Crenicichla yaha Casciotta, Almirón & Gómez, 2006

Říčan, Oldřich, Almirón, Adriana & Casciotta, Jorge, 2017, Rediscovery of Crenicichla yaha (Teleostei: Cichlidae)., Ichthyological Contributions of PecesCriollos 50, pp. 1-8 : 2-5

Crenicichla yaha Casciotta, Almirón & Gómez, 2006

Rediagnosis. A molluscivorous species as suggested by stout lower pharyngeal jaw (LPJ) with molariform teeth along midline and posterior edge, and robust head (head depth, interorbital width) with short jaws and subterminal (hypognathous) mouth. Most similar in these characters and in overall body and head shape and coloration patterns to the other two molluscivorous species in the C. mandelburgeri group ( C. tesay from the Iguazú and C. taikyra from the lowermost Middle Paraná). Crenicichla yaha is the most robust of the three species. Distinguished from C. tesay by 1) lacking spotted body in both sexes (vs. present in both), 2) developing an orange branchiostegal membrane and an orange diffuse area on lateral belly below midlateral blotches in breeding females (vs. absent), 3) having the suborbital stripe composed of neatly arranged horizontal rows of equally-sized and equally-spaced spots (vs. more irregular spotted pattern as in most other Crenicichla species except C. taikyra and C. hu which have a similar suborbital stripe spot-arrangement), 4) midlateral blotches usually with an H-like shape and dorsally continuing double bars (as in the sympatric species C. ypo , but otherwise unique among the C. mandelburgeri species group vs. rectangular or roundish with much less distinct laterodorsal double bars), 5) dorsal body and head of a slightly different color (usually more brownish) compared with the rest of the body rather than the uniform coloration in C. tesay (usually whole more greyish) and 6) slightly less scales in E1 row. Distinguished from the other molluscivorous species C. taikyra by points 4 and 5 (point 2, breeding coloration of females, is not known in C. taikyra ), by having a distinctly more robust head and body (both almost without overlap) and by having distinctly less scales in E1 row (also without overlap). Distinguished from all other species in the C. mandelburgeri group by the molluscivorous-associated characters (robust LPJ, robust LPJ teeth, robust head with short jaws and hypognathous mouth). Distinguished from all species in the C. missioneira group (that also include molluscivorous species) by well developed suborbital stripe (vs. very weakly developed and diffuse, composed of a few isolated spots at best).

Remarks. Specimens from AI 199 (1 ex., 116.6 mm SL, Argentina, Misiones Province, arroyo Benavente, coll. Gómez et al. February, 1983) and AI 315 (1 ex. (C&S) 77.6 mm SL, río Iguazú superior, Parque Nacional Iguazú) were previously erroneously included in the type material (AI 199) or referred to C. yaha , respectivelly. Both specimens represent C. tesay . The AI 199 lacks the distinguishing spotting on body of C. tesay because of it long-term exposure to sunlight during storage at NP Iguazú.

In the original diagnosis and description erroneously reported as a non-molluscivorous species due to examination of a juvenile specimen (47.7 mm SL, Figure 2 in the original description; Casciotta et al., 2006). In the description of C. taikyra specimens referred to C. yaha represent both C. yaha (the majority of specimens but one) and C. tesay (one specimen AI 315; see below) and this C. yaha is correctly reported as a molluscivorous species. Adult specimens of C. yaha as treated here and in Piálek et al. (2015; i.e. as a distinct species from C. tesay ) and as examined here (partial dissections including large female MLP 11215 DNA1043, 122.0 mm SL) have stout LPJs and robust molariform LPJ teeth. The figured LPJ referred to a larger young C. yaha ( Figure 2b in Casciotta et al., 2013) is from a specimen from the Iguazú river and hence based on our reexamination ( Piálek et al., 2015) belongs to C. tesay . The comparison of LPJ shape and LPJ teeth (and microbranchispines) in the original diagnosis of C. taikyra ( Casciotta et al., 2013) is thus with C. tesay and not with C. yaha . Comparable sized young fish of C. taikyra and C. tesay ( Figure 2 in Casciotta et al., 2013) show that the LPJ and LPJ teeth are more robust in C. taikyra than in C. tesay . The LPJ of the adult female C. yaha (MLP 11215, 122.0 mm SL) is more robust with more robust teeth than in C. tesay and more similar in robustness to C. taikyra .

The three molluscivorous species of the C. mandelburgeri complex ( C. yaha , C. tesay , C. taikyra ) are distinct in a number of characters (see rediagnosis of C. yaha above). Crenicichla yaha is the most robust species in both head and body while C. taikyra is the least robust species. Crenicichla yaha has the largest interorbital distance (id in percents of SL; mean 8.1, SD 0.56, range 7.5–9.0), the largest head depth (hd mean 18.9, SD 1.02, range 17.9–20.8) and the largest body depth (bd mean 25.7, SD 1.61, range 23.3–27.7). Intermediate is C. tesay (id mean 7.2, SD 0.61, range 6.1–8.6; hd mean 18.2, SD 1.15, range 16.4–19.9; bd mean 23.4, SD 1.22, range 20.9–25.9) while the C. taikyra is the least robust (id mean 6.7, SD 0.50, range 5.7–7.5; hd mean 17.3, SD 0.79, range 16.2–19.4; bd mean 22.1, SD 0.90, range 20.8–23.8).

The three species differ also in the number of scales in E1 row where C. yaha and C. taikyra do not overlap and C. yaha again is the most robust species (i.e. with the lowest number of largest scales). The type series of C. yaha ( Casciotta et al., 2006) has 48–51 (mean 51) scales in E1 row [48(2), 49(1), 51(7)], the type series of C. taikyra ( Casciotta et al., 2013) has 54–60 (mean 56-57) scales in E1 row [54(2), 55(1), 56(7), 57(5*), 58(3), 60(3)] and the rediagnosed C. tesay ( Piálek et al., 2015) has 49–59 (mean 54) scales in E1 row [49(1), 50(1), 52(4), 53(3), 54(10), 55(3), 56(5), 57(2), 58(2), 59(1)]. Based on morphological character distribution it is possible that the three molluscivorous species in the C. mandelburgeri group (i.e. C. yaha , C. tesay and C. taikyra ) are closely related and that the molluscivory has originated only once. In fact a close relationship between C. tesay and C. taikyra is supported by both mtDNA ( Piálek et al., 2012) and nDNA (Piálek et al., in prep.) phylogenies suggesting separation of one ancestral species into two by dispersal of C. taikyra ancestors downstream over the Iguazú falls (as already postulated by Casciotta et al., 2013). Crenicichla yaha however on the other hand uniquely among the three species shares several characteristics (H-like midlateral blotches, orange flank coloration of breeding females, the lowest number of E1 scales) with the sympatric C. ypo [number of E1 scales 47-55, mean 53; 47(2*), 48(1), 51(3), 53(5), 54(3), 55(3)], while C. tesay is uniquely identical in coloration to the sympatric C. iguassuensis ( Piálek et al., 2015) . The phylogenetic position of C. yaha (whether it is with C. tesay and C. taikyra or with C. ypo ) and the potential of hybridization (e.g. with the sympatric C. ypo or with other species in the Paraná) thus remains to be ascertained with nuclear phylogenomic data (Piálek et al., in prep.).

Live coloration constitutes the most important character complex in morphologically very similar (and often closely related) species of cichlids. Several examples of this fact are available from the studied genus in our study area and from the three here treated molluscivorous species. The lack of live coloration lead e.g. Varella (2011) to conclude that two very dissimilar species ( Crenicichla tapii and C. tuca ; Piálek et al., 2015) in live coloration (and in a number of morphological characters) are conspecific (treated as C. sp. Iguacu in Varella, 2011). The species treated by Varella (2011) as C. tesay is in fact an undescribed species from the Rio Jordão (and possibly Rio Areia and other nearby rivers including the mainstem of the Iguazu in this area ( Frota et al. 2016; pers. comm. 14.12.2016) distinctive from C. tesay in live (and also preserved) coloration patterns and in phylogenetic relationships based on both mtDNA and nDNA markers (Říčan et al., unpublished results) while the C. yaha of Varella (2011) is C. tesay ( Piálek et al., 2015) . Apart from the aquarist community and a handful of dedicated cichlid researchers it is unfortunately still very rare to photograph cichlids in the field immediately after capture during general collection efforts and very valuable and all-important information is thus still being lost. Live coloration of cichlid fishes is of key importance for both cichlids systematics and their biology and we urge all Neotropical ichthyologists to photograph all cichlids when still alive immediately after collection.

Coloration in live. Overall coloration on head and upper back brownish (with orange tones in breeding females) contrasting with paler greyish-whitish flanks and belly up to the midlateral blotches (vs. uniform head and body coloration in C. tesay and C. taikyra ). Crenicichla yaha lacks the black spotting on body of C. tesay (present in both sexes). Orange coloration in form of a diffuse band below the midlateral blotches on flank in breeding females also distinguishes C. yaha from C. tesay , but is similar to the sympatric C. ypo and all related species in the Middle Paraná. Orange coloration of branchiostegal membrane in breeding females also distinguishes C. yaha from C. tesay and the sympatric C. ypo (where in both cases grey). Breeding females with a black elongated spot in dorsal fin with white margin as in all related species in the Paraná /Iguazú (including C. tesay ) except the sympatric C. ypo (among the C. mandelburgeri complex the orange band in ventral portion of the dorsal fin and a black band above it without a white margin is unique). This character difference in the dorsal fin from the sympatric C. ypo suggests sexual segregation and species recognition suggesting long-term sympatry. Males of C. yaha with spotted dorsal fin distinguishing them from females. Midlateral blotches are distinctly H-shaped (as in the sympatric C. ypo ) and the double bars dorsad from the H-shaped blotches are also distinct (as in C. ypo ). Suborbital stripe composed of neatly arranged horizontal rows of equally-sized and equally-spaced spots (shared with C. taikyra and C. hu vs. more irregular spotted pattern as in most other Crenicichla species including C. tesay and the sympatric C. ypo ).

Distribution and ecology. Crenicichla yaha is endemic to the Urugua-í basin above the original 28 m high waterfall, i.e. above the present dam. It does not however occur in the artificial lake which has everywhere a muddy bottom but is apparently only found in the middle stretches of the main stream and its main tributary (arroyo Falso Urugua-í; figure 6) in areas with bottoms made of stones, boulders and solid rock. Here C. yaha is syntopic with the much more common C. ypo and in rare cases with the undescribed predatory C. sp. Urugua-í line which is common only in the artificial lake. Crenicichla yaha is apparently not present in the upper parts of the main river and the larger tributaries (Falso Urugua-í, Uruzu) and also not in the small tributaries where in all cases only C. ypo is present or where cichlids are absent (headwaters of small tributaries).

Crenicichla yaha has only been collected in pools and not in the shallow running stretches. Crenicichla yaha is a molluscivorous species and its prey item, the snail Potamolithus , is absent from the artificial lake and present in only very small numbers in the riverine rocky stretches compared to other tributaries of the Middle Paraná, Iguazú and Uruguay which all also include specialized molluscivores ( C. taikyra , C. tesay and C. minuano plus C. jurubi , respectively) and which occur at much higher densities (pers. obs.). The generalistic C. ypo is on the other hand common throughout the Urugua-í basin.

Conservation. All original localities of C. yaha were riverine habitats with bottoms of stones, boulders and solid-rock. These are the same habitats in which we have rediscovered the species. Two of the original localities are now within the artificial lake with completely altered conditions (stagnant water with muddy bottoms). Based on our ten year efforts (2007-2016) to capture C. yaha we can claim that the species is absent from these artificial environments and the construction of the dam has thus severely limited the distribution and abundance of C. yaha , one of several endemic species of the Urugua-í river. Crenicichla yaha probably lives within the Urugua-í basin only in a limited central area between the lake influence and most upper reaches where it also appears to be absent. Only the right bank of the Urugua-í river falls within an area of nature protection while the whole arroyo Falso Urugua-í and the left bank of the Urugua-í are areas of severe degradation for agriculture and non-native tree plantations (pine). Crenicichla yaha should thus be considered a rare and vulnerable species in addition to its narrow endemism.

Figures

fig. 2. Detail of head of the same female of C. yaha. fig. 3. Detail of lower portion of head of the same female Note sub-terminal hypognathous mouth similar of C. yaha showing orange branchiostegal to C. tesay but different from the prognathous membrane distinguising C. yaha from C. tesay and mouth of the sympatric C. ypo. the sympatric C. ypo (where in both cases grey).