Determinants of Host Specificity and Comments on Attachment Site Specificity of Tetraphyllidean Cestodes Infecting Rajid Skates from the Northwest Atlantic

Abstract

The objectives of this study were to (1) describe the host range for 6 tetraphyllidean species and quantify their host specificity using 5 specificity indices; (2) determine the role of morphological determinants in the host specificity of tetraphyllideans by comparing villar and bothridial measurements of species examined herein; and (3) determine the role of a physiological component in the host specificity of tetraphyllideans by exposing tetraphyllideans to blood sera from different fish species and other solutions. Our results indicate that Echeneibothrium dubium abyssorum (ex Amblyraja radiata), Echeneibothrium canadensis (ex A. radiata), and Zyxibothrium kamienae (ex Malacoraja senta) exhibit the highest degree of specificity, followed by Echeneibothrium vernetae (ex Leucoraja erinacea and Leucoraja ocellata), Pseudanthobothrium hanseni (ex A. radiata and M. senta), and Pseudanthobothrium purtoni (ex Leucoraja erinacea and L. ocellata). However, these results vary based on the specificity index used. Compatible bothridial and villar measurements indicate that there is no morphological determinant of host specificity but that there is a morphological determinant to attachment site specificity. Our data indicate that attachment site specificity may also be phylogenetically determined. Additionally, the exposure of parasites to blood sera from various hosts confirms that host specificity in this system has a physiological determinant. Therefore, host specificity in this system is determined, at least in part, by physiological factors, whereas attachment site specificity is an extension of host specificity and is phylogenetically determined.

The phylogenetic position of the enigmatic Balkan Aulopyge huegelii (Teleostei: Cyprinidae) from the perspective of host-specific Dactylogyrus parasites (Monogenea), with a description of Dactylogyrus omenti n. sp.

“…In evolutionary time, this leads to a selection for improvements in host–parasite recognition mechanisms [ 1 ]. The high degree of host specificity among parasites (generally, a parasite species is restricted to a single host species), reflecting parasite specialization, may arise from such coevolutionary interactions [ 2 – 4 ] In the case of high host specificity, the phylogeny of host-specific parasites may even follow the phylogeny and historical biogeography of their hosts as a result of co-speciation [ 5 , 6 ]. However, parasite diversification can also be driven by host specialization following host switching resulting from strong ecological association, as was shown for monogeneans of marine fish [ 7 ].…”

Evolution of host specificity in monogeneans parasitizing African cichlid fish

“…Host specificity is considered to be a result of various factors including phylogenetic, physiological and ecological aspects [1-5]. Most parasites exhibit at least some degree of host specificity or host preference [6,7]; however, the basics of features governing the evolution of host specificity are not yet fully understood.…”

Description of a new species of rhinebothriidean tapeworm from the skate Dipturus batis in the Mediterranean Sea

“…It is well established that host and attachment-site specificity in skates are determined, to a certain extent, by the close fit between a tapeworm's scolex and the host intestinal mucosa (Williams, 1960, 1966, 1968; Randhawa and Burt, 2008 and references therein). The adaptation of the scolex to the host mucosa allows tapeworms to remain attached despite physiological processes occurring in the digestive tract, such as peristaltic movements, which could mechanically expel them from their microhabitat.…”

“…As adults, these tapeworms reside in the spiral intestine and demonstrate a noticeable specificity to their definitive elasmobranch host (Williams, 1966; Caira and Jensen, 2014). This specificity has been attributed to morphological adaptations of the attachment structures to the host gut mucosa, host physiological adaptations allowing or preventing establishment of parasites, and ecological features of the hosts, such as resource availability, substrate preference, diet and phylogenetics (Randhawa and Burt, 2008, and references therein). Furthermore, congeners sharing hosts have been shown to exploit separate niches by exhibiting attachment-site preferences within the spiral intestine of rajid skates (Carvajal and Dailey, 1975; Randhawa, 2012).…”

“…Globally, several studies have focused on the taxonomy, systematics, distribution, and host specificity of tapeworms infecting elasmobranchs (e.g. Euzet, 1959; Alexander, 1963; Williams, 1966, 1968, 1969; Caira et al ., 1999, 2017a; Jensen, 2005; Tyler, 2006; Randhawa and Burt, 2008; Ruhnke, 2011; Caira and Jensen, 2017). Many outcomes were the subject of passionate discussions, others spurred complementary or corrective research, especially regarding the advance of taxonomic and systematics research with the advent of molecular tools (e.g.…”