Krobia petitella, Steele, Sarah E., Liverpool, Elford & López-Fernández, Hernán, 2013

Steele, Sarah E., Liverpool, Elford & López-Fernández, Hernán, 2013, Krobia petitella, a new species of cichlid fish from the Berbice River in Guyana (Teleostei: Cichlidae), Zootaxa 3693 (2), pp. 152-162 : 154-159

Krobia petitella , new species

Figs. 2–5, Table 1

Holotype. UG/CSBD 1662 (Ex ROM 86851). 80.1 mm SL. Guyana: East Berbice River: Just upstream of Kwakwani, 5o 14’ 57.8” N; 58o 5’ 11.5” W. 0 1 April 2010 (Fig. 2). D. Bloom, D. Taphorn, E. Holm and F. Gonzales.

Paratypes: All specimens from Guyana, Berbice River drainage. ROM 86793. 1, 39 mm SL; Guyana: East Berbice River: Marlissa Falls in rapids (4o 54’ 24.5” N; 58o 14’ 41” W); D. Taphorn, D. Bloom, J. Maldonado and E. Holm, 24 March 2010.—ROM 86851. 6, 58– 86 mm SL. Collected with holotype; Guyana: East Berbice River: Just upstream of Kwakwani (5o 14’ 57.8” N; 58o 5’ 11.5” W); D. Bloom, D. Taphorn, E. Holm and F. Gonzales, 0 1 April 2010.—ROM 87070. 2, 27– 34 mm SL; Guyana: East Berbice River: Ituni Creek and Berbice River: Mouth of Ituni Creek and its surroundings on the Berbice River (5o 31’ 14.6” N; 57o 55’ 33.1”W); H. Lόpez-Fernández, L. Wilson, J. Maldonado, C. Bernard and H. Gonzales, 31 March 2010.—ROM 87097. 1, 66.2 mm SL; Guyana: East Berbice River: About 14 air km upstream of Kwakwani at Mappa Lagoon camp (5o 10’ 28.4” N; 58o 9’ 48.1”W); H. Lόpez-Fernández, D. Taphorn, D. Bloom, J. Maldonado, C. Bernard, and E. Holm, 20 March 2010.—ROM 87193. 1, 36 mm SL; Guyana: East Berbice River: Side channel with sandy beach and emerging boulders, left bank forest (4o 54’ 33.8” N; 58o 14’ 25.6” W); H. Lόpez-Fernández, C. Bernard, J. Maldonado, L. Wilson, 25 March 2010.—ROM 88525. 22, 16– 61 mm SL; Guyana: East Berbice River: 1km downstream of Cat Creek (4o 57’ 56.1” N; 58o 14’ 35.6” W); D. Bloom, D. Taphorn, C. Bernard, H. Lόpez-Fernández, J. Maldonado, L. Wilson and R. Vandenburg, 27 March 2010.—ROM 88574. 3, 70– 102 mm SL; Guyana: East Berbice River: Downstream of Marlissa Falls (4o 54’ 39.2” N; 58o 14’ 16.7” W); D. Taphorn, D. Bloom, E. Holm, J. Maldonado and R. Vandenburg, 25 March 2010.—ROM 88616. 3, 28– 44 mm SL; Guyana: East Berbice River: Side channel (left side looking downstream) by island (5o 9’ 3.9” N; 58o 11’ 46.2”); C. Bernard, J. Maldonado and E. Holm, 28 March 2010.—ROM 88658. 1, 34 mm SL; Guyana: East Berbice River: Side channel with sandy beaches and emerging boulders, left bank forest (4o 54’ 33.8” N; 58o 14’ 25.6” W); H. Lόpez-Fernández, C. Bernard, J. Maldonado, D. Bloom, D. Taphorn, F. Gonzales and E. Holm, 26 March 2010.

FIGURE 2. Krobia petitella n. sp., UG/CSBD 1662. Holotype, 80.1 mm SL. Guyana, Berbice, just upstream of Kwakwani, 5o 14’ 57.8” N; 58o 5’ 11.5” W, 0 1 April 2010.

Diagnosis. Krobia petitella n. sp. can be distinguished from described Krobia species by tubed scales of the upper lateral line extending caudally into a line bisecting the lateral band blotches posterior to the mid-lateral spot (vs. ULL tubed scales lying dorsal to lateral band). Krobia petitella n. sp. can be further diagnosed by the anterior lateral band spots lying immediately ventral to the upper lateral line, instead of being separated from the upper lateral line by a complete row of scales in all other described species. Krobia petitella n. sp. also has a unique combination of six distinct vertical bars and four lateral band spots (vs. K. itanyi 5 bars/3 or 4 spots, K. guianensis 5/5, K. xinguensis 7/6, ‘ Aequidens’ potaroensis 6/6, ‘ A’. paloemeuensis 5/5). Krobia petitella n. sp. is further distinguished from K. guianensis and K. itanyi and from ‘Aequidens’ potaroensis and ‘A.’ paloemeuensis by separation of the caudal spot on the dorsal caudal fin lobe from the lower lateral line by one scale length (vs. no separation). Krobia petitella n. sp. can be distinguished from K. guianensis , ‘Aequidens’ potaroensis and ‘A.’ paloemeuensis by lacking a lateral band spot in bar 2 (vs. spot in bar 2 in K. guianensis , ‘A. potaroensis’ and ‘A. paloemeuensis’). Krobia petitella n. sp. can be distinguished from K. guianensis by the presence of two distinct interorbital stripes and a prominent preorbital stripe (vs. absence of interorbital and preorbital stripes). Krobia petitella n. sp. can be further distinguished from K. guianensis by a significantly longer snout and longer fins on average. Krobia petitella n. sp. can be further distinguished from K. itanyi by having the lateral band extending to the posterior base of the dorsal fin (vs. ending well before the base of the dorsal fin). Krobia petitella n. sp. can be further distinguished from K. xinguensis by lacking anterolateral spots on the lower jaw and a lateral band blotch located in the second vertical bar as seen in K. xinguensis (spot in bar 2 also occurs in K. guianensis ) in addition to having a longer snout and shallower body than K. xinguensis on average. Krobia petitella n. sp. is distinguished from ‘Aequidens’ potaroensis and ‘A.’ paloemeuensis by lacking lateral band spots on the caudal peduncle. Krobia petitella n. sp. can further be distinguished from ‘ A.’ potaroensis by having a significantly deeper head, body and caudal peduncle as well as longer fins on average.

Description. General aspect and colour pattern illustrated in Figs. 2–3, measurement data summarized in Table 1 .

Body moderately elongate and ovoid in lateral profile. Dorsal head contour straight or slightly convex on snout then convex dorsally to orbit. Predorsal contour slightly convex, slope shallower than head contour. Contour of spinous dorsal fin slightly convex, descending from first dorsal spine with increase in convex curvature from 12th spine, slope increases strongly at soft dorsal fin base toward caudal peduncle. Ventral head contour straight or slightly concave below jaws, shallower slope than dorsal surface. Chest convex in lateral profile. Contour between pelvic fin origin and first anal spine slightly convex, ascending to caudal peduncle, with contour curving strongly dorsally toward caudal peduncle at soft anal fin base. Head and snout short, lower jaw reaching or almost reaching vertical of anterior margin of orbit. Mouth subterminal, narrower than interorbital width; lips thin, discontinuous lower lip fold symphysially. Orbit slightly larger than one-third of head length, just inferior to predorsal contour in approximate middle of head length.

Scales: Scales in E1 row 23(15), 24(11). Five rows of scales between lower lateral line (LLL) and base of anal fin. Three scale rows between upper lateral line (ULL) and dorsal fin origin, three scale rows between ULL and dorsal fin base, occasionally additional row of small scales at base of dorsal fin.

Opercle, subopercle, interopercle and cheek fully scaled, cycloid. Postorbital region with one, occasionally two, columns of cycloid scales, equal in size to dorsal scales. Dorsal scales mildly ctenoid. Small, imbricated ctenoid scales on lateral chest, belly, and anal-genital region, gradually transitioning to larger flank scales; flank scales ovoid. Ventral chest fully scaled, imbricated, cycloid. Single row of large scales posterior to isthmus, flanked by two adjacent rows of smaller scales on either side; transitioning abruptly to larger lateral chest scales; large interpelvic scale present between pelvic fin insertions.

Upper and lower lateral line separated by two rows of scales. Lateral line scales 15/8(4), 15/9(5), 16/8(13), 16/ 9(4). Lower lateral line extends anteriorly to last anal spine. Tubed scales of ULL and LLL overlapping two on left (7) and one (3) or two on right side (3). Two tubed scales on caudal fin base (10 of 14 specimens examined). Short (1-2 scales) accessory lateral line extensions on caudal fin between D3-D4(1) or D4-D5(1) and V3-V4 (1) or V4- V5 (3).

Fin scales: pectoral and pelvic fins naked. Anal and dorsal fins variable: naked (3), two uniserial interradial scale series on soft dorsal fin base (3), two uniserial interradial scale series on soft dorsal fin base and soft anal fin base (1). Anterior third of caudal fin scaled, single series of minute cycloid scales on interradial membranes; scales in three anterior series much larger than posterior series.

Fins: Dorsal XII.11 (1), XIII.9(1), XIII.10(1), XIV.7(1), XIV.9(6), XIV.10(16); first and second dorsal-fin spines anterior to vertical of opercle margin in specimens <66.3 mm SL, at vertical in specimens> 74.8 mm SL, including holotype; first dorsal spine length 1/3-3/4 of last; fourth soft dorsal-fin ray longest, extending to 1/3-3/5 of length of caudal fin, reaching to end of caudal fin in one specimen (79.5 mm SL). Anal-fin III.7 (2), III.8 (24); fourth soft anal-fin ray longest, extending at most to 2/3 of caudal fin, in most specimens ending before midline. Pelvic fin pointed, first ray longest extending to AI-A5, generally between AIII-A2 (18 of 26 specimens).

Jaw teeth: Anterior row with larger and stronger teeth, inner series small with irregular placement in about 4 or 5 series. Teeth blunt-tipped, thin, unicuspid. Teeth slightly larger medially in outer and inner series. Dentary 18– 21 left, 10–23 right, no gap between outer and inner series; premaxilla 11–14 left, 14–16 right, no symphysial separation, clear gap between outer and inner series.

Gill rakers: 5 or 6 externally on first ceratobranchial, widely spaced.

Lower pharyngeal jaw plate: short and wide, length about 75% of width ( Fig. 4 ). Teeth in posterior row 21, along midline 6 or 7.

Vertebrae: 12+13=25 (9), 12+12=24 (1)

Colouration in preservative. Ground colour and opercle greyish brown dorsally, ventral surfaces pale brownish to yellow. Six faint vertical bars ( Fig. 3 a) observed in preserved specimens: (1) across posterior margin of caudal peduncle, typically originating anteriorly at middle of caudal peduncle and extending to posterior edges of last series of body scales; (2) between posterior base of dorsal and anal fins, originating approximately below D7, extending posteriorly to midline of caudal peduncle; bars 1 and 2 often intercept at lower lateral line and are only distinct at dorsal and ventral margins of peduncle, bars not distinguishable and entire caudal peduncle appears dark in some specimens; (3) between first three or four soft rays of dorsal and anal fin, (4) between posterior three dorsal spines and spinous anal fin; (5) from midline to area just anterior to base of AI; (6) between anterior spinous dorsal fin and base of pelvic fin, curving slightly posteriorly around pectoral fin base; distinct from bar 5. Lateral band spots ( Fig. 3 a): (1) within bar 6 below the upper lateral line; (2) mid-lateral spot within bar 5, often darker than adjacent spots, 3–4 scales wide, extending from E1 to just below ULL, occasionally from E1 to scale row above ULL; (3) within bar 4; (4) within bar 3. Third spot commonly distinct from adjacent markings, posterior and slightly dorsal to mid-lateral spot, extending to dorsal margin of scales containing ULL (E3), tubed scales intersecting upper third of spot. Fourth spot in bar 3, typically smaller, approximately 2 scales wide in E3 and E4, ULL intercepts spot approximately in middle. Upper margin of bar 2 darkened in most specimens; no specimens show spot on bar 2. Dark brown, non ocellated spot on base of dorsal caudal lobe, separated from LLL by approximately one scale. Fins hyaline to dusky grey, darker margins on dorsal, caudal and anal fin. Soft dorsal fin, upper caudal lobe, and soft anal fin with some spotting, clear to light grey in colour; little to no spotting on ventral caudal lobe, especially in larger specimens. Prominent dark preorbital stripe from anterior margin of orbit curving slightly across snout and extending onto upper jaw. Two fainter wide interorbital stripes straight across nape and curving sharply upward toward orbit margin, particularly in anterior band. Suborbital stripe dark and straight, extending from orbit to ventral margin of preopercle. Prominent and straight postorbital band from posterior margin of orbit to supracleithrum, colour matching first lateral band spot.

Comparative morphometrics. Size corrected data was used for comparisons between K. petitella n. sp. and K. guianensis , K. itanyi or K. potaroensis to account for the differences in the range of standard lengths in available specimens. Krobia petitella n. sp. has a slightly longer snout on average compared to K. guianensis (p adj = 0.052, marginally significant). In addition, K. petitella n. sp. has proportionately longer pectoral (p adj <0.05) and pelvic fins (p adj <0.001) as well as a taller dorsal fin noted by a significantly longer last dorsal spine (p adj = 0.01). Krobia petitella n. sp. differs from ‘Aequidens’ potaroensis by the former having a deeper head (p adj = 0.012), body (p adj = 0.039) and caudal peduncle (p adj <0.001). Krobia petitella n. sp. also has a taller dorsal fin (p adj <0.001) as well as longer pectoral (p adj = 0.018) and pelvic fins (p adj = 0.002) than ‘Aequidens’ potaroensis . Few K. itanyi specimens were available for comparison, however K. petitella n. sp. typically had longer snouts and narrower head width than K. itanyi specimens of comparable size. Insufficient specimens of K. xinguensis and no ‘Aequidens’ paloemeuensis were available for direct linear morphometric comparison.

Distribution. Krobia petitella n. sp. is only known from the Berbice River drainage in northeastern Guyana ( Fig. 5 ). Specimens were collected primarily in the main stem of the Berbice River upstream of the Ituni River confluence. The most downstream collecting locality of K. petitella n. sp. was at the mouth of the Ituni River. The species was also collected in Cat Creek, a small tributary of the Berbice River upstream of Ituni River. The Berbice is a black water river and Krobia was generally collected in pH ranging from 4.2–7.1, conductivity of 2.0–39.0 μS and temperature of 25.0–33.3o C. Current velocity typically ranged between 0.1–0.3 m /s, with dissolved oxygen of 5.1–6.7 mg /L and Secchi depth 0.7–1.0m.

Etymology. From the Latin petitus, reaching out for or inclining towards. In reference to the lateral band spots lying adjacent to the upper lateral line anteriorly and intercepting posteriorly. To be regarded as an adjective in feminine form.

Figures

FIGURE 3. Diagrammatic representation of lateral band, vertical bars, and facial markings distinguishing Krobia species. a, K. petitella, n. sp.; b, K. xinguensis; from holotype photo (Kullander 2012); c, K. guianensis; from ROM 87784; d, K. itanyi from AUM 50759 and ANSP 189588 (posterior spot in hatch marks of bar 3 may be present or absent, see Kullander and Nijssen 1989); e, K. potaroensis; from holotype illustration (Eigenmann 1912, Plate LXVI, Fig. 2) and descriptions from Kullander and Nijssen (1989); f, K. paloemeuensis; from holotype photo (Kullander and Nijssen 1989).

FIGURE 4. Krobia petitella n. sp.. Lower pharyngeal jaw toothplate, from ROM 86851, 57.3 mm SL.

FIGURE 5. Collection sites of Krobia petitella n. sp.. Type locality is represented by an empty circle. One point may represent more than one collection locality.

Tables

TABLE 1. Standard length and proportional measurements presented as percentage of standard length of Krobia petitella n. sp.. SD, standard deviation. Measurements of the holotype are given separately.

	N	Holotype Mean	Min	Max	SD
Standard length (mm)	26	80.1 53.9	29.9	98.9	18.7
Head length	26	33.6 35.0	32.8	37.8	1.3
Head width	26	20.8 19.7	17.9	21.3	0.7
Snout length	26	11.2 10.7	8.9	13.7	1.0
Orbit diameter	26	11.4 12.9	10.5	15.2	1.2
Preorbital depth	26	7.8 8.0	6.3	9.7	0.8
Head depth	26	34.9 33.5	31.7	36.7	1.6
Interorbital width	26	13.6 11.7	9.5	14.1	1.3
Body depth	26	44.3 43.5	38.9	48.4	2.10
Pectoral length	26	40.9 38.1	32.4	42.4	2.0
Pelvic length	26	40.6 39.7	35.3	50.9	3.4
Caudal peduncle depth	26	17.4 17.0	14.7	19.3	1.0
Caudal peduncle length	26	10.3 11.5	8.8	13.7	1.3
Last dorsal spine length	26	15.8 16.6	14.5	18.9	1.1