Reexamining Pseudoglaridacris confusus (Hunter, 1929) nom. nov. (Cestoda: Caryophyllidae) from buffalo fish, Ictiobus spp. in Arizona, USA

Introduction

Mackiewicz [1] reviewed the morphology, anatomy, development, zoogeography, and systematics of the Caryophyllidea van Beneden (Cestoidea) and indicated the existence of 89 species and 37 genera in these monozoic cestodes. Mackiewicz [2] provided perspectives on the evolution, biology and zoogeography of 128 species in 45 genera of caryophyllids from the Nearctic, Neotropical, Palearctic, Ethiopian, Oriental, and Australian regions. Mackiewicz [3] later recognized about 150 species in 41 genera worldwide (except for the Neotropical Region). Of these, 14 genera and 90 species belonging to 3 families were described from the Indo-Malayan region from catfishes (Siluriformes: Bagridae, Clariidae, Heteropneustidae, Schilbeidae and Siluridae), cyprinid, and cobitid fishes [3]. Ash, et al. [4, 5] invalidated a large number of inadequately described species from clariid and hetero-pneustid catfishes in India and neighboring countries. Most recently, however, Scholz, et al. [6] and Scholz, et al. [7] recognized only 117 species and 46 genera in order Caryophyllidea Carus, 1863 parasitizing teleost fish (Cypriniformes, Siluriformes, and some catfish). Chubb [8] reviewed the seasonal ecology of the Caryophyllidea in the various climate zones of the world.

The order consists of four families (Balanotaeniidae, Capingentidae, Caryophyllaeidae, Lytocestidae) [3]. Mackiewicz [1, 3] stated that “The caryophyllideans are exclusively intestinal parasites of freshwater teleosts with 85 species reported from cypriniform and 29 from siluriform fishes. Only few species of the Lytocestus with 2 species and monotypic Lytocestoides are known from mormyrids (Osteoglossiformes), characiform and cichlid (Perciforms) fishes, respectively.” Within families, 40 % of caryophyllideans parasitize North American suckers (Catostomidae), 26 % cyprinids, 10 % clariid catfishes and just a few caryophyllideans have been reported from 12 additional fish families” [7]. Freshwater annelids of the family Naididae, especially species previously placed in the Tubificidae (Tubifex tubifex, Limnodrilus spp.), serve as the only intermediate hosts [1].

Amin [9, 10, 11, 12] recognized 15 species in 8 families of caryophyllid cestodes mostly from suckers (Catostomidae) in lake and river systems in Arizona and Wisconsin (Table 1). These included Pseudoglaridacris confusus (Hunter, 1929) Oros, Uhrovič, Scholz, 2018 nom. nov. for Pseudoglaridacris confusa Oros, Uhrovič, Scholz, 2018. These latter authors redescribed the genus Glaridacris and created a new genus, Pseudoglaridacris with 2 additional species: Pseudoglaridacris laruei (Lamont, 1921) Oros, Uhrovič, Scholz, 2018, and Pseudoglaridacris oligorchis (Haderlie, 1953) Oros, Uhrovič, Scholz, 2018. See collections, following, for details.

In Arizona, Amin [9, 10] gave a new description of P. confusus as Glaridacris confusus from 3 species of buffalo fish, Ictiobus spp., in 2 lakes, Apache and Roosevelt lakes on the Salt River. Since its original description in Hunter (1930), it has been reported from hosts along the Mississippi River and the New York (Amin [9]). Buffalo fish appear to be the common usual hosts. Later reports list 8 species of fish hosts in wider geographical areas of the US and Canada [13, 14]. The southernmost distribution of P. confusus appears to be Oaxaca and Veracruz, Mexico from Ictiobus meridionalis (Günther) [15]. The number of true hosts of P. confusus appears to be considerably less than has been reported (Amin [9]). In his Ph.D. dissertation, Mackiewicz [16] reviewed reports that were based on its erroneous identification from various hosts confusing it with Pseudoglaridacris laruei (Lamont, 1921) Oros, Uhrovič, Scholz, 2018, Glaridacris catostomi Cooper, 1920, and Spartoides wardi Hunter, 1929. In addition to buffalo fish, P. confusus was also verified from Dorosoma cepediaum Lesueur (Gizzard shad) in Tallahatchie River, Mississippi by Hunter (1930) and from Carpiodes carpio Rafinesque (common carp sucker) and from I. cyprinellus in Lake Texoma, Oklahoma by Mackiewicz JS [17] and McAllister CT [18].

Materials, Collections and Methods

Although P. confusus has been reported in all the 4 impoundment lakes on the Arizona Salt River (Apache, Roosevelt, Canyon, and Sahuaro lakes), only the first two lakes appear to be significantly populated by this cestode. Apache Lake (33°34′43″N 111°15′48″W), the second largest of the 4 Salt River Project Reservoirs, is about 104  km northeast of Phoenix in Maricopa and Gila counties. Apache Lake, was formed by Horse Mesa Dam impounding the Salt River, which was completed in 1927. Apache Lake is located about 8 km downstream from Roosevelt Lake, the largest in Gila County, created in 1911 about 170 km from Phoenix by car; (47°57′22″N 118°58′50″W, at Grand Coulee Dam), and upstream from the smaller Canyon Lake and Saguaro Lake closest to Phoenix.

The 3 species of buffalo fish, Ictiobus cyprinellus (Valenciennes) large-mouth buffalo fish, I. bubalus (Raf.) small mouth buffalo fish, and I. niger (Raf.) black buffalo fish, inhabit Apache Lake (collected at Burnt Corral) whereas Roosevelt Lake is inhabited only by I. cyprinellus (collected at Tonto, Grape, Vine, and 3 Bar). Fish were captured by netting and boat shocking using current from 123-v, 2650-3000-w generator.

A total of 154 specimens were collected from 96 individuals of 3 species of buffalo fish examined (18.75%) from both lakes, Apache and Roosevelt lakes in 1966 and 1967. The zoo-plankton feeder with large terminal mouth, I. cyprinellus, from both lakes showed the lowest infection prevalence (12.12% and 7.14%) and intensity (0.24 and 0.09) in Roosevelt and Apache lakes, respectively. The small benthic invertebrate feeders with small fleshy subterminal mouths, I. bubalus and I. niger from Apache Lake, had considerably higher prevalence (38.46% and 75.00%) and intensity (4.00 and 11.25), respectively.

After capture and transfer to the laboratory in coolers on ice, the fish were dissected within a few hours after capture. Upon recovery, worms were placed at once in warm 70% ethanol then processed and stained with Semichon’s carmine. Worms were then processed in ascending concentrations of ethanol for dehydration reaching 100%. Worms were ultimately cleared in oil of winter green before whole mounting in Canada balsam. Measurements are in mm as noted in Table 2; the range is followed by the mean values between parentheses. Width measurements represent maximum width. Microscope images were created using 10X and 40X objective lenses of a BH2 light Olympus microscope (Olympus Optical Co., Osachi-shibamiya, Okaya, Nagano, Japan) attached to an AmScope 1000 video camera (United Scope LLC, dba AmScope, Irvine, California), linked to an ASUS lab top equipped with HDMI high-definition multimedia interface system (Taiwan-USA, Fremont, California). Images from the microscope were transferred from the labtop to a USB and stored for subsequent processing on a computer. We found microscope images to be considerably more informative than schematic line drawings as they depict the natural appearance of anatomical structures.

Results

Buffalo fish eggs (unknown species) were introduced in Roosevelt Lake in 1918 by the US Bureau of Fisheries [18, 19] and buffalo fish have been reported in all 4 lakes on the Salt River. Buffalo fish do not limit their feeding to any particular depth. Diet does not appear to be affected by fish size (age) but mouth position, feeding habits and diet are definitely related to their parasitic fauna (Amin [10] and others included therein).

Pseudoglaridacris confusus was the only species of caryophyllid cestode found in all 3 species of buffalo fish introduced to Arizona over 100 years ago. Mackiewicz [17], however, listed 8 species of Caryophyllidae in I. bubalus and I. cyprinellus from Lake Texoma. It is suggested that the parasite fauna of fish is reduced following introduction into new habitats because of the differential distribution of supporting intermediate hosts.

Amin [9, 10] redescribed Pseudoglaridacris confusus, as Glaridacris confusus, from the Arizona population collected from the 3 species of buffalo fish captured in Apache and Roosevelt lakes. He included 8 line drawings; one of a whole worm, 5 of scolex variations and 2 of immatures. We have restudied specimens in our personal collection. Measurements from about 100 specimens were made in 1967-1968 [9, 10] and new measurements and observations from an additional 50 specimens from the original collection were recently made and added to the earlier measurements creating composite measurements included in Table 2. We provide below a brief revised description of our qualitative morphological findings and a comparative morphometrical data (Table 2) high-lightening variations from the only other description of Hunter [20] which included line drawings of a scolex, reproductive system, and a few sections.

*Range (mean); all measurements in mm. Table 2: Morphometric description of Pseudoglaridacris confusus collected from buffalofish, Ictiobus spp., in Arizona and Mississippi.

Discussion

The taxonomic status of Glaridacris confusus Hunter, 1929 has not been challenged until Oros, et al. [21] erected the genus Pseudoglaridacri_s Oros, Uhrovič, Scholz, 2018 and included 3 former members of _Glaridacris in it: Pseudoglaridacris confusa Oros, Uhrovič, Scholz, 2018, Pseudoglaridacris laruei (Lamont, 1921) Oros, Uhrovič, Scholz, 2018, and Pseudoglaridacris oligorchis (Haderlie, 1953) Oros, Uhrovič, Scholz, 2018. Oros, et al. [21] diagnosed the new genus, differentiated it from Glaridacris, provided systematic summaries and remarks but did not redescribe or measure these 3 species. Pseudoglaridacris was distinguished from Glaridacris in having compact rather than follicular ovary, bothrioloculodiscate rather than cuneiform scolex, genital atrium rather than well separated gonopores, lateral position of vitelline follicles rather than also having median follicles, and a smaller size body. We accept the designation of Pseudoglaridacris with qualifications based on our specimens from Arizona. In our specimens:

1. The male and female gonopores ARE separate even though they may appear to be in a genital atrium depending on the state of contraction of the specimen.
2. The scolex appeared dome-shaped apically in all our specimens (Figures 1-5), a shape not mentioned in Oros, et al. [21] who depicted a different bluntly-apically- pointed scolex (Figure 3A) with what appears to be additional smaller anterior loculi.

The scolex, however, appeared cuneiform (wedge-shaped) in Hunter’s [20], Figure

Morphometrically, our specimens from Arizona were considerably smaller than those of Hunter [20] (Table 2) from Mississippi but the ovary was shorter and wider (Figures 7-10) making the total mass of ovarian tissue about the same. The state of contraction of this and may be of other structures, could be related. All other structures were of comparable sizes. The scolex in our Arizona specimens characteristically was dome-shaped, apically (Figure 1-5), never wedge-shaped or pointed anteriorly. The arrangement of testes vs. pre-ovarian vitelline band is shown in a young specimen (Figure 6).

Quantitatively, infection parameters appear to be related to the anatomy and position of the buffalo fish mouth parts since all 3 species appear to have the potential of serving as definitive hosts. Ictiobus cyprinellus has a thin-lipped terminal mouth and feed by scooping the water for zoo-planktons. Ictiobus bubalus and I. niger, in another category, have small, thick-lipped sub-ventral mouth and they bottom feed mostly on benthic invertebrates including a larger concentration of intermediate hosts rendering them considerably more frequently and heavily infected than I. cyprinellus. Mixed infections of more than one species of caryophyllid cestodes in the same host do not appear to be uncommon. Up to 4 species of cestodes may be found in the same host individual but double infections are usually more common [16]. The argument that earlier infections may elicit immunological reactions preventing subsequent infections does not appear to be true for caryophyllid cestodes [16]. The absence of competition in the fish intestinal tract is an important factor in cases of multiple infections. Niche segregation might not only be of spatial nature but the mode of attachment may also be involved. Pseudoglaridacris confusus is weakly attached to mucosal folds and its lack of intimate mechanical and possibly physiological association with host tissue may be partially responsible for its wide range of host specificity in up to 8 host species. On the other hand, other caryophyllid cestodes like Monobothrium hunteri Mackiewicz, 1963 is firmly attached [16] and more host specific.

In P. confusus, allometric growth was observed to proceed at a considerably larger rate in regions containing reproductive structures posterior to first vitellaria compared to pre-vitelline region of scolex and neck. Hunter ([20], Tables 1&2, graphic chart 2) demonstrated this phenomenon from a study of 106 specimens in 7 length classes reaching 20 mm long worms. Hunter’s [20] pioneering concept applied also to other caryophyllid as well as pseudophyllid examples. Amin [10] also studied growth patterns in Isoglaridacris hexacotyle (Linton, 1897) Mackiewicz, 1968 from Catostomus insignis Baird & Girard in the lower Salt River, Tempe, Arizona, and demonstrated the acceleration of growth of the post -vitelline region, the region of reproductive activity, compared to the pre-vitelline region including the scolex and neck, as well as the growth in the scolex, cirrus sac, and in width at the common gonopore region. Fischthal, et al. [22] showed comparable growth of the post-vitelline region of Glaridacris laruei from the C. commersoni in New York. We have additionally observed the same phenomenon in non-tapeworm helminths also enhancing the increased reproductive potential of worms. Amin [10] also studied a total of 136 metacercariae of Clinostomum marginatum Rudolphi, 1819 collected from 17 C. insignis and 4 C. clarkii Baird & Girard in the Upper Salt River, Arizona, placed in 6 size classes ranging from 2.49 to 6.04 mm in length. The hind body posterior to the constriction at the level of the ventral sucker including the developing reproductive structures grew at a considerably faster rate than the forebody anterior to the ventral sucker.

Click to enlarge

Figures 1-6: Microscope images of adult Pseudoglaridacris confusus from 3 species of buffalo fish in Apache and Roosevelt lakes, Arizona. 1-5. Variations in shape of scolex. Note the dome-shaped apical end, the wide middle and the well ribbed loculi. 6. Part of a young specimen showing the medullary testicular field and the vitelline bands confined to two lateral fields.

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Figures 7-10: Microscope images of adult Pseudoglaridacris confusus from 3 species of buffalo fish in Apache and Roosevelt lakes, Arizona. The posterior portion of 4 specimens showing the thick and short ovarian arms and the open U-shaped post- ovarian vitelline characteristic of the Arizona population. Also note the unusual arrangement of the asymmetrical and unequal sides of the post-ovarian vitelline bands (Figure 8) and the cirrus sac (Figure 9).

Acknowledgments: This project was supported by an Institutional Grant from the Parasitology Center, Inc. (PCI), Scottsdale, Arizona.

Declarations

• Compliance with Ethical Standards
• Conflict of Interest: The authors declare no conflicts of interest or competing interests.
• Ethical Approval: The authors declare that they have observed all applicable ethical standards.
• Availability of Data: All presented and related data are available by contacting the senior author.