Hypopygus hoedemani, De Santana & Crampton, 2011

De Santana, Carlos D. & Crampton, William G. R., 2011, Phylogenetic interrelationships, taxonomy, and reductive evolution in the Neotropical electric fish genus Hypopygus (Teleostei, Ostariophysi, Gymnotiformes), Zoological Journal of the Linnean Society 163 (4), pp. 1096-1156 : 1125-1127

HYPOPYGUS HOEDEMANI SP. NOV.

( FIG. 19 ; TABLE 4)

Hypopygus sp. Lima et al. 2005: 260 [first illustration; Rio Tiquié, Amazon basin].

Diagnosis: Hypopygus hoedemani is diagnosed from congeners by the following combination of characters: the absence of the sixth infraorbital bone (versus presence in all congeners except H. lepturus and H. minissimus ), the total number of anal-fin rays (102–118 versus 136–174 in all congeners, except for H. lepturus and H. minissimus ), the length of the caudal filament (31.1–48.1% of LEA versus 48.4–80.9 in H. lepturus ), the presence of oblique bands (versus absence in H. minissimus ), the presence of scales at midbody (versus absence in H. minissimus ), and the dorsal rami of intermittent branch of anterior lateral line nerve visible as two black parallel lines (versus not visible in H. ortegai ).

Description: Head and body shape, and pigmentation illustrated in Figure 19 . Morphometric data for examined specimens are presented in Table 4. Body size small, maximum examined TL 75 mm (N = 22). Maximum examined length from snout to end of BC 17.8 mm. No sexual dimorphism in body or head shape. Snout slightly convex. Upper and lower jaws approximately equal in length. Pectoral-fin rays 11–13 [13] (N = 17). Postpectoral EO with two columns and four to six rows of electrocytes, its dorsal groove extending anteriorly to approximately one to two orbital diameters before posterior border of eye. Scales present on mid-dorsal region of body. Scales above lateral line at midbody 5–8 [8] (N = 17). Scales below lateral line 4–6 [4] (N = 4). Total anal-fin rays 102–118 [110] (N = 15). Caudal filament moderate. Precaudal vertebrae 16 [16] (12–15 anterior; 1–4 transitional; N = 4).

Distribution: Hypopygus hoedemani is known from small terra firme streams and rivers in the Rio Negro and Rio Preto da Eva drainages of the Amazon basin, Brazil ( Fig. 20 ).

Pigmentation ( Fig. 19 ): Small specimens 40.3– 45.4 mm, and one examined individual of 59.2 mm with light to dark brown body background, pale oblique bands from nape to end of caudal, and 14 to 17 clear bands crossing dorsal region of body (counted from nape to last anal-fin ray). Remaining specimens (to 75 mm), including holotype, with light to dark brown background, pale bands restricted to postpectoral portion of body and region below lateral line, middorsal portion of body even brown – occasionally with sparse clear bands, mainly in posterior region. Head of all specimens light to dark brown, sometimes with a depigmented area ventroposterior to eye. Pectoral-fin ray and inter-radial membrane hyaline, sporadically speckled with dark chromatophores. Anal-fin rays hyaline with dark pigmentation on anterior and posterior portions of fin. Inter-radial membrane hyaline anteriorly and darkly pigmented posteriorly.

Dorsal rami of intermittent branch of anterior lateral line nerve visible as two black parallel lines, on each side of upper back from approximately one to one-half pectoral fin length behind the occiput, running posteriorly to mid-dorsal portion of body.

Lateral line nerve visible as dark line, extending from above pectoral fin to approximately two-thirds into caudal filament.

Electric organ discharge: Unknown. Ecology: Lima et al. (2005) presented short notes on H. hoedemani . They reported finding this species in submerged vegetation and the bed of lakes, pools, and small streams of the Rio Tiquié, a tributary of the Rio Uaupés, Rio Negro drainage. They reported that it feeds on aquatic invertebrates, including termites, insect larvae, and oligochaetes.

Etymology: The specific epithet, hoedemani , is a patronym in honour of J. J. Hoedeman for his contributions to Neotropical ichthyology, including the description of H. lepturus , the type species of the genus.

Remarks: The absence of extrascapular bones and the presence of two ossified mandibular canal bones (see Character description and analysis) are autapomorphies for the species.

Material examined: (22 specimens.)

Holotype. Brazil. Amazonas. INPA 30375 , 1 , 52.9 mm; Igarapé Toari , Rio Preto da Eva drainage, 02°47′35″S, 059°38′21″W; L. N. Carvalho, 11.viii.2006.

Paratypes. Brazil. Amazonas. INPA 29855 , 1 , 56.0 mm; Rio Preto da Eva , 02.74078°S, 059.67142°W; L. N. Carvalho, 08.vi.2006. INPA 30049 , 1 , 28 mm; Rio Preto da Eva , Igarapé Toari, 02.74078°S, 059.67142°W; L. N. Carvalho, 04.x.2006. INPA 33948 (ex. 30375), 2, 49.4–55.4 mm (1 CS); Igarapé Toari , Rio Preto da Eva drainage, 02°47′35″S, 059°38′21″W; L. N. Carvalho, 11.viii.2006. MZUSP 30169 , 3 , 35.2 – 53.1 mm; Rio Negro , below Rio Daraá ; M. Goulding, 16.ii.1980. MZUSP 59196 , 1 , 45.8 mm; stream at São João, near Tapurucuara (= Santa Isabel do Rio Negro); Expedição Permanente à Amazônia, 23.x.1972. MZUSP 62744 , 75.0 mm; Igarapé Jaradá, right margin of the Rio Cuieiras, c. 40 km above the mouth; Alpha Helix Amazon Expedition, 1.ii.1977. MZUSP 74277 (part), 1, 49.5 mm; Igarapé Jaradá, branch of the right Description: Head and body shape, and pigmentation illustrated in Figure 21 . Morphometric data for examined specimens are presented in Table 4. Body size moderate, maximum examined TL 90.0 mm (N = 9). Maximum examined length from snout to end of BC 20 mm. Snout slightly convex. Upper and lower jaws approximately equal in length. Pectoral-fin rays 12–16 [14] (N = 9). Postpectoral EO with two columns and five to seven rows of electrocytes, its dorsal groove extending anteriorly to approximately one and a half to two orbital diameters behind posterior border of eye. Scales present on mid-dorsal region of body. Scales above lateral line at midbody 7–8 [8] (N = 9). Scales below lateral line 5–7 [7] (N = 4). Total anal-fin rays 136–152 [150] (N = 9). Caudal filament moderate. Precaudal vertebrae 14 (11–12 anterior; 2–3 transitional; N = 3) .

margin of the Rio Cuieiras, c. 40 km of the mouth; Alpha Helix Amazon Expedition , 31.i.1977 . MZUSP 74299 (part), 3, 50.4–62.9 mm; Igarapé Sirinau, right margin of the Rio Cuieiras, c. 25 km from the mouth, Rio Negro drainage, 02°42′S, 060°20′W; Alpha Helix Amazon Expedition , 30.i.1977 . MZUSP 81488 , 8 , 40.3 – 65.1 mm (1 CS); Rio Tiquié, Igarapé Mipiriyapotemakãya , branch of Igarapé Açaí , 00°15′55″N, 069°58′16″W; F. Lima et al., 29.x.2002 .

Figures

Figure 19. Hypopygus hoedemani, holotype, head, and lateral and dorsal views of body, 52.9 mm, INPA 30375; Brazil, Igarapé Toari, Rio Preto da Eva drainage. Scale bars = 5 mm.

Figure 20. Map of northern South America showing collection records of Hypopygus hoedemani (circles), and Hypopygus isbruckeri (squares). Some symbols represent more than one nearby collecting locality.

Figure 21. Hypopygus isbruckeri, holotype, head, and lateral and dorsal views of body, UF 148539, 90 mm, immature; Venezuela, Amazonas, stream at Caño Magua, approximately 1 km from Magua, 13 km from San Fernando de Atabapo, 3°58′50.22″N, 67°36′28.08″W. Scale bars = 5 mm. Note. Scales are missing along mid section of flank because of specimen damage.