Urophycis tenuis (Mitchill, 1814)

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 : 86

Urophycis tenuis (?)

Figures 2C , 3C , 5

Genetic confirmation.— n ¼ 0.

Formalin-fixed larvae examined.— n ¼ 47; 1.9–5.8 mm SL.

Identification.— The most recently hatched larvae of U. tenuis are undescribed and were not included in our analyses. The traits described here are based on specimens collected when and where U. tenuis are believed to spawn ( Fahay and Able, 1989; Lang et al., 1996) and that were morphologically different from the genetically confirmed U. chuss and U. regia . The lower jaw pigment forms a line on either side of the jaw near the symphysis (jaw tip). These melanophores were larger and closer together than on U. chuss and U. regia . Internal pigment on the forebrain, between the eyes, was most visible on the dorsal view. This trait was only observed in the preflexion stage of suspected U. tenuis . At later stages of larval development in U. tenuis , the forebrain has surface pigment, which is also uncommon on the other two species, although U. regia do occasionally have pigment over the forebrain during the preflexion stage. Pelvic fins begin budding at 2–2.5 mm and are unpigmented until approximately 2.5 mm. Pelvic-fin development is earlier than the other two species (3–3.5 mm). The pelvic fins are fully pigmented at small sizes and pigmented heavily over half to one third of the membrane between rays in medium and larger larvae. Pigment may occur on the pelvic fins of all species, but does appear to be more extensive on U. tenuis . The membrane between pelvic rays is often damaged on net-collected larvae, and is not always present. Dorsal pigment occurs on the midline of the tail immediately post anus, similar to larvae of U. chuss . Ventral pigment is present on small larvae, but was absent in medium sized fish (approx. 3.5 mm), similar to U. chuss .

Figures

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.

FIG. 5. Line illustrations and images of Urophycis tenuis at (A) 1.9 mm, (B) 3.2 mm, and (C) 4.5 mm.