Corynosoma magdaleni in gray seals from the Gulf of Bothnia,with emended descriptions of Corynosoma strumosum and Corynosoma magdaleni

Because of the likelihood that Corynosoma magdaleni Montreuil, 1958. has been confused with C. strumosum (Rudolphi, 1802) in reports of parasites from seals and to clarify its distribution in the Baltic Sea, acanthocephalans from 26 young gray seals from the southwestern Finnish archipelago (western Baltic Sea) were examined. All harbored C. semerme (Forssell. 1904). In addition to C. semerme, 12 had both C. strumosum and C. magdaleni, 3 had only C. strumosum, and 9 had only C. magdaleni. Most anatomical structures of C. strumosum are similar to, but larger than, those of C. magdaleni. The most conspicuous differences are the longer and more robust trunk of C. strumosum, the routinely longer proboscis (mean, 653 vs. 476 microm) and larger proboscis hook (mean, 69 vs. 58 microm) of C. strumosum, and the greater extent of ventral trunk spines (mean, 61 vs. 47%) in C. magdaleni. In addition, C. strumosum consistently possesses 18 longitudinal rows of proboscis hooks, whereas C. magdaleni has 17-23, with 20 being the usual number by far. In seals aged 3.6 mo, on average, C. strumosum was more prevalent and abundant than was C. magdaleni, whereas in seals of age 2.0-3.0 mo the reverse was true, with C. strumosum being nearly absent. These differences might reveal the age-dependent food habits of the very young seals. No site segregation was found between C. strumosum and C. magdaleni in the small intestine, but they clearly segregated from C. semerme, which occurred mainly in the cecum, large intestine, and rectum. All species matured equally well in gray seals, with 62, 67, and 53% of the C. magdaleni, C. strumosum, and C. semerme, respectively, comprising gravid worms (possessing eggs with fully formed acanthors).     

Corynosoma acanthocephalans in their paratenic fish hosts in the northern Baltic Sea

Cystacanth stages of three Corynosoma (Acanthocephala) species, C. strumosum and C. semerme, and a new species in the Bothnian Bay, C. magdaleni, were studied in the fourhorn sculpin (Myoxocephalus quadricornis) in 1996-1997. The length of the trunk and proboscis differentiated the three species in the fish. The stability of the Corynosoma infection was studied by comparing the present results with those collected from the same areas (central and coastal) in 1977-1982 (Valtonen, 1983a). As C. magdaleni and C. strumosum were not separated at that time, the joint infections of these two species (called "C. strumosum") were compared. The stability of infection with C. semerme in the central Bothnian Bay was noticeable (prevalences were 82.9 in earlier period and 81.9% in later period), while the prevalences of "C. strumosum" in the same areas had decreased (21 and 13.5%, respectively). This is suggested to be due to the disappearance of the marine bull-rout, Myoxocephalus scorpius, from the Bothnian Bay during the 1990s due to an overall decline in salinity throughout the Baltic Sea. In the coastal area Corynosoma infection was clearly lower than in central area in both periods.     

The behavioral response of amphipods harboring Corynosoma constrictum (Acanthocephala) to various components of light

Many studies have shown that photic behavior of amphipods is subject to parasitic manipulation. However, all these investigations have focused on but one property of light (i.e., intensity). This study investigated the possibility that variable wavelength sensitivity, as a potentially important component of amphipod ecology, is subject to parasitic manipulation. The photic behavior of freshwater amphipods Hyalella azteca, infected with the duck acanthocephalan Corynosoma constrictum, was tested. The phototactic responses of infected and uninfected amphipods to various wavelengths in the visible spectrum were compared, and to delineate the effects of intensity and wavelength on behavior, the preferences of amphipods for environments characterized by various combinations of light intensity and wavelength were determined. Response to blue light (400-450 nm) was little affected by infection. Amphipod response to higher red region wavelengths (600-700 nm) was altered by infection. Infected amphipods were significantly less responsive to green region light (500-550 nm), which could lead to increased wandering throughout the water column, thereby facilitating increased parasite transmission through increased predation risk. This study reinforces the subtlety with which parasites can alter their host's behavior, presumably resulting in an increased probability of being transmitted from the intermediate host to a definitive host.     

Host-parasite relationships between two seal populations and two species of Corynosoma (Acanthocephala) in Finland

Ringed seals ( Phoca hispida botnica ), from the Bothnian Bay, north-eastern Baltic Sea were examined for acanthocephalan parasites in 1977–1982, and specimens from Lake Saimaa in south-eastern Finland ( P. h. saimensis ) were examined in 1980–1981. The two seal stocks have been isolated from Arctic stock for 11,000 years and from each other for 8,000 years. Corynosoma strumosum and C. semerme were found in the Baltic seals, but only C. strumosum in those from the lake.
Eighty two of the ringed seals caught in the Bothnian Bay were infected with both Corynosoma species, one with a single infection of C. strumosum and one with C. semerme in autumn. The total number of C. semerme increased in relation to the number of C. strumosum in each set of seals both in autumn and spring. Corynosoma semerme was dominant in most seals in spring, but in only an average of 60% in autumn. The predominance of C. strumosum in 40% of the autumn material (range 33–80%) is of interest because species ratio favouring C. strumosum is not found in any more heavily infected paratenic fish host of Corynosoma in the Bothnian Bay. The change in the Corynosoma species ratio of seals in autumn may be explained by their exceptional feeding behaviour at this time of the year (total or partial fasting) and the suggested longevity of C. strumosum as compared with C. semerme . The stability of the acanthocephalan populations in ringed seals is documented.     

Corynosoma spp. may be useful biological tags for saithe in the northern North Sea

The acanthocephalan parasites Corynosoma spp. could be useful biological tags for estimating the proportions of saithe recruiting from nursery areas in Scottish and Norwegian coastal waters to the central northern North Sea.     

Presence of genital spines in a male Corynosoma cetaceum Johnston and Best, 1942 (Acanthocephala)

We collected 83 females and 80 males of Corynosoma cetaceum from 2 common dolphins, Delphinus delphis, collected in northern Patagonia (Argentina). Worms were most similar to specimens collected in other South American localities. However, 1 male had 2 spines adjacent to the genital pore and isolated from the rest of body spines. This finding confirms the recent reassignment of C. cetaceum to Corynosoma. Absence of genital spines is suggested to be avoided as the sole criterion to exclude specimens from Corynosoma or Andracantha.     

Reduction and variability of trunk spines in the acanthocephalan Corynosoma cetaceum: the role of physical constraints on attachment

Abstract. In this study, we investigated a functional trade-off between trunk attachment and trunk-spine development in the acanthocephalan Corynosoma cetaceum . The worms live attached to the stomach and upper intestine of their cetacean definitive hosts, using the proboscis and spiny foretrunk as the main holdfast; the spiny hindtrunk can also attach by bending ventrally. When the hindtrunk bends, ventral compression generates an anterior fold (AF) and a posterior fold (PF). A morphological analysis based on 7,823 individuals collected from 10 franciscana dolphins, Pontoporia blainvillei , revealed that spines were smaller and more variable in size and occurrence in the folds than on neighboring areas; the growth of fold spines seemed to be inhibited to various degrees. Spines were more reduced in the AF than in the PF, and spines of both folds were more reduced in females than in males. Patterns of reduction appeared to be directly related to the intensity of fold compression associated with hindtrunk bending. Fold compression could induce plastic inhibition of spine growth, and/or could make fold spines maladaptive, spines being reduced by natural selection. Apparently, fold spines neither contact the substrate, nor are they exposed to the environment when the hindtrunk attaches. Therefore, fold spines could have reduced, or lost, their primary function, at least in the definitive host. The reduction and variability of spines in C. cetaceum seem to be unique among Corynosoma species.     

Dependence of the structure of the capsule surrounding the acanthocephalan Corynosoma strumosum on the species of its natural paratenic host

The fine and ultrafine structure of the capsules surrounding the acanthocephalan Corynosoma strumosum in natural paratenic hosts of three species—the whitespotted greenling Hexagrammos stelleri, Steller’s sculpin Myoxocephalus stelleri, and the saffron cod Eleginus gracilis—was studied. The results of this study, together with earlier data, support the hypothesis that the structure of the capsule depends on the paratenic host species. Three types of capsules differing in the ratio of fibroblasts and inflammatory cells have been identified: fibroblastic (in Japanese smelt, rainbow smelt, and saffron cod), intermediate (in whitespotted greenling), and leukocytic (in Steller’s sculpin and the yellowfin sole). It was assumed that the structure of the capsule is determined by the degree of mutual adaptation of organisms in a given host-parasite system.     

Virulence of Corynosoma constrictum (Acanthocephala: Polymorphidae) in Hyalella azteca (Amphipoda) throughout parasite ontogeny

Development and growth of parasites depend on resources provided by the host and the parasite's ability to use them. Identifying specific costs incurred by the host provides insight for assessment of parasite energy budgets, which differ among taxa and ontogenetic stages. Data from this study were analyzed using an accelerated failure-time model with intensity as a covariate. Results indicated significantly reduced survival of amphipods, Hyalella azteca, infected with the acanthocephalan Corynosoma constrictum compared with uninfected controls. Male and female amphipod survivorship and infection intensity did not differ; however, amphipods with high-intensity infections (> 16 larvae) died earlier compared with amphipods with low-intensity infections (< 3 larvae). The majority of infected amphipods died between 12 and 24 days postexposure, a period of rapid larval development. It is hypothesized that host death may be due either to an increase in overall larval nutritional demands or to parasite-mediated depletion of a specific host substance. Results from this study suggest that developing C. constrictum satisfies energy requirements by depriving amphipod hosts of resources normally used for somatic growth and maintenance.     

The occurrence of Corynosoma strumosum in the grey seal,Halichoerus grypus,caught off the Atlantic coast of Ireland

The occurrence, location and sex ratio of Corynosoma strumosum (Acanthoceophala: Polymorphidae) from 26 juvenile grey seals, Halichoerus grypus, by-caught from around the Inishkea Islands, Co. Mayo, from March to June 1997 were recorded. The location of C. strumosum within the seal did not vary, with all worms being found in the small intestine. The prevalence of infection was 100%, with no other acanthocephalan species being recorded. The mean abundance was 416 (range 80-846) C. strumosum per seal. There was no significant change in abundance by month. The sex ratio of mature female to mature male parasites was 1.2:1. The lengths of female and male worms did not differ significantly.     

First morphological and molecular characterization of cystacanths of Corynosoma evae Zdzitowiecki, 1984 (Acanthocephala: Polymorphidae) from Antarctic teleost fishes

Cystacanths of the polymorphid acanthocephalan Corynosoma evae Zdzitowiecki, 1984 were examined and redescribed based on newly collected material from teleost fishes from coastal waters of the Galindez Island (Argentine Islands, West Antarctica). Detailed morphological data, measurements and photomicrographs, including scanning electron microscopy images, are presented. Our morphological and morphometrical analyses confirmed the validity of C. evae; however, three key characteristics of taxonomic importance (i.e., the number of rows of hooks on the proboscis, and the number and arrangement of genital spines in males) showed significant morphological variability. In addition, a genital spine in the posterior body end of a female is reported for the first time. This study provides the first sequences of the small and large subunits nuclear ribosomal RNA genes (SSU and LSU) and the mitochondrial cytochrome c oxidase subunit 1 (cox1) for C. evae. Maximum likelihood and Bayesian inference analyses of the SSU + LSU + cox1 and the cox1 datasets placed C. evae as a sister lineage to a clade formed by C. validum Van Cleave, 1953 and C. villosum Van Cleave, 1953, although with low support. In contrast, the position of C. evae in the phylogenetic analysis of the SSU + LSU dataset remained unresolved. Finally, C. arctocephali Zdzitowiecki, 1984 from pinnipeds from the subantarctic and Antarctic regions is considered as a valid species.     

Polymorphus arctocephali Smales, 1986, a synonym of Corynosoma cetaceum Johnston & Best, 1942 (Acanthocephala: Polymorphidae)

Polymorphus arctocephali (Acanthocephala: Polymorphidae) was differentiated from P. cetaceum based on patterns in the trunk spine distribution and slight morphometric differences. The comparison of both species involved samples from South Australia and did not include P. cetaceum from South America. In this paper we re-examine the systematic position of P. arctocephali based on a more detailed morphological and geographical analysis. Results indicate that P. arctocephali does not differ in trunk spine distribution with respect to P. cetaceum, and that its morphometric differences can be subsumed under the natural variation found within P. cetaceum populations. Therefore, P. arctocephali becomes a junior synonym of P. cetaceum. P. cetaceum was transferred from Corynosoma to Polymorphus due to the absence of genital spines in both sexes. However, adopting the less restrictive definition of genital spines used by several authors, females of P. cetaceum could be considered as bearing genital spines. Species of the genus Andracantha also have genital spines, but specimens of P. cetaceum possess a continuous field of trunk spines, which precludes the assignment of this species to Andracantha. Other generic level characters, as well as ecological data, support clearly the transference of P. cetaceum back to Corynosoma. Therefore, this species becomes Corynosoma cetaceum Johnston & Best, 1942.     

Assessing host-parasite specificity through coprological analysis: a case study with species of Corynosoma (Acanthocephala: Polymorphidae) from marine mammals

In this paper we report an investigation of the utility of coprological analysis as an alternative technique to study parasite specificity whenever host sampling is problematic; acanthocephalans from marine mammals were used as a model. A total of 252 scats from the South American sea lion, Otaria flavescens, and rectal faeces from 43 franciscanas, Pontoporia blainvillei, from Buenos Aires Province, were examined for acanthocephalans. Specimens of two species, i.e. Corynosoma australe and C. cetaceum, were collected from both host species. In sea lions, 78 out of 145 (37.9%) females of C. australe were gravid and the sex ratio was strongly female-biased. However, none of the 168 females of C. cetaceum collected was gravid and the sex ratio was not female-biased. Conversely, in franciscanas, 14 out of 17 (82.4%) females of C. cetaceum were gravid, but none of 139 females of C. australe was, and the sex ratio of C. cetaceum, but not that of C. australe, was female-biased. In putative non-hosts, the size of worms was similar to that from specimens collected from prey. Results suggest that both acanthocephalans contact sea lions and franciscanas regularly. However, C. australe and C. cetaceum cannot apparently reproduce, nor even grow, in franciscanas and sea lions, respectively. Coprological analysis may represent a useful supplementary method to investigate parasite specificity, particularly when host carcasses are difficult to obtain.