Balaenoptera physalus, , Linnaeus, 1758

Marcer, F., Negrisolo, E., Franzo, G., Tessarin, C., Pietrobelli, M. & Marchiori, E., 2019, Morphological and molecular characterization of adults and larvae of Crassicauda spp. (Nematoda: Spirurida) from Mediterranean fin whales Balaenoptera physalus (Linnaeus, 1758), International Journal for Parasitology: Parasites and Wildlife 9, pp. 258-265 : 260-261

3.1. Morphological description of nematodes collected from B. physalus

3.1.1. Adult nematodes

Specimens of C. boopis (1 head, 2 male tails and 2 female tails) were deposited at the NHMUK ( Crassicauda boopis 2015.10.11.1–4) .

Morphometric data of adult nematodes isolated from the kidneys of fin whales were in accordance to the description of C. boopis in literature ( Baylis, 1920; Delyamure, 1955; Lambertsen, 1985).

Female. Elongated body with maximum length of cephalic fragments of 60.5 cm. The anterior end (measured specimens: n = 2) lying free in the lumen of vena cava, narrowing towards the head, with an evident constriction at 53.5 ± 2.12 μm (range 52–55 μm) from the buccal opening, with a diameter of 90.5 ± 10.5 μm (83–98 μm). The buccal cavity appeared laterally compressed (21.5 × 108 μm); two lips in lateral position, triangular in shape (74 μm wide at the base and 30 μm high), each with a small apical labial papilla. Two lateral and four submedial cephalic papillae were visible on the anterior end ( Fig. 1a , lower inset; Fig. 3i ). The esophagus was encircled by a nerve ring at 275 ± 0.7 μm (274.0–275.0 μm) from anterior extremity ( Fig. 1a ) (esophagus length 1200 μm). Paired ovaries and uteri were visible.

The posterior end (measured specimens n = 3), found in the ureters, had a genital constriction at 5600 ± 503 μm (range 5000–6000 μm) from the tip of the tail, where the vulva opened ventrally ( Fig. 1b ). The pineal appendage contained last part of intestine that ended at 417 ± 38.6 μm (range 375–451) from the terminal end.

Male. A cephalic extremity (measured specimens: n = 1) was strongly fixed in the renal parenchyma and the fragment was 8.5 cm long. In the anterior part of the parasite a constriction was observed at about 50 μm from the top, giving the extremity a triangular shape. The mouth was characterized by a slit with two evident triangular lips (88 μm wide at the base and 33 μm high) with two small labial papillae and two well visible lateral cephalic papillae. The buccal cavity appeared laterally compressed (20 × 110 μm).

The posterior end (measured specimens n = 3), found in ureters, was narrowing with a coiled tail (2 turns); the cloaca opened at 1040.6 ± 57.2 μm (999-1106 μm)-from the tip of the tail, with no spicules. Eighteen caudal papillae were visible ( Fig. 1c ).

Figures

Fig. 1. Adult Crassicauda boopis. a) Female. Cephalic end (bar = 120 μm) with particular of the buccal cavity (arrowhead in the upper inset, lateral view; bar = 60 μm) and of lateral and submedial cephalic papillae situated along the margin of a cuticular plate (arrowheads in lower inset, apical view; bar = 25 μm). b) Female. Paired uteri opening in the vulva (arrowhead) (bar = 600 μm). c) Male. Coiled caudal extremity with caudal papillae (arrowhead) (stereomicroscope) (bar = 1 mm).

Fig. 3. Features of the larvae isolated from fin whales. a, b, anterior end of larvae included in intestinal nodules, showing cephalic papillae and excretory pore (a, lateral view, bar = 35 μm; b, dorsoventral view, bar = 50 μm). c, tail of the same larvae, showing the cloacal pore (bar = 60 μm). d, anterior end of larvae from the mesenteric arteries, showing bulging of the triangular-shaped head (lateral view, bar = 30 μm); e, tail of the same larvae with intestinal tube evident, ending in the cloacal opening (bar = 60 μm). f, anterior end of larvae found free within intestinal lumen, showing triangular shape of the anterior region, with cephalic papillae, buccal cavity and excretory pore (lateral view, bar = 25 μm); g, h, posterior end of the same larvae, showing either presence of a cloaca with multiple papillae (g, bar = 50 μm) or a genital pore (h, bar = 80 μm); i, anterior end of adult C. boopis, displaying triangular shaped lips and labial and cephalic papillae (sublateral view, bar = 50 μm).