Redescription of Pseudacanthostomum panamense - BioNames

J. Helminthol. Soc. Wash.66(2), 1999 pp. 146-154

Redescription of Pseudacanthostomum panamense Caballero, Bravo-Hollis, and Grocott, 1953 (Digenea: Acanthostomidae), a Parasite ofSiluriform Fishes of the Family Ariidae, with Notes on Its Biology

TOMAS ScHOLZ,1-7 LEOPOLDINA AouiRRE-MACEDO,2 GUILLERMO SALGAOO-MALDONADO,3JOAQUIN VARGAS-VAZQUEZ,2 VICTOR VlDAL-MARTINEZ, 2 JAN WOLTER,4 ROMAN KUCHTA,5

AND WOLFGANG KoRTiNG6

1 Institute of Parasitology, Academy of Sciences of the Czech Republic, Branisovska 31, 370 05 CeskeBudejovice, Czech Republic (e-mail: [email protected]),2 Center for Investigation and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN)Unidad Merida, Carretera Antigua a Progreso Km 6, A.P. 73 "Cordemex," C.P. 97310 Merida, Yucatan,Mexico,3 Institute of Biology, National Autonomous University of Mexico (UNAM), A.P. 70-153, C.P. 04510,Mexico D.F., Mexico,4 Wexstrasse 39, 10715 Berlin, Germany,5 Faculty of Biology, University of South Bohemia, Branisovska 31, 370 05 Ceske Budejovice,Czech Republic, and6 Fish Diseases Research Unit, School of Veterinary Medicine, Biinteweg 17, 30559 Hannover, Germany.

ABSTRACT: The acanthostomid trematode Pseudacanthostomum panamense Caballero, Bravo-Hollis, and Gro-cott is redescribed on the basis of examination of its holotype and new material from Galeichthys (=Ariopsis)seemani (Giinther) (type host) from Colombia (new geographical record), and Ariopsis assirnilis (Giinther) andArius guatemalensis (Giinther) (new host records) (all Siluriformes: Ariidae) from the Atlantic and Pacific coastsof Mexico (new geographical record). It was found that P. panamense possesses intestinal ceca that are connectedwith the excretory bladder near the posterior extremity and opening outside by an uroproct. The actual numberof circumoral spines of the holotype is 27; the number of spines is stable, with most specimens possessing 27spines and a very few 26 or 28. Pseudacanthostomum floridensis Nahhas and Short, described from Galeichthys(= Arius) fells (Linnaeus) from Florida, U.S.A., is considered a synonym of P. panamense. Metacercariae of P.panamense from the eleotrid fishes Dormitator latifrons (Richardson) and Gobiomorus maculatus (Giinther)from the Pacific coast of Mexico (Jalisco state) are described for the first time.

KEY WORDS: Pseudacanthostomum panamense, Digenea, metacercariae, Acanthostomidae, taxonomy, catfish,Siluriformes, Ariidae, Pisces, Mexico, Colombia.

During parasitological examination of fish and geographical regions. Metacercariae of thisfrom Colombia and Mexico, acanthostomid trematode are described for the first time, andtrematodes were found, both as adults in catfish the taxonomic status of Pseudacanthostomumof the family Ariidae and as metacercariae in floridensis Nahhas and Short, 1965, the onlyeleotrid fish. They were identified as Pseuda- congeneric species, is discussed.canthostomum panamense Caballero, Bravo-Hollis, and Grocott, 1953, a species described Materials and Methodsfrom Galeichthys (_= Ariopsis) seemani (Giinther, Trematodes studied were found in Ariopsis seemani1864) from Panama (Caballero et al., 1953). Ex- (7 specimens examined) from Colombia (locality notanimation of the holotype of P. panamense known; May 1996)MnV^,, ™///, (Cninther, 1864),

, , . . . , , . . . , from Laguna Bacalar near the village of Bacalar, Qum-showed that its original description had not pro- tana Roo Mexico January 1995 (, specimen)> and

vided data on some taxonomically important from Chetumal Bay, Quintana Roo, Mexico, Octoberfeatures such as the morphology of the intestinal 1996 (96 specimens); and Arius guatemalensis (Giin-ceca; in addition, no information about intraspe- ther' 1864> <3 specimens) from Marismas de Chala-

.,- . ,.,.. <- i • - j j catepec, Jalisco, Mexico, May 1995. Metacercariaecifi c variability or this taxon was provided. f , • ., , . , r , ̂ -t t , , ,J * were found in the eleotrid fish Dormitator latifrons

Therefore, P. panamense is redescribed here on (Richardson, 1844) from Boca del Rio San Nicolas,the basis of new material from different hosts Jalisco, Mexico, September and November 1994 (21

fish examined), from Marismas de Chalacatepec, Jal-isco, Mexico, March 1995 (24 specimens), and from

7 Corresponding author. the Cuitzmala River at the village of Emiliano Zapata,

146

Copyright © 2011, The Helminthological Society of WashingtonCopyright © 2011, The Helminthological Society of Washington

SCHOLZ ET AL.—REDESCRIPTION OF PSEUDACANTHOSTOMUM PANAMENSE 147

Jalisco, Mexico, September 1995 (7 specimens); andin Gobiomorus maculatus (Giinther, 1859) from theCuitzmala River at Emiliano Zapata, Jalisco, Mexico,January, March, and September 1995 (89 specimens).

Holotypes of P. panamense from Ariopsis seemanifrom Panama (National Helminthological Collection ofthe Institute of Biology, National Autonomous Uni-versity of Mexico, Mexico City, Mexico-CNHE 947)and P. floridcnsis from Galeichthys (= Arius) felis(Linnaeus, 1766) from Florida (U.S. National ParasiteCollection, Beltsville, Maryland, U.S.A.-USNPC60087) were compared with the present material.

Measurements (length and width) of 59 undeformed,uncollapsed eggs of P. panamense (from Ariopsis see-mani, Panama and Colombia and A. assimilis, Bacalarand Chetumal, Mexico) and P. floridensis (from Ariusfelis, Florida, U.S.A.) were compared by ANOVA (Tu-key's HSD for unequal N; Spojotvoll/Stoline test).

The specimens studied are deposited in the helmin-thological collections of the Institute of Parasitology,Ceske Budejovice, Czech Republic (IPCAS D-384);Institute of Biology, National Autonomous Universityof Mexico, Mexico City, Mexico (CNHE 3239); Lab-oratory of Parasitology, CINVESTAV-IPN Merida,Mexico (CHCM 181); and the U.S. National ParasiteCollection, Beltsville, Maryland, U.S.A. (USNPC87809, 87810). The nomenclature of the fish hosts(catfish) follows that presented by Eschmeyer (1998).Measurements are in micrometers unless otherwisenoted.

Results

Comparison of acanthostomid trematodes oc-curring in Ariopsis seemani from Colombia andA. assimilis and A. guatemalensis from Mexicowith the holotype of Pseudacanthostomum pan-amense from A. seemani from Panama revealedtheir conspecificity (Figs. 1, 2; Table 1). Allspecimens, including the holotype of P. pana-mense (Fig. 1), possess long intestinal ceca con-nected near the posterior extremity with the ex-cretory bladder, thus forming an uroproct (Figs.ID, 2D, F). Vitelline follicles are distributed be-tween the ventral sucker and the anterior testis(Figs. IB, 2A, C, F, G), ventrally forming 2 sep-arate fields and, in the same specimens, are dor-sally confluent at the ovarian level (Figs. 1F-H,2C). The uterine loops are sinuous, fillin g thespace between the ventral sucker and the pos-terior extremity (Figs. 1C, 2A, C, G). A thin-walled, coiled seminal vesicle is situated poster-odextrally to the ventral sucker (Figs. IB, 2C,F), and a genital pore is located just anterior tothe ventral sucker (Fig. IB). With the exceptionof 3 specimens, all trematodes (TV = 40), includ-ing the holotype (Fig. 1A), had 27 circumoralspines (Table 2).

The present study also demonstrated that the

trematodes studied are identical in all but 1 mor-phological and biometrical character to P. flori-densis, a species described from Arius felis fromFlorida, U.S.A (Nahhas and Short, 1965; see Ta-ble 1). No significant difference between these2 taxa was found in the size (length and width)of eggs (Fig. 3). The only difference between P.panamense and P. floridensis is the more ante-rior position of the vitelline follicles in the latterspecies. However, the distribution of the vitellinefollicles is rather variable (Fig. 1E-H), and itssuitability as a discriminative character betweenP. panamense and P. floridensis is doubtful.Consequently, P. floridensis is considered a ju-nior synonym of P. panamense.

Because the original description of P. pana-mense was incorrect in some features (the num-ber of circumoral spines, the presence of an uro-proct, and the spination of the posterior part ofthe body), its redescription based on extensivematerial from 4 fish hosts is provided herein. Inaddition, metacercariae from the eleotrid fishesDonnitator latifrons and Gobiomorus maculatusfrom Mexico, considered to be conspecific withP. panamense, are described.

Pseudacanthostomum panamense Caballero,Bravo-Hollis, and Grocott, 1953

(Figs. 1, 2)

SYNONYMS: Pseudacanthostomum floriden-sis Nahhas and Short, 1965 (new synonymy).

Pseudacanthostomum sp. of Pineda-Lopez etal. (1985) (new synonymy).

Pelaezia sp. of Scholz and Vargas-Vazquez(1998) (new synonymy).

DESCRIPTION: Adult (measurements in Table1): Body elongate, densely covered with fine teg-umental spines, including post-testicular region.Oral sucker terminal, cup-shaped, with large buc-cal cavity; ventral sucker small, pre-equatorial.Oral sucker surrounded by 1 row of 27 large,straight circumoral spines (Figs. 1A, 2B, J, K);exceptionally 26 or 28 spines present (Table 2).Prepharynx present and short (Fig. 1A) or absent(Fig. 2A); pharynx strongly muscular; esophagusvery short. Intestinal bifurcation pre-equatorial;intestinal ceca long, connected with excretorybladder and opening outside by uroproct (Figs.ID, 2D). Testes tandem, close to posterior ex-tremity. Vas deferens forming numerous loops,widened near ventral sucker to form coiled sem-inal vesicle; cirrus-sac lacking, ejaculatory ductslightly curved, opening into hermaphroditic


148 JOURNAL OF THE HELMINTHOLOGICAL SOCIETY OF WASHINGTON, 66(2), JULY 1999

Figure 1. Pseudacanthostomum panamense. A-D, holotype from Galeichthys (=Arius) seemani, Panama(IBUNAM 947), ventral view. A: oral sucker; B: ventral sucker and terminal genitalia; C: anterior partof body; note extent of vitelline follicles; D: posterior extremity; note connection of intestinal ceca withexcretory bladder and presence of uroproct; E-H, acetabular region; note variation in anterior extent ofvitelline follicles (E, F: specimens from Ariopsis assimilis, Mexico; G, H: specimens from A. seemani,Columbia; E: dorsal view, ventral follicles omitted; F, G: ventral view, dorsal follicles dashed; H: ventralview but dorsal follicles drawn in full and ventral follicles dashed). Scale bars in millimeters. Abbrevia-tions: e, eggs; exb, excretory bladder; gp, genital pore; ic, intestinal ceca; sr, seminal receptacle; sv, seminalvesicle; u, uterus; up, uroproct; vf, vitelline follicles; vs, ventral sucker.

duct; genital pore close to anterior margin of ven-tral sucker (Fig. IB). Ovary transversely elon-gate, slightly lobate (Fig. 1C) or with almost in-distinct lobes (Fig. 2A), pretesticular. Seminal re-ceptacle oval, preovarial or anterolateral to ovary(Fig. 1C). Vitelline follicles numerous, dorsallyfillin g space between ventral sucker and ovary,ventrally forming 2 lateral bands starting at ace-tabular level or posterior to ventral sucker andreaching posteriorly to anterior margin of anterior

testis (Figs. 1E-G, 2G); exceptionally, vitellinefollicles preacetabular. Uterus sinuous, with nu-merous loops, reaching to body extremity poste-riorly and completely fillin g body posterior toovary (Fig. 2A, G, F). Metraterm thin-walled,opening into hermaphroditic duct. Eggs opercu-late, rather variable in size (Figs. 3, 4). Excretorybladder Y-shaped, long, with anterior branchesanterolateral to intestinal ceca, reaching to phar-ynx (Figs. 1C, 2A, C, F).


SCHOLZ ET AL.—REDHSCRIPTION OF PSEUDACANTHOSTOMUM PANAMENSE 149

Figure 2. Pseudacanthostomum panamense. Adults from Ariopsis seemani, Colombia (A—D, G); nieta-cercariae from Dormltator latifrons, Mexico (E, H, I); adults from A. assimilis, Mexico (F, J, K). A, E, F:total view. B, H-K: oral sucker with circumoral spines. B: tegumental spines on only the right side andsubtegumental gland cells on the left side are illustrated. C: detail of acetabular region with terminalgenitalia; note connection of dorsal vitelline follicles (dashed) at level of ovary. D: posterior extremity withconnection of intestinal ceca, opening to the outside, with the excretory bladder (uroproct). G: posteriorpart of body; note vitelline follicles reaching posteriorly to level of anterior testis. Scale bars in millimeters.



Table 1. Measurements of Pseudacanthostomum panamense from different hosts* (in micrometers).

Species

HostLocality

Author

N

Body lengthBody widthOral sucker

LengthWidth

Spines (no.)Spine lengthSpine widthPrepharynxPharynx

LengthWidth

EsophagusVentral sucker

LengthWidth

Sucker ratioAnterior testis

LengthWidth

Posterior testisLengthWidth

OvaryLengthWidth

EggsLengthWidth

Uroproct

P. panamense

A. seemaniPanama

Caballeroet al., 1953

3

2,440-2,540332-481

76-133171-228

2630-38

1195-133

122-17195-10611-19

87-114106-114

0.33-0.50

175-232114-194

194-285125-228

103-1291 33-236

19-2111

absent

Presentdatat

1

2,784360

21 12142731-3712-13

154

1259914

8386

0.40

173118

202128

112141

21.5-2512.5-13.5

present

A. assimilisMexico

Presentdata

8

2,150-3,650230-370

123-195130-23826-2728-458-13

30-138

78-10563-9813-42

70-10368-103

0.41-0.68

1 80-30078-180

180-3801 1 5-220

90-17055-190

20-27.510-14

present

A. seemaniColombia

Presentdata

4

1,850-2,580408-5 1 2

186-208227-259

2737-549-12

45-56

99-12285-10222—23

82-10883-118

0.38-0.51

214-250179-256

208-272205-266

99-122230-272

23-2812-14.5

present

P. floridensis

A. fellsU.S.A.

Nahhas andShort, 1965

2

2,630-3,000489-750

1 80-294309-330

2842-6018-24

—

1 29-206—

v. short

118-155155-170

0.54

283-3091 80-283

——

232-260298-309

20-251 1-14

present

Presentdatav

1

3,050730

2663142826-5915-1915

218144—

154170

0.56

278173

317176

224317

23-2612-13.5

present

* Specimens from A. asximili.i from Bacalar, Mexico, are not included because they were flattened during fixation.t Measurements of the holotypes (CNHE 947 and USNPC 60087).

Table 2. Number of circumoral spines of Pseud-acanthostomum panamense.

Host and country

Ariopsix seemani (Panama)Ariopsis seemani (Colombia)Ariusfelis (U.S.A.)Ariopsis assimilis (Mexico)Arius gitatemalensis (Mexico)Dormitator latifrons* (Mexico)

Total

Numberof spines

26 27 28

— 1 —— 4 —— — 1

1 14 2174

1 40 3

Num-berof

speci-mens

1

4

1

17

17

4

44

Metacercariae.

HOSTS: Ariopsis seemani (type host), A. as-similis, Arius guatemalensis, and A. felis (all Sil-uriformes: Ariidae) (Table 3).

SITE: Intestine.GEOGRAPHIC DISTRIBUTION: Panama Viejo,

Pacific coast, Panama (type locality); Colombia;Mexico (states of Tabasco and Quintana Roo,Atlantic coast; state of Jalisco, Pacific coast),U.S.A. (state of Florida) (Caballero et al., 1953;Nahhas and Short, 1965; Yamaguti, 1971; Pi-neda-Lopez et al., 1985; Scholz and Vargas-Vazquez, 1998).

METACERCARIA: (based on 4 specimens fromDormitator latifrons; Fig. 2E, H, I): Body ofexcysted metacercariae elongate, 630-845 longby 147-182 wide. Oral sucker terminal, cup-


SCHOLZ ET AL.—REDESCRIPTION OF PSEUDACANTHOSTOMUM PANAMENSE 15 1

LENGTH

5 24z

A.a. MB A.a. MC A.s. C A.s. P A.f. U

GROUP

I Min-Max CH 25%-75% D Median value

WIDTH

15.5

14.5

13.5

11.5

10.5

9.5

8.5A.a. MB A.a. MC A.s. C

GROUP

A.s. P A.f . U

Figure 3. Length (above) and width (below) ofeggs of Pscudacanthostomum panamense from dif-ferent hosts and geographical regions. Measure-ments in micrometers. Groups: A.a. MB, Ariopsisassimilis, Bacalar, Mexico; A.a. MC, A. assimilis,Chetumal Bay, Mexico; A.s. C, A. seemani, Colom-bia; A.s. P, A. seemani, Panama (holotype: CNHE947); A.f. \J, Arius felis, Florida, U.S.A. (holotype ofP. floridensis: USNPC 60087).

shaped, 111-124 long by 115-147 wide. Ventralsucker small, equatorial, 35-44 long by 35-41wide. Sucker ratio 1:0.31-0.34. Oral suckerarmed with 1 circle of 27 spines; spines on dor-sal side 21-28 long by 4-7 wide; on ventral side15-21 long by 4-5 wide. Prepharynx 49-90long; pharynx oval, 52-59 long by 36-52 wide;esophagus short. Intestinal ceca long, connectedwith excretory bladder near posterior extremityand opening outside by uroproct. Primordium ofovary postacetabular; testis primordia tandem,near posterior extremity.

HOSTS: Dormitator latifrons and Gobiomo-rus maculatus (both Perciformes: Eleotridae)(Table 3).

SITE: Liver, more rarely musculature of gills,mesentery, intestinal wall, occasionally muscles,heart, gonads, fins, scales.

GEOGRAPHICAL DISTRIBUTION: Mexico (stateof Jalisco, Pacific coast).

DiscussionAcanthostomid trematodes from 3 different

definitive hosts, the ariid catfish Ariopsis see-mani, A. assimilis, and Arius guatemalensis, and2 geographical regions (Colombia and Mexico)were found to be conspecinc with Pseudacan-thostornum panamense. Examination of the ho-lotype of P. panamense has shown that the orig-inal description (Caballero et al., 1953) was in-correct in reporting the following characters: 1)26 circumoral spines (there are in fact 27 spinesin the holotype; Fig. 1A); 2) the absence of teg-umental spines in the post-testicular region,which is actually spined; and 3) the absence ofan uroproct (i.e., a connection of the intestinalceca with the excretory bladder), which is ac-tually present (Fig. ID). Consequently, the spe-cies diagnosis of P. panamense, the type speciesof the genus Pseudacanthostomum Caballero,Bravo-Hollis, and Grocott, 1953, is emended ac-cordingly.

In 1965, Nahhas and Short described anotherspecies, P. floridensis, to accommodate 2 spec-imens from Galeichthys (= Arius) felis fromFlorida, U.S.A. The authors differentiated thisspecies from P. panamense by the number ofcircumoral spines (28 compared with 26), thegreater extent of the vitellaria, and the presenceof an uroproct.

The presence of an uroproct in P. panamensewas not reported by Caballero et al. (1953), whostated that there is no connection between theintestinal ceca and excretory bladder ("Los cie-gos intestinales . . . no se abren en la vesiculaexcretora" [p. 121] and "Los ciegos intestinalesno desembocan a la vesicula excretora" [p.122]). However, this study has demonstrated thatan uroproct is in fact present in P. panamense(Fig. ID). Consequently, P. panamense and P.floridensis do not differ in this character (Table1).

Although the number of circumoral spines isfairly stable in acanthostomid trematodes andcan be species-specific (Brooks, 1980), some



15.515.014.514.013.513.012.5

JE 12.0Q 11.5% 11.0

10.510.09.59.08.5« n

O 0o o o

0 0 0 0

o o oo o o

o0 O O

oo o o

oo

oo o o

o o o oo o o o ooo o o

o

oO O O 0

o

18 19 20 21 22 24 25 26 27 28

LENGTH

Figure 4. Range of size of eggs (length and width) of Pseudacanthostomum panamense. Measurementsof all eggs measured (N = 59) grouped together. Values in micrometers.

variability apparently exists (Brooks and Over-street, 1977; Ostrowski de Nunez, 1984; Scholzet al., 1995a, b). This is also the case in thepresent material (Table 2). Although a majorityof specimens (93%) had 27 spines, including theholotype of P. panamense (see Results and Fig.1A), a few specimens had a different number ofspines. One trematode from A. assimilis fromBacalar (Mexico) possessed 26 spines, and 2specimens from the same host (A. assimilis)from Chetumal (Mexico) had 28 spines (i.e., theidentical number reported for P. floridensis) (Ta-ble 2).

The extent of distribution of vitelline folliclesin the holotype of P. floridensis is actually more

anterior than in P. panamense specimens. How-ever, there is great variability in this feature.Trematodes from Ariopsis seemani have folliclesreaching to the acetabular level (Fig. 1G) oreven to the anterior margin of the ventral sucker(Fig. 1H), whereas those from A. assimilis havevitelline follicles mostly restricted to the post-acetabular region (Fig. IE, F) with vitelline fol-licles reaching to the posterior border of the ven-tral sucker in only a few specimens. It alsoseems that contraction of the body influences theposition of follicles; in contracted specimens vi-telline follicles usually reach to the acetabularlevel (Fig. 1G, H), whereas in protracted worms,the follicles start rather far posterior to the ven-

Table 3. Survey of hosts, localities, dates of collection, and parameters of infection with Pseudacantho-stomum panamense.

Host Country and locality

No. offish Mean

infected/ inten- Minimum-Date examined sity maximum

Adults

A riopsis see man iA riopsis assim His

A rius guatemalensis

Metacercariae

Dormitator latifronx

Gobiomorus maculatus

ColombiaBacalar, Quintana Roo, MexicoChetumal Bay, Quintana Roo, MexicoMarismas Chalacatepec, Jalisco, Mexico

Marismas Chalacatepec, Jalisco, MexicoRio San Nicolas, Jalisco, Mexico

Rio Cuitzmala, Jalisco, MexicoRio Cuitzmala, Jalisco, Mexico

5/961/95

10/963/95

3/9511/949/959/951/953/959/95

4/71/1

39/963/3

1/241/52/165/70/252/37

22/31

1.5 1-2127.5 1-30

24 9-52

39 3952 52

1 1(not counted)— —3 1-5(not counted)


SCHOLZ ET AL.—REDESCRIPTION OF PSEUDACANTHOSTOMUM PANAMENSE 153

tral sucker (Fig. IE). It is evident that this char-acter is not sufficiently stable and its taxonomicimportance is questionable. Because P. floriden-sis was described on the basis of only 2 speci-mens, the anterior position of vitellaria shouldbe confirmed in much more extensive material.

Statistical analysis of egg measurements hasrevealed a great intraspecific variability in egglength and width (Fig. 4). Nevertheless, thisanalysis has not demonstrated any significantdifferences in the length and width of eggs ofP. panamense and P. floridensis (Fig. 3). Eggsof P. panamense specimens from Colombiawere larger than those of conspecific wormsfrom Mexico, thus being more similar to eggsof P. floridensis (Fig. 3). Because of the identityof P. floridensis with P. panamense in almost allmorphological and biometrical characters (thedistribution of vitelline follicles is considered adoubtful and unsuitable taxonomic criterion fordifferentiation of these taxa), the former speciesis synonymized with P. panamense.

On the basis of the proposed synonymy, thegenus Pseudacanthostomum becomes monotyp-ic, currently containing only 1 species, P. pan-amense. In the presence of an uroproct, P. pan-amense resembles members of the genus Pelae-zia Lamothe-Argumedo and Ponciano-Rodri-guez, 1986, of the subfamily AcanthostominaeNicoll, 1914 (see Lamothe-Argumedo and Pon-ciano-Rodriguez, 1986). However, Pelaezia dif-fers, as all other genera of the Acanthostominae,in that the uterus is never situated posterior tothe testes (mostly completely preovarial), where-as its loops reach to the posterior extremity inPseudacanthostomum, the type genus of the sub-family Pseudacanthostominae Yamaguti, 1958.In addition, both species of Pelaezia, P. unami(Pelaez and Cruz-Lozano, 1953), the type spe-cies, and P. loossi (Perez-Vigueras, 1957), havedifferent numbers of circumoral spines (30 and23, respectively; Pelaez and Cruz-Lozano, 1953;Perez-Vigueras, 1957; Brooks, 1980; Salgado-Maldonado and Aguirre-Macedo, 1991).

The subfamily Pseudacanthostominae Poche,1926 contains only 2 genera, Pseudacanthosto-mum and Pseudallacanthochasmus Velasquez,1961, members of which parasitize marine fishin the Americas and Southeast Asia, respectively(Yamaguti, 1971). This subfamily differs fromthe Acanthostominae in possessing a long pre-pharynx (Yamaguti, 1971, p. 212). However, asdemonstrated in this study, the prepharynx is

usually short or even absent (Fig. 2A, F) inmany P. panamense specimens. Moreover, thelength of the prepharynx is highly variable, de-pending mainly on the state of contraction of theworms. Therefore, this feature should not beused as a differential criterion for the diagnosisof this subfamily. In other features, the subfam-iliar diagnosis presented by Yamaguti (1971)—i.e., the uterus extending to the posterior extrem-ity (different from other acanthostomid subfam-ilies except for Anisocladiinae Yamaguti,1958)—the ceca being equal and reaching to theposterior extremity, the ventral sucker beingwell apart from the anterior extremity, and thevitelline follicles being both anterior and poste-rior to the ovary (differing from Anisocladiinae)well characterize the subfamily Pseudacanthos-tominae.

Metacercariae found in eleotrid fishes fromthe Pacific coast of Mexico are considered to beconspecific with P. panamense because of theirmorphology (Fig. 2E, H, I), in particular thepresence of 27 circumoral spines (Fig. 2H, I)and the morphology of the intestinal ceca, whichare connected with the excretory bladder nearthe posterior extremity, thus forming an uroproct(Fig. 2E). This is the first record of P. pana-mense from the second intermediate host. It canbe assumed that the lif e cycle of this taxon re-sembles that of other acanthostomid trematodes(Yamaguti, 1975). The first intermediate host isa mollusk (snail), in which the cercariae devel-op; the second intermediate hosts are fish inwhich the metacercariae are encysted. The de-finitiv e host, an ariid catfish, becomes infectedby ingesting fish with metacercariae. Dormitatorlatifrons and Gobiomorus maculatus are fish liv-ing in brackish water, i.e., in the same habitat inwhich ariid catfish occur; the latter become in-fected after consuming prey fish harboring meta-cercariae.

Pseudacanthostomum panamense seems to bea common parasite of catfishes of the familyAriidae. Existing records of P. panamense fromthe southern U.S.A. (Florida), Mexico (both At-lantic and Pacific coasts), Panama (Pacificcoast), and Colombia indicate that it is a specieswith a wide distribution in the Neotropical zoo-geographical region on both the Pacific and At-lantic coasts.

AcknowledgmentsThe authors are indebted to Elizabeth Mayen

Pena, Guillermina Cabanas-Caranza, Juan Ma-



nuel Caspeta-Mandujano, Rafael Baez-Vale, andIsabel Jimenez-Garcia, Institute of Biology, Na-tional Autonomous University of Mexico(UNAM) , Mexico City, for help in sampling andexamining fish in the state of Jalisco and to RaulSima-Alvarez, Clara Margarita Vivas-Rodri-guez, Ana Maria Sanchez-Manzanilla, Isabel Ji-menez-Garcia, Sandra Martha Laffon-Leal, Son-ia Zarate-Perez and Victor Ceja-Moreno, Centerfor Investigation and Advanced Studies of theNational Polytechnic Institute (CINVESTAV-IPN), Unidad Merida, Mexico, for help in col-lecting fish in Quintana Roo. Thanks are due toDrs. J. Ralph Lichtenfels and Patricia Pilitt, U.S.National Parasite Collection, Beltsville, Mary-land, U.S.A., and Dr. Rafael Lamothe-Argume-do and Luis Garcia-Prieto, Institute of Biology,National Autonomous University of Mexico(UNAM) , Mexico City, for the loan of types ofPseudacanthostomum species. Dr. Patricia Pilittis further acknowledged for her valuable helpwith egg size analysis, Martina Borovkova (In-stitute of Parasitology, Ceske Budejovice) forexcellent technical help, and Luis Garcia-Prietofor providing the original description of P. pan-amense.

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Redescription of Pseudacanthostomum panamense - BioNames

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