ray images.
Upper jaw with two to four rows, lower jaw with three to four rows.All teeth pointed and slightly curved posteriorly.Outer row teeth larger than inner row teeth.

Vertebrae. 17+13=30(2), 17+14=31(3), 17+15=32(3), 18+14=31(1).
Color in life.Broad longitudinal band along midlateral line of body densely black from tip of snout to opercle, dark grey from this point to end of caudal peduncle.Nine short, dark, vertical and irregular bars, with uncolored areas inside, connected to large and broad longitudinal band.Dorsum and top of head dull yellow, abdomen light yellow.Pectoral and pelvic fins hyaline.Dorsal and anal fins light yellow.Dorsal fin, in females, with thin, distal greyish submarginal band, followed by reddish orange stripe below, stretching from 15th spine to third or sixth soft ray.Caudal fin largely hyaline, with greyish borders and with four to five dark vertical elongate blotches.Largest and most conspicuous caudal-fin blotch centrally on base of fin, followed by three to four less conspicuous bars.Middle caudal-fin rays yellowish.Diagonal white stripes dorsoposteriorly on caudal fin (Fig. 2).Color in alcohol.Similar to live specimens but without orange and yellow pigments (Fig. 1).

Sexual dimorphism.
Examined females presenting a color pattern different from males, as cited above on "Color in life" section (Fig. 2).Geographic distribution.All specimens were collected in middle rio Xingu and in rio Bacajá, upstream of Volta Grande do Xingu (Fig. 4).

Ecological notes. All specimens of Crenicichla anamiri
were collected during the dry season (Fig. 5) using seine or dip-nets, close to the shore or on sandy beaches next to roots of the riparian vegetation.Etymology.The name anamiri is a noun in apposition referring, in tupi-guarani, to the word "Anãmiri", meaning "dwarf", in allusion to the small size of the new species.
Remarks.The dark oval blotch on the middle of the base of the caudal fin is present only in three species of the C. wallacii group: Crenicichla urosema Kullander, 1990 (rio Tapajós drainage), C. virgatula Ploeg, 1991 (rio Branco drainage) and in C. anamiri (rio Xingu drainage).In the description of C. urosema, Kullander (1990) examined specimens of an undescribed species of rio Xingu (described herein as C. anamiri) and suggested that both species should be very close based on the presence of the midbasal caudal blotch.In another species, Crenicichla virgatula, the blotch on the caudal fin reaches from the sixth to the tenth ray and has an irregular elliptical shape, being round with a curved tail.In C. urosema, it extends from the fourth to the eleventh ray and it is larger.In C. anamiri, the caudal-fin blotch shows an intermediate position: it extends from the sixth to the eleventh caudal-fin ray and it is more centrally positioned on the fin, differently from C. virgatula and C. urosema, whose blotches are more dorsally concentrated (Fig. 6).
Conservation status.The ongoing discovery of new taxa from the rio Xingu points out to the importance, lack of knowledge and concerns about the future of the ichthyofauna of this river basin.Crenicichla anamiri, like many other fish species in the rio Xingu, is apparently dependent of roots of trees on sandy beaches, and its area of occurrence includes Volta Grande do Xingu, one of the sites that is going to be largely affected by the construction of Belo Monte dam.This is a major hydroelectric power facility, almost completed, that will deviate the main course of the river towards a large reservoir.Considering the sample sites recorded for the species, C. anamiri would be classified as a NT (Nearly Threatened) species, according to the IUCN (International Union for Conservation of Nature) categories and criteria (IUCN Standards and Petitions Subcommittee, 2014).The estimated extent of occurrence (EOO) was 12,064.326km² (to be considered in the vulnerable category -VU, it would need to fall into the B1 criterion < 20,000 km²).The estimated area of occupancy (AOO) was 3,958.125 km² (to be considered VU, it would need to reach the criterion B2 < 2,000 km²).In both cases, EOO and AOO fall short to a threatened category.Even with the Belo Monte dam, it seems that C. anamiri will not be strongly affected as other species that are heavily dependent on fast waters and rocky substrates.Besides, C. anamiri is registered to occur in the National Park (PARNA) of Serra do Pardo, a protected area located away from Belo Monte influence.Additional collecting efforts would certainly provide more information about the biology and resilience of this species.

Fig. 4 .
Fig. 4. Map of Northern Brazil and part of rio Xingu drainage showing collecting sites of Crenicichla anamiri.Some dots may represent more than one lot (star = holotype).
4.0% SL on C. anamiri); four series of scales between the upper and lower lateral line on C. urosema, three series on C. virgatula and C. anamiri; upper/lower lateral line scales with 23/9 on C. virgatula; 22/9 on C. urosema and 21/8 on C. anamiri.

Fig. 5 .
Fig. 5. Type locality of Crenicichla anamiri on the beach on rio Xingu, Itapuama, below the confluence between rio Xingu and rio Iriri, with roots of marginal trees.Photo taken during the Xingu expedition in the dry season (November 2014).
Xingu basin, rio Xingu below confluence with rio Iriri at beach margin with tree roots, 03°36'31"S 52°20'58"W, 04 Nov 2014, K. Winemiller.Distinguished from all other species of Crenicichla except C. notophthalmus, C. regani, C. urosema, and C. virgatula by the presence of serrations on supracleithrum (vs.absent).Distinguished from C. notophthalmus and C. regani by the presence of a black vertical elliptic blotch centrally positioned at caudal-fin base (vs.presence of ocellated blotch dorsally on caudalfin base).Distinguished from C. regani, C. urosema and C. virgatula by the presence of two to four rows of teeth in both jaws (vs.more than four rows); from C. virgatula and C. urosema also by the presence of vertical bars on the caudal fin (vs.absence).

Table 1 .
Morphometric data of Crenicichla anamiri sepatared for the holotype and remaining specimens examined.SD = Standard deviation; n = number of specimens.