Heterandria tuxtlaensis, Mceachran, John D. & Dewitt, Thomas J., 2008

Mceachran, John D. & Dewitt, Thomas J., 2008, A new livebearing fish, Heterandria tuxtlaensis, from Lake Catemaco, Veracruz, Mexico (Cyprinodontiformes: Poeciliidae), Zootaxa 1824, pp. 45-54 : 49-54

Heterandria tuxtlaensis sp. nov.

( Figs. 1–4 , Tables 1–3)

Heterandria bimaculata [non Xiphophorus bimaculatus Heckel] Rosen, 1979 (in part, specimens listed as H. bimaculata from Arroyo Esciunopan, USNM 214151) Heterandria cf. jonesi Miller and Conner, 1997

Holotype: UMMZ 248620, 44.0 mm SL, mature male; Veracruz: Laguna Catemaco, south shore near Miniagua; J.V. Conner and J.R. Mayer, 11 Aug. 1964.

Paratypes: AMNH 242324 (15 specimens, 38.4 to 72.2 mm SL), TCWC 762.03 (77 specimens, 15.5 to 69.6 mm SL). UMMZ 248621 (15 specimens, 37.5 to 61.5 mm SL), IBUNAM, 14632 (15 specimens, 34.2 to 60.5 mm SL), and USNM 14632 (15 specimens 29.9 to 59.3 mm SL), same data as holotype.

Other material: AMNH 78581 (26 specimens) Veracruz, small stream through a pasture 0.5 km from Lake Catemaco on road beyond Coyame; AMNH 78593 (113 specimens) Veracruz, small stream running into Lake Catemaco, just S of outflow; AMNH 78597 (61 specimens) Veracruz, stream below Sihuapan flowing into outflow (Río Grande) of Lake Catemaco above falls; AMNH 78604 (44 specimens) Veracruz, small river near Quetzalan flowing into Lake Catemaco; GCRL V71: 6828 (107 specimens) Veracruz, Lake Catemaco, road from San Andres Tuxtla to Tehuantepec, 10 km South of San Andres Tuxtla; TCWC 752.01 (22 specimens) Veracruz, Río Quezelapam, 3 km east of Lake Catemaco; TCWC 756.02 (8 specimens) Veracruz, Río Grande at hydroelectric plant, about 9 km southwest of San Andrés Tuxtla; TCWC 757.02 (30 specimens) Veracruz, Lake Catemaco at dam spillway; TCWC 760.01 (94 specimens) Veracruz, Lake Encantada, 3.0 km northeast of San Andrés Tuxtla; TCWC 762 (139 specimens) Veracruz, Lake Catemaco, south shore of lake; TCWC 775.01 (9 specimens) Veracruz, Río Grande, at spillway below dam, about 1 km west of highway 180; TCWC 776.01 (52 specimens) Veracruz, Río Grande, reservoir of hydroelectric dam, about 1 km west of highway 180; TCWC 809.03 (12 specimens) Veracruz, Lake Catemaco, south shore of lake; TCWC 1847.03 (1 specimen) Veracruz, Lake Catemaco, at Cemolapan; TCWC 1849.02 (2 specimens) Veracruz, Lake Catemaco, at Coyame; TCWC 1850.01 (14 specimens) Veracruz, Lake Chalchoapan, just west of mouth of Río Grande west of Lake Catemaco; TCWC 1854.01 (6 specimens) Veracruz, Lake Catemaco; TU uncat. Veracruz, Lake Catemaco, at outlet of Río San Andres, about 21.8 km east of San Andres, highway 180; UMMZ 178556 (30 specimens) Veracruz, Lake Catemaco at Playa Azul, ca 3 km E of Catemaco; UMMZ 178557 (164 specimens) Veracruz, tributary of Lake Catemaco on hwy 3.2 km SE lake.

Diagnosis. The following characters distinguished H. tuxtlaensis from the other species of Heterandria : body depth in males 23.2 to 27.1% (=25.3%) of SL; dorsal fin base length 26.5 to 31.3% (=28.9%) of SL in males and 21.9 to 28.2% (=25.6%) SL in females; dorsal fin rays 12 or 13 (=12.7); basicaudal spot relatively small, subcircular to bar-shaped, and limited to area above midlateral line and not extending to dorsal midline; serrae on gonopodial ray 4p arched away from ray 4a; subdistal small segments on gonopodial ray 4a number 5 to 10; and terminal segment on gonopodial ray 4a long and strongly recurved.

Description. Heterandria tuxtlaensis is a moderate-sized Heterandria (up to 49 mm SL for males and 75 mm SL for females). Meristic and morphometric variables are summarized in Table 3 . This species is relatively slender, with a short dorsal fin, shallow caudal peduncle, and a short caudal fin. In females head is relatively narrow and anal fin is relatively short. Pectoral fin rays 15 or 16, lateral line scales 28 to 32, and vertebrae 29 to 33 ( Fig. 4 ).

Measurements Holotype Paratypes ( H. tuxtlaensis ) Non-types ( H. bimaculata ) Ray 3 of gonopodium terminating at level of second to last subterminal segment of ray 4a in holotype (terminating at level of last subterminal or terminal segment in male paratypes), distal segments of ray 3 enlarged ventrally to form elbow and running contiguous with ray 4a, segments distal to elbow number 7 to 9 ( Fig. 4 ). Subdistal 7 to 10 segments of ray 4a abruptly shortened, anterior 4 to 6 forming peg-like processes and posterior 3 to 5 squarish. Distal segment of ray 4a greatly elongated, about 5 to 7 times length of proximal squarish segment, and decurved about 110º to 120º. Subdistal 10 to 14 segments of ray 4p bear serrae, distal segments of ray 4p number 5 to 10 and lack serrae. Ray 5a arches downward toward upwardly arched ray 4p and terminates medial to tip of ray 4a.

Coloration in alcohol. Body is tan, with edges of scale pockets dark brown producing cross hatching pattern on dorsal and lateral surfaces, dark pigment thickest along center of scale pockets. Scale pockets, except for ventral most, are about equally pigmented and mid lateral stripe is absent. Single irregular dark spots are located on upper anterior aspect of operculum and on flank above base of operculum. Dark pigment spots along basal section and mid section of dorsal fin membranes produce two irregular dark stripes on fin. Dark spots located on anal fin membranes of females produce streak-like patterns. Subcircular to bar-shaped dark spot (basicaudal spot) is located on caudal peduncle and base of caudal fin, it is restricted to area above lateral midline and fails to reach dorsal midline.

Etymology. Named for the type and only known locality of the species the Tuxtla Mountains of Veracruz, Mexico.

Distribution. This species is endemic to Lake Catemaco and tributaries of the lake and the Río Grande de Catemaco above the falls at El Salto de Eyipantla.

Comparison and relationships. Within Heterandria , H. tuxtlaensis is most similar to H. bimaculata and can be identified as this species in Rosen’s (1979) key to species of Heterandria . Interestingly, however, the state of the basicaudal spot does not agree with the states of this character in any of the other species of Heterandria . The basal caudal spot of H. tuxtlaensis is not difuse, pale, or obsolescent as in the case of H. attenuata , is not bordered by a clear area and broken dark pigment as in the case of H. litoperas , is not elongated as in the case of H. obliqua , does not have ventral and posterior comet-like extensions as in the case of H. anzuetoi , is not irregular and horizontally elongated as in the case of H. cataractae , and is not large and round as in the case of H. dirempta and H. bimaculata . However, the other character states in the key, e.g. body depth, head width, caudal peduncle depth, number of lateral line scales, number of pectoral fin rays, vertebral number, and gonopodial traits are more similar to the states in H. bimaculata than to the states in any of the other species of Heterandria . The gonopodium of H. tuxtlaensis cannot be distinguished from that of H. bimaculata . Rosen (1979) also provides 12 tables comparing meristic and morphometric values of the species of Heterandria and H. tuxtlaensis falls within the ranges of H. bimaculata , with exception of values related to size and position of the dorsal fin, the number of pectoral fin rays, and width of the head in females. Heterandria tuxtlaensis has fewer than the modal number of dorsal fin rays of H. bimaculata , although the dorsal fin ray counts for H. tuxtlaensis are within the lower part of the range of values for H. bimaculata from Mexico. Dorsal fin rays counts for Mexican H. bimaculata given by Rosen are from Miller (1974). Specimens of H. bimaculata from Miller’s study are from Veracruz and Oaxaca, and include specimens from the Río Papaloapan but not from Lake Catemaco. Heterandria tuxtlaensis has a smaller range and mean number of dorsal fin rays than any of the 50 collections of H. bimaculata examined in this study. Heterandria tuxtlaensis can be further distinguished from H. bimaculata by its shorter and more forwardly placed dorsal fin base, greater number of pectoral fin rays, narrower head width in female specimens, and smaller size of the basicaudal spot. Furthermore the specimens of H. bimaculata from the Río San Juan of the Papaloapan Drainage below the falls of the Río Grande at Eyipantla, the remainder of the Río Papaloapan drainage, and the coastal drainages of the Tuxtlas are deeper bodied, have a longer dorsal fin base, longer depressed dorsal fin, longer caudal fin, higher dorsal fin ray count and a basicaudal spot typical of H. bimaculata ( Tables 2, 3 ; Figs. 2 , 3 ). These differences may have led Miller and Conner (1997) to consider the Lake Catemaco population to be close to or identical with H. jonesi rather than a species most similar to H. bimaculata . Apparently they based this decision on a collection of H. tuxtlaensis (UMMZ 178556) that lacks mature males. Thus they were unaware of the gonopodial characters of the species.

It is likely that the new species shares an ancestor with H. bimaculata because of the above listed similarities between the two species and because H. bimaculata is the only other species of Heterandria found in the Río Papaloapan drainage. Only one other species, H. jonesi occurs in Mexico and it has not been reported south of the Río Nautla in central Veracruz ( Miller, 1974). The other species of Heterandria are either limited to the southern United States ( H. formosa ) or are endemic to Guatemala, and of all of these, the most similar congeners are limited to the Río Senizo in the head waters of the Río Usumacinta drainage, in Alta Verapaz, Guatemala ( H. cataractae ) and the Río Chajmaic, in the headwaters of the Río Usumacinta drainage in Alta Verapaz, Guatemala ( H. dirempta ) ( Rosen, 1979).

Remarks. Heterandria tuxtlaensis constitutes the sixth endemic species of the 12 indigenous fish species of Lake Catemaco. According to Miller and Conner (1997) four of the 12 indigenous fish species in the lake were endemic and that future research might reveal that six of the remaining species were undescribed, and thus also endemic to the lake. One of these six putative new species ( Xiphophorus kallmani ) was described by Meyer and Schartl (2003) and herein we describe the sixth endemic species. Thus endemicity within Lake Catemaco lies between 50% and 83%, depending on the status of the possibly new species. This range of endemicity is high considering the lake is a maximum of 2 million years old ( West, 1964). Mateos et al. (2002) investigated the historical biogeography of the poeciliid genus Poeciliopsis , which includes a species, P. c a t e m a c o, endemic to the lake. Based on a molecular clock for cyt b divergences, Mateos et al. (2002) estimated that P. c a t e m a c o has been isolated from other members of its gracilis species group for 0.75 to 1.5 million years. This estimate is within the age given by West (1964) for the lake and it is reasonable to assume that all of the endemic species to Lake Catemaco are 0.75 to 1.5 million years old.

The endemic fishes in Lake Catemaco are predominantly poeciliids (five species in four genera). The other endemic species is a characid, Bramocharax caballeroi . The putative new species in the lake include a clupeid of the genus Dorosoma , similar to D. mexicana , two pimelodids of the genus Rhamdia , and a cichlid, similar to Vieja fenestrate . This high level of endemicity complements genetic and geological findings suggesting the lake is ancient and well separated from surrounding fish populations.

Finally we hope to be indulged to make a methodological point, be it removed from our major goal of describing H. tuxtlaensis . We wish to advocate general use of geometric morphometrics in describing new taxa. Such information is a useful addition to traditional measures if reported in a manner to facilitate comparisons among taxa. To this end we report the direction of individual landmark deviations across the species gradient. Correlations of partial warps or principle components with species gradients would not be general, because these variables change in each new analysis. Landmarks retain homology across studies. We also report effect sizes in a manner conducive to comparison with other taxa, and to meta-analysis ( Gurevitch and Hedges 2001). Thus we hope this approach can be used or expanded in future work in the valuable service of describing new taxa.

Other material examined. Heterandria bimaculata (Veracruz, Mexico): FMNH 4601, 3726, TCWC 755.02, 759.01, 779.02, 1852.01, UMMZ 108614, 184547; (Tabasco, Mexico): AMNH 20401, 27489, UMMZ 184718, 209339, 210842; (Oaxaca, Mexico): UMMZ 178533, 178546, 183902, 234799; (Chiapas, Mexico): NMW-59796 (Syntypes of Heterandria bimaculatus ), AMNH 24649, 59805, 59806, 69807, 59808, UMMZ 163778, 186370, 191730, 196644, 209324, 209353, 209361, 210814, TCWC 3207.01; (Campeche, Mexico): UMMZ 190856, 196612; (Yucatan, Mexico): UMMZ 102078 (Holotype of Heterandria b. peninsulae), 102079 (Paratype of H. b. peninsulae); ( Quintana Roo , Mexico): UMMZ 210881; ( Belize): AMNH 78703, FMNH 82180, UMMZ 190424, 202737; ( Guatemala): AMNH 24584, 24663, 24486, 36339, 36353, 36357, 36361, 36362, 36363.

Heterandria anzuetoi ( Guatemala) : UMMZ 197389 (Paratypes).

Heternadria attenuata ( Guatemala) : UMMZ 197091 (Paratypes).

Heterandria cataractae ( Guatemala) : UMMZ 193888 (Paratypes)

Heterandria dirempta ( Guatemala) : UMMZ 187950 (Paratypes)

Heterandria litoperas ( Guatemala) : UMMZ 197134, 146107 (Paratypes) Heterandria obliqua ( Guatemala) : UMMZ 197079, 193893 (Paratypes)

Figures

FIGURE 1. Radiograph negative of a male H. tuxtlaensis showing landmarks used for the body shape analysis. 1 — anterio-dorsal-most position on the snout; 2 — top of head where skull breaks away from the body outline; 3, 4 — origin and insertion of the dorsal fin, respectively; 5 — dorsal origin of the caudal fin (anterio-dorsal-most procurrent ray); 6 — middle of caudal fin base (between hypural plates); 7 — ventral origin of caudal fin (anterio-ventral-most procurrent ray; 8, 9 — insertion and origin of anal fin, respectively; 10 — anterior margin of pelvic fins; 11 — anterio-ventral corner of interoperculum; 12 — first branchiostegal ray at the body outline; 13 — center of orbit (eye position); 14 — junction between cranium and first vertebral centrum; 15 — vertebral centrum bearing third gonapophysis; 16 — reticular point of lower jaw.

FIGURE 2. Shape difference between H. tuxtlaensis from Lake Catemaco and H. bimaculata from Sontecomapan. Transformation grids show the linear regression of shape on habitat controlling for allometry. A) Males. The shape gradient for males explained 29.6 % of total shape variance. B) Females. The gradient for females explained 30.5 % of total shape variance. Multivariate least squares means (i. e. group centroids) are plotted and their 95 % confidence limits are given as ellipses.

FIGURE 3. Most extreme individuals on the species axis, for males, from our sample of 30 fish. Left: the new species, H. tuxtlaensis. Right: the presumed sister taxon H. bimaculata. Differences in size are incidental and are not responsible for the shape differences observed. The correlation between the species axis and the axis of allometry was r = 0.08.

FIGURE 4. Heterandria tuxtlaensis. A. Mature male (Holotype, UMMZ 248620, 44.0 mm SL). B. Mature female (Paratype, TCWC 762.03, 41.3 mm SL). C. Gonopodium tip of Holotype.

Tables

TABLE 3. Traditional morphometrics and meristics of Heterandria tuxtlaensis and H. bimaculata. Except for SL and meristics, data are given in percentage of standard length.

	Male	Males	Females	Males	Females
Standard length	44	Range Mean 31.8–49.4 43	Range Mean 33.7–74.5 55.8	Range Mean 30.1–40.0 36.3	Range Mean 39.6–64.6 52.2
Depth	26.4	23.2–27.1 25.3	23.9–27.6 24.3	26.2–29.9 28.1	25.7–29.5 27.5
Predorsal length	50.9	48.3–53.3 51.1	54.7–58.1 56	49.3–54.2 51.9	53.1–59.6 55.6