Umbra pygmaea

Robert E. Schmidt & Robert A. Daniels, 2006, Hybridization in Umbridae in the Hudson River, New York, with Designation of Neotypes for Umbra limi and Umbra pygmaea., Zootaxa 1113, pp. 1-20 : 10-13

Umbra pygmaea - Eastern Mudminnow

Neotype (Fig. 4)

NYSM 1405 , adult, 84.6 mm SL, Sparkill Creek, near Piermont , Rockland County, New York, 1855, S.F. Baird .

Paratopotypes

NYSM 56472 , adults, 2 specimens taken with neotype , 84.6-85.4 mm SL . NYSM 14319 , adults, 4 specimens, 31.0-42.4 mm SL, Sparkill Creek, downstream of Palisades Interstate Parkway, about 1 km south of the village of Sparkill , Rockland County, New York, June 1978, C.A. Beebe . NYSM 52430 , adults, 3 specimens, 35.9-42.1 mm SL, Sparkill Creek, about 100 m downstream of Palisades Interstate Parkway, about 1 km south of the village of Sparkill , Rockland County, New York, 23 July 1977, C.A. Beebe, E. Kiviat, R. St. Pierre .

Diagnosis

Umbra pygmaea is one of three members in the genus Umbra , in the family Umbridae . All workers agree that Umbra is monophyletic, with the European Mudminnow, U. krameri , as the sister species to the two North American species. However, the relationships among the esocoid fishes is controversial (Nelson 1994 for review; López et al. 2004). Umbra pygmaea and U. limi are very similar in appearance based on morphometrics and meristics. Umbra pygmaea tends to have a snout that is shorter than its eye diameter. Its caudal peduncle depth is usually greater than 60% body depth, although this measurement is greatly affected by individual condition. The color pattern of U. pygmaea is its most distinctive feature; it has dark, longitudinal stripes separated by lighter stripes of equal or slightly greater depth. There are usually more than 8 stripes on each side. It differs from U. krameri , which lacks a prominent vertical black bar at the end of the caudal peduncle, has a mandibular lateral line with two pores (absent in U. pygmaea , Nelson 1972), and tends to have more dorsal rays (Lelek 1987). It differs from U. limi in color pattern and usually in the relative length of its snout.

Description

This is a robust, compact fish, body terete forward, tapering to being slab-sided in the caudal peduncle region. Dorsal profile is slightly arched and the ventral profile is almost flat. Deepest part of the body is just anterior to the dorsal-fin origin, at about 25% SL (see Table 5 for means and ranges of all measurements). Caudal peduncle depth is about 15% SL, so the body profile varies little. Caudal peduncle is longer than deep. Dorsal-fin origin is about 60% SL; anal-fin origin about 70% SL; however, both fins extend back to about 80% SL, so that the insertion of the anal fin is below the midpoint of the dorsal fin. Caudal fin is rounded. Pectoral fins are thoracic and ventral; pelvic fins are abdominal and ventral. The body is entirely scaled, with modified scales encroaching onto the caudal rays.

The head is about 30% SL. The postorbital length is slightly greater than 50% head length (HL). The snout, at 20% HL, is blunt, relatively short, and usually its length is less than the orbit diameter. General shape of the head is conical, with greatest depth posterior, tapering to snout. Eyes are dorsal. Mouth is terminal, horizontal and non-protractile. There are teeth on the premaxillary, dentary, vomer and palatine. Paired nostrils are on the snout anterior to the eyes, each has simple incurrent and excurrent openings. Head is scaled; only the chin, anterior part of the snout, and gular and branchiostegal areas are free of scales. Cephalic lateral line system comprises supraorbital, infraorbital, temporal and preopercular canals, each with relatively few pores. All canals are separate. The supraorbital canal is branched and has four pores; the anterior pore is near the excurrent nostril opening, the third pore is on a branch, the posterior pore is posterior to the orbit and very near the anterior pore of the temporal canal. The infraorbital is Y-shaped, has three pores, is anterior of the orbit and does not extend below the orbit. The temporal canal has two pores, the anterior pore near the terminus of the supraorbital canal, the posterior pore just above the terminus of the preopercular canal. The preopercular canal is branched and has four pores. The anterior pore is below the mid-point of the eye, the second and third pores are on branches and the fourth pore is just below the temporal canal. Pitlines are numerous (see Nelson (1972) for details). The operculum is rounded, relatively large and has a flap of skin along its entire margin; its angle is slightly obtuse. The preoperculum is right-angled and is free only at its angle. The four or five branchiostegal rays are short and thick. Gill membranes are free from the isthmus.

All fins have convex margins. Caudal fin is rounded and symmetrical with 16-18 total rays, 10-12 branched. Ventral and dorsal procurrent rays present. The 12-14 dorsal fin rays are progressive, although the posteriormost rays may be shorter that those immediately anterior. Anal fin typically has 9 rays with the longest rays in the middle. Pectoral fin insertion is just posterior to angle of operculum and its base is small and oblique. Pectoral fin rounded, slightly asymmetrical, with 13-14 rays. Usually both pectoral fins have the same number of rays and the middle rays are longest. Pelvic fin insertion is just anterior to dorsal fin origin. There are six pelvic rays with middle rays longest.

Scales are cycloid. Scales have diffuse foci, lack radii, and ridges are not concentric (Daniels 1996). No modified lateral-line scales. Lateral series counts range from 32-34 scales. There are 12-13 transverse scale rows.

Dorsum dark brown, venter light tan or cream. There are several dark, usually more than eight, thin stripes that run the length of the body, each is separated by a light stripe of equal or greater width. There is a prominent vertical dark bar at the distal edge of the caudal peduncle. Head is dark; operculum is heavily pigmented; cheek is lighter than operculum. The cheek is framed by either an oblique, pigment-free line just below the eye or by an inverted “V” without pigment that includes the suborbital lateral-line canal and a second line that parallels the preopercular canal. The opercular flap is lightly pigmented. The proximal edge of the caudal fin is also heavily pigmented. Fins often have a weak red or maroon tint in life.

Comparison to original description

DeKay (1842) described Umbra pygmaea as Leuciscus pygmaeus , the “pigmy dace”, based on specimens that were no larger than 1 inch (25.4 mm) collected from vicinity of Tappan, Rockland County, New York (Fig. 5). Although he is clearly describing the species recognized today as Umbra pygmaea , there are several errors in the text and figure (Fig. 134, DeKay 1842). The original description notes that a lateral line is present, that teeth are absent, and nostrils are inconspicuous. However, it is DeKay’s descriptions of the fins that are most puzzling. The caudal fin is described as lanceolate and is figured as long and tapering. The pelvic fins are described as filiform (although not illustrated as such). The dorsal fin is described and illustrated as emarginate. He described the vertical fins as annulate, which is difficult to understand unless he was referring to the structure of the rays. The illustration is labeled as “Nat Size”, but measures 1.5 inches in contradiction to DeKay’s statement of maximum size.

Etymology

When James DeKay (1842) described this species, he noted that this was the smallest of the North American Cyprinidae . So, he named them after the Pygmaioi (Latin Pygmaea), who are, in Greek mythology, a diminutive, dark-skinned tribe that lived on the shores of the River Okeanos and who were tenacious in fighting a never-ending battle with cranes. DeKay probably knew his mythology well and thought the name appropriate for several reasons: pygmaea refers to the small size of the fish, its dark coloration, and its tenacity for life, DeKay (1842) having mentioned that they are “frequently left in shallow pools dried up by the sun”.