Dicrossus gladicauda sp . n . – a new species of crenicarine dwarf cichlids ( Teleostei : Perciformes : Cichlidae ) from Colombia , South-America

The South American cichlid genus Dicrossus was fi rst established as a monotypic genus for Dicrossus maculatus by STEINDACHNER (1875). Later REGAN (1905) regarded Dicrossus as a synonym of Crenicara, a view followed by other authors (AHL, 1936, LADIGES, 1959, KULLANDER, 1978). In 1990 KULLANDER briefl y discussed the taxonomic status of Dicrossus. He pointed out that Dicrossus and Crenicara are distinct enough to be treated as separate taxa and consequently revalidated it. KULLANDER (1998) thought Dicrossus a genus of the tribus Crenicarini (also including Biotoecus STEINDACHNER, Crenicara STEINDACHNER and Mazarunia KULLANDER). But this group (including Biotoecus) was not verifi ed as monophyletic in the cladistic analysis of geophagine Cichlids by LÓPEZ-FERNÁNDEZ et al. (2005). In both studies, however, Dicrossus and Crenicara are recognized as sister taxa sharing a serrated posterior margin of the preopercle. This is a conspicuous, relatively rare character state within SouthAmerican cichlids (KULLANDER, 1990). At present the genus includes two valid species (KULLANDER, 1990; 2003), viz. Dicrossus maculatus Dicrossus gladicauda sp. n. – a new species of crenicarine dwarf cichlids (Teleostei: Perciformes: Cichlidae) from Colombia, South-America


Introduction
The South American cichlid genus Dicrossus was fi rst established as a monotypic genus for Dicrossus maculatus by STEINDACHNER (1875).Later REGAN (1905) regarded Dicrossus as a synonym of Crenicara, a view followed by other authors (AHL, 1936, LADIGES, 1959, KULLANDER, 1978).In 1990 KULLANDER briefl y discussed the taxonomic status of Dicrossus.He pointed out that Dicrossus and Crenicara are distinct enough to be treated as separate taxa and consequently revalidated it.KULLANDER (1998) thought Dicrossus a genus of the tribus Crenicarini (also including Biotoecus STEIN-DACHNER, Crenicara STEINDACHNER and Mazarunia KULLANDER).But this group (including Biotoecus) was not verifi ed as monophyletic in the cladistic analysis of geophagine Cichlids by LÓPEZ-FERNÁNDEZ et al. (2005).In both studies, however, Dicrossus and Crenicara are recognized as sister taxa sharing a serrated posterior margin of the preopercle.This is a conspicuous, relatively rare character state within South-American cichlids (KULLANDER, 1990).
At present the genus includes two valid species (KULLANDER, 1990;2003) ER, 1990ER, , 2003)).In addition at least three undescribed species have been known for some time (KULLANDER, 1990, STAWIKOWSKI & WERNER, 2004).The purpose of the present paper is to give a formal description of one of these species, which has been known for several years in the aquarium hobby and was provisionally referred to as Dicrossus sp."Obenschwert" in the aquarium literature (BORK, 2002;STAWIKOWSKI & WERNER, 2004).

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).Data from KULLANDER (1978KULLANDER ( , 1990)), KULLANDER & STAECK (1990), STAWIKOWSKI & WERNER (2004) and STEINDACHNER (1875) were used for comparison.

Diagnosis.
A small crenicarine cichlid with a marked secondary sexual dimorphism.It differs from all the other species in the genus by the conspicuously asymmetrical caudal fi n characterized by the long fi lamentous streamer of its dorsal lobe in adult males.The new species is most similar to Dicrossus fi lamentosus, which differs in having a lyreate caudal fi n (i.e. both the marginal rays of the dorsal and the ventral part of caudal fi n are distally produced into a fi lamentous streamer).

Description.
Based on all type-specimens.Osteological characters from one dissected paratype (female, 32.4 mm SL).See Figs.1-3 for general appearance and colour pattern.Body elongate (depth up to 26% of SL in males, up to 29% in females), moderately compressed laterally.Predorsal-and preventral contour about equally arched.Abdominal contour in females slightly convex, in males more or less straight.Caudal peduncle longer than deep.Head elongate (HL 29-31% of SL), narrowing to snout tip.Snout round in dorsal and lateral view.
Scales in E1 row 24 (1) or 25 (7).Lateral lines not overlapping.Upper lateral line with 13 to 17 scales, reaching to below last dorsal spine.Lower lateral line with 5 to 7 scales.Fins naked, except caudal fi n which is scaled on about one fourth or one third of its principal length (measured without fi lamentous streamer).Dorsal fi n origin above posterior edge of operculum or slightly behind.Anterior fi ve (or six) spines of dorsal fi n increasing rapidly in length (length of fi rst spine about one fourth of the fi fth spine), then slightly decreasing in length to about the 9 th or 10 th , from there about equal in size.Soft portion of dorsal fi n pointed (not fi lamentous) in males, round in females.Caudal fi n asymmetrical in adult males: Dorsal lobe of caudal fi n distally with conspicuous fi lamentous streamer, medial part truncate or slightly concave, ventral lobe rounded.Caudal streamer of upper lope produced by elongation of rays D3 and D4; rays V3 to V8 form a roundish or subtruncate margin.In females and young specimens caudal fi n round to slightly truncate.Each lobe of caudal fi n with 8 principal rays.Anal fi n pointed in males, rounded in females.Pelvic fi ns pointed, fi lamentous in males (reaching soft part of anal fi n).Pectoral fi n rounded, 10 (6) or 11 (2) rays, fi fth ray usually longest.Dorsal fi n rays XIV.8 (2) or XV.8 (6).Anal fi n rays III.6 (1) or III.7 (7).
Teeth in three series in both jaws (outer series dominating inner ones), caniniform, straight or moderately recurved.Length of dentigerous arm of premaxilla shorter than length of ascending arm (AL/DL = 1.7); width of the ascending arm about 17% of its length.Angle formed by confl uence of both arms about 83°.Ventral margin of dentigerous arm slightly concave.Anterior four or fi ve teeth of outer row of premaxilla erected, conspicuously longer than posterior ones.Outer hemiseries of upper jaw with 20/23

Colouration in alcohol.
Ground colour yellowish or whitish, duskier above upper lateral line.A series of six (two specimen) or seven dark, squarish or rectangular blotches along middle of fl anks.First covering the anterior two or three scales of row 0 and adjacent parts of row E1 and row H1; second above belly; third (most prominent) above anterior part of anal fi n; fourth above soft part of anal fi n; fi fth and sixth on caudal peduncle (less intense, without well defi ned edges, often ventrally extended on H2 scale row).Seventh blotch (if present) on posterior end of caudal peduncle and anterior part of caudal fi n (intensely blackish, quadratic or ventrally slightly extended).Arrangement and position of the fourth to seventh blotch somewhat variable.
A second series of seven or (rarely) six dark squarish or rectangular blotches along back and on dorsal edge of caudal peduncle.Blotches on caudal peduncle not well defi ned, often fused with each other.Head whitish below eye, above dark grey.With prominent dark preorbital stripe; postorbital stripe short; no suborbital stripe.Dorsal fi n of males with mottled pattern of irregularly arranged dark dots and short oblique streaks.In females dorsal fi n with an indistinct dusky intramarginal band.Anal fi n of males dusky or clear, posterior soft part with distinct dark spots.In females anterior and distal part of anal fi n dusky.Caudal fi n of males dusky (dorsal lobe darker than ventral lobe), with small dark spots arranged in six to eight cross lines (anterior series more distinct than distal ones).In females anterior central part dusky with a few spots (more prominent in dorsal lobe).Ventral fi n of males dusky, without or only tiny blackish spots at fi n base.Females with a distinct black spot at fi n base, extending along anterior margin.Pectoral fi ns hyaline in both sexes.

Discussion
The new species shares all the diagnostic characters of Dicrossus described by STEINDACHNER (1875) and KULLANDER (1990), viz.small size, elongate shape, laterally only moderately compressed body, serrated preoperculum, supracleithrum and posttemporal, elongated anguloarticular without bony enclosed mandibular sensory canal, two series of dark blotches arranged in the pattern of a checkerboard on the body sides and lack of both suborbital stripe and prominent dark lateral stripe in preserved specimens.
Dicrossus gladicauda is most closely related to Dicrossus fi lamentosus.Both species are very similar and cannot be separated by proportional or meristic characters, but differ signifi cantly in the shape and colour pattern of the caudal fi n of adult males.In Dicrossus fi lamentosus the caudal fi n of males is lyreate and distally produced into two fi lamentous streamers, while in adult males of Dicrossus gladicauda the fi n is asymmetrical, for only its upper lobe has a fi lamentous prolongation while the lower lobe is rounded.The reduction of the length of V3 and V4 in the ventral part of the caudal fi n in Dicrossus gladicauda correlates with the lack of the dark margin and the submarginal bluish stripe of the caudal streamers characteristic of the male Dicrossus fi lamentosus.
Dicrossus gladicauda is distinguished from Dicrossus maculatus by the shape of the caudal fi n in adult males (upper lobe with streamer versus lanceolate) and the shape of the dark blotches on the body sides (squarish or rectangular versus more rounded; cf.STAECK & LINKE, 2006;STAWIKOWSKI & WERNER, 2004).An asymmetrical caudal fi n with a rounded lower lobe and a prolongation of the upper lobe ending in a fi lamentous streamer is a unique feature among South American cichlids.In spite of the overall similarity between Dicrossus gladicauda and Dicrossus fi lamentosus, we describe the new form as a separate species and refrain from using a subspecifi c category for we agree with KULLANDER (1999KULLANDER ( , 2004) that every single diagnosable form deserves its own specifi c treatment Geographical distribution.At present Dicrossus gladicauda is known only from the type locality in the drainage of the lower río Atabapo in Colombia.The species, however, is said to be exported for the aquar-ium hobby from the río Reita in the vicinity of the village Cumaribo in Colombia (BORK, 2002).This small river is a tributary to the río Tomo, a western tributary to the río Orinoco.
Ecological notes.The type locality of Dicrossus gladicauda is a typical blackwater habitat with clear, acid and very soft tea-coloured water (pH 4.4; electrical conductivity 10 μS/cm; total and temporary hardness < l °dH; water temperature 24.4 °Celsius).The fi sh were collected along the banks of the small rivulet in zones of extremely shallow water, i.e. in a water depth between approx.10 and 50 cm, where they were found either in a layer of dead leaves covering the bottom of the bank side or among the submerged terrestrial vegetation.Field observations under water indicated that in this microhabitat the associated fi sh fauna includes several small characid species, e. g.Hemigrammus bleheri, Hyphessobrycon stictus, Nannostomus eques, Paracheirodon axelrodi, Copella meinkeni and the dwarf cichlid Apistogramma uaupesi.In the adjacent deeper water the cichlids Mesonauta insignis and Biotodoma wavrini were observed.
Reproductive behaviour.Observations under aquarium conditions revealed Dicrossus gladicauda to be a polygynous substrate spawner and that the male defends 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 other open brooders these dwarf cichlids place their eggs on a horizontal surface.The preferred spawning site is a stout plant leaf or drift wood.At 27 °C hatching occurs about three days postspawning, and the fry attempt swimming six 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.
Etymology.The specifi c epithet is a noun in apposition derived from the Latin gladius (= sword) and cauda (= tail).It is an allusion to the sword-like streamer of the dorsal lobe of the caudal fi n in adult males.

(
left/right) teeth along entire arm.Lower jaw long and comparatively low (anguloarticular depth about 52% of length).Coulter area wider than deep, without bony mandibular canal.Anterior teeth on dentary procumbent; outer hemiseries with 19/22 teeth along entire arm.Lower pharyngeal tooth plate triangular in dorsal aspect (width/length ≈ 1.2), with 12 teeth in posterior row and 14 in median row.Anterior teeth pointed, uniscuspid, rather scattered.Posterior inner teeth regularly arranged; a few of the innermost teeth laterally compressed and biscupid.First caretobranchial with 4 or 5 (n=4) external gill rakers.Colouration in life.Body of males with yellowish ground colour, upper portion usually tan or greyish, ventral region white.Two longitudinal series of alternating squarish or rectangular black spots along middle of fl anks (fl ank spots) and in dorsal region (dorsal spots).Six or seven fl ank spots of variable shape (longer than deep, shorter than deep or squarish) between operculum and caudal fi n.Seven dorsal spots between nape and dorsal edge of caudal peduncle, last two very narrow.Frequently a few black scales irregularly spread over the ventral region.With broad preorbital stripe from orbit to snout tip; postorbital stripe
pale.No suborbital or superorbital stripe.Dorsal fi n in males clear, with red spots in posterior and red streaks in anterior portion; with narrow red margin and blue submarginal band.Caudal fi n in males bluish, in its central portion with tiny red spots arranged in about 7 wavy vertical cross-lines.Caudal streamer with narrow red margin and bright blue submarginal band.Anal fi n bluish or violet with small red spots in posterior and red streaks in anterior part.Ventral fi ns with blue and red longitudinal markings.Pectoral fi ns colourless and hyaline.Colouration of females similar, but fi ns hyaline, without any red or blue markings.