Krobia xinguensis, Kullander, Sven O., 2012

Kullander, Sven O., 2012, Krobia xinguensis, a new species of cichlid fish from the Xingu River drainage in Brazil (Teleostei: Cichlidae), Zootaxa 3197, pp. 43-54 : 45-50

Krobia xinguensis , new species

Figs. 1–9 , Tables 3–4

Holotype. INPA 35653. Adult male, 74.4 mm SL. Brazil, State of Pará, Ilha de Babaquara, rio Xingu, 03°12’43’’S, 52°12’12’’W. 5 Oct 1990. L. Rapp Py-Daniel & J. Zuanon ( Fig. 1 ).

Paratypes: All from Brazil, rio Xingu drainage. BMNH 1985.6.20: 1223–1242 pt. 1, 40.1 mm SL. Mato Grosso, córrego do Gato. 22 Apr 1968. R.H. Lowe-McConnell. — INPA 4219. 16, 35.3–77.2 mm SL; NRM 61781. 3, 45.5–84.6 mm SL. Collected with holotype. — IRSNB 877. 1, 67.7 mm SL. Mato Grosso, laguna at margin of rio Tuatuari upstream of Posto Leonardo Vilas-Boas. 12 Oct 1964. J.-P. Gosse & Léopold III. — IRSNB 878. 1, 47.1 mm SL. Mato Grosso, igarapé of Lago Yamarikumao, at Suiá village on rio Suiá-Missu. 3 Nov 1964. J.-P. Gosse & Léopold III. — IRSNB 879. 10, 38.6–60.5 mm SL. Mato Grosso, small igarapé tributary to Lago Upavi, Kamaiurá village, Posto Leonardo Vilas-Boas. 19 Oct 1964. J.-P. Gosse & Léopold III. — IRSNB 880. 1, 86.0 mm SL. Mato Grosso, laguna and inundated forest on right bank of rio Xingu upstream of Posto Diauarum. 15 Nov 1964. J.-P. Gosse & Léopold III. — USNM 235640. 2, 80.6–82.9 mm SL; USNM 329625. 1, 50.8 mm SL. Mato Grosso, small tributary of rio Batovi. Sep 1964. H. Schultz.

Non-types: NRM 60938–60939, 2, 65.8–76.1 mm SL. Aquarium specimens. E. Åhlander, 23 Jul 2010.

Diagnosis. Distinguished from other species of Krobia by slightly deeper caudal peduncle (17.6–19.6% SL, vs. 15.6–17.4 % in K. itanyi ), dark lateral band reaching to end of dorsal-fin base (vs. ending well before in K. itanyi ) ( Figs. 1–2 ), two prominent dark interorbital stripes (vs. faint or obsolete in K. itanyi , absent in K. guianensis ) ( Fig. 3), slightly curved suborbital stripe (vs. straight); presence of dark brown spot anterolaterally on each side of the lower jaw (vs. absence).

Description. General aspect and colour pattern is illustrated in Figs. 1–3 . Measurement data are summarised in Table 3 . Sexes are very similar, with slightly shorter soft dorsal and soft anal fins, and pelvic fin in females.

Body deep and high, ovoid in profile. Head and snout short. Head and anterior half of trunk broad; trunk above anal-fin base and caudal peduncle strongly compressed. Predorsal contour steep, curved above orbits; spinous dorsal-fin base straight or slightly curved, soft dorsal-fin base strongly recurved. Predorsal contour commonly slightly steeper than prepelvic contour which may be straight or slightly curved. Orbit large, diameter greater than snout length, greater part in anterior half of head and slightly removed from interorbital contour. Mouth small; jaws isognathous; maxilla reaching to or almost to vertical from anterior margin of orbit; lower jaw articulation below middle of orbit. Lips thin, lower lip fold broadly interrupted symphysially. Caudal peduncle notably short and deep, incorporating last half centrum or last halfcentrum and part or all of preceding vertebra.

Jaw teeth similar in upper and lower jaw. Outer row of mostly blunt-tipped unicuspid, subcaniniform, erect, straight or slightly recurved, fixed or slightly movable, slightly increasing in size from posterior to symphyseal; symphyseal teeth about 0.6 mm long in large specimens. Teeth in upper jaw left outer hemiseries 14–21, in lower jaw left outer hemiseries 14–20. Several (2–5, commonly 3) irregular rows of much smaller inner teeth in a band, short, slender, subcaniniform, slightly recumbent, straight or slightly recurved, slightly depressible, of about uniform size, or innermost slightly smaller.

Lower pharyngeal tooth plate ( Fig. 4) short and wide (length 75% of width of tooth plate). Dentigerous area length 56 % of width of dentigerous area. Teeth in posterior row 19, along midline 6 or 7. Marginal teeth compressed, central and posteromedian teeth coarser; anterior pair with retrorse major cusp, remainder bicuspid with antrorse pointed posterior cusp and lower anterior bulge, except central teeth considerably worn, some with rounded tip. Marginal teeth short, teeth gradually longer caudad and mediad. Gill rakers short, well spaced, externally on first gill arch one epibranchial, one in angle, and 4 (17), 5 (5), 6 (1) ceratobranchial. Ceratohyal with a distinct lateral furrow for the hyoid artery; anterior ceratohyal posteriorly with a short indentation in the dorsal margin, immediately lateral to a short elevation from the lateral face. Supraneurals 2 (15). Vertebrae 12+13 (14), 13+13 (1).

Scales in E1 row 22 (5), 23 (18). Scales cycloid on cheek and gill cover. Predorsal and prepelvic scales cycloid or with a few marginal cteni. Cheek scales in three rows. Preopercular scales absent. Flank scales with narrow marginal band of cteni. Predorsal scales about as large as flank scales. Prepelvic scales slightly smaller than flank scales. Two horizontal rows of scales passing between pectoral and pelvic fins. Predorsal squamation anteriorly with a scale on each side of coronalis pore, followed by midline row of usually seven scales with slightly convex, truncate, or slightly concave posterior margin. Scales flanking first dorsal-fin spine may overlap anterior to the spine, or a small midline scale may be present immediately anterior to first dorsal-fin spine, commonly concealed by larger predorsal midline scale. Circumpeduncular scale rows 16 (7 above, 7 below lateral lines). Lateral lines separated by two horizontal scale rows. Lateral line scales 14/6 (2), 14/7 (1), 14/8 (2), 15/5 (1), 15/6 (1), 15/7 (1), 15/8 (8), 15/9 (1), 16/7 (5), 16/8 (1). One or two scales continuing lower lateral line on caudal-fin base. One canalbearing scale present basally on dorsal lobe in three specimens, positioned between rays D2-3 (1) or D3-4 (2); one or two canal-bearing scales present basally on ventral lobe in six specimens, between rays V3–4 (1) or V4–5 (5). Scales between upper lateral line and dorsal-fin base 3 anteriorly, 1 (occasionally 1.5) posteriorly. Usually 4–5 small scales along base of soft dorsal fin. Caudal fin with small scales proximally, covering approximately 1/3 of fin length.

Dorsal-fin rays XIV.8 (1), XIV.9 (14), XIV.10 (7), XIV.11 (1). First dorsal-fin spine short, spines increasing in length to fourth after which subequal in length, last two slightly longer. Soft dorsal fin pointed, fourth and fifth rays longest, reaching to middle or end of caudal fin. Anal-fin rays III.7 (1), III.8 (21). Soft anal fin similar to opposite dorsal fin, but reaching at most to 2/3 of caudal fin. Pectoral-fin rays 12 (6), 13 (16), 14 (1). Pectoral fin pointed, fourth ray longest, reaching to vertical from first or second anal-fin spine. Pelvic fin pointed, first ray longest, reaching to third anal fin spine or at most to base of third soft anal-fin ray. Caudal-fin rays ii. i7 + 8i. iii (2), iii. i7 + 7i. iii (12). Caudal fin rounded.

Colour pattern in preservative. Ground colour whitish, pale greyish or pale brownish yellow, depending on preservation. Seven faint vertical bars, as counted from the posteriormost rostrad: (1) Bar 1 across caudal peduncle, (2) Bar 2 between ends of dorsal- and anal-fin bases, (3) Bar 3 between dorsal and anal fins above middle of analfin base, (4) Bars 4+5 between dorsal and anal fins above spinous anal fin, (5) Bar 6 across side above posterior part of abdomen, (6) Bar 7 from dorsum down to middle of side, below dorsal-fin spines 3-4 usually indistinctly delimited, (7) Bar 8 a broad blotch around beginning of dorsal fin and top of head. Dark brown lateral band starting from posterior margin of orbit, forming elongate blotch where crossing Bar 7, and continued usually with constrictions between bars and expansions where crossing bars, ending at end of dorsal-fin base. Bar 6 including a dark brown or blackish blotch, approximately round, about 1½ scale deep and 3 scales long; incorporated in lateral band, but more prominent than rest of band. Dark brown suborbital stripe from lower margin of orbit, slightly curved across cheek, ending ventrally on preopercle. Suborbital stripe may be faded on middle producing dark blotch below orbit and another on preopercle. Dark brown preorbital stripe from anteroventral margin of orbit across tip of snout. Two dark brown bands between opposite side orbits. Lower jaw anterolaterally on each side with dark brown blotch close to lower lip ( Fig. 3). Lower sides with indistinct pattern of parallel light and dark horizontal stripes formed by slightly darker overlapping parts of scales and lighter scale centres. Dorsal fin pale brownish, posterior interradial membranes lighter, with several rows of dark spots. Dorsal-fin lappets dark brown with hyaline distal margin. Anal fin pale brownish, posterior interradial membranes lighter, with several rows of dark spots. Caudal fin pale brownish or hyaline, with indistinct pattern of rows of small dark spots dorsally or across all of fin. Over most of base of dorsal lobe of caudal fin a round or vertically oval dark brown blotch, margined by narrow whitish ring. Pelvic fin only slightly pigmented, outer rays brownish.

Live coloration ( Fig. 5). Considerable information on live colours of Krobia xinguensis is available from images in ornamental fish literature (e.g., Stawikowski, 2007). The major difference from preserved specimens consists in the rich orange to red or orange markings. Upper lip, lachrymal, part of cheek, anterior and posterior margins of opercle, and pectoral axilla red or orange. Bases of most flank scales marked with short red or orange vertical stripe.

Comparative morphometrics. In a comparison with Krobia guianensis and K. itanyi ( Tables 1–2 ), K. xinguensis is distinguished by proportionally deeper caudal peduncle ( Fig. 6 ), and averaging slightly deeper body ( Fig. 7 ), shorter snout, and shorter caudal peduncle ( Tables 1–3 ). The principal component analysis separates K. xinguensis mainly by caudal peduncle distances and body depth ( Table 4 , Fig. 8 ).

Distribution. Known only from the Xingu river drainage, with several localities in headwaters in Mato Grosso and the type locality at the Ilha Babaquara, close to Altamira ( Fig. 9 ). No detailed habitat information has been available for the samples included in the type series. Lowe-McConnell (1991) reported Krobia xinguensis as “Nov. gen. spec. cf. Aequidens guianensis ” from the córrego do Gato in the Suiá-Missu drainage, a clear water habitat including a stream, a pool, and a small lake, with abundant vegetation and aquatic invertebrates. It is the type locality of Crenicichla rosemariae Kullander (1997) . A small rocky stream at São Felix on the middle rio Xingu was figured by Stawikowski (2007) as habitat of K. xinguensis .

Etymology. The specific name xinguensis is an adjective referring to the river basin inhabited by the species.

Figures

FIGURE 1. Krobia xinguensis, INPA 35653. Holotype, adult male, 74.4 mm SL. Brazil, State of Pará, Ilha de Babaquara, rio Xingu.

FIGURE 6. Comparative morphometrics of species of Krobia. Caudal peduncle depth plotted against Standard Length.

FIGURE 7. Comparative morphometrics of species of Krobia. Body depth plotted against Standard Length.

FIGURE 8. Comparative morphometrics of species of Krobia. Plot of scores of sheared principal component II against sheared principal component III, based on distance data.

FIGURE 9. Collecting sites of Krobia xinguensis.

Tables

TABLE 3. Standard length (in millimeters) and proportional measurements in percents of standard length of Krobia xinguensis. SD, standard deviation. Holotype (INPA 35653) data given separately (HT), as well as included in pooled data. Regression line parameters, a (intercept), b (slope), and r (Pearson’s correlation coefficient) are calculated from measurements expressed in millimeters.

	n	HT	Min	Max	Mean	SD	a	b	r
Standard length (mm)	22	74.4	38.6	84.6	59.2	14.2
Head length	22	24.7	33.2	36.8	34.6	1.0	1.349	0.322	0.996
Snout length	22	5.3	6.3	9.2	7.6	0.7	-1.055	0.095	0.972
Body depth	22	37.1	45.2	53.3	48.6	2.4	-4.992	0.575	0.994
Orbit diameter	22	10.1	12.6	16.0	14.1	1.0	2.115	0.103	0.979
Head width	22	15.7	18.5	21.7	20.2	0.8	-1.024	0.220	0.991
Interorbital width	22	9.9	9.7	14.1	11.8	1.3	-2.444	0.162	0.970
Preorbital depth	22	5.0	4.2	7.6	6.0	1.1	-2.376	0.102	0.980
Caudal peduncle depth	22	14.1	17.6	19.6	18.9	0.6	-0.772	0.203	0.995
Caudal peduncle length	22	7.6	9.1	11.7	10.4	0.8	0.236	0.100	0.952
Pectoral-fin length	22	27.9	32.4	40.3	36.1	2.2	-3.188	0.417	0.980
Pelvic-fin length	22	29.3	29.3	44.4	35.7	3.5	-6.902	0.479	0.975
Last dorsal-fin spine length	22	14.4	16.5	21.6	18.9	1.2	-2.243	0.229	0.982