Systematics and Metapopulation Dynamics of Pomphorhynchus Sphaericus N

SYSTEMATICS AND METAPOPULATION DYNAMICS OF POMPHORHYNCHUS SPHAERICUS N. SP. (ACANTHOCEPHALA: POMPHORHYNCHIDAE) FROMFRESHWATER SILURIFORM FISHES IN THE SUBTROPICAL REGION OF ARGENTINA

A.A. GIL DE PERTIERRA, L. SPATZ & I.L. DOMA Departamento de Ciencias Biologicas, Faculiad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellon 11,Ciudad Universitaria, 1428 Buenos Aires, Argentina

Received 5 March 1996; accepted 29 October 1996 REFERENCE:GILDEPERTIERRA(A.A.), SPATZ(L.) & DOMA(LL.), 1996.- Systematics and metapopulation dynamics of Pomphorhynchus sphaericus n. sp. (Acanthocephala: Pomphorhynchidae) from freshwater siluriform fishes in the Subtropical Region of Argentina. Research and Reviews in Parasitology, 56 (1): 33-39. ABSTRACT:Pomphorhynchus sphaericus n. sp. is described from De La Plata River, Province of Buenos Aires, Argentina. The new species is characterized by having a spherical or slightly subspherical bulb and 12 longitudinal rows, each one armed with 14to 16proboscideal hooks. Hooks4 are stout, hooks 5 slender and slightly shorter, hooks 6 and 7 are larger than the preceding series, hooks 8 and subsequent series are longer than the others. The hooks of the basal crown of the proboscis are larger than in the preceding ones. The hook roots are similar to those of P. laevis (MUller, 1776).The relative positions in the trunk of the proboscideal receptacle, lemnisci, testes, and cement gland are herein considered. Accessory copulatory structures in the bursa, two suckers and a penial stylet are present in the new species. The seasonal prevalence, mean intensity of infection, abundance, and other ecological aspects are analyzed for two siluriform fishes of the family Pimelodidae. KEYWORDS:Acanthocephala, Pomphorhynchus sphaericus n. sp., systematics, ecology, siluriform fishes, subtropical region, Argentina.

INTRODUCTION prevalence, mean intensity of infection and abundance. We also compare preferencial site, size of trunk and The genus Pomphorhynchus is widely distributed all bulb, developmental stages of the females, and colour of over the world, except New Zealand and Australia. The Pomphorhynchus sphaericus n. sp. in the different hosts. members of this genus parasitize both freshwater and marine fishes (GOLVAN & BURON, 1988). Only 2 species of Pomphorhynchus have been descri- MATERIAL AND METHODS bed so far for South America, namely: P. yamagutii Three species of autochthonous siluriform fishes, Iheringichthys Schmidt et Hugghins, 1973 (in Percichthys melanops) platanus Steindachner, 1908, Pimelodus maculatus Lacepede, and P. patagonicus Ortubay, Ubeda, Semenas et Ken- 1803, and Pimelodus albicans Valenciennes, 1840, from De La nedy, 1991 (in Patagonina hatcheri, Galaxias platei, Plata River were studied throughout a 2-year period (September Percichthys trucha, and the introduced salmonids On- 1989 to August 1991). Only Pimelodus spp. were sampled corhynchus mykiss and Salvelinus fontinalisv. Both spe- monthly for ecological aspects. A total of 546 P. albicans (9 to 21 cies are characterized by possessing an asymmetric bulb. cm standard length), 542 P. maculatus (9 to 27 cm standard length), and 211. platanus (7 to 16 cm standard length) were cap- The acanthocephalan species herein described was tured by using 50-70 mm stretch mesh gillnets. Fish were transpor- found in fishes of the family Pimelodidae (Silurifor- ted alive to the laboratory, where they were measured, weighed, mes). Pimelodid catfishes are autochthonous to South sexed, and examined within 5 days of capture. Another catfish, Lu- America and common dwellers in the large hydrogra- ciopimelodus pati Valenciennes, 1840, was also examined during phical systems of the continent, such as the rivers Ama- 1995 to look for additional hosts. The entire alimentary tract was zonas, Orinoco, Magdalena, Parana, Uruguay, De la removed and analyzed. The intestine was divided into 3 equal seg- Plata, and others. ments, anterior, middle and posterior, for its analysis. Site, number, and sex of the parasites recovered from each segment were re- Like the North American members of the genus corded. Maturation only refers to females, which were classified Pomphorhynchus (P. bulbocolli Van Cleave, 1919, P. into 5 stages according to the degree of development of the ovary, rocci Cordonier et Ward, 1967, and P. lucyi Williams et namely: 1) immature ovary, unfragmented in ovarian balls; 2) ova- Rogers, 1984), P. sphaericus n. sp. possesses a symme- rian balls present; 3) ovarian balls and eggs into the ovarian liga- trical bulb. Although eggs and proboscideal hooks are ment; 4) ovarian ligament full of eggs, few eggs in the body cavity; taxonomically valuable characters (AMIN, 1987a), shape 5) ovarian ligament broken, eggs filling the body cavity. The use of general ecological terms follows MARGOLISet al. (1982). The and morphometric features of the hook roots, as well as term metapopulation is used in the sense of RIGGS,LEMLY& ESCH the relative position in the trunk of the proboscideal re- (1987). ceptacle, lemnisci, testes, and cement glands are herein Parasites were removed from the intestinal wall, then relaxed in considered. The present study aims at describing the new lukewarm water, fixed in AFA, stained with carmine hydrochlo- acanthocephalan species and to determine its seasonal ride, cleared in creosote, and mounted in Canada balsam. Thirty 34 A.A. GIL DE PERTIERRA, L. SPATZ & I.L. DOMA specimens were selected for general description and measurement. a bifid hook (Fig. 2B). Fusiform eggs with polar prolon- Ten males and 10 females were examined for hook dimensions. gations (Fig. 2C). Only the morphometric features of the hook roots of the females were considered, since these structures were not clear enough in Male: Trunk 2,6-8,2 mm (5,4) long and 0,4-1,1 mm the permanent mounts of males. Observations and descriptions were made using an optical interference microscope. Unless other- (0,7) wide. Proboscis 510-726 (606) long and 117-242 wise stated, measurements are expressed in micrometers, with ran- (203) wide. Hooks 1-3,24-31 (27) long; hooks 4, 25-30 ges followed by mean size in parentheses. (27) long; hooks 5, 21-25 (24) long; hooks 6 and 7, 22- 28 (25) long; hooks 8 and subsequent series, 23-35 (29) long. Basal crown of large hooks, 35-37 (36) long. Bulb RESULTS 642-1400 (1025) long and 665-1587 (1169) wide. Neck without bulb, 968-2392 (1667) long and 257-467 (358) Pomphorhynchus sphaericus n. sp. wide. Proboscideal receptacle 1,9-4,2 mm (3,1) long and Type host: Pimelodus maculatus, common name: pain- 105-152 (132) wide. Lemnisci: the larger 758-1610 ted catfish or yellow catfish. (1191) long and 105-210 (165) wide and the smaller Additional hosts: Iheringichthys platanus, common 618-1482 (1070) long and 105-245 (165) wide. Anterior name: thick-lipped catfish or long-snouted catfish; testis 432-1167 (699) long and 315-642 (480) wide, pos- Pimelodus albicans, common name: white catfish or terior testis 420-1237 (680) long and 303-627 (390) «moncholo»; Luciopimelodus pati, common name: wide. Cement glands 245-758 (444) long. Penis 115 «patf». long and 81 wide. Suckers 128-142 (135) and 85-98 (92) Infection site: Attached to the intestine; proboscis and wide. Stylet 96 long and 19 wide. bulb penetrating the intestinal wall, trunk in the intestinal lumen. Female: Trunk 3,2-9,5 mm (6,0) long and 0,5-1,0 (0,8) Type locality: De La Plata River, Province of Buenos Ai- wide. Proboscis 550-810 (669) long and 143-290 (219) res, Argentina. wide. Hooks 1-3, 24-36 (29) long; hooks 4, 23-39 (30) Type material: Specimens deposited in the Helmintholo- long; hooks 5: 21-38 (27) long; hooks 6 and 7, 22-36 gical Collection of the Museo Argentino de Ciencias (28) long; hooks 8 and subsequent series, 28-38 (34) Naturales «Bemardino Rivadavia». Holotype # long.Hook roots 1-6, 25-46 (39) long and 9-16 (13) 37711; allotype # 37712; paratypes # 377/3, # 377/4, wide; hook roots 7 and subsequent ones, 11-19 (14) long # 377/5 and # 377/6. and 2-6 (3) wide. Basal crown of large hooks, 37-44 (40) Etymology: The species name describes the shape of the long. Bulb 782-1645 (1133) long and 968-1178 (1284) bulb. wide. Neck without bulb, 1073-2392 (1654) long and 233-490 (381) wide. Proboscideal receptacle 2,4-3,8 mm (3,15) long and 128-198 (168) wide. Lemnisci: the lar- General description ger 980-2043 (1374) long and 140-222 (175) wide and With the characters of the genus Pomphorhynchus. In- the smaller 817-1668 (1208) long and 128-245 (192) dividuals parasitizing different fish species are diffe- wide. Eggs 34,5-57,5 (46,8) long and 6,9-9,2 (7,7) wide. rently coloured: light orange, light yellow, white or cream. Trunk cylindrical with its anterior region swollen Prevalence, intensity, and abundance (Fig. IC). Proboscis cylindrical, enlarged at its anterior of P. sphaericus n. sp. third. Hooks arranged in 12 slightly spiralling longitudinal rows, each one armed with 14, 15 or 16 hooks (Fig. In Pimelodus maculatus: The seasonal prevalence was lA). In each longitudinal row (Fig. IB): hooks 4 stout, low throughout the year (Table 1); its maximum occu- hooks 5 usually shorter and slenderer than the preceding rred in spring (9,18%), with a slight peak in autumn series, hooks 6 and 7 larger than the preceding series, (2,7%). The mean intensity by season was also low, with hooks 8 and subsequent series longer than the others. a maximum in summer. The seasonal mean abundance Roots of hooks 1-6 formed by a wide sheet that splits showed its maximum in spring (0,34) and a slight peak into 2 apophyses (Fig. IB). Hooks 7 and subsequent se- in autumn (0,17). ries with 2 slender roots directed posteriorly, and qua- drangular sheets directed anteriorly (Fig. IB, D). Basal In Pimelodus albicans: The seasonal prevalence was crown with large hooks in some individuals. Neck for- higher in spring (20,28%), declining markedly throug- ming a spherical or subspherical bulb. Proboscideal re- hout the other seasons (Table 2). The mean intensity by ceptacle extending deeply into the trunk, with its ex- season showed maxima in winter and spring. The seaso- treme generally bent. Lemnisci unequal. Two testes in nal mean abundance showed its maximum in spring the anterior third of the trunk. Six pyriform cement (0,74) and declined gradually during the other seasons. glands occupying the middle part of the trunk. Bursa (Fig. 2A) with accessory copulatory structures, two suc- In Iheringichthys platanus: This host was found occa- kers on its inner surface. Penis located at the base of the sionally, in only 7 samples out of 24. Only 5 out of 21 bursa between the suckers. Stylet lanceolate ending into captured fishes were infected. Therefore, for this fish Pomphorhynchus sphaericus n. sp. from fishes in Argentina 35

A c

100

Fig. 1.- Pomphorhynchus sphaericus n. sp.: A) proboscis; B) two complete longitudinal rows of proboscideal hooks in fronto-Iateral view; C) complete male holotype; D) postero-Iateral view of hooks 6, 7, 8 and 9. Scale bars of A, Band 0 in urn, C in mm. 36 A.A. GIL DE PERTIERRA, L. SPATZ & I.L. DOMA

species we could not calculate seasonal prevalence or intensity. However, certain biological characteristics observed and their comparison with those of other pimelodids are worth mentioning.

Colour, preferential infection site, size of trunk and bulb, and maturity of P. sphaericus n. sp.

In Pimelodus maculatus: The parasites are light yellow or cream coloured. The mean size of trunk is 5,40 mm in males and 6,12 mm in females. The maximum size of bulb is 1260 in males and 1435 in females. The total percentage of mature females (stages 4 and 5) was high (70%)(Table 3). In P. maculatus, P. sphaericus n. sp. o reached its maximum maturation in spring (64,7%). Du- o N ring summer, autumn, and winter the number of parasitized fish and acanthocephalans found was low (Table 1). P. sphaericus n. sp. was attached all along the intestinal wall, mostly to its posterior segment (41 %). The sex ratio was slightly higher for females 1:1, I5.

In Pimelodus albicans: The parasites are cream or white c coloured. The mean trunk size is 3,9 mm in males and 4,5 B in females. The maximum size of bulb is 1365 in males and 1750 in females. The total percentage of mature females (stages 4 and 5) was 51%. Maturation seems to incre- ase as a function of temperature; therefore, gravid females reached their highest proportion during spring (60%) and 100 50 summer (62%). The maximum percentage of individuals Fig. 2.- Pomphorhynchus sphaericus n. sp.: A) bursa of male sho- was found in the posterior segment of the intestine (39%), wing two lateral suckers and penial stylet; B) penial stylet ending in followed by the anterior segment (33%). (Table 3). The a bifid hook; C) eggs with polar prolongations. Scale bars in pm. sex ratio was slightly higher for females I: 1,23.

Season No. Fish No. Fish Prevalence Mean Range Abundance examined parasitized % intensity

Spring 196 18 9,18 3,72 1-12 0,34 Summer 107 I 0,93 3 3 0,06 Autumm III 3 2,70 2,67 1-5 0,17 Winter 128 3 2,34 1,00 I 0,D2

Total 542 25 4,60 3,65 1-12 0,18

Table 1.- Seasonal prevalence, mean intensity of infection, and abundance of Pomphorhynchus sphaericus n. sp. in Pimelodus maculatus.

Season o. Fish No. Fish Prevalence Mean Range Abundance examined parasitized % intensity

Spring 212 43 20,28 3,63 1-32 0,74 Summer 103 10 9,71 2 1-4 0,19 Autumm 154 11 7,14 1,64 1-3 0,12 Winter 77 I 1,3 4 4 0,05

Total 546 65 11,9 3,05 1-32 0,36

Table 2.- Seasonal prevalence, mean intensity of infection, and abundance of Pomphorhynchus sphaericus n. sp. in Pimelodus albicans. Pomphorhynchus sphaericus n. sp. from fishes in Argentina 37

Host Colour Medium trunk Maximum bulb Maturation Infection site size (11111) size (urn) Male Female Male Female % %

I. pia/anus Light orange 6,1 7,13 1575 1715 91 P.I.: 100

A.I.: 21 P. macula/us Light yellow, 5,4 6,12 1260 1435 70 M.I.: 35 cream P.I.: 40

A.I.: 32 P. albicans Cream-white 3,9 4,5 1365 1750 51 M.I.: 27 P.I.: 39

Table 3.- Comparison of different aspects of Pomphorhynchus sphaericus n. sp. from three fish hosts of De La Plata River. A.1. = anterior intestine; M.1. = middle intestine; P.1. = posterior intestine.

In Iheringichthys platanus: The parasites are light to and subsequent series. P. bulbocolli possesses 12 to orange. The mean trunk size is 6, lO mm in males and 14 hooks in each longitudinal row, but among the speci- 7, l3 mm in females. The maximum bulb size is 1575 in mens studied by HUFFMAN& NICKOL(1978) the num- males and 1715 in females. The total percentage of ma- ber of hooks per row varies from 10 to 19. P. sphaericus ture females was very high (91 %). The parasites were n. sp. does not present such a wide range of variation in only found in the posterior segment of the intestine (Ta- the number of hooks per row. As stated by AMIN ble 3). (1987a), the length of P. bulbocolli ranges between 2 and 16 mm, with a neck considerably longer than in P. sphaericus n. sp. Similarly, in P. bulbocolli the basal DISCUSSION crown of the hooks reaches a maximum length of 54 mm, being larger than in P. sphaericus n. sp.The maxi- Systematic aspects mum diameter of the bulb neck in P. bulbocolli is 2,09 The differential diagnosis of Pomphorhynchus sphae- mm, also much larger than in P. sphaericus n. sp. The ricus n. sp. is based on the shape and measurements of maximum length of the anterior testis in P. bulbocolli is the hooks and hook roots of the proboscis, as well as on 1,40 mm, also larger than in P. sphaericus n. sp. AMIN the morphology and position of the reproductive organs. (1987a) did not refer to the hook roots of P. bulbocolli to The new species differs from the other South American differentiate this species from P. rocci; therefore it can members of the genus, P. yamagutii and P. patagonicus, be assumed that these structures may be similar in both by possessing a symmetrical bulb. On the other hand, it species. It must be pointed out that the hook roots of P. is similar to the North American species P. bulbocolli, P. sphaericus n. sp. are similar to those of P. laevis (Mi.i- rocci, and P. lucyi, in having a spherical bulb and 12 lon- ller, 1776) (as cited in GOLVAN, 1969). The differences gitudinal rows of hooks. P. lucyi has 20 to 30 much lar- between these 2 species are based on the number of longer hooks in each longitudinal row, a larger proboscis, gitudinal rows of hooks (18-20 vs. 12) and hooks per approximately equal in length to the trunk, a very large row (12-13 vs. 14-16). proboscideal receptacle, and a long neck. P. sphaericus In the new species the proboscideal receptacle extends n. sp. has the smallest trunk as compared to P. rocci and deeply into the trunk and its extreme is generally bent. P. bulbocolli. Conversely, in P. rocci the proboscideal receptacle ex- P. rocci possesses 15 to 18 hooks in each longitudinal tends only slightly into the trunk. The lemnisci are une- row (hooks 1-4 short, hooks 5 long, hooks 6 and 7 short, qual in P. sphaericus n. sp., while they are equal in P. and hooks 10 and subsequent series longer than the rest). rocci. As stated by BROWN(1987), the populations show P. sphaericus n. sp. has 14 to 16 hooks in each longitudi- anatomical variability, and the presence of bilobate lem- nal row; hooks 1-3 approximately similar; hooks 4 stout; nisci has been observed in some specimens. Like in P. hooks 5 slender and shorter than the preceding series; rocci, the testes of the new species are situated in the an- hooks 6 and 7 slightly longer than the preceding series, terior third of the trunk; only juvenile males have antero- hooks 8 and subsequent series, which are longer than the medial testes. The cement glands are extensive and oc- others. The hook roots 1-6 have a uniform shape, sho- cupy most of the trunk, reaching the testes in some wing a wide sheet that splits into 2 apophyses while the specimens. The anterior ligament, which holds up the hook roots 7 and subsequent series, consist of a quadran- glands, can be seen in juvenile males. Although the size gular sheet directed anteriorly and 2 slender pieces direc- of the glands of P. sphaericus n. sp. corresponds to the ted posteriorly. In P. rocci, CORDONIER& WARD(1967) size ranges of P. rocci and P. bulbocolli, the trunk of the described the presence of small posterior roots in hooks new species is much smaller. Two suckers and penial 1-7, and roots directed anteriorly, or manubria, in hooks stylet can be observed in specimens having their bursa 38 A.A. GILDEPERTIERRA,L. SPATZ& I.L. DOMA relaxed and extended. These structures were also descri- location overiap by other parasites in the anterior and bed in P. bulbocolli by DOYLE & GLEASON(1991). In middle segments of the intestine in P. albicans and P. the latter species the stylet is conical, whereas in P. maculatus during all seasons, suggests that competition sphaericus n. sp. it is a lanceolate piece ending poste- may not be involved in site selection. In spite of the rioriy in a bifid hook. The eggs of P. sphaericus n. sp. much lower number of other helminths found in the an- are 40% smaller than in P. rocci and 13% smaller than in terior and middle segments of the intestine of I. plata- P. bulbocolli. P. sphaericus n. sp. damages its hosts th- nus, as compared to Pimelodus spp., P. sphaericus n. sp. rough the penetration of its proboscis, bulb and neck into was only found in its posterior intestine. the intestinal wall of the fish, while its trunk remains in The different colours of the parasites depending on the lumen. An intense host reaction against the parasite their presence in P. albicans, P. maculatus or I. plata- was observed, consisting in the deposition of fibrous nus, might be related to the different diets of the hosts, in connective tissue around the proboscis, forming a cap- accordance with UBEDA et al. (1994). Comparing size, sule that can be seen from the coelomic cavity. The same colour, prevalence, mean intensity, preferencial infec- intense host reaction has been reported in P. bulbocolli tion site, and proportion of gravid females of the three (McDoNOUGH & GLEASON,1981). metapopulations did not allow us to determine the status According to AMIN (l987a), the adults of P. bulbocolli of each host, according to the categories proposed by and P. rocci (SAMUEL,NICKOL& MAYES, 1976; HUFF- AMIN (1987b), HOLMES (1979), and KENNEDY, MAN& NICKOL,1978; GLEASON& HUFFMAN,1981) are BROUGHTON& HINE (1978). In all the studied hosts, P. very similar and consequently difficult to discriminate. sphaericus n. sp. showed successful maturation and a Populations from different localities and hosts are highly high proportion of gravid females. Therefore, they may variable in the meristic features of their hooks. As oppo- be classified as «principal», «required», or «preferred» sed to these observations, the morphological and meris- hosts (the first categories of each author) for P. sphaeri- tic characters of P. sphaericus n. sp. are homogeneous, cus n. sp., depending on the categorization schemes sug- and present narrow ranges of variability. BURON, RE- gested by different authors. In spite of the slight diffe- NAUD& EUZET(1986) affirm that the slight morphologi- rences displayed by populations of P. sphaericus n. sp. cal differences observed between acanthocephalan spe- found in different hosts, they may still be ranked as: first cimens do express taxonomic diversity and evolutionary (I. platanus), second (P. albicans), and third (P. macula- divergence, resulting in parasite speciation and host spe- tus) suitable hosts. Studies on the ecological aspects of cificity. parasitism should cover other fish groups of De la Plata River in order to establish the right status of each host. Our observations indicate that P. sphaericus n. sp. pa- Parasite ecology rasitizes at least 4 fish species belonging to the family Some life cycles of Pomphorhynchus spp. are known Pimelodidae, in the De La Plata River. However, consi- and all of them developed in an amphipod intermediate dering that other siluriform fishes have similar feeding host (SCHMIDT, 1985). SEMENAS,ORTUBAY & UBEDA habits, this acanthocephalan species is likely to be wi- (1992) described from the amphipod Hyalella patago- dely distributed among other members of the local nica, intermediate host of P. patagonicus, early and ad- ichthyofauna. It is interesting to remark that the finding vanced stages of acanthella. Three species of amphipods of P. sphaericus n. sp. is the second record of this genus inhabit De la Plata River: Hyalella curvispina, H. pam- for Argentina and the third one for South America. peana, and Corophium rioplatense. ltis possible that one of these amphipods could be the intermediate host of the new acanthocephalan species. ACKNOWLEDGEMENTS Prevalence values were low for both hosts, indepen- The authorswant to expresstheir thanksto Dr. M.I. Hamannfor dently of sex or season. It was higher in P. albicans than his help in collectingfishesand parasites,and to Dr. M. Ostrowski in P. maculatus. Mean intensities were low during the de Nuriezfor her valuablesuggestions.Financialsupportwas pro- whole year for both hosts, and differences involving sex videdby a researchgrant from the ConsejoNacionalde lnvestiga- or season were not detected. Abundance was also very cionesCientfficasy Tecnicasof Argentina(CONICET). low in both pimelodids. These parameters indicate that there was no marked infection pattern by P. sphaericus REFERENCES in any of the host species of Pimelodus herein considered. Values were much lower than those reported for P. AMIN(O.M.), 1987a.- Acanthocephalafrom lake fishes in Wis- bulbocolli (MUZZALL, 1980) or P. patagonicus (UBEDA consin: morphometric growth of Pomphorhynchus bulbocolli et al., 1994). (Pomphorhynchidae).Journal of Parasitology, 73: 806-810. According to KENNEDY,BROUGHTON& HINE(1976), AMIN(O.M.), I987b.- AcanthocephalafromlakefishesinWiscon- sin:ecologyand host relationshipsof Pomphorhynchus bulboco- the location of P. sphaericus n. sp. in all the hosts was lli (Pomphorhynchidae).Journal of Parasitology, 73: 278-289. always posterior to the opening of the biliary duct. How- BROWN(A.F.), 1987.- Anatomical variabilityand secondary se- ever, no clear preferences for infection sites were detec- xual characteristics in Pomphorhynchus laevis (MUller,I776) ted either in P. albicans or P. maculatus. The persistent (Acanthocephala).Systematic Parasitology, 9: 213-219. Pomphorhynchus sphaericus n. sp. from fishes in Argentina 39

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