Peniculus truncatus Shiino, 1956

Maran, B. A. Venmathi, Moon, Seong Yong, Oh, Sung-Yong, Ho Young Soh, & Myoung, Jung-Goo, 2012, Redescription of two Pennellids (Copepoda, Siphonostomatoida) from Korea with a key to species of Peniculus von Nordmann, 1832, ZooKeys 243, pp. 1-14 : 5-6

Peniculus truncatus Shiino, 1956 Figures 45

Peniculus truncatus Shiino, 1956: 593; Yamaguti 1963: 1104.

Peniculus ostraciontis : Choi et al. 1996: 117.

Material examined.

4 ♀♀ (NIBRIV0000252624) and 1 ♀ (MABIK CR00178440) from Sebastes schlegelii , Tongyeong, Gyeongsangnam-do, Korea, 15 February 2012.

Description.

Postmetamorphic adult female . Body (Figure 4A), 4.59 (4.14-5.41) mm long (n=4) comprising oval head, long slender neck, large trunk and reduced abdomen. Head (cephalothorax) ovoid, flattened dorsally but convex ventrally with pair of rounded swellings anteriorly bearing antennae (Figure 4B, C). Mouth tube prominent, directed posteroventrally (Figure 4C). Neck long (0.47-0.55 mm) (Figure 4B, C), slender, comprising about one sixth of trunk length; consisting of three somites bearing legs 1, 2 and 3 (Figure 4B, C). Fourth pedigerous somite incorporated into trunk. Trunk slender, cylindrical, longer than wide, 6 times longer than neck, bearing leg 4 proximally. Abdomen (Figure 4D), reduced with subterminal caudal rami on ventral surface. Caudal rami (Figure 4E) bearing 6 setae. Egg sacs long and uniseriate with 30-37 eggs. Antennule not observed. Antenna (Figure 4F) 2-segmented, chelate; proximal segment bearing 2 pointed projections overlapping each other; terminal segment claw-like, acutely pointed with minute seta at base. Mandible (Figure 4G) moderate-sized, broad, provided with 10 teeth terminally.

Maxillule (Figure 5A) with 2 lobes having one short and two long setae. Maxilla (Figure 5B) 2-segmented; proximal segment broad with robust spiniform process, projecting laterally, 2 rows of setules distally; distal segment blunt and curved with transverse striations and rows of spinules. Maxilliped absent. Leg 1 (Figure 5C) forming blunt plate-like structure derived from protopodal segments, with 2 minute setae laterally. Legs 2-4 (Figure 5 D–F) as for leg 1, but without seta. Leg 5 absent.

Attachment site.

Only on dorsal fin-rays.

Remarks.

Comparison between our material and the original description of Peniculus truncatus provided by Shiino (1956) revealed some omissions in that the antennae and mandibles were not shown, and possible differences, since the striation of setules on maxilla was not shown. The characteristic features of Peniculus truncatus are: (1) the rudimentary abdomen; (2) the long neck (more than half as long as cephalothorax); (3) the maxilla wi th transverse striations of setules and rows of spinules on the distal segment; (4) the leg 1 is tipped with 2 minute setae laterally. Peniculus truncatus differs from Peniculus minuticaudae in its rudimentary abdomen (vs. well developed abdomen); long neck (vs. short neck); and in the presence of setae on leg 1 (vs. absence of seta). It differs from Peniculus ostraciontis in its moderately slender trunk (vs. stout trunk); long neck, ie: neck more than half as long as cephalothorax (vs. short neck, ie: neck less than half as long as cephalothorax); and in the presence of setae on leg 1 (vs. absence of setae) ( Yamaguti 1939; Shiino 1956).

Choi et al. (1996) reported the same pennellid collected from the fins of Stephanolepis schlegelii as Peniculus ostraciontis . We compared our material with their illustrations (specimens were not deposited in the museum). It showed the features of Peniculus truncatus : (1) long neck; (2) slender trunk [not as stout as like Peniculus ostraciontis illustrated by Yamaguti (1939)] and the host was Stephanolepis schlegelii ( Choi et al. 1996), as in the present study.