Urophycis chuss (Walbaum, 1792)

Marancik, Katrin E., Richardson, David E. & Konieczna, Małgorzata, 2020, Updated Morphological Descriptions of the Larval Stage of Urophycis (Family: Phycidae) from the Northeast United States Continental Shelf, Copeia 108 (1), pp. 83-90 : 84

Urophycis chuss

Figures 1 , 2A , 3A

Genetic confirmation.— n ¼ 196; 1.4–10.7 mm SL.

Formalin-fixed larvae examined.— n ¼ 18,685; 1.1–6.5 mm SL.

Identification.— The earliest stages of development in U. chuss were described by Miller and Marak (1959) from reared eggs and larvae collected from strip-spawned adults. These recently hatched specimens have melanophores on the mid- and forebrain and multiple dorsal and ventral melanophores on the tail. Specimens at this stage were not included in our genetic analyses and are not described here, but were observed at sizes 1–1.5 mm notochord length (NL) in our preserved samples. Based on Miller and Marak’s (1959) work, an abrupt change in pigmentation occurs after 24 hours post hatch.

The traits described here were observed on larvae as small as 1.1 mm NL and were common by 1.5 mm NL. The lower jaw is lightly pigmented with two small melanophores, one on either side of the jaw, usually about midway down the jaw rami. The forebrain is unpigmented until external melanophores develop late in the postflexion stage. Pelvic fins begin to form at approximately 3–3.5 mm, later than on U. tenuis (2–2.5 mm), and are pigmented on the tissue between the fin rays, especially on the outer one third by 4 mm. Pelvic filaments are often damaged on net-collected larvae, so this pigment is often absent. Dorsal tail pigment is approximately mid-tail in small larvae and remains postanal until postflexion (6–7 mm). Ventral tail pigment is present about mid-tail on the smallest larvae. Ventral pigment is absent by 3.5 mm and reappears by 10 mm SL. The caudal area is unpigmented until late in the postflexion stage (7–10 mm).

Figures

FIG. 1. Line illustrations and images of Urophycis chuss at (A) 2.2 mm, (B) 3.3 mm, (C) 4.3 mm, and (D) 6 mm.

FIG. 2. Line illustrations of dorsal view showing location of head and dorsal midline pigment of (A) 2.2 mm Urophycis chuss, (B) 2.7 mm Urophycis regia, and (C) 1.9 mm Urophycis tenuis.

FIG. 3. Line illustrations of ventral view showing lower jaw and ventral midline pigment of (A) 2.2 mm Urophycis chuss, (B) 2.7 mm Urophycis regia, and (C) 1.9 mm Urophycis tenuis.