Apistogramma erythrura sp. n. – a new geophagine dwarf cichlid (Teleostei: Perciformes: Cichlidae) from the río Mamoré drainage in Bolivia

The South American genus Apistogramma REGAN is one of the most species rich cichlid genera. At present there are almost 70 valid species. In addition more than 30 undescribed species are listed in the popular aquarium literature (RÖMER, 2006; STAECK, 2003a; STAECK & LINKE, 2006). All Apistogramma species are small cichlid fi shes for the male individuals, which are usually greater than females, generally have a SL length of less than 60 mm. Pronounced sexual dimorphism in morphology, fi n shape and colour patterns is common in this genus. Males of different species are usually more distinct from each other than females. STAECK & LINKE (2006) recorded Bolivian localities for 11 Apistogramma species. Since then two additional species have been collected in the drainages of the Amazon tributaries in the north of Bolivia (STAECK, 2007; 2008). The species described below from the drainage of the río Mamoré is an example of the many Apistogramma species which have become well-known in the popular aquarium literature long Apistogramma erythrura sp. n. – a new geophagine dwarf cichlid (Teleostei: Perciformes: Cichlidae) from the río Mamoré drainage in Bolivia


Introduction
The South American genus Apistogramma REGAN is one of the most species rich cichlid genera.At present there are almost 70 valid species.In addition more than 30 undescribed species are listed in the popular aquarium literature (RÖMER, 2006;STAECK, 2003a;STAECK & LINKE, 2006).All Apistogramma species are small cichlid fi shes for the male individuals, which are usually greater than females, generally have a SL length of less than 60 mm.Pronounced sexual dimorphism in morphology, fi n shape and colour patterns is common in this genus.Males of different species are usually more distinct from each other than females.STAECK & LINKE (2006) recorded Bolivian localities for 11 Apistogramma species.Since then two additional species have been collected in the drainages of the Amazon tributaries in the north of Bolivia (STAECK, 2007;2008).The species described below from the drainage of the río Mamoré is an example of the many Apistogramma species which have become well-known in the popular aquarium literature long before material was available for a formal description.It was introduced into the German aquarium trade in 1995 (STAECK, 1996) and provisionally referred to by the popular name Apistogramma sp."Mamoré".Subsequently colour photos were frequently published in the aquarium literature.As now suffi cient material of this species is available, the objective of this paper is to present its formal description.

Materials and Methods
Some type specimens were fi xed in ethanol, others in formalin and later transferred into 75% ethanol.The holotype and paratypes are deposited in the fi sh collection of the Museum für Tierkunde Dresden (MTD F).The techniques for taking measurements and meristic data follow those described in KULLANDER (1980KULLANDER ( , 1986) ) and KULLANDER & NIJSSEN (1989).Measurements were made with an electronic digital caliper reading to the nearest 0.1 mm.Numbers in brackets after counts indicate the number of specimens examined with that condition.Terminology and methods of measurements of jaws and teeth follow CASCIOTTA & ARRATIA (1993).Scale rows are numbered as described in KULLANDER (1990).The description follows the general format used by KULLANDER & FERREIRA (2005).

Diagnosis.
A small, relatively high-bodied (body depth 34-38% of SL) geophagine cichlid with a marked secondary sexual dimorphism, differing from other Apistogramma species by the combination of (1) only two postlacrymal infraorbital lateralis canal pores, (2) fi ve dentary lateralis canal pores, (3) a broad lateral band with even borders that widens posteriorly to a height of at least two and a half scale rows and extends into the anterior half of the caudal fi n without a caudal spot, (4) the absence of both an oblique dark stripe between the pectoral-fi n base and the anal fi n origin and of any other dark markings below the lateral band, and in adult males (5) usually a partly or even completely bright red rounded caudal fi n, (6) extremely produced anterior dorsal-fi n lappets (those of 4 th to 6 th spine longest) and (7) prolonged pelvic-fi n fi laments reaching the posterior end of the anal-fi n base.
Etymology.The species epithet is a compound derived from the Greek erythro (= red) and ura (= tail).
The name refers to the conspicuous colour of the caudal fi n in the majority of adult males.
Description.Refer for general appearance and colour pattern to Figs. 1-6.Morphometric data of 14 speci-mens are summarised in Tab. 1. Description of osteological characters from two dissected paratypes.
Relatively high-bodied species (body depth 34.0-38.2% of SL).Predorsal and preventral contours about equally steep.Snout short, rounded in lateral and dorsal views.Mouth terminal, jaws equal anteriorly; maxilla extending to margin of orbit.Eye located supralateral, margin slightly distant from predorsal contour.
Head length about 1/3 of SL.Caudal peduncle slightly deeper than long.Dorsal fi n in adult males with anterior lappets extremely elongated, those of 3 rd to 5 th spine longest.From 7 th spine lappets immediately shorter, but still extending beyond tips of spines.Dorsal fi n lappets in females rounded or slightly truncate.Soft dorsal and anal fi n in males pointed, in females rounded.Caudal  fi n in males and females rounded, comparatively short (29-38% of SL in males, 25-28% of SL in females), with 3 procurrent and 8 principal rays in each lobe.Pelvic fi ns pointed, fi rst ray in males extremely elongated (up to 64% of SL).Pectoral fi ns rounded (pectoral-fi n length about 25% of SL).Dorsal fi n XIV.7(1), XV.6(5), XV.7(6) or XVI..6(2).Anal fi n: III.6(9) or III.7(5).

Colouration in life.
Based on observations immediately after capture and on specimens kept in aquarium.As Apistogramma erythrura is an exceptional example of distinct polychromatism in males of the same population, variation of the live colouration is notable among adult males of this species.Basically there are two different colour morphs having either a blue or a yellowish ground colour.Blue males are characterized by a predominantly light blue body.Forehead, nape and dorsal region dark grey; cheeks, operculum, breast and ventral region whitish.In some specimens, however, the lower region of the head is yellow with a number of blue dots instead of whitish.Lower portion of infraorbital stripe usually reduced to a conspicuous spot in the corner of the preopercle.This mark is bright red in some specimens, in others black.All these colour variations occur in the same population.Dorsal, anal and pelvic fi ns blue.Dorsal fi n usually with a dark base and a narrow yellowish margin.Caudal fi n either completely or only in its lower portion bright red and with several ill-defi ned tiny dark vertical spot-stripes in its distal part.But in all the populations examined a fraction of the male individuals had a completely hyaline caudal fi n with a reticulated pattern of tiny dark vertical spot-stripes.
The yellow colour morph has a yellowish ground colour ranging from dull in the dorsal to light yellow in the ventral region and the lower portion of the head.A number of light blue dots on cheeks and operculum.Above the lateral band some scales often with a maroon dot in their centre.Anal fi n and ventrals yellowish.Dorsal fi n grey with darker base and narrow orange margin.Colouration of caudal fi n as described for blue morph.
All colour morphs with broad lateral band with sharp borders.It is usually more intense posteriorly, widens from postorbital stripe posteriorly to a height of at least two and a half scale rows and extends into the anterior half of the caudal fi n without a caudal spot.Inner margin of iris bright red in all morphs and in both sexes.
Females beige-coloured with yellow head, grey dorsal, anal and pelvic fi ns, hyaline caudal fi n and conspicuous dark lateral band.During brood care body lemon yellow, with black spot in the corner of the preopercle and lateral band usually reduced to lateral spot.First two anterior dorsal-fi n membranes and anterior portion of ventral fi ns black.
All the colour varieties occur independently of each other and in different combinations among the males of the same population.Experience gained from several broods raised in aquaria confi rms that the different phenotypes may even occur in a single brood.
Among one brood of a pair of Apistogramma erythrura from the Laguna Piranha there were 34 females and 31 males.The male parent was a specimen of the blue morph with a yellow head, a red mark in the corner of the preopercle and a hyaline caudal fi n.
Among its offspring there were 20 males with a red and 11 with a hyaline caudal fi n, 21 males with a yellow and 10 with a white head; 19 males had a black, 12 a red mark in the corner of their preopercle (see Tab. 2).Polychromatism of males is not uncommon in the genus Apistogramma (see KULLANDER & STAECK;1988;STAECK, 2003b).

Colouration in alcohol.
Based on holotype and paratypes.Body and fi ns yellowish grey, with dark grey markings; forehead, nape, back close to dorsal fi n and basal dorsal fi n darker.Lateral band in males with sharp edges, more intense posteriorly, extending into the anterior half of the caudal fi n without a caudal spot and broadening to a height of at least two and a half scales from postorbital stripe to caudal peduncle.No abdominal stripes or markings.Roundish lateral spot (if visible) not extended beyond lateral band.Caudal spot replaced by continuation of dark lateral band to middle portion of caudal fi n.Anterior two dorsal-fi n membranes dark grey.Caudal fi n either with reticulated pattern of dark vertical stripes of tiny spots or only with ill-defi ned stripes in its distal part.Infraorbital stripe usually reduced to a spot in the corner of the preopercle.

Geographical distribution.
Apistogramma erythrura is known from several localities in the drainage of the lower río Mamoré in the province of Beni in Bolivia.Confi rmed collecting sites are situated between the drainage of the río Yata in the west (Laguna Larga and Laguna Piranha in the northwest of Santa Ana de Yacuma) and the drainage of the río Itonamas (Laguna Mapawa in the north of Magdalena) in the east of Bolivia.In addition the species is also said to be exported for the aquarium hobby from the Lago das Cobras in the drainage of the Río Pacaás Novos in the southeast of the town Guajará-Mirim in the state of Rôndonia in Brazil (KOSLOWSKI, 2002).
Tab. 2. Different colour varieties (R = red caudal fi n, H = hyaline caudal fi n, Y = yellow head, W = white head, P = preopercle with red mark, B = preopercle with black mark) among the males (n = 31) of a single brood of Apistogramma erythrura.

Male phenotype Number of individuals
Ecological notes.All our collecting sites of Apistogramma erythrura are typical clear-water habitats with acid, very soft transparent and colourless water.
The following water data were gathered in July, Au-    The fi sh were exclusively collected in dense macrophyte vegetation along the banks of lakes and sometimes small rivulets.Apistogramma erythrura is most abundant in fl oating meadows where the fi sh hide inside the dense carpet of large crops of Eichhhornia azurea mixed with fl oating Paspalum repens, Cabomba furcata or Utricularia spp.When scared they jump out of the water and often lie motionless for ten or twenty seconds on the surface of emersed leaves of the vegetation.In a few cases the dwarf cichlids were also found in extremely shallow water in the submerged grass-like terrestrial vegetation extending into the water or in a layer of dead leaves covering the bottom of the bank side.According to our under water fi eld observations in the fl oating meadows the associated fi sh fauna includes Moenkhausia australis, Hyphessobrycon elachys, Hyphessobrycon meglopterus, Hyphessobrycon herbertaxelrodi, Nannostomus trifasciatus and Nannostomus unifasciatus.In the adjacent deeper water the cichlid Mesonauta festivus was observed.
Intestinals (length about 75 % of SL) of three specimens (20.9-30.8mm SL) from the Laguna Larga were used for diet analyses.Arrangement of the stomachintestinal tract is similar to stage C in ZIHLER (1982).In stomachs and adjacent intestines anomopod cladocera were the dominant food item.A few copepoda, some mites (acari) and different insect larvae (nematocera and other not identifi ed insects) were additional major food matter.These observations suggest that Apisto-gramma erythrura feeds mainly on small autochthonous invertebrates.
Reproductive behaviour.Observations under aquarium conditions revealed Apistogramma erythrura to be a polygynous secretive spawner.Males defend a territory containing several potential spawning sites.Each of them may serve as the focus of a smaller territory occupied by a female.Like most cave brooders these dwarf cichlids place their eggs on the bottom side of a horizontal surface.The preferred spawning site is the underside of a stout plant leaf.
At 27 °Celsius hatching occurs about three days postspawning, and the fry attempt swimming approximately fi ve days thereafter.After spawning the female drives the male energetically from the close proximity of the spawning site.Parental care is exclusively maternal in this species, although the male may indirectly assist by defending the territory against predators.
The development of the oblique dark stripe from the pectoral to the origin of the anal fi n in Apistogramma trifasciata depends on collecting site, mood, size and age (HASEMAN, 1911;KOSLOWSKI 2002;pers. obs.).In live and preserved specimens of Apistogramma trifasciata from the drainage of the lower río Yata in the vicinity of Riberalta the stripe is very faint or in some specimens even missing.Nevertheless this marking is a diagnostic feature distinguishing adult specimens of Apistogramma trifasciata from all its congeners.
Apistogramma erythrura differs from A. trifasciata by a slightly deeper body (body depth 34-38%, mean       36.1% of SL in adult males of A. erythrura vs. 32-34%, mean 33.4% of SL in the comparative material of A. trifasciata), absence of any abdominal markings below the lateral band (vs.dark oblique stripe from lower margin of pectoral fi n to anal-fi n origin), reduction of infraorbital stripe to a black spot on the lower posterior edge of the gill cover in breeding females (KOSLOWSKI, 2002) or to a bright red spot in some males (vs.no reduction of infraorbital stripe), the at least partly bright red caudal fi n in the majority of adult males and by a broader lateral band that widens posteriorly to a height of at least two and a half scale rows (vs.max.height one and a half to two scales) and usually covers almost the whole caudal peduncle.
The relationships of Apistogramma erythrura and A. trifasciata with their congeners are not clear, for there are several possible relationship hypotheses (KULLANDER, 1982;KOSLOWSKI, 2003;RÖMER, 2006).With regard to derived character states (e. g. pronounced sexual dimorphism and dichromatism, 2 postlacrymal infraorbital lateralis canal pores, produced anterior dorsal-fi n membranes in males) the similarity of both seems strongest with species of the Apistogramma cacatuoides and Apistogramma nijsseni species groups (KOSLOWSKI, 2003;RÖMER, 2006).But unlike most of those species Apistogramma erythrura and A. trifasciata have a rounded caudal fi n (vs.produced marginal caudal fi n rays).Only four species of theses two species groups also have a rounded caudal fi n and produced anterior dorsal-fi n membranes, viz.Apistogramma atahualpa RÖMER, 1997, A. baenschi RÖMER et al., 2004, A. norberti STAECK, 1991and A. rositae RÖMER et al., 2006.Apart from other character states Apistogramma erythrura differs from them in the absence of conspicuous dark dorsal markings, vertical bars and a wide suborbital stripe.In contrast to the occurrence of Apistogramma erythrura the distribution of these four species is restricted to the upper drainages of the Amazon river in Peru.

Fig. 2 .
Fig. 2. Live topotypic adult male of the yellow colour morph of Apistogramma erythrura sp.n. immediately after capture in a photographic tank.

Fig. 6 .
Fig. 6. Adult female of Apistogramma erythrura sp.n. from type locality during brood care in aquarium.

Figs. 13
Figs.13 A-C.Selected teeth (medial aspect) of lower and upper pharyngeal tooth-plate of Apistogramma erythrura sp.n.; A and B are in correspondence with indicated teeth of lower pharyngeal tooth-plate in Fig.12; C = largest tooth of 3 rd pharyngobranchial.