New Host and Ocean Records for the Parasitic Copepod Bobkabata kabatabobbus (Lernaeosoleidae: Poecilostomatoida)

Abstract

The parasitic copepod Bobkabata kabatabobbus Hogans & Benz is reported for the first time from the Pacific Ocean and from the darkfin sculpin, Malacocottus zonurus (Psychrolutidae: Scorpaeniformes). Based on five specimens, several morphological features are reported for the first time for B. kabatabobbus, including a second protuberance on the cephalothorax, a pair of vestigial legs on the neck, and two dark-staining sclerites on the trunk that may represent body segment boundaries or interpodal bars.

Bobkabata Hogans & Benz, 1990, is one of two monotypic genera within Lernaeosoleidae Yamaguti, 1963 (Poecilostomatoida: Copepoda). Until this report, B. kabatabobbus Hogans & Benz, 1990, was known only from two collections consisting of three individuals taken from the pallid sculpin, Cottunculus thomsoni (Günther, 1882) (Psychrolutidae: Scorpaeniformes) in the western North Atlantic (Hogans and Benz 1990, Benz and Braswell 1998). Herein we present the first record of B. kabatabobbus from the Pacific Ocean as well as a new host fish for this parasite. We also provide new information regarding the morphology of B. kabatabobbus.

Materials and Methods

A total of five B. kabatabobbus adult females was collected from two formalin-fixed darkfin sculpins, Malacocottus zonurus Bean, 1890 (Psychrolutidae: Scorpaeniformes). One host, 114 mm standard length, was captured 24 March 1976 in a fishing trawl at 360 m in the western North Pacific Ocean east of Cape Erimo, Hokkaido (42° 1.9´ N, 143° 44.4´ E). This host was infected with one B. kabatabobbus adult female that was attached at the base of the soft-rayed portion of the dorsal fin. This intact specimen has been deposited in the National Science Museum, Tokyo, Japan (NSMT-Cr 14164). The second host was captured 4 April 1984 in a fishing trawl at an unknown depth in the western North Pacific Ocean east of Cape Erimo, Hokkaido (42° 18´ N, 144° 2.2´ E). This host was infected with four B. kabatabobbus adult females, one at the base of the spiny-rayed portion of the dorsal fin and three along the base of the soft-rayed portion of the dorsal fin. One intact specimen and the posterior portion of a second specimen from this collection have been deposited in the NSMT (NSMT-Cr 14165 and NSMT-Cr 14166, respectively).

Bobkabata kabatabobbus is a mesoparasite (sensu Kabata 1979), and all five specimens reported here were found embedded in the musculature of the hosts with only a short portion of the thoracic "neck" and the horse-shoelike posterior of the body protruding. After they were dissected from their hosts, the copepods were studied using light (LM) and scanning electron microscopy (SEM). For LM studies copepods were cleared and stained in a solution of lactic acid and lignin pink and subsequently examined using the wooden slide technique of Humes and Gooding (1964). One specimen was examined using SEM. This specimen was prepared for gold-palladium sputter coating by placing it in 100% ethanol (two changes, 1 hr each) followed by immersion in a small volume of hexamethyldisilazane (15 min). Before mounting on a metal stub with two-sided sticky tape, drying was achieved by placing the specimen under a slight vacuum to remove the hexamethyldisilazane. Illustrations were prepared with the aid of a camera lucida (LM) or they were drawn with some interpretation from SEM micrographs. Specimens were measured using an eyepiece graticule (LM) and measurements in millimeters are reported as the mean followed in parentheses by the standard deviation, range, and sample size. Conventions for measurements are shown in Figure 1A. Terminology regarding copepod morphology follows Huys and Boxshall (1991). Host systematics follows Nelson (1994).

Results and Discussion

All of the specimens of B. kabatabobbus reported here generally matched the descriptions of the species provided by Hogans and Benz (1990) and Benz and Braswell (1998). However, some specimens exhibited features not previously observed, and based on these new specimens the following additional information on the species is provided: total length, 9.46 (±1.515, 8.32-12.06, 5); head length, 2.08 (±0.232, 1.80-2.42, 5); head width, 1.77 (±0.364...