Parorchis longivesiculus, Dronen & Blend, 2008

Dronen, Norman O. & Blend, Charles K., 2008, Observations on the Parorchis acanthus complex (Philophthalmidae: Parorchiinae) with the description of three new species of Parorchis Nicoll, 1907 and the replacement of the preoccupied junior homonym Paratrema Dronen & Badley, 1979 with Stenomesotrema nomen novum, Zootaxa 1843 (1), pp. 1-23 : 10-13

Parorchis longivesiculus n. sp.

( Figs. 10–12)

Type host: Laughing gull, Larus atricilla Linnaeus , Charadriiformes , Laridae .

Type locality: Vicinity of Galveston , Galveston County, Texas, U.S.A. (29 º 18' N latitude, 94 º 48' W longitude) .

Site of infection: Rectum.

Deposited specimens: USNPC holotype 100619 ; USNPC paratypes (2) 100620, 100621; USNPC voucher (1) 100622 .

Prevalence: 3 of 8 laughing gulls, 38%.

Intensity: 3–5 per infected bird.

Etymology: The species is named for the unusually long external seminal vesicle.

Description: Based on 10 adult specimens. Body distinctly pyriform, heavily spinose along periphery and on ventral surface on anterior 50% of body, moderately large, 4,375 (4,110 –4,950) long by 1,845 (1,660 – 2,125) wide; body spines, generally scale-like anteriorly, more thorn-like posteriorly, 20 (10–29) long by 10 (5–13) wide; forebody 1,115 (1,025 –1,200, approximately 25% of body length) long by 955 (890–970) wide, anterior end surrounded by well-developed, shoulder-like head collar 610 (590–690) wide, bearing a single row of 65 (64–66) thumbnail-shaped, almost rectangular, scale-like spines; dorsal collar spines, 26 (20–29) long by 16 (13–21) wide; ventral corner spines 32 (23–39) long by 20 (15–31) wide, typically 10–12 per side. Mouth subterminal; oral sucker wider than long, 324 (290–350) long by 378 (350–400) wide; prepharynx short in smaller specimens, 15 (10–20) long, absent in fully-developed adults; pharynx longer than wide, 188 (180–210) long by 138 (130–140) wide, ratio of width of pharynx to width of oral sucker 1:2.7 (1:2.6–2.9); esophagus long with 9–10 short, pouch-like diverticuli, 430 (350–500) long; ceca long, terminating near posterior extremity. Acetabulum large, 905 (850–975) long by 930 (875–975) wide, sucker ratio 1:2.5 (1:2.4– 1:2.5). Testes side by side, contiguous, deeply lobed, near posterior extremity; left testis 535 (420–680) long by 560 (405–700) wide; right testis 575 (450–640) long by 480 (370–530) wide; posttesticular space 328 (200–440) long. Genital pore immediately anterior to acetabulum near midline of body; cirrus sac lateral width 214 (174–260), enclosing cirrus and numerous large prostate gland cells, lacking an internal seminal vesicle; external seminal vesicle enclosed in a sac-like membrane, overreaching the acetabulum posteriorly, extending into hindbody to about midway to testes from acetabulum, 1,505 (1,475 –1,550) long by 159 (150– 175) wide. Ovary oval to round, situated immediately anterior to intertesticular space, about 122 (50–220) anterior to testes, near midline of body, 218 (200–230) long by 205 (150–250) wide; ratio of width of ovary to average width of testes 1:2.5 (1:2.4–1:2.6). Ootype immediately postovarian on midline of body, details of female genital complex not visible. Morphologically distinct seminal receptacle absent. Laurer’s canal not observed. Vitelline follicles distributed in lateral fields from level of posterior margin of acetabulum posteriorly to level of posterior margin of ovary. Uterus filling hindbody from midlevel of testes to level of acetabulum, extracecal uterine loops present, proximal end unmodified, filled with spermatozoa; metraterm well developed 255 (234–275) long by 53 (40–60) wide. Eggs variable in size, eggs prior to miracidial eyespot development 66 (46–72) long by 34 (28–37); eggs with fully developed miracidia 83 (75–91) by 42 (39–47); extended miracidia free in uterus 81 (75–92) by 41 (39–42). Excretory vesicle slender, Y-shaped, branching at level of mid-posttesticular space; excretory arms with moderate branching, anterior extent of arms not observed. Excretory pore slightly subterminal on dorsal surface.

Remarks: Parorchis longivesiculus n. sp. is unlike P. acanthus , as originally described by Nicoll (1906) (subtype 1 of the Parorchis body type), by having a larger body size (4,375 long compared to 3,910); a longer esophagus with prominent diverticuli (430 compared to short to “absent” [“the intestine almost immediately divides into two wide branches” after the pharynx] without diverticuli); and more collar spines (65 [64–66] compared to “about 60” [actual count = 54]). The new species also has a smaller oral sucker (378 wide compared to 500); a smaller pharynx (188 long compared to 240); a smaller acetabulum (930 wide compared to 1,080); an external seminal vesicle that overreaches the acetabulum posteriorly, extending into hindbody to about midway to testes from acetabulum; and the testes of P. longivesiculus n. sp. are deeply lobed compared to being “circular” and smooth to slightly irregular.

The new species is similar to the specimens used in the redescription of P. acanthus by Nicoll [1907b] (subtype 2 of the Parorchis body type) by having a long esophagus that has diverticuli, a ratio of the width of the pharynx to the width of the oral sucker that is similar (1:2.7 compared to 1:2.9), testes that are irregular and deeply lobed, and both species are about the same size (4,110 –4,950 compared to 3,000 –5,000). It differs from these specimens by having an oral collar that is not as wide (590–690 wide compared to 820–870); more collar spines (64–66 compared to about 60); a smaller oral sucker (350–400 wide compared to 500; although Nicoll [1907b] reported the width of the oral sucker to be 500, it appears to be only about 370 wide, as calculated from Figure 1 of Nicoll [1907b], in which case, the oral sucker would be larger in the new species); a shorter prepharynx (15 long compared to 110); and a smaller pharynx (188 long by 138 wide compared to 240 by 170; although Nicoll, [1907b] reported the width of the pharynx to be 170, it appears to be about 280 as calculated from Figure 1 of Nicoll [1907b]). The new species also has a somewhat larger sucker ratio (1:2.5 compared to approximately 1:2.2 using 500 as the width of the oral sucker and 1,080 as the width of the acetabulum, as was reported by Nicoll [1907b] or 1:2.3 using approximately 370 and 840, respectively, as calculated from Figure 1 of Nicoll [1907b]); an external seminal vesicle that overreaches the acetabulum posteriorly, extending into hindbody to about midway to testes from acetabulum; and P. longivesiculus n. sp. has contiguous testes.

The new species can be distinguished from all species of Parorchis , including Parorchis catoptrophori n. sp. and P. ralli n. sp. described herein, except P. chauhani by having the seminal vesicle extending posteriorly well beyond the acetabulum to midway between the acetabulum and the testes, rather than being shorter and either not extending past the acetabulum, or extending only a short distance past the posterior margin of

the acetabulum. It can also be distinguished from all species assigned above to subtype 2 of the Parorchis body type by having contiguous testes. Parorchis chauhani is a distinctive species in that it has a bipartite pharynx, which is wider than it is long (110 long by 118 wide), and an ovary (240 wide) that is larger than the testes (159 average width). The new species further differs from P. chauhani by having a larger body size (4,375 long by 1,845 wide compared to 2,795 by 1,298), larger suckers (oral sucker 378 wide compared to 240; acetabulum 930 wide compared to 580), a larger pharynx (138 wide compared to 118; ratio of the width of the pharynx to the width of the oral sucker 1:2.7 compared to 1:2.0), a smaller ovary (205 wide compared to 240), larger testes (average testes width 520 compared to 159), and by having generally larger eggs (75–91 long by 39–47 wide compared to 61–72 by 26–32). Parorchis longivesiculus n. sp. can be distinguished from P. parvicollis and P. snipis because of their smaller body sizes (2,530 long and 2,580), and their smaller suckers (oral sucker 286 wide and 270 wide; acetabulum 584 wide and 550 wide). The new species is similar in overall size to P. schachtachtinskoi (4,375 long by 1,845 wide compared to 4,448 by 1,408); however, it differs from this species by having a smaller pharynx (188 long by 138 wide; ratio of the width of the pharynx to the width of the oral sucker 1:2.7 compared to 240 by 210, 1:1.7), a smaller acetabulum (930 wide compared to approximately 1,080), a slightly smaller sucker ratio (sucker ratio 1:2.5 compared to 1:2.9), a shorter forebody (1,115 long compared to 1,408), and by having a longer external seminal vesicle (1,505 long compared to 950, as calculated from Figure 1 of Dadasheva & Filimonova [1978]). The new species has a smaller body size than P. proctobium (4,110 –4,590 long by 1,660 –2,125 wide compared to 5,000 –7,000 by 3,000 –4,000 [measurements from Shtrom 1927]), smaller suckers (oral sucker 378 wide compared to 530, acetabulum 875–975 wide compared to 1,000 –1,159 [measurement from Shtrom 1927]), a smaller pharynx (138 wide compared to 190), smaller gonads (ovary 205 wide compared to 400; average width of testes 520 compared to 870), and by having smaller eggs (75–91 long compared to 134–142). Parorchis longivesiculus n. sp. is most like P. avitus , but in addition to the differences given above, the new species has a smaller pharynx (138 wide compared to 188), smaller gonads (ovary 205 wide compared to 245; average width of testes 520 wide, compared to 585, as calculated from Figure 3 of Linton [1914]), and a longer external seminal vesicle (1,505 long compared to 1,145, as calculated from Figure 3 of Linton [1914]). Parorchis magnus n. comb. is much larger (7,500 –7,800 compared to 4,375 [4,110 –4,950]), it has a larger oral sucker (464–485 wide compared to 350– 400), a larger pharynx (260–274 compared to 130–140), a smaller ratio of the width of the pharynx to the width of the oral sucker (1:1.8 compared to 1:2.7), a longer esophagus (886–949 compared to 350–500), a smaller sucker ratio (1:1.9 compared to 1:2.5), and smaller testes (average testes width 178 compared to approximately 520).