Devario micronema (Bleeker, 1863 a)

Sudasinghe, Hiranya, Pethiyagoda, Rohan & Meegaskumbura, Madhava, 2025, Species without borders: the diversification of giant danios in Sri Lanka (Teleostei, Danionidae, Devario), Evolutionary Systematics 9 (2), pp. 229-258 : 229-258

Devario micronema (Bleeker, 1863 a)

Danio micronema Bleeker, 1863 a .

Devario annnataliae Batuwita, de Silva & Udugampala, 2017 .

Devario udenii Batuwita, de Silva & Udugampala, 2017 .

Material examined.

137 ex., see Suppl. material 1.

Diagnosis.

Devario micronema is distinguished from Sri Lankan congeners by the combination of the following characters and character states: anal-fin origin posterior to origin of dorsal fin, beneath 3 rd branched dorsal-fin ray (vs anal-fin origin on vertical through dorsal-fin origin in D. memorialis ); 1 st infraorbital with an infraorbital process (vs infraorbital process absent in D. malabaricus and D. memorialis ); interstripe I + 1 short, usually not extending uninterrupted anterior to vertical through pelvic-fin origin (vs long, extending uninterrupted anterior to pelvic-fin origin in D. altus ); caudal peduncle length 13.2–20.0 % SL (vs 19.2–21.4 % SL in D. altus ); body depth 23.5–36.6 % SL (vs 15.9–22.6 % SL in D. memorialis ); dorsal-fin base length 16.6–23.3 % SL (vs 13.5–16.3 % SL in D. memorialis ); pelvic-fin height 13.8–18.5 % SL (vs 11.6–13.3 % SL in D. memorialis ); head depth 16.0–23.0 % SL (vs 14.1–15.8 % SL in D. memorialis ); predorsal scales 13–17 (vs 17–19 in D. memorialis ); circumpeduncular scales 12–15 (vs 15–18 in D. memorialis ); scales between lateral line and dorsal-fin origin 7 ½ - 9 ½ (vs 7 ½ in D. memorialis ); branched dorsal-fin rays 9 ½ - 12 ½ (vs 8 ½ in D. memorialis ).

Devario micronema is genetically distinct from D. pathirana , its closest congener by 1.2–1.6 % in the cox 1 DNA barcoding marker, and from the remaining Sri Lankan species of Devario by over 2.8 %. Among these, D. micronema shows, across its range, the greatest phenotypic diversity in terms of color-pattern and habitus (Fig. 14 ) as well as greatest genetic diversity among the Sri Lankan species of Devario . Several of our specimens are suggestive of mitonuclear discordance and / or phenotypes that are intermediate between D. malabaricus and D. micronema . These specimens are considered in this study as potential hybrids. Sexual dimorphism in D. micronema is apparent, with males exhibiting tubercles on the branched rays of the pectoral fin, a character absent in females ( Sudasinghe 2024).

Habitat and distribution.

Among the endemic species of Devario , D. micronema is the most widely distributed giant danio in Sri Lanka. It is recorded from clear, shaded, undisturbed, low-elevation rainforest streams in the perhumid southwestern wet zone, from sea level to about 500 m asl in Kelani, Kalu, Bentara, and Gin River basins.

Remarks.

The Sri Lankan fishes described by Bleeker (1863 a) have not been reported on since their original description: they were presumed lost. The collection was, however, located among uncatalogued material in RMNH by Martien J P. Van Oijen and Maurice Kottelat ca 2015 ( Sudasinghe et al. 2025). One of us (HS) examined the holotype of D. micronema , a 60.0 mm SL specimen (Fig. 13 D ). This is entirely consistent with our conception of the species based on the material examined here.

Figures

Figure 13. Coloration of Devario altus sp. nov., A. In aquarium (~ 50 mm SL); B. In preservative, holotype, 2025.04. 01. NH, 48.7 mm SL; C. Paratype, DZ 5260 C, 52.1 mm SL. Bopathalawa, Menik Palama Farm, Agra Oya (Mahaweli basin), Sri Lanka. Holotype of D. Danio micronema Bleeker, 1863 a, RMNH. PISC. 2746 A, 60.0 mm SL, Ceylon; and syntype of E. Danio lineolatus Bleeker, 1863 a, RMNH. PISC. 2746 B, 59.2 mm SL, Ceylon.

Figure 14. Phenotype and mitochondrial haplotype variation along the elevation gradient in Devario micronema and D. pathirana. The areas of the circles are proportional to the number of individuals sharing a given haplotype. Sampled localities are on the x axis; numbers in parenthesis represent the sampling localities as listed in Table 1. The frequency of the presence or absence of the infraorbital process in specimens examined at each locality is shown as a bar plot.