Studies on Monogenetic Trematodes. XXII. Dactylogyrus californiensis sp. n. from the Sacramento Squawfish

Abstract

This species is of moderate size (0.377 mm average length by 0.045 mm average greatest width) and differs from other known species of the genus by the presence of three to six (usually five) thickened cuticular folds on the left margin of the trunk near its mid-length. The cirrus and accessory piece resemble corresponding structures of D. banghami Mizelle and Donahue, 1944 (pl. II, figs. 33 to 36) but differ from them by the absence of a proximal process on the cirrus, and the presence of a dual articulation of the accessory piece to the base of the cirrus. Twenty specimens were used in the description. Host specimens of the Sacramento squawfish, Ptychocheilus grandis (Ayres), were obtained from Folsom Lake (Sacramento Co.) through the courtesy of Mr. D. A. LaFaunce and Mr. J. B. Kimseyl of the California Department of Fish and Game, to whom the author wishes to express his gratitude. The branchial material and the accompanying parasites were treated as described by Mizelle and Klucka (1953). Measurements were made with a compound microscope and a calibrated filar micrometer. Curved structures were measured as a straight line extending between the two most distant points of such structures. Measurements of anchor length, for example, extend from the tip of the superficial root to the most distant point on the curved portion in the area of junction of the shaft and point. Measurements of the length of the accessory piece extend from the tip of the base at its articulation with the cirrus, to the termination of the pointed ramus. Measurements of anchor widths (base) were made between the margin of the base on the deep-root side to a parallel line extending from the margin of the tip of the superficial root. In the following description all measurements are in millimeters. Dactylogyrus californiensis sp. n. Host and locality: Ptychocheilus grandis (Ayres), Folsom Lake, Sacramento Co., California. Specimens studied: Twenty. Type specimens: Type USNM Helm. Coll. No. 59656, Washington, D. C. Paratypes in author's collection. Received for publication 22 January 1962. Present address: Bureau of Commercial Fisheries, Galveston, Texas. Description: Moderate-size dactylogyrid provided with a smooth cuticle; length 0.377 (0.254 to 0.481), greatest body width 0.045 (0.038 to 0.062). Left margin of trunk near mid-length with a dorsal (or ventral) cavity in which three to six (usu lly five) conspicuous cuticular folds are contained (figs. A, G). Eye spots four; members of posterior pair slightly larger and closer together than those of the anterior pair. Often some of the melanistic granules forming the eye spots are dissociated (fig. All). Cephalic area bifurcated to produce two terminal lobes each of which may possess one or two secondary lobes (figs. A, B). Head organs and associated cephalic glands not observed. Pharynx inconspicuous, ovoid in outline (dorsal view) and 0.015 (0.012 to 0.018) in transverse diameter (fig. A 10). Peduncle of moderate dimensions; haptor subpentagonal in outline (dorsal view), 0.049 (0.035 to 0.066) long and 0.058 (0.044 to 0.088) in greatest width. Anchors and connecting bar situated dorsally in haptor. Each anchor composed of: (1) a base with an elongate superficial and a small deep root; (2) a solid shaft; and (3) a recurved point (fig. C). Anchor wings inconspicuous. Anchor length 0.049 (0.044 to 0.052), greatest width of base 0.020 (0.017 to 0.022). Dorsal bar well developed, usually slightly bent posteriad in mid-region and with an indentation on posterior border near each end (fig. C 1); length 0.036 (0.033 to 0.038). Vestigial ventral bar inconspicuous, platelike anteriorly, and bifurcated near middle to produce two rami which project laterally and whose ends frequently are bent anteriorly (fig. D). Distance between ends of rami 0.025 (0.021 to 0.029). Hooks 14 (seven pairs) in number and normal in arrangement (Mizelle 1938) with members of pair number 6 often shifted somewhat ventrad. Each hook composed of: (1) a solid elongate base; (2) a shaft much shorter than the base; and (3) a sickle-shaped termination provided with an opposable piece (figs. H 1, 2). Hook bases infrequently inflated proximally (fig. H 2). Posteriorly projecting process of sickle-shaped termination apparently absent. Hooks of pairs 1 and 5 usually shorter than those of remaining pairs. Hook lengths: pair no. 1,