Phenacogaster julliae, Lucena & Lucena, 2019

Lucena, Zilda Margarete Seixas de & Lucena, Carlos Alberto Santos de, 2019, A new glass tetra species of Phenacogaster from the rio Salitre, rio São Francisco drainage, Brazil (Characiformes: Characidae), Neotropical Ichthyology 17 (1), pp. 1-6 : 1-4

Phenacogaster julliae , new species

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Figs. 1-3 , Tab. 1

Holotype. MZUSP 123642 , 27.4 mm SL, unsexed; Brazil, Bahia, Campo Formoso, rio Salitre, on the road to Lage , ca. 40 km east of Lage , Poços de Doce , rio São Francisco drai- nage, approx. 10°01’S 40°42’W, 4 Jan 1997, F. C. T. Lima & P. Gerhard.

Paratypes. MCP 53629, 5 (2 c&s), 18.2-27.5 mm SL (2, 25.5 and 26.7 mm SL), and MZUSP 51375, 63 , 13.0- 29.5 mm SL (8, 24.7-29.5 mm SL), same data as holotype .

Diagnosis. The presence of a conspicuously deep caudal peduncle spot, which reaches the upper and lower margins of the caudal peduncle, with a short extension onto the middle caudal fin rays and another weaker extension over the lower lobe of the caudal fin ( Figs. 1-2 ) helps clearly distinguish Phenacogaster julliae from all its congeners, which lack the caudal peduncle spot or the extension over the lower lobe of caudal fin. Two species of the genus inhabit areas near the distribution of Phenacogaster julliae : P. franciscoensis , sympatric in the rio São Francisco basin, and Phenacogaster calverti Fowler of the coastal rivers of northeastern Brazil, immediately to the north of the rio São Francisco. In addition to the clearly differentiating feature mentioned earlier, P. julliae differs from P. franciscoensis in having a humeral spot in contact with, or slightly anterior to, the posterior margin of the pseudotympanum, corresponding to the posterior limit of the second rib, or immediately anterior to it (= to the first rib in Lucena, Malabarba, 2010) (vs. humeral spot distant from posterior margin of pseudotympanum by at least one scale, situated from the third rib, or immediately in front of the third rib); P. julliae differs from P. calverti in having a small third infraorbital, distant from the horizontal and vertical margins the preoperculum (vs. a large third infraorbital, with posterior margin reaching the vertical margin of preoperculum and lower margin separated from the horizontal margin of preoperculum by a small space); two or three teeth in the medial region of the external premaxillary row (vs. one, rarely two); and the gently curved snout (vs. usually abrupt snout).

Description. Morphometric data presented in Tab. 1 . Body compressed. Dorsal profile of head convex from anterior tip of upper jaw to vertical through anterior border of orbit; straight to end of supraoccipital, or slightly convex in interorbital region, and convex to origin of dorsal fin. Dorsal profile between dorsal fin origin and origin of dorsal pro- current caudal-fin rays straight or slightly concave in pedun- cle. Ventral profile slightly convex from tip of mandible to anal-fin origin, or straight between pelvic-fin insertion and anal-fin origin. Body profile along anal-fin base straight or slightly convex. Ventral profile of caudal peduncle straight to slightly concave. Preventral area flattened.

Mouth slightly subterminal; posterior tip of maxilla reaches midway or immediately posterior to midway along infraorbital 2. Third infraorbital small, ventral and posterior margins of third infraorbital separated from preopercle by a broad space, and ventral margin separated by a larger space. Pseudotympanum extends from region immediately ahead of first rib to posterior border of second rib.

Two rows of teeth in premaxilla. External row with 6(2), 7(2), or 8*(5) total teeth, complete or divided in medial sections by gap; medial section with 2(5) or 3(1) tricuspid teeth; lateral section with 4(3), 5(1), or 6(2) typically conical teeth. Three specimens with external row complete with 8* teeth, and one cleared and stained with 9 teeth (two first teeth wide and tricuspid, followed by seven narrow and conical teeth). Internal row with 8*(2), 9(3), 10(1), 11(1), or 12(1) teeth, first five teeth wide and tricuspid, followed by four narrow, tricuspid, conical teeth (in one cleared and stained specimen). Some specimens have one conical tooth lodged between internal and external rows on posterior portion of premaxilla. Maxilla with 26(1), 27(3), 30(1), 31(1), 32(1), or 35(1) conical teeth distributed along almost its entire length. Dentary with 16 or 18 teeth, in single row, with 6 tricuspid teeth followed by 1 bicuspid and 11 conical teeth, or by 10 conical teeth ( Fig. 3 ).

Dorsal-fin rays ii,7*(3), 8(3), or 9(9). Anal-fin rays iii*, (9) or iv(1), 25(1), 26*(6), 27(5), 28(2), 29(6), its origin at vertical drawn between base of third or fourth branched ray of dorsal fin. Pectoral fin with i, 10*(6), 11(6), or 12(2) rays. Posterior tip of longest ray reaches approximately middle of pelvic-fin length in females and surpasses middle of pelvic- -fin length in males. Pectoral-fin rays fully developed in spe- cimens from SL of 16.0 mm; and not developed or partially developed in smaller specimens. Posteroventral portion of cleithrum with gentle notch. Pelvic-fin rays i,7* (one speci- men with i,6), tip of fin reaching last unbranched anal-fin ray or first or second branched anal-fin ray.

Longitudinal scales 34(3), 35(3), 36*(8), or 37(1) usually interrupted with 9 to 17 perforated scales followed by non-perforated and perforated scales, last 3 or 4 scales are non-perforated; two specimens with complete lateral line (34 and 36 perforated scales) and one with incomplete lateral line (32 perforated scales followed by 3 non-perforated scales). Scale rows between dorsal fin and lateral line 6 (one specimen with 7). Scale rows between lateral line and anal- -fin origin 4*(20) or 5(3).

Gill rakers on upper limb of first gill arch 3(4), 4(12), or 5*(6); gill rakers on lower limb 7(1), 8(14) or 9*(7).

Total vertebrae 33(2): precaudal 14(1) or 15(1), caudal 18(1) or 19(1). Supraneurals 4(2).

Color in alcohol. General coloration of the body is yellowish. Laterodorsal region with brown chromatophores on the edge of scales near back and more scattered below. Lateroventral region, between origins of pectoral fins until region in the front of anal fin, is less pigmented. Chromatophores are spread and/or arranged in the form of “>” throughout the region between lateral line and anal fin, demarcating myo- septa. Dorsal region of head and back of the body pigmen- ted; pigments are principally present on the border of scales in the anterior region of smaller individuals (around 20 mm SL). Humeral spot large, conspicuous, ovate, with a pale area around it, positioned above 5th or 6th to 9th scale of lateral line, extending from the end of pseudotympanum, or immediately before, to right after 6th or 7th rib. Center of humeral spot slightly below or at horizontal line through the dorsal border of pseudotympanum.

Dark midlateral line on the body from immediately af- ter humeral spot until the origin of caudal peduncle spot. Band of chromatophores are present throughout and above midlateral line, and below is a pale hypopigmented band. Conspicuous, deep caudal peduncle spot reaches upper and lower margins of the caudal peduncle, extending on middle caudal-fin rays and more weakly on the lower lobe of caudal fin ( Figs. 1-2 ). Anal fin with scarcer pigments, less intense in the medial region of the fin starting from 6th or 7th branched ray, leaving a pale area between the margin and the base; holotype relatively more pigmented in this area. Pectoral fin with pigments along ray margins. Pelvic fin with pigments along the rays, extremely pale, last ray pale or has signifi- cantly little pigment. Adipose fin is pale.

Sexual dimorphism. Eight specimens of 21.1-26.3 mm SL exhibit retrorse bony hooks on anal- and pelvic-fin rays. Hooks on last unbranched to 7th or 11th branched anal-fin rays. One, rarely two, hooks per segment of lepidotrichia. First unbranched ray to last or penultimate branched ray of pelvic fin bearing retrorse bony hooks located along medial border of second branch and on the principal branch. One hook per segment of lepidotrichia.

Geographical distribution. Known only from the type locality ( Fig. 4 ).

Etymology. The species name is julliae , named in honour of our granddaughter Jullia, who was born during the description of this species.

Conservation status. Phenacogaster julliae is described based on 69 specimens collected in January 1997 from the middle rio Salitre basin, about 40 km from Lage, Bahia. The rio Salitre basin is considered intermittent and is located in the lower middle rio São Francisco in an area with low rainfall index, irregular rains, and water deficit because of elevated evaporation rates ( Oliveira et al., 2010). In an email from Flávio Lima in July 2018, we were informed that the species was found in a narrow stretch of the river with a noticeable aquatic vegetation, transparent water, and slow flow, alternating between shallow areas with rapid flow and other slower, deeper areas reaching a depth of about 2 m. We do not have information on current conditions of the locality; however, the rio Salitre basin, which has a history of conflict over water use, faces various threats: incompatible irrigation methods, development of soil cultivation on the banks of the rivers and lakes of dams, superficial water with a high level of salinity and pollution caused by anthropic activity (untreated sewage, among others) (FEP, 2003). Furthermore, there are transposition projects, specifially the Sertão Baiano or Eixo-Sul Canal [transposition of the rio São Francisco] that runs from the rio São Francisco, starting from the Sobradinho Reservoir to the rio Itapicuru and Jacuípe water basins, influencing some basins along this path, including the Salitre (Nemus, 2015). Considering these threats faced by the rio Salitre basin and the apparent rarity of the species, Phenacogaster julliae can be categorized as Data Deficient according to the IUCN criteria (IUCN, 2017).

Figures

Fig. 1. Phenacogaster julliae, MZUSP 123642, holotype, unsexed, 27.4 mm SL, rio Salitre, Bahia state, Brazil.

Fig. 2. Phenacogaster julliae, MZUSP 51375, paratype, male, 26.3 mm SL, rio Salitre, Bahia state, Brazil.

Fig. 3. Phenacogaster julliae, MCP 53629, 24.7 mm SL, paratype: maxilla (top right), premaxilla (top left), and lower jaw (bottom). Lateral view, left side.

Fig. 4. Known distribution of Phenacogaster julliae. Red dot represents the type locality.

Tables

Tab. 1. Morphometric data of holotype and paratypes of Phenacogaster julliae (n = number of specimens, holotype included). SD = standard deviation.

	Holotype	n	Range		Mean	SD
Standard length (mm)	27.4	10	24.7	29.5	27.2	-
Percents of standard length
Depth at dorsal-fin origin	33.9	10	30.9	35.9	33.5	1.50
Predorsal distance	54.0	10	49.2	54.0	51.4	1.58
Prepelvic distance	40.9	9	36.6	40.9	38.8	1.29
Preanal distance	55.5	10	51.7	58.6	53.9	1.96
Caudal-peduncle length	7.3	10	7.3	10.3	8.8	0.90
Caudal-peduncle depth	10.9	10	8.6	10.9	9.9	0.76
Head length	28.8	10	25.3	28.8	27.0	1.02
Percents of head length
Snout length	24.0	10	22.1	28.4	24.5	1.96
Orbital diameter	41.7	10	39.7	47.1	43.1	2.37
Interorbital width	26.7	10	24.1	30.7	27.1	2.02