by RH Robins · 2020 · Cited by 1 — acara species, the Chanchita, Cichlasoma dimerus (Heckel, 1840). Cichlasoma-bimaculatum-final-April2018.pdf (accessed 12 July 2019).
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BioInvasions Records Cichlasoma Robert H. Robins 1, Mary E. Brown 2,* and Ryan A. Crutchfield 3 1Florida Museum, University of Florida, 1659 Museum Rd., Gainesville, Florida, USA 2U.S. Geological Survey, Wetland and Aquatic Research Center, 7920 NW 71 st Street, Gainesville, Florida, USA 3FishMap.org, 1503 Haven Bend, Tampa, Florida, USA firstname.lastname@example.org (RHR), email@example.com (MEB), firstname.lastname@example.org (RAC) *Corresponding author Cichlasoma bimaculatum Cichlasoma dimerus Acara are small- to medium-sized Sout h American cichlid fishes (Teleostei: Cichliformes: Cichlidae) . Kullander (1983), henceforth Kullander, revised Cichlasoma Swainson, 1839, restricted Cichlasoma to twelve species of acara, and created groupings based upon th e number of anal-fin spines. He assigned six species to a th ree anal-fin-spine group and six to a four anal- fin-spine group. Only rarely did sp ecimens examined by Kullander not conform to these groupings. A thirteen th species, assignable to the four anal-fin-spine group, was described by Ottoni (2011) bringing the number of four anal-fin spine acara to seven. Acara have an asymmetric caudal-fin dot pattern or no caudal-fin pattern at all (Kullander 1983; Kullander and Nijssen 1989). Recent cichlid phylog enetic research, using combined morphological and molecular approach es, has not provid ed a definitive alternate hypothesis for the composition of Cichlasoma (e.g., Musilová et al. 2009) and thus the arrangement set forth by Kullander is followed here. Cichlasoma BioInvasions Records
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BioInvasions Records The Black Acara, Cichlasoma bimaculatum (Linnaeus, 1758), is an acara usually with four anal-fin spines. The Bl ack Acara is gray to silver, beige, or yellow-gray to dark green in body co lor (Page and Burr 2011; Robins et al. 2018). It was introduced and established in South Florida in the early 1960s (Rivas 1965). Black Acara were of valu e to the aquarium trade in the 1950s but may have lost market share as jet aircraft cargo permitted the importation of a greater variety of ex otic fishes, including more colorful forms (Courtenay and Stauffer 1990). Published accounts of acara in Florida to date refer to Black Acara (e.g., Sh afland et al. 2007; Page and Burr 2011; Crutchfield 2016 and Robins et al. 2018) though early reports confused the species with Cichlasoma portalegrense (Hensel, 1870) (e.g., Rivas 1965 and Kushlan 1972, as “ Aequidens portalegrensis”). The Chanchita, Cichlasoma dimerus (Heckel, 1840), is an acara usually with three anal-fin spines. The Chanch ita is silver-gray in body color but frequently colorful. It may be metallic green (present study), opalescent blue, or blue-green to greenish (Ku llander 1983), though the presence or absence of bright colors varies accordin g to condition and social hierarchical status (Alonso et al. 2007). The co mmon name “Chanchita” appears in research papers utilizing C. dimerus as a model laboratory organism (e.g., Pandolfi et al. 2009; Ramallo et al. 2014; Morandini et al. 2015) and though the name may be more aptly applied to a variety of small cichlids (Menni 2004) its use is adopted here. Publishe d photos of Chanchita appear in Crutchfield (2016) and Robins et al. (2018; pg. 372, plate 198) as misattributions of Black Acara. Herein we report widespread popu lations in Florida of Chanchita, Cichlasoma dimerus , dating to July 27, 2000, describe their distribution based on museum specimens, provide ke y characters for identification, and discuss potential concerns for natural resource managers. Field collections were made by the authors on five separate occasions between August 31, 2018 and June 6, 2019. Specimens were collected using dip nets and hook-and-line fishing and were deposited in the Florida Museum (University of Florida). Online specimen records were accessed in FishNet2 (FishNet2 2019) including records from the California Academy of Sciences (CAS) and Royal Onta rio Museum (ROM). Institutional acronyms for museum collections follow Sabaj (2016). Counts and measurements were made of newly collected and legacy specimens. All counts were made on the left side, unless damage was present (count or measure then made on right sid e), using a Leica MZ75 dissecting microscope. All measurements were ma de with Helios dial calipers and rounded to the nearest tenth millimeter. Specimens less than 32 mm standard length (SL) and heavily damaged specimens were excluded. To
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BioInvasions Records Cichlasoma C. bimaculatum C. dimerus document color in life, photographs were taken i mmediately after capture in the field and of fishes held in aquaria. To examine the lower-jaw teeth and micro-gill rakers of the fourth br anchial arch of two specimens, which could not be seen with a microscope , computed tomography (CT) scans were generated using a GE Phoenix v| tome|x m CT scanner. X-ray data were processed using datos|x software v. 2.3 and segmented and visualized using Volume Graphics StudioMax v. 3. Manual dissection and visual examination of the fourth branchial arch of these and one additional specimen were performed for comparative purposes. All acara from Central Florida examined by this study were identified as Chanchita, Cichlasoma dimerus . Ninety-five percent (N = 52/55) had three anal-fin spines; three specimens had four spines (UF 241328 (n = 2 of 5) and UF 242256 (n = 1 of 6)). Chanch ita were from the Alafia (HUC- 0310024), Kissimmee (HUC-03090101), Pithlachascotee (HUC-03100207), Tampa Bay (HUC-03100206), and Upper St. Johns (HUC-03080101) river drainages (USGS watershed hydrologic unit codes in parentheses). All acara from South Florida examined by this study were identified as Black Acara, Cichlasoma bimaculatum . Ninety-six percent (N = 49/51) had four anal-fin spines; one specimen each had three (UF 239097 (n = 1 of 9)) or five spines (UF 238812 (n = 1 of 3)). Black Acara were from the Caloosahatchee (HUC-03090205) and Everglades (HUC -03090202) drainages. Anal-fin spine counts are presented in Table 1. The distribution of Chanchita and Black Acara in Florida, based on muse um records, is presented in Figure 1 (Supplementary material Table S1). Counts of other fin elements did not show substantial differences between Chanchita and Black Acara useful for discriminating species (Table S2). Body and fin color was examined for 30 live Chanchita (UF 241006 n = 2; UF 241009 n = 3; UF 241107 n = 6; UF 241150 n = 3; UF 241318 n = 2; UF 241328 n = 5; UF 242525 n = 6; UF 242732 n = 1; UF 242528 n = 1; UF 242740 n = 1). While live, fish larg er than approximately 45 mm SL (n = 24) exhibited a brilliant metallic green to light blue on the body and occasionally the pelvic fins (Figur e 2). A Black Acara maintained in captivity was consistently beige in body color with clear to light gray fins (Figure 2). The caudal fins of Chanchita an d Black Acara differed. Greater asymmetry was found between the upper and lower lobes in Chanchita than
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BioInvasions Records Cichlasoma bimaculatum Cichlasoma dimerus in Black Acara (Figure 3). In Chanchita, the caudal rays were nearly as dark as the vertical, excurved bands that cr ossed the caudal rays and caudal-fin membrane, resulting in a web-like pa ttern. The dark bands and nearly as dark caudal rays formed the “web” an d the clear caudal membrane formed the spaces in between. These clear spaces in the caudal membrane were largest in the upper-posterior caudal fi n. These spaces were far larger than the pigmented bands that separate them and contributed to the asymmetry between the upper and lower halves of the caudal fin. In extreme cases the clear spaces between the uppermost one to four caudal rays were as long or nearly as long as the caudal rays (i .e., they were not crossed by vertical banding). That vertical bands were more excurved in the lower half of the caudal fin than the upper also contribu ted to asymmetry; the lower lobe of the caudal fin appeared obliquely banded and the upper lobe more clear. In Black Acara, the caudal rays were not as dark as the vertical bands crossing the caudal rays and caudal membrane and these bands were less excurved. The resulting pattern was one of nearly even rows of spots (the “dotted” pattern of Kullander) rather than web-like. The clear spaces in the caudal- fin membrane were largest in th e center of the fin but nowhere proportionally as large as the clear sp aces found in Chanchita. The overall pattern was nearly symmetric from upper to lower lobe. Scale rimming, or the presence of a gray to black margin on the posterior edge of the scales of the head, nape, and anterior-upper flanks, though most prominent in large fish, was present in all Chanchita. Unlike color that fades or is lost in alcohol, this feature remain ed observable in preserved specimens. All Chanchita had scale rimming that was dark, thick,
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BioInvasions Records Cichlasoma bimaculatum Cichlasoma dimerus and at times uneven; when uneven the pigment was thickest at the center of the scale edge. The darkest and thickest rimming was found on the scales of the head and nape. In Black Acara, scale rimming was ab sent to light; when present the pigment was narrow and even along the scale edge. Scale rimming was nowhere more pronounced in any one area of the body. A comparison of scale rimming in Chanchita and Blac k Acara is presented in Figure 4. Two of the Chanchita that had 4 anal -fin spines, UF 241328 (n = 2 of 5), were in all other respects typical of other Chanchita examined (body and fin color, caudal-fin pattern, and sc ale rimming). While UF 242256 (n = 1 of 6), a legacy collection, could not be examined for color, it was typical of other Chanchita examined in caudal-fin pattern and scale rimming. Two Black Acara specimens that had more or less than 4 anal-fin spines (UF 239097 (n = 1 of 9) and UF 238812 (n = 1 of 3) were in all other respects typical of othe r Black Acara examined.
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BioInvasions Records the lower sides in the majority of ad ults. The three remaining species, the Chanchita, Cichlasoma dimerus , C. portalegrense, and C. pusillum Kullander, 1983 form a species group characteri zed by the most asymmetrically patterned caudal fins within Cichlasoma and the darkest, most extensive scale rimming (Kullander 1983). Within this group, the presence or absence of micro-gill rakers on the in ner fourth branchial arch and counts of lower-jaw teeth were the most inst ructive features for diagnosing acara from Central Florida as the Chanchita, Cichlasoma dimerus . A discussion of a number of these features and their relative value for diagnosing the species of acara in Central Florida follows here. In body and fin color, Chanchita fr om Florida compare favorably with the description provided by Kullander of the scales on the head and flanks as “opalescent blue (blue-green to greenish)” with the same color, but fainter, filling the spaces “between dark dots in the unpaired fins (pg. 204).” Kullander noted further: “The blue or green flank and head color of living C. dimerus is unique to this species, amon g those for which color is known (pg. 205).” While not the metallic green to light blue of Chanchita examined during the present study, these differences in observed color likely reflect the qualitative way in which color is perceived and described. Observing fish in laboratory aquaria, Pandolfi et al. (2009) characterized the appearance of Chanchita as “greenish to light or dark greyalso golden-yellow and light blue reflections” and attributed color variation to mood or social ranking. According to Alonso et al. (2007) color in captive Chanchita changed with behavior, social status, and reproductive condition with gregarious, non-reproductive indi viduals having a “pale body color”, territorial individuals “bright body co lor” and non-territorial individuals “opaque gray.” Kullander was unable to observe live color in Cichlasoma portalegrense and Cichlasoma pusillum . A color photo of a live C. portalegrense collected within its natural range appears in Corrêa et al. (2010) and shows a fish with a light green to yellow sheen on th e body and pelvic fins with all other fins dusky to yellowish. This appear ance, though less metallic green and light blue than Chanchita from Florida is not so substantially different as to eliminate C. portalegrense from consideration as the species in Florida. Images of preserved C. portalegrense appear in Abrahão et al. (2015), Azevedo and Bertaco (2016), and Hono rio and Martins (2018) but are not informative with respect to body and fin color. No color photos of live C. pusillum that could be reliably traced to the known range of the species were available to this study. It is likely C. pusillum also exhibits a blue, green, or yellow sheen on its body and fins and that blue, green, and yellowish body and fin color is a shared feature of the Cichlasoma dimerus species group. Accordingly, body and fin color would appear unreliable for diagnosing species of acara within this group.
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BioInvasions Records A diagnostic character in Kullander’s description of C. pusillum , “irregularly arranged dark spots on gill-cover” (pg. 221), described elsewhere within the same work as “scattered dark dots on operculum, suboperculum, and corner of preoperculum” (pg. 225), is absent from acara in Central Florida, eliminating C. pusillum as the species introduced to Central Florida. It should be noted, however, that the image of C. portalegrense in Honorio and Martins (2018; pg. 5, figu re 4) shows extensive spotting on the gill cover of a fish from the Una River, tributary to the Paraiba do Sul River, in the state of São Paulo. This locality is north of the known range of C. portalegrense in Brazil, where it is reported only from the states of Rio Grande do Sul and Santa Catarina (K ullander 1983; Abrahão et al. 2015). It is also outside the known range of C. pusillum , which was described from the Upper Rio Paraná and Rio Uruguay system of Paraguay (Kullander 1983; Ottoni 2011) and southern Brazil but is more definitively known from the Yguazú reservoir and the Ri o Monday (Kullander and Santos de Lucena 2013). The presence of micro-gill rakers on the inner surface of the fourth branchial arch is typical of Cichlasoma, though variably present in Chanchita, Cichlasoma dimerus , and absent in Cichlasoma portalegrense (Kullander 1983). CT scans of 2 specimens of Central Florida acara (UF 241009 n = 2 of 3) were inconclusive in revealing the presence of these structures (see results). Because micro-gi ll rakers of the fourth gill arch in Cichlasoma are nowhere illustrated in the li terature available to this study, the fourth gill arch was removed from a large Black Acara (UF 239097) in order to visualize these structures (see results). Micro-gill rakers detected on the inner surface of the fourth gi ll arches dissected from two scanned specimens of Central Florida acara are instructive in eliminating C. portalegrense . The number of lower jaw teeth in ou ter hemi series is an additional discriminating character between Cichlasoma dimerus (16–24 teeth) and Cichlasoma portalegrense (11–15 teeth) (Kullander 1983). All four outer hemi-series examined having > 17 t eeth (see results) also eliminates C. portalegrense . The Chanchita, Cichlasoma dimerus in Florida The first record from Florida of Chanchita, Cichlasoma dimerus , for which voucher specimens are available is six specimens from Lake Tarpon, north Pinellas County, Tampa Bay drainage, collected on July 27, 2000 (UF 242256). The species appears to have been firm ly established by November/December 2001 in nearby Brooker Creek, northeast Pinellas County, Tampa Bay drainage (UF 160700, UF 160701, UF 160705, UF 160635, UF 160895, UF 160898 and UF 160900; n = 281 individu als total). A single specimen of Chanchita was taken in the Pithlachascotee River headwaters, Pasco County, Pithlachascotee River drainage on Ja nuary 24, 2002 (UF 124513). The origin
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BioInvasions Records Cichlasoma dimerus of populations of Chanchita in Fl orida is unknown but based on these museum records would appear likely to be West-Central Florida, likely within northern Pinellas County, around the turn of the century. Chanchita have recently been collec ted or observed in Central Florida springs of the Upper St. Johns River system, including Rock Springs Run, Wekiva River, October 11, 2018 (UF 241318) and Volusia Blue Spring, March 30, 2017 (Figure 6; Kirsten Work pers. comm.; USGS 2019). The Chanchita is native to the Pa raguay and Paraná river basins, encompassing areas of northeastern Ar gentina, southern Brazil, eastern Paraguay, Uruguay, and eastern Bolivia where it prefers densely vegetated lentic waters (Kullander 1983; Alonso et al. 2007). Chanchita occupy the tropical and subtropical zone from approximately 19°S (CAS 14771) to 34.5°S (CAS 31728). The Black Acara, Cichlasoma bimaculatum is native to the upper Rio Branco drainage, Amazon as basin, in Brazil; Rio Cuyuni in Venezuela and isolated river basins of western French Guiana Suriname and Guyana. Black Acara are tropical, ranging from 3.28°N (CAS 78173) to 9.5°N (ROM 41511). The extent to which Ch anchita introduced to Florida will spread is unknown. Pandolfi et al. (2009) found Chanchita tolerate a wide variety of water conditions and temperatures betwee n 10 to 30 °C. An ecological risk screening summary performed by the United States Fish & Wildlife Service, sourcing climate data from weather stations within the native range of Chanchita, yielded a high match for an area within the U.S., extending along the southeastern coast from the southern tip of Maryland to Texas (USFWS 2018a). The same ri sk screening process conducted for Black Acara yielded a high match for Florida and coastal Georgia (USFWS 2018b). Schofield and Huge (2011) found the average lower lethal limit for Black Acara collected from Florida to be 8.6 °C. Captive Chanchita formed monogamous pair bonds, bred year round, and spawned on average every 29.4 days during the spring (Vázquez et al.
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BioInvasions Records 2012). Varela et al. (2017) found captiv e females ten days post spawn had ovarian histology comparable to that of pre-spawning females and concluded female Chanchita are functionally capa ble of a spawning interval equal to the shortest recorded for fishes under laboratory conditions. As is common to most substrate spawning cichlids, parent fish cooperatively guard and care for the eggs and developing larvae (Pandolfi et al. 2009); larvae are free swimming in approximately 174 hours an d the juvenile stage is reached in 42 days at approximately 14.7 mm total length (Meijide and Guerrero 2000). In asserting that Chanchita likely po ssess a strong capacity for dispersal, Kullander speculated that Chanchit a possibly use the stomach for air breathing and cited the observations of Sucksdorff (1981), who reported on “small green cichlids” capable of ov erland migration during the rainy season in the Pantanal of the state of Mato Grosso do Sul, Brazil. A photo appearing in Sucksdorff of a live Cichlasoma on its side on a footpath in approximately 2 cm of water and partia lly exposed to the air is identified by Kullander as a Chanchita. Effective invasive species management requires accurate species identification. The Chanchita, Cichlasoma dimerus , present in Florida waters for at least 19 years, has spread through several Central Florida river drainages and counties while misidentified as the Black Acara, Cichlasoma bimaculatum. Despite morphological simil arity to Black Acara, the Chanchita is likely to tolerate a wide r temperature range, as evinced by a latitudinally broader native range. Ca pable of breeding year round under optimal conditions, Florida’s environments may facilitate higher levels of fecundity for Chanch ita than their native range. Further attributes of the Chanchita’s biology, including biparental care and a hypothesized capability for overland migration during wet pe riods and a tolerance for low oxygen environments may portend further colonization in the state. Environmentally sensitive areas including springs habitat, which has already been partially colonized, and those areas adjacent to them, could be monitored for the presence of Chanchita. Greater care is needed in the identification of nonindigenous species of fishes.
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