Characidium dule, Agudelo‐Zamora & Tavera & Murillo & Ortega‐Lara, 2020

Agudelo‐Zamora, Henry D., Tavera, José, Murillo, Yiskar D. & Ortega‐Lara, Armando, 2020, The unknown diversity of the genus Characidium (Characiformes: Crenuchidae) in the Chocó biogeographic region, Colombian Andes: Two new species supported by morphological and molecular data, Journal of Fish Biology 97 (4), pp. 1-14 : 8-10

3.12 | Characidium dule , new species

urn:lsid:zoobank.org:act:FFF769BD-AA23-4FEC-

AF33-1770A612D41D.

Characidium sp. 4 “ Arquia ” – Agudelo-Zamora et al., 2020, p. 14 (material examined).

3.13 | Holotype

IMCN 8941 , 37.4 mm L S, Colombia, Chocó , Unguia , río Arquía, at the village of Arquía, 08 00 ' 07.1 '' N, 77 06 ' 56.2 '' W, A. Ortega-Lara. 05 April 2017 .

3.14 | Paratypes

All from Colombia. IMCN 8929 , 7 + 1 C&S female, 32.8 – 44.7 mm L S from the same locality of the holotype ; IMCN 8942 , 1, 30.9 mm L S from the same locality of the holotype ; CHIFF 0012 , 1, 31.3 mm L S, Colombia, Chocó , Quibdó, Tutunendo river, 5 44 ' 39.7 '' N, 76 31 ' 54.2 '' W. A. Ortega-Lara, N. Lujan. 01 August 2019 .

3.15 | Diagnosis

Characidium dule can be differentiated from all other Characidium species by having a unique colour pattern in the humeral region that consists of a small marking, similar to a black line, between the supraoccipital and the beginning of the opercle, followed by a light point (golden in live specimens or white in preserved specimens), and a humeral round blotch which is formed by two to three scales ( Figures 5 , 6 ), in addition to a triangular blotch at the end of the caudal peduncle where pigmentation varies in size starting at ½ scale, followed by 1 scale and its base is 2 scales. In mature specimens (recognized by their purplish colour) the caudal triangular point is less visible. It is distinguished from C. purpuratum Steindachner 1882 and C. marshi Breder 1925 by having lower number of dorsal (7 – 9 vs. 11) and anal (6 – 7 vs. 8 in C. purpuratum and 7 – 9 in C. marshi ) fin rays. It is also distinguished from C. purpuratum by the presence of scales in the isthmus and the area between the pectorals (vs. isthmus and area between the pectoral without scales). It is also distinguished from C. marshi by having a smaller number of scales in the lateral line (30 – 33 vs. 31 – 35) and by the absence of postcleithrum I (vs. presence of postcleithrum).

3.16 | Description

Morphometric data can be seen in Table 2 , the largest known specimen not exceeding 44.7 mm L S. Body slightly compressed laterally with slightly convex dorsal profile from snout to supraoccipital fontanelle, ascending slightly convex to origin of dorsal fin, and ascending at another convex angle from beginning of dorsal to adipose fin, descends slightly in a straight line and right angle from adipose to first procuring radius of tail fin. Slightly concave ventral profile, vertex on pelvic fin, ends dentary at anterior part and ventral procurrent rays at posterior. Greatest body depth is at or just before origin of dorsal fin. Slightly convex pointed snout from dorsal margin of orbit. Maxilla short, just barely exceeding anterior margin of orbital, exceeding posterior nostril. Circular orbit larger than snout length, similar in size to maxilla; iris round. Dorsal base fin with chromatophores forming a band.

Dorsal-fin rays ii7(1), 9*(8); anal-fin rays i6(7), 7*(2); pectoral-fin rays iii7 (1), 8*(6), 9(2); pelvic-fin rays i6(1), 7*(8); principal caudal-fin rays in dorsal lobe 9*(9), in ventral lobe 8*(9).

Scales cycloid. Lateral line complete; pored lateral-line scales 30(2), 31*(2), 32(3), 33(2) Scales above lateral line 4*(9), below 2*(9). Predorsal scales 8*(4), 9(5). Circumpeduncular scales 11*(2), 12*(7). Isthmus and area between the pectoral with scales.

Mesethmoid bone separated from frontal, parietal fontanel reduced width size of the post-parietal bars, postcleitrum (PC) I absent but PC II and III present. Medial process of first rib with ventral vertex paddle-shaped, wider in vertex which decreases ventrally to tip of rib, dorsal upper process has an L shape without concave space between process and base to vertebral join ( Figure 8c .); swimbladder with two chambers, anterior bilobulated and laterally wider than that of C. tatama , posterior chamber shorter than anterior chamber and rounded ( Figure 8d .).

3.17 | Colour in live specimens

Mature specimens purplish. This colour is observed predominantly on dorsal, anal, adipose, caudal and pelvic fins, extending also over ventral area ( Figure 9 ). Lateral line with golden shades predominantly between pelvic and anal fins. Head, with golden line behind eye, followed by a black line and golden point at end of opercle, as well as a black humeral blotch. First portion of dorsal fin (first two rays) golden in colour. Head with a band that is smaller than pupil, extending from front edge of eye to beginning of maxillary bone.

3.18 | Colour in alcohol

Mature specimens purple with 7 – 8 bars, with highly pigmented dorsal, anal and caudal fins ( Figures 6 and 8 ). In all the specimens, transverse band present and smaller in size (1/2 scale) than humeral and caudal spots. Unmarked belly. Humeral blotch reaching two to three scales and concave extension towards pectoral fin, being faint in immature specimens and dark in mature specimens and coming into contact with last rays of the pectoral fin ( Figure 7 ). Dorsal anterior portion of maxilla pigmented forming a line reaching the eye, ventral posterior portion of maxilla without pigment.

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Ecology

The Arquía River (type locality) is a tributary of steep banks with large slopes, with good riparian coverage on both flanks and a predominance of a rocky substrate with large edges, which allow the formation of backwaters and small pools where sand and organic materials are deposited. A tributary of transparent waters (Figure 10).

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Distribution

Characidium dule is endemic to the Chocó biogeographical region and inhabits rivers or streams tributaries to the Atrato River, from its upper reaches to near the mouth into the Urabá Gulf (Figure 1).

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Etymology

A noun in apposition dedicated to the Dule (Kuna) ethnic group of Maggilagundiwala or Resguardo de Arquía in the Colombian Chocó, whose language is under a high risk of extinction and where most of the type specimens were collected.

3.22 | Conservation assessment

Characidium dule is so far known from two localities in tributaries of the Atrato River. The EOO estimated for the species is 5.701. 2 km 2, and the AOO estimated is 21 km 2 (sensu Bachman et al., 2011). Additional collecting efforts should be conducted in the region to better understand the geographic distribution of the species and the existent threats. From the points assessed here for the distribution of C. dule , the species is tentatively categorized as Vulnerable (VU) D2 under the geospatial aspect because the population is restricted to less than 20 km 2 and the number of localities is less than five (IUCN Standards and Petitions Subcommittee, 2019), with accelerated deforestation inside Colombian national parks ( Clerici et al., 2020).

Figures

FIGURE 5 Typical habitat of C. dule, Ingará River, San José Del Palmar, Chocó, Colombia

FIGURE 6 C. dule n. sp. IMCN 8941, Holotype 37.4 mm LS. Scale bar = 1 cm

FIGURE 7 Detail of the composition of spots in C. dule n. sp. IMCN 8929, Paratype 38.24 mm LS, arrows show the detail. Scale bar = 1 cm

FIGURE 8 Detail in the shape of the first rib (a)–(c) and swimbladder (b)–(d) in (a) and (b). C. tatama n. sp. (b, ventral view) IMCN 8924 (1C&S) and (c) and (d) C. dule n. sp. (d, dorsal view) IMCN 8929 (1C&S). The right lobule in (d) is damaged. Scale bar = 1 mm

FIGURE 9 C. dule n. sp. IMCN 8929, Paratype. Live specimen. Scale bar = 1 cm

Tables

TABLE 2 Morphometric data from C. dule n. sp. (n = 9)

	Holotype	Minimum	Maximum	Range	Mean	S.D.
TL	45.07	41.9	54.3	41.9 – 54.3	48.2
SL	37.42	32.8	44.7	32,8 – 44.7	38.8
% SL
Head length	21.9	21.7	27.2	21.7 – 27.2	23.7	1.6
Pectoral distance	23.1	20.9	25.9	20.9 – 25.9	23.4	1.7
Predorsal distance	44.3	44.8	49.5	44.8 – 49.5	46.8	1.4
Prepelvic distance	49.5	52.1	56.3	52.1 – 56.3	53.7	1.6
Preanal distance	71.1	74.9	80.3	74.9 – 80.3	76.7	1.8
Anal-apex distance	77.9	82.1	88.6	82.1 – 88.6	85	1.8
Body width	12.4	11.2	12.9	11.2 – 12.9	11.9	0.7
Body depth at DO	22.4	20.7	24.6	20.7 – 24.6	22.3	1.5
Body depth at AO	17.3	15.7	18.2	15.7 – 18.2	16.9	1
Caudal peduncle depth	11.1	10.6	12	10.6 – 12	11.4	0.5
% HL
Snout length	22.8	23	25.7	23 – 25.7	24.2	1
Snout-maxillary tip	25.6	23.2	27.1	23.2 – 27.1	24.9	1.2
Anterior naris-eye	9.7	7.1	9.5	7.1 – 9.5	8.5	0.8
Posterior naris - eye	5.1	1.8	5.8	1.8 – 5.8	4	1.3
Cheek	21.8	19.7	22,6	19.7 – 22.6	20.9	1
Orbital diameter	26.3	22.5	29.2	22.5 – 29.2	25.7	2
Interorbital distance	11.3	8,3	15.5	8.3 – 15,5	12.8	2.7

Abbreviations: DO, dorsal origin; AO, anal origin; HL, head length; S.D; standard deviation; LS, standard length; TL, total length.