Pennella benzi, Hogans, W. E., 2017

Hogans, W. E., 2017, Review of Pennella Oken, 1816 (Copepoda: Pennellidae) with a description of Pennella benzi sp. nov., a parasite of Escolar, Lepidocybium flavobrunneum (Pisces) in the northwest Atlantic Ocean, Zootaxa 4244 (1), pp. 1-38 : 13

Pennella benzi sp. nov.

( Fig. 6 )

Host. Escolar ( Lepidicybium flavobrunneum Smith, 1843 )

Type Locality. Holotype and paratype 1: Host caught in the northwest Atlantic (no specific locality)

Paratype 2: Host caught off coastal North Carolina, northwest Atlantic

Site of infestation. Embedded in deep musculature, along base of dorsal fin

Etymology. The species is named for Dr. George W. Benz, in honor of his contributions to the study of parasitic Copepoda

Type material. Holotype: United States National Museum ( USNM) 180162 ; Paratype 1: USNM 180163; Paratype 2: Fisheries and Oceans Canada, Atlantic Reference Center ( ARC), ARC 29529

Description. Ovigerous female ( Fig. 6 a, b): cephalothorax bulbous, spherical, apical end flattened, armed with numerous roughly spherical cephalothoracic papillae of various sizes ( Fig. 6 d). Configuration of papillae unorganized and different between all three specimens. Three holdfast horns radiating from below cephalothorax: two lateral, and one shorter dorsal horn bifurcate at tip ( Fig. 6 c, i). Thoracic neck tubular, elongate, posterior end enlarged to form anterior end of trunk. Trunk one-half length of entire parasite, cylindrical, with parallel sides. Trunk tapering abruptly at its posterior end to form the abdomen. Abdomen about one-half length of trunk, annulated, with rounded dorsal surface and flattened ventral surface. Abdominal plumes arising from ventral surface of abdomen in two rows; individual plume (24-28) sets arise from a single stem and then branch repeatedly to form a mass of digitiform plumules ( Fig. 6 h). Number of plumules per set variable. Genital complex ( Fig. 6 g) at posterior end of abdomen, exhibiting two small oviduct orifices on ventral surface. Egg strings paired, filiform, about 1.5x length of each parasite, eggs uniseriate.

First antenna ( Fig. 6 e), observed clearly on one specimen only (paratype 2), two- segmented. Apical armature of 9 setae of various lengths. Setae of middle portion shorter and more numerous. Second antenna ( Fig. 6 f), distinctly three-segmented; terminal segment with prehensile large re-curved hook which closes on a blunt, distal spine; small spine at base of hook. Buccal complex (mouth), mandibles, first and second maxillae and maxillipeds not observed on any specimen. Swimming legs (4) reduced to sympods only, rami lost or atrophied and not observable. Total length (anterior end of cephalothorax to posterior end of abdomen) of three specimens: 131, 157, 162.

Remarks. This new species is erected based on a newly collected specimen and on two others previously assigned to Pennella filosa also collected from the escolar (oilfish) in the northwest Atlantic ( Benz & Hogans 1993). Benz & Hogans (1993) considered their two specimens to be phenotypic variations of P. filosa , but finding a new and third specimen on the same species of host shows P. benzi sp. nov. to be a different species than P. filosa which it closely resembles. Pennella benzi sp. nov. has several features which are unique and distinguish it from P. filosa : P. benzi sp. nov. is a somewhat smaller parasite (150 mm) than P. filosa (180mm); a unique host (escolar) which has not previously been recorded as parasitized by any other Pennella sp.; dorsal horn configuration: all three known specimens of P. benzi sp. nov. have a bifurcate dorsal horn, a feature never previously reported within the genus. Pennella benzi sp. nov. possesses a three-segmented second antenna; P. filosa exhibits two segments on this appendage. It can be easily distinguished from the other large Pennella found on fish, P. instructa , based on the cepahlothoracic papillae (not arranged in distinct groups) and possessing a dorsal horn (not found in P. instructa ).

Figures

FIGURE 6. Pennella benzi sp. nov. a. Habitus, holotype, dorsal (USNM 180162). b. Habitus, holotype, ventral. c. Anterior end showing holdfast horns, lateral. d. Apical end showing cephalothoracic papillae, ventral. e. First antenna, paratype 2 (from ARC 29529), dorsal. (ae = aesthetae), f. Second antenna, dorsal. g. Genital complex, ventral. h. Abdominal plumes of mature female, i. Anterior end of female, paratype 2 (from ARC 29529), dorsal. (a, b, c, d, f, g, h reproduced from Benz and Hogans, 1993). (scale bars = a, b— 10.0; c— 0.5; d— 0.2; e— 0.02; f— 0.01; g— 1.0; h— 5.0; i— 2.0)