Ancistrus greeni (Isbrücker, 2001)

Bifi, Alessandro Gasparetto & Ortega, Hernán, 2020, Redescription of Ancistrus greeni (Siluriformes: Loricariidae), and description of a new species from the río Madre de Dios basin, Peru, Neotropical Ichthyology (Neotrop. Ichthyol.) 18 (1), No. e 190070, pp. 1-18 : 3-6

Ancistrus greeni (Isbrücker, 2001)

( Figs. 1–2 , Tab. 1 )

Chaetostomus maculatus Regan, 1904:246 , pl.14 ( Fig. 4 ) [original description; type locality: Rozmaiu, Upper Peru].

Chaetostoma maculatum . —Isbrücker, 1980:62 [check list]. —Ortega, Vari, 1986:17 [check list]. —Burgess, 1989:436 [check list]. —Isbrücker, 2001:26 [check list].

Chaetostoma greeni Isbrücker in Isbrücker et al., 2001:24 [replacement name for Chaetostomus maculatus Regan 1904 , preoccupied by Chaetostomus (Ancistrus) cirrhosus var. maculata Steindachner 1881 ]. —Isbrücker 2001:26 [check list]. —Fish-Muller, 2003:380 [check list]. —Ferraris, 2007:228 [check list].

Ancistrus greeni . —Lujan et al., 2015:673 [comments; new combination].

Diagnosis. Ancistrus greeni is diagnosed from all congeners, except A. maldonadoi , by having unicuspid teeth (vs. bicuspid). Ancistrus greeni is diagnosed from A. maldonadoi by smaller eye (orbital diameter 8.8–13.0% of HL, vs. 13.8–20.6%); a slender caudal peduncle (depth of caudal peduncle 8.4–10.6% of SL, vs. 12.2–14.0%); smaller adipose-fin spine (adipose spine length 3.7–6.3% of SL, vs. 7.2–9.5%). Furthermore, A. greeni can be distinguished from the species described from río Madre de Dios basin by having 4–8 preadipose plates (vs. 2–3 in A. montanus ); and smaller orbital diameter (8.8–13.0% of HL vs. 14.0–16.7% in A. marcapatae ; and 16.9–20.1% in A. megalostomus ).

Description. Morphometric data and counts in Tab. 1 . Head and trunk moderately depressed with greatest body depth at supraoccipital. Dorsal profile of body convexly raising from tip of snout to dorsal-fin origin, then straight or slightly convex to adipose fin, and concave from that point to caudal fin. Ventral profile of body straight, slightly convex on caudal peduncle. Caudal peduncle compressed; slightly flattened ventrally.

Head moderately large and wide; snout large and rounded in dorsal view, with large naked margin bordered by dermal platelets on lateral portion in males. Adult males with middle- to large-sized tentacles, sometimes branched on dorsal region of snout. Females usually with two small tentacles on each side of snout border. Evertible cheek plates supporting (8–19) hypertrophied odontodes (cheek spines).

Eye small-sized, 8.6–11.9% of HL, dorsal orbit not raised; dorsolaterally positioned. Interorbital region slightly concave. Exposed portion of opercle roughly triangular, supporting odontodes; supra-opercular region with few platelets near compound pterotic.

Oral disk circular covered with small papillae; lower lip large almost reaching pectoral girdle, with papillae reducing in size toward its margin; maxillary barbel short, attached to lip by membrane and with reduced free tip. Branchial opening small. Premaxillary and dentary tooth rows from moderate to large width; teeth short, thin, numerous, unicuspid ( Fig. 3A ), curved inward. Only one small central buccal papilla positioned between premaxillae.

Head covered by dermal bones; dorsum covered by dermal plates, except at dorsal-fin base. Supraoccipital process limited posteriorly by first pair of predorsal plates and posterolaterally by the first plate of the mid-dorsal series. Trunk with five series of lateral plates, three lateral series on the narrowest portion of caudal peduncle. Mid-dorsal and mid-ventral series not surpassing adipose fin. Median series supporting lateral line. Short odontodes on fin rays and body plates. Ventral surface devoid of plates from snout tip to anal-fin insertion. Base of first anal-fin pterygiophore covered by skin.

Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin origin; dorsal fin usually reaching preadipose plate when adpressed; dorsal-fin spine flexible, shorter than head length. Adipose-fin spine short, with small membrane. Pectoral-fin spine inflexible and slightly curved inward, with hypertrophied odontodes and tentacles on distal portion; pectoral fin reaching or slightly surpassing pelvic-fin origin when adpressed. Pelvic fin flexible and curved inward, depressed pelvic-fin unbranched ray surpassing origin of anal fin. Anal fin short. Caudal-fin margin obliquely truncate with ventral unbranched ray longer than dorsal one. Fin-ray formula: dorsal II,7; pectoral I,6; pelvic i,5; anal i,3–4; caudal i,14,i.

Color in alcohol. Body background color yellowish-brown to dark brown. Dorsal surface of head and trunk with rounded light small spots. Ventral surface of head and abdomen yellowish to light brown, brown on ventral surface of caudal peduncle. All fins with alternating dark and light spots on the rays, sometimes organized into transverse bands.

Sexual dimorphism. Largest male and female with 85.2 mm and 74.5 mm SL, respectively. Mature males have small- to middle-sized tentacles on dorsal region and border of snout. Females sometimes with fewer and shorter tentacles than males limited to one series on lateral border of snout, usually two to four on each side of snout. Males have smaller dentary length 21.8–27.1% of HL (mean = 25.0%) than females 26.1–31.4 % of HL (mean= 27.9%).

Geographical distribution. Ancistrus greeni is only known from the río Madre de Dios and río Inambari basins ( Fig. 5 ).

Conservation status. Ancistrus greeni occurs along a well-conserved region, with good water quality and little or no human pressure. Thus, considering the good environmental conditions of the known area of occurrence for the species, we suggest that A. greeni be classified as LC (Least Concern) in the International Union for Conservation of Nature ( IUCN) categories and criteria ( IUCN, 2019) of extinction risk.

Material examined. All from Peru: Lectotype [designated here]: BMNH 1903.10 .12.3, female, 51.4 mm SL, syntype of Chaetostomus maculatus Regan, 1904 , “Rozmaiu, Upper Peru”, Kalinowski . Paralectotype [designated here]: BMNH 1903.10 .12.4, female, 44.8 mm SL, syntype of Chaetostomus maculatus Regan, 1904 , “Rozmaiu, Upper Peru”, Kalinowski . Non-type specimens: río Madre de Dios basin: INPA 58909 , 8 , 30.1–61.9 mm SL (4, 55.1–61.9 mm SL), Cuzco, río Inambari basin, tributary of río Araza, main road crossing vicinity of Quincemil , 13º18’52”S 70º49’13”W, 25 Jul 2004, M. Sabaj, N. Salcedo, B. Rengifo, M. Arce; MUSM 25426 , 12 , 31.2–55.6 mm SL (1, 55.6 mm SL), Tambopata , río Inambari basin, quebrada Miraflores, 13º21’41”S 70º53’40”W, 25 Jul 2004, M. Hidalgo; MUSM 26312 , 2 , 31.9–85.2 mm SL (1, 85.2 mm SL); Quispicanchi , Camanti , río Araza basin, quebrada Sirihua, 13º23’46”S 70º53’59”W, 17 Out 2005, M. Hidalgo; MUSM 56232 , 7 , 34.0– 74.5 mm SL (5, 51.6– 74.5 mm SL), Carabaya , Ollachea , San Gaban , río Inambari basin, quebrada San Isidro, 13º37’45”S 70º26’46”W, 12 Out 2006, M. Hidalgo; MUSM 56233 , 1 , 82.8 mm SL, Carabaya , Ollachea , San Gaban , río Inambari basin, quebrada San Isidro, 13º37’45”S 70º26’46”W, 12 Out 2006, M. Hidalgo; MUSM 57367 , 1 , 73.6 mm SL, Carabaya , San Gaban , río Inambari basin, quebrada Yuri Yuri, 13º33’09”S 70º26’15”W, 13 Out 2006, M. Hidalgo; MUSM 57771 , 8 , 39.0– 62.4 mm SL (4, 51.9–62.4 mm SL), Paucartambo , Kosñipata, río Quita Calzon, 13º02’01”S 71º31’32”W, 11 May 2006, M. Hidalgo; MUSM 57776 , 1 , 53.6 mm SL, Paucartambo , Kosñipata, quebrada Euaraya, 13º02’05”S 71º31’01”W, 11 May 2006, M. Hidalgo; MUSM 57794 , 15 , 27.5–64.8 mm SL (4, 54.6–64.8 mm SL), Paucartambo , Pillcopata, río Tono, 12º57’31”S 71º31’45”W, 13 May 2006, M. Hidalgo; MUSM 57798 , 74.8 mm SL, Cusco Department , Paucartambo Province and District of Pillcopata, río Tono, 12º57’31”S 71º31’45”W, 13 May 2006, M. Hidalgo. Non-measured material: río Madre de Dios basin: MUSM 25428 , 36 , 24.7–55.6 mm SL, Tambopata , río Inambari basin, tributary of río Araza, 13º18’52”S 70º49’13”W, 25 Jul 2004, M. Hidalgo; MUSM 57372 , 24 , 24.5 –40.0 mm SL, Carabaya , San Gaban , río Inambari basin, quebrada Prodocarpa, 13º25’50”S 70º19’45”W, 17 Out 2006, M. Hidalgo; MUSM 57750 , 1 , 37.5 mm SL, Paucartambo , Kosñipata, río San Pedro, 13º03’18”S 71º32’49”W, 10 May 2006, M. Hidalgo; MUSM 57758 , 1 , 42.4 mm SL, Paucartambo , Kosñipata, río Kosñipata, 13º03’23”S 71º32’40”W, 10 May 2006, M. Hidalgo; MUSM 58517 , 11 , 30.7–48.4 mm SL, Paucartambo , Kosñipata, quebrada km 160 AMD 16, 13º02’03”S 71º30’55”W, 12 May 2006, M. Hidalgo .

Figures

FIGURE 1 | Dorsal, lateral and ventral views (left to right) of Ancistrus greeni: BNHM 1903.10.12.3, female, 51.4 mm SL, lectotype; BNHM 1903.10.12.4, female, 44.8 mm SL, paralectotype.

FIGURE 2 | Ancistrus greeni, MUSM 57798, 74.8 mm SL, male, río Tono; MUSM 56232, 67.6 mm SL, female, quebrada San Isidro.

FIGURE 3 | Details of the teeth showing lack of lateral cusp in A. Ancistrus greeni and B. Ancistrus maldonadoi. Bars = 0.1mm.

FIGURE 4 | Ancistrus maldonadoi, MUSM 57733, holotype, 114.7 mm SL, male, Peru, Manu, río Madre de Dios basin, río Salvación.

FIGURE 5 | Partial map of Peru, showing the collecting sites of Ancistrus greeni (yellow) and Ancistrus maldonadoi (white). Star indicates type locality. Both symbols can represent more than one lot and/or locality.