versión On-line ISSN 0717-6538
Gayana (Concepc.) v.73 n.1 Concepción 2009
Cayana 73(1): 102-110,2009
NEW RECORDS OF HATCHERIA MACRAEI (SILURIFORMES, TRICHOMYCTERIDAE) FROM CHILEAN PROVINCE
NUEVOS REGISTROS DE HATCHERIA MACRAEI (SILURIFORMES, TRICHOMYCTERIDAE) EN LA PROVINCIA CHILENA
Peter J. Unmack1, Evelyn M. Habit2,3 & Jerald B. Johnson1,4
1Department of Biology, WIDB 401, Brigham Young University, Provo UT 84602, USA
2Unidad de Sistemas Acuáticos, Centro de Ciencias Ambientales EULA-Chile, Universidad de Concepción, Casilla 160-C, Concepción, Chile. firstname.lastname@example.org
3Centro de Investigaciones en Ecosistema Patagónicos C.I.E.P Coyhaique, Chile
4Monte L. Bean Life Science Museum, Brigham Young University, Provo UT 84602, USA
Describimos nuevos registros de Hatcheria macraei (bagre Patagónico) en el área sur-central de Chile. Ello representa una ampliación significativa del rango de distribución de esta especie. Estos nuevos registros tienen importantes implicancias biogeográficas, dado que reportamos a H. macraei dentro de la Provincia Chilena, bastante más al norte de su límite distributional previo en Chile, restringido a la Provincia Patagónica. Además, informamos en este trabajo de un nuevo carácter, correspondiente a la forma de la aleta dorsal, el cual permite una rápida y fácil discriminación entre H. macraei y Trichomycterus areolatus, tanto en terreno como en laboratorio. Este estudio alerta sobre la necesidad de identificar cuidadosamente los bagres de la familia Trichomycteridae del sur de Chile.
Palabras Clave: Trichomycteridae, Hatcheria macraei, Trichomycterus areolatus, morfología, merística.
We describe collections oiHatcheria macraei (Patagonian catfish) from south-central Chile. This represents a significant range extension for this species. These new records have important biogeographic implications as H. macraei is now recorded within Chilean Province, far north of its previous distributional limit in Patagonian Province. We document a new character, the shape of the dorsal fin, which allows quick and easy discrimination between H. macraei and Trichomycterus areolatus in the field or laboratory. This study highlights the need for careful identification for trichomycterid catfishes from southern Chile.
Keywords: Trichomycteridae, Hatcheria macraei, Trichomycterus areolatus, morphology, meristics.
Hatcheria is a monotypic genus of catfish in the family Trichomycteridae. Its recorded distribution is mostly within Argentina and to a lesser extent in Chile. Within Argentina H. macraei (Patagonian catfish) is widespread and typically common in Atlantic draining rivers from the Rio Colorado south
to the Rio Chubut (Figure 1). It is also known in Argentina from the headwaters of most Pacific draining rivers from the Río Manso south to Rio Blanco (Liotta 2006, Gomez 1990). In Chile the distribution is poorly documented. Several records exist for Río Aysén including Eigenmann (1909), Arratia et al. (1981,1983), Zama & Cardenas (1984) and Campos et al. (1984). Campos et al. (1998) listed them from General Carrera Lake (Rio Baker) and the Aysén River. We could not find any other specific details of H. macraei records from Chile. Dyer (2000) listed them as being present in rivers of continental Chiloé and Aysén, but no further details were provided, and none of the works he cited list any other records beyond those mentioned above. Here we focus on morphological characters to confirm the validity Hatcheria macraei samples collected in Chile. We verify H. macraei records from various basins in southern Chile where this species has been reported, and provide new records from as far north as to the Rio Imperial, an area well beyond the previous recorded distribution for this species.
MATERIALS AND METHODS
Fishes were sampled using electrofishing as part of two broader projects examining the phylogeography of another trichomycterid catfish, Trichomycterus areolatus (Unmack et al. in press) and H. macraei as well as another project on the ecology of the San Pedro River. We sampled range wide for both species in all major drainages, and many smaller coastal systems, from the Rio Baker in the south to the Rio Limari in the north (Unmack et al. in press). This included sampling >50 localities, with up to 30 fish collected from each locality. All individuals captured were preserved in 95% ethanol. Fishes were examined under a dissecting microscope. Only principal fin rays were counted, with the last two rays being counted as one since they usually are joined at the base of that ray. Specimens are deposited in the Monte L. Bean Life Science Museum, Brigham Young University (BYU), USA, and in the laboratories of EMH (the second author) and JBJ (the third author). We also included all of the samples in JBJ's collections from Argentina to provide at least some comparison to specimens from Chile.
Arratia & Menu-Marque (1981) revised the genus Hatcheria based on a large collection of fish taken from throughout the Rio Colorado basin in Argentina. They listed a suite of traits for distinguishing the genus Hatcheria, with the following traits being useful for separating H. macraei from T. areolatus (L. Fernandez pers. comm.): narrow and strongly compressed caudal peduncle; slightly concave dorsal fin, anus placed between the distal end of the pelvic fins, slightly emarginated caudal fin, and a long dorsal fin with more than 17 rays (based on procurrent and principal rays, counted from cleared and stained specimens, G. Arratia pers. comm.). Arratia & Menu-Marque (1981) does note that there is some variation in the position of the anus relative to the pelvic fins, and some fish have slightly lower dorsal ray counts (as low as 15 principal rays). We examined principal dorsal ray counts, position of anus relative to pelvic fins, dorsal and caudal fin shape and caudal peduncle depth.
While examining specimens of T. areolatus as part of our phylogenetic work, we noticed the presence of a second species in our collections from Chile. We subsequently examined the morphology of all of our trichomycterid collections in the southern portion of the range of T. areolatus to determine if other individuals of H macraei were present. We confirmed the presence of H. macraei in Rio Imperial, Río Valdivia and Río Bueno, where H macraei occur in small numbers sympatrically with T. areolatus (Figure 1, Table I). Only one external morphological characterthe shape of the dorsal finprovided complete discrimination between H macraei and T. areolatus. A second characterfin ray countwas nearly diagnostic. We elaborate on these two traits below. All other characters that we examined showed considerable variation between species.
The best diagnostic character we observed to distinguish H macraei from T. areolatus was the difference in the overall shape of the dorsal fin between the two species. The dorsal fin of T. areolatus is shaped like an isosceles triangle (two sides of the same length), with the fin base being longer, with the leading edge of the fin, and margin of the fin being approximately the same length (Figure 2). In contrast, the dorsal fin iriH macraei is shaped like a scalene triangle (where all sides are different lengths), with the base being longest, the fin margin is a little bit shorter, and the front edge of the fin is quite short (Figure 2). In other words, the dorsal fin ofH macraei is not very tall, but it is quite long (relative to its height); whereas in T. areolatus the fin is higher and shorter. The second best character to quantify for identification was dorsal fin ray number. Almost all H. macraei had dorsal ray counts of 13 or higher, while almost all T. areolatus from the region of sympatry with H. macraei have counts of 10 or lower (Table II). However a few fish from both species have counts of 11 or 12, while the Río Manso sample contained three individual H. macraei with 10 rays (Table II). These counts are lower than reported by Arratia & Menu-Marque (1981) for H. macraei; however, the specimens they examined were all from one river system, the Rio Colorado in the northern portion of the range ofH. macraei, and no information exists on how dorsal ray counts vary across the range of H. macraei. Arratia & Chang (1975) reported that counts for T. areolatus from a broader geographic sample varied from 9 to 13 (based on principal counts on cleared and stained specimens). Four out of the five populations they examined are from north of our study area; this may partly explain why counts we obtained were typically lower than reported by Arratia & Chang (1975).
Table I. Locality data for specimens examined: TA = Trichomycterus areolatus, HM = Hatcheria macraei. The number in parentheses after the term TA or HM represents the total number of individuals of each species found at that site. Note that not all specimens were counted for all traits.
Tabla I. Localidades de los individuos examinados: TA = Trichomycterus areolatus, HM = Hatcheria macraei. El número entre paréntesis después del término TA o HM representa el número total de individuos de cada especie encontrados en cada sitio. No todos los individuos fueron incluidos en el conteo de caracteres.
Table II. Dorsal fin ray counts in Trichomycterus areolatus and Hatcheria macraei. Note that not all H. macraei specimens could be counted. Under basin, AR = Argentina.
Tabla II. Conteo de rayos de la aleta dorsal en Trichomycterus areolatus y Hatcheria macraei. No todos los individuos de H. macraei pudieron ser contados. En la columna de cuenca, AR indica Argentina.
All other characters examined had considerable variation and were not diagnostic. Generally, most H. macraei had a slightly emarginated caudal fin, but the margin varied such that some caudal fins were clearly truncate. The opposite was true in T. areolatus where most caudal fins were truncate, although some were emarginated with variation between, making clear characterizations difficult. The same characteristics were observed in the shape of the dorsal fin margin, with variation in both species from essentially a straight margin to slightly concave. This shape variation was often quite difficult to observe in many individuals due to the fin not being outstretched during preservation. The position of the anus relative to the tips of the pelvic fin also varied considerably, with essentially complete overlap in variation, although in many T. areolatus the anus tended to be anterior to the tips of the pelvic fins; in H. macraei the anus in many fish was near the pelvic fin tips (Table III). We did not formally measure caudal peduncle depth because differences in preservation techniques among our samples could lead to differences in body shape (ethanol causes considerable shrinkage relative to formalin). However, cursory examination of this trait in H. macraei suggests that it shows considerable variation, ranging from quite narrow to a width similar to that found in T. areolatus. We did not observe a narrow caudal peduncle in any T. areolatus. Lastly, there appears to be a diagnostic difference in the maximum size that each species attains. From the Rio Imperial south, T. areolatus rarely grow larger than 130 mm TL (BYU 113992), with most specimens being considerably less, whereas one of our specimens ofH. macraei is 193 mm TL (BYU 113993), and they are reported to reach up to 208 mm TL (Arratia & Menu-Marque 1981).
Figure 1. Collection records for Trichomycterus areolatus (small hollow circles) and Hatcheria macraei (solid dots) based on our collections. Overlapping records have both the small hollow circle with a thick black rim. We also included our Argentinean records of H. macraei from Pacific draining rivers. The dashed line represents the approximate boundary between the Chilean and Patagonia provinces.
Figura 1. Registros de colectas de Trichomycterus areolatus (cículos pequeños vacíos) y Hatcheria macraei (círculos negros sólidos) basados en nuestras colectas. Con un pequeño círculo vacío de borde negro grueso se indican los registros sobrepuestos para ambas especies. También incluimos registros de H. macraei provenientes de cuencas Argentinas que drenan al Pacífico. La línea punteada indica el límite aproximado entre las Provincias Chilena y Patagónica.
Figure 2. Examples oí Hatcheria macraei (top row) and Trichomycterus areolatus (bottom row) from Río San Pedro (top left, BYU 113962 and bottom left, BYU 113969) Rio Rahue (top right BYU 67221) and Rio San Pedro (bottom right BYU 113981). The triangles drawn on left hand fish highlight the difference in dorsal fin shape between the two species. The scale bar is in centimeters.
Figura 2. Ejemplos de Hatcheria macraei (fila superior) y Trichomycterus areolatus (fila inferior) del Rio San Pedro (izquierda arriba, BYU 113962, izquierda abajo BYU 113969) Rio Rahue (derecha arriba BYU 67221) y Río San Pedro (derecha abajo BYU 113981). Los triángulos dibujados en las fotos de la izquierda indican la diferencia en la forma de la aleta dorsal de ambas especies. La escala está en centímetros.
Lack of previous records Why have H. macraei not been recorded earlier from these "southern" Chilean rivers? Three factors may have resulted in the lack of detection. The first factor is that H. macraei appears to be quite rare relative to T. areolatus, with most populations being represented by three or fewer individuals (Table I). This is not simply due to differences in the habitats sampled. Both species are typically abundant in similar habitats when they occur allopatrically, and at most sites all available habitats were sampled. Hatcheria macraei may simply be rare due to competition with T. areolatus, as typically, H. macraei are more common where they occur in allopatry. The second reason these populations may have escaped detection is that one of the key characters used previously for field identification is lacking in these new Chilean populations. Most references to identification of Hatcheria highlight the narrow caudal peduncle (e.g., Arratia et al 1981; Ruiz & Marchant 2004). However, none of the fish from this area of Chile have a thin caudal peduncle. Moreover peduncle depth appears to vary considerably, both within populations and among populations across the range ofH macraei (Arratia & Menu-Marque 1981). Thus, without closer inspection of the dorsal fin it would be easy to overlook the presence ofH. macraei. Quantification of variation in the caudal peduncle depth across the range ofH macraei will be helpful in determining its value in identification relative to T. areolatus. We suspect that some fish identified as T. areolatus from Argentina (Arratia & Menu-Marque 1981; Baigún & Ferriz 2003) may be based onH. macraei that have low dorsal ray counts and thicker caudal peduncles which making them quite similar in appearance to T. areolatus. The third factor hindering earlier detection ofH macraei is that most of these rivers that expand the range of this species are poorly sampled, with little published information on specific collections (Campos et al. 1987; Dyer 2000; Habit et al 2006). Hatcheria macraei appear to be absent from smaller coastal drainages in this area and from the Rio Maullin; our collections from these areas only contain T. areolatus. Given the small populations sizes ofH. macraei, it is possible that this species could not persist in smaller rivers. It is possible that H. macraei are present in Rio Toltén, although additional sampling is required to demonstrate this.
These new records extend the range ofH. macraei across the boundary between the Patagonian and Chilean biogeographic provinces of southern Chile (Dyer 2000; Figure 1). Interestingly, this new northern limit identically matches another predominately Patagonian species, Galaxiasplatei (Campos 1985; Cussac et al. 2004). Of the eight or nine species known from Patagonian Province in Chile (Dyer 2000; Cussac et al. 2004), only the silverside fish Odontesthes hatcheri does not extend into Chilean Province. This boundary represents a strong barrier to the southern movement of many species due to recent glaciation, but apparently most Patagonian species have managed to cross this boundary at some stage of their biogeographic history. For some species this pattern might be explained by a diadromous life cycle that allows individuals to move easily between river mouths via the ocean. For strictly freshwater species, such as H. macraei and Percichthys trucha, explanations may be more complicated as populations could have reinvaded glaciated areas from either non-glaciated regions of Argentina and Chile, or from refugia within the glaciated area. Ongoing phylogeographic work on both species will likely provide information on the origins and relationships of these populations as well as a time frame for their biogeographic history.
Many people assisted with fieldwork, but especially Andre Bennin, Néstor Ortiz, Waldo San Martin, Pedro Victoriano and biologists of the San Pedro lab station of the Eula Center, Universidad de Concepción. Thanks to Katherin Solis-Lufi for counting and examining all of the specimens in the lab of EMH. Thanks to Luis Fernandez for his advice relative to species identifications and to Gloria Arratia for feedback on an earlier draft. This work was funded by a grant from the U.S. National Science Foundation PIRE program (OISE 0530267) and projects FONDECYT 1080082 and DIUC-Patagonia 205.310.042-ISP from Universidad de Concepción to EMH and San Pedro Project funded by Colbún S.A. Additional funding to JBJ from the BYU Kennedy Center and Monte L. Bean Life Science Museum supported field work.
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