A new species of Bryconamericus ( Characiformes , Stevardiinae , Characidae ) from the Pacific coast of northwestern Ecuador , South America

A new species of Bryconamericus (Characiformes, Stevardiinae, Characidae) from the Pacific coast of northwestern Ecuador, South America.— A new species of Bryconamericus (Characiformes, Characidae, Stevardiinae) is described from the Pacific coast of northwestern Ecuador, South America. The new species is distinguished from all congeners by the presence in males of bony hooks on the caudal fin rays (vs. absence). The different layers of pigment that constitute the humeral spots have differing degrees of development and structure that are independent of each other. Brown melanophores are distributed in a thin, vertical, superficial layer of the epithelium (layer 1) and in another deeper (layer 2) that overlaps the first and is centered over the lateral–line. B. ecuadorensis has a horizontally oval or elliptical shape layer 2 pigment in the anterior humeral spot (vs. a rectangular or circular layer 2). The new species further differs in having an anterior extension of the caudal peduncle spot (vs. no anterior extension of the caudal peduncle spot) and by having a dark lateral stripe overlaid by the peduncular spot and by the regularly distributed pigmentation on scales on the sides of the body (vs. peduncular spot and other body pigments not superimposed over a dark lateral stripe). Hooks present on all fins of males (vs. hooks present only on anal and pelvic fins of males) distinguishes the new species from B. dahli, the only sympatric congener. Seven other diagnostic characters separating the new taxon from B. dahli are reported. We also include physical, chemical and biological habitat parameters and analyse the impacts from mining on this new species and other organisms present at the type locality.

The discovery of a new species of Bryconamericus from the Pacific versant of western Ecuador is a result of the ongoing revision of Bryconamericus (Román-Valencia, 2000, 2002Román-Valencia et al., 2011, 2013 by the first author and further demonstrates the undocumented biodiversity of the genus.

Material and methods
Fish were collected using seine nets, preserved in the field in 10% formalin, and later stored in 70% ethanol. Measurements were taken using digital calipers, recorded to hundredths of millimeters and usually expressed as percentages of standard length (SL) or head length (HL) (table 1). Counts were made using a stereoscope with a dissection needle to extend the fins. Counts and measurements were taken from the left side of specimens when possible, according to guidelines in Vari & Siebert (1990). Observations of bones and cartilage were made on cleared and stained adult specimens (C&S) prepared according to techniques outlined in Taylor & van Dyke (1985) and Song & Parenti (1995). Bone nomenclature follows Weitzman (1962) and Vari (1995). In the lists of paratypes, the number of individuals is given immediately after the catalog number, which is followed by the range of standard length in mm (SL) for each lot. For example: MEPN 4004 (2) 63.5-73.9 mm SL indicates two individuals in lot MEPN 4004. The smallest fish was 63.5 mm SL and the largest was 73.9 mm SL. In reporting counts, the values for the holotype are indicated with an asterisk (*). All collections were made in Ecuador. Acronyms used follow Sabaj-Pérez (2010) except CEMZ-p-(Pontificia Universidad Católica del Ecuador sede Esmeraldas, colección de peces). Meters above sea level is abbreviated as m a.s.l. Departamento is translated as Province. Municipio is translated as Canton.

Bryconamericus ecuadorensis
Scale rows between anal-fin origin and lateral line 6 5-8 Scale rows between pelvic-fin and lateral line 6 5-6 Predorsal median scales 12 10-12 Dorsal-fin rays iii, 9 iii, 9 Anal-fin rays vi, 27 vi, 25-29 Pelvic-fin rays i, 7 i,7 Pectoral-fin rays i, 11, i i, 10-12, i melanophores are distributed in a thin vertical superficial layer of the epithelium (layer 1), and another deeper layer (layer 2, see fig. 1) centered over the lateral-line canal overlaps the first. In B. ecuadorensis the anterior humeral spot has a horizontally oval or elliptical shape for pigment layer 2 (vs. layer 2 of anterior humeral spot rectangular or circular) ( fig. 1). The new species further differs by having an anterior extension of the caudal-peduncle spot (vs. no anterior extension of caudal peduncle spot) and a dark lateral stripe overlaid by the peduncular spot and by the regularly distributed pigmentation on scales on the sides of the body (vs. peduncular spot and other body pigments not superimposed over a dark lateral stripe), except for B. oroensis, from which it differs by the number of unbranched anal-fin rays (vi vs. iii-iv) and by the distribution and number of hooks on the anal and pelvic fin of sexually mature males. B. oroensis is found in the Amazon basin in the states of Loja, El Oro and Azyay row with four pentacuspid teeth that do not diminish gradually in size. Posterior tip of maxilla surpasses anterior half of second infraorbital; its anterior margin continuous, with one or two pentacuspid teeth ( fig. 2). Lateral ethmoid lateral surface covered by cartilage. Dentary with four large pentacuspid teeth with the central cusp largest, followed by six or eight small conical and tricuspid teeth, the anterior tooth the largest. Six infraorbitals present, the first long and with sensorial canal running its entire length, reaching posterior margin of antorbital. Second infraorbital short and wide, covering the dorsal part of the angulo-articular. Third infraorbital the widest and longest, its ventral border in contact with the sensorial canal of preopercle. Fourth and fifth infraorbitals short and narrow, covering the dorso-posterior margin of the hyomandibular. Sixth infraorbital covers anterior half of sphenotic foramen over the postero-lateral tip of frontal. Supraorbital absent. Rhinosphenoid present and cartilaginous along border, attached to orbitosphenoid and extending to vomer. Orbitosphenoid wide, short and united to pterosphenoid with or without a band of cartilage. The frontal sensory canal not extended to reach parietal.

Secondary sexual dimorphism
Sexually mature males have rows of hooks on branched anal-fin rays 1 to 26; each simple ray has 15-22 hooks located along the entire length of rays. There are also from 14-16 small hooks on all branched pelvic-fin rays, located on both branches of the rays, also extending along the entire length of rays. Small hooks are also present on pectoral-fin rays located on all branched rays with 10-15 hooks extending on the middle and most posterior portions. Dorsal fin with hooks located on branched rays, with 10-18 hooks found on both branches of rays; short hooks present on caudal-fin rays with 1-12 hooks located on posterior part of 8-10 middle rays. Males have more prominent, darker lateral stripes, deeper and wider caudal peduncles, and thicker caudal-fin  B. dahli B. ecuadorensis n. sp.  . 4). Bryconamericus ecuadorensis n. sp. was captured in rivers and creeks in lentic habitats over detritus and decomposing vegetal material with low transparency. The pH was near neutral, dissolved oxygen values, conductivity and total solids were high; turbidity and hardness were low (table 2), as is typical of eutrophic environments. These parameters indicate a highly disturbed environment that affects the survival of this new species and those that share its habitat.

Etymology
Bryconamericus ecuadorensis is named for the country of Ecuador, where the type series was collected.
rays than females. Male B. ecuadorensis show darker colors, related to higher concentration of melanophores along posterior margins of scales that are strongly concentrated along the lateral stripe and also along the infraorbitals, opercle and lateral surface of the cranium, whereas females have a lighter pigmentation pattern, with only the humeral and peduncular regions pigmented ( fig. 3). Thus, males and females have sexually dimorphic pigmentation patterns, a condition rarely observed in other species of Bryconamericus, with the exception of B. oroensis.

Color in alcohol
Dorsum dark brown. Body with silvery lateral stripe from posterior edge of opercle to base of caudal fin. Anterior humeral spot consists of two overlapping layers of pigment: one layer runs transverse from ventral margin of second layer to posterior margin of opercle and crosses lateral line. The second pigment layer is a horizontal ellipse that extends over the series of scales above lateral line. Posterior humeral spot is present over lateral stripe. The caudal peduncle spot extends over the lateral stripe and continues on the middle caudal-fin rays. Sides and ventral region are yellow from tip of snout to caudal peduncle. Fins hyaline (figs. 1, 3).    The new species presented here differs from the sympatric B. dahli by the presence of hooks on all fins in males (vs. hooks present only on anal and pelvic fins). In B. dahli, there is a foramen over the lateral tips of the premaxillary that is absent in B. ecuadorensis; in B. dahli, the teeth of the outer premaxillary row stick out, but in B. ecuadorensis they are covered or not visible. An ongoing analysis has shown seven informative character-states that distinguish Bryconamericus ecuadorensis n. sp. from B. dahli: (1) margin of pigment layer two of the anterior humeral spot is well defined (vs. irregular in B. dahli) ( fig. 1); (2) layer two of the anterior humeral spot is horizontally oval or elliptical (vs. rectangular or circular in B. dahli); (3) anterior extension of caudal peduncle spot extended over the lateral stripe of the body to reach an imaginary vertical through the last anal-fin pterygiophore l (vs. spot restricted to caudal peduncle); (4) area of dermal tissue beneath pectoral fin narrow, the area narrower than one scale in diameter (vs. area of dermal tissue beneath pectoral fin wider than one scale in diameter) (fig. 5); (5) sheath of scales over pectoral-fin origin consisting of more than four scales (vs. two or three scales) (fig. 5); (6) maxillary teeth orientation vertical, not inclined (vs. maxillary teeth inclined internally); and (7) anterior process of orbitosphenoid not narrowed to filament at union with rhinosphenoid (vs. anterior process of orbitosphenoid narrowed to filament at union with rhinosphenoid) (fig. 6).
Males of some species of Characidae usually have hooks on the anal and pelvic fins but less frequently on the dorsal and caudal fins, a character that has been used as a synapomorphy for several genera of Characidae (Malabarba & Weitzman, 2003). The presence of bony hooks on all fins including the caudal fin is not common for species of Knodus, Hemibrycon Hyphessobrycon or Tyttocharax; hooks on all fins of males have only been reported diagnostic in B. ecuadorensis described herein, Hemibrycon brevispini (Román-Valencia & Arcila-Mesa, 2009), Hyphessobrycon natagaima (Garcìa-Alzate et al., 2015), H. togoi (Miquelarena & Lopez, 2006), H. taguae (García-Alzate et al., 2008) and Tyttocharax metae (Román-Valencia et al., 2012). Moreover, the presence of bony hooks on the rays of the caudal fin of males (vs. absent) is diagnostic for Acrobrycon (Arcila et al., 2013) and has been used as a phylogenetically informative character by Mirande (2010) (coded as state 1 but only in some species of Characidae).

Conservation status of the ichthyofauna and in particular
Bryconamericus from the Pacific slope of northwestern Ecuador Calvo (2008) listed, for low and highlands in the Andes, common causal elements that typically result in loss of biodiversity and habitat quality: (1) increased human population leading to intensification of resource exploitation; (2) climate change; and (3) pollution from mining activities. While these impacts increase in spatial extension and local intensity we continue to confront vast information gaps for Neotropical fish distribution, biology and taxonomy (Sarmiento & Barrera, 2008). Gold mining activities have completely destroyed natural waterways in some areas and dangerously increased mercury levels in many species of fish and tadpoles (Carnegie Institution for Science, 2013; Hernández et al., 2013). For the particular case of the fishes in the Pacific versant of Ecuador, and especially those in Esmeraldas Province (the type locality of the new species) in the rivers of the Santiago-Cayapas drainage: Tululbí, Cachaví, Bogotá, Wimbí, Santiago, Estero María, Zabaleta and Zapallito (Rebolledo-Monsalve & Jiménez-Prado, 2013), current conditions are regrettably negative for the survival of fishes and health of human communities, having been affected by both legal and illegal mining activities, uncontrolled tourism, destruction of mangroves and the shrimp cultivation industry (Jiménez Prado, 2012a, 2012bRebolledo-Monsalve & Jiménez-Prado, 2013). Levels of Cr, N, V, Co, Hg and S in soils and sediments exceed established maximum limits and heavy metals have been found in the tissues of fishes and other organisms. One example that stands out is the presence of elevated levels of Zn and Cu in tissues of the Cagua (Gobiomorus maculatus), in more than ten localities examined from the middle and lower sections of the Santiago-Cayapas River, and also the presence of Hg, Al, As, Cd or Cr, in some of them. The elements analyzed also included Fe, Zinc, Mn, and fecal coliforms were found to exceed the legal limits permitted (table 2).
The type of exploitation observed along the length of the Santiago-Cayapas is not so different from that recorded in other drainages of the Pacific coast, where fluvial gold mining occurs (Idárraga et al., 2010;González, 2013;Hernández et al., 2013). The process is very similar: a cut is made to expose the hillside, and then the area is flooded by blasts of water from high pressure hoses to flush the soil into the sluice where a machine is used to separate gold particles from the remaining matrix of soil and stone. This gravity washing system accelerates erosion and liberates toxic materials from the matrix that then are flushed into the river. This explains why high levels of arsenic have been found in some rivers (CID-PUCESE & PRAS-MAE, 2012, even though arsenic is not used in the mining process. The huge amounts of sediments dangerously increase the turbidity of the water and downstream transport of materials that directly affect water quality downstream (table 2). This activity has greatly increased since 2008, when there were just a few mines, to over 200 in 2012, along almost the entire length of the Santiago River (Lapierre-Robles, 2012), and the practice shows no signs of diminishing, since gold prices remain high, a fact that underlies the great increase observed since 2008.
(Esmeraldas Campus) for financing an expedition to Esmeraldas Province in the Pacific versant of Ecuador, and the organization of (PJ-P) and participation in (CR-V, RI-RC, CAG-A) the First National Meeting of Ichthyology that took place in Esmeraldas, Ecuador from 23-28 September 2014. We thank Eduardo Rebolledo (CEMZ-P) for help with sampling and Ramiro Barriga (MEPN) for the loan of specimens. Cristian Román-P (UV & IUQ) made figure 4. We thank the editor of ABC, Rafael Zardoya, and Marcos Mirande and an anonymous referee for their comments and corrections which helped to improve this paper.