Intestinal helminth fauna of the shortfin mako Isurus oxyrinchus (Elasmobranchii: Lamnidae) in the northeast Atlantic Ocean

Abstract

Large oceanic sharks represent a suitable model to investigate the influence of a host's oceanic conditions on the structure of its helminth communities. In this study, we describe the intestinal helminth fauna, and investigate determinants of infracommunity structure, in 39 specimens of shortfin mako Isurus oxyrinchus collected in the NE Atlantic. Six cestode species were found in the spiral valve of makos: 3 are typical from lamnid sharks, namely, gravid specimens of Clistobothrium montaukensis, Gymnorhynchus isuri and Ceratobothrium xanthocephalum, and 3 are immature specimens of cestode species common to several elasmobranchs, namely, Dinobothrium septaria, Nybelinia lingualis, and Phyllobothrium cf. lactuca. In addition, L3 larvae of Anisakis sp. type I were detected. Infracommunities were species poor and had low total helminth abundance. The result of Schluter's variance ratio test was compatible with the hypothesis of independent colonization of helminth taxa. These results conform to previous studies on oceanic predators that have hypothesized that these hosts should have depauperate and unpredictable helminth infracommunities because oceanic conditions hamper parasite transmission. However, mean species richness and mean total abundance of cestodes of shortfin mako and other oceanic sharks did not significantly differ from those of elasmobranchs from other habitats. This suggests that the large body size and prey consumption rates of oceanic sharks offset the negative 'dilution' effect of oceanic habitat on transmission rates. Additionally, or alternatively, parasites of oceanic sharks may have expanded the use of intermediate hosts through the trophic web to spread out the risk of failure to complete their life cycles.

New Parasite Records for the Sunfish Mola mola in the Mediterranean Sea and Their Potential Use as Biological Tags for Long-Distance Host Migration

“…To the best of our knowledge, only G. gigas has to date been reported from the Mediterranean basin in the swordfish Xiphias gladius Linnaeus, 1758, the Ray's bream Brama brama (Bonnaterre, 1788), and the silver scabbardfish Lepidopus caudatus (Euphrasen, 1788) (49,50). Gymnorhynchus isuri is known from the north, southwestern, and northeast Atlantic and the Tasmanian Sea in the southwestern Pacific, infecting the shortfin mako Isurus oxyrinchus Rafinesque, 1810 and the blue shark Prionace glauca (Linnaeus, 1758) (30,51,52), and no record exists of G. isuri in Mola species anywhere.…”

Molecular Characterization of Clistobothrium sp. Viable Plerocercoids in Fresh Longfin Inshore Squid (Doryteuthis pealeii) and Implications for Cephalopod Inspection

“…The same author also described for the first time the species C. montaukensis from the spiral intestine of the shortfin mako shark ( Isurus oxyrinchus ) [ 44 ]. Subsequent studies confirmed the occurrence of C. montaukensis in shortfin mako [ 48 ] and of C. carcharodoni in the great white shark [ 37 ], while, as mentioned, a specific identification could not be achieved for the specimens identified as C. cf. montaukensis found in the porbeagle Lamna nasus [ 36 ].…”

Determinants of diversity and composition of the tapeworm fauna of blue sharks, Prionace glauca: a geographical and host-specificity analysis

“…We interpret that these immature forms are likely specific to other elasmobranchs and do not reproduce in blue sharks; thus, they could be considered as accidental parasites such as, for example, Anisakis spp. are in other sharks (Penadés-Suay et al, 2017). The degree of preservation of samples of the remaining tapeworm taxa, all containing adults, allowed reliable specific identifications (see below) except for Scyphophyllidium sp.…”

“…To globally compare the infracommunity diversity and composition of cestode faunas infecting blue sharks around the world, we searched all parasitological surveys for which at least the prevalence of all tapeworm taxa found in the intestine was reported. These surveys generally did not provide data on mean species richness per host; thus we calculated this parameter by summing up prevalence (expressed as decimals) of all intestinal tapeworm taxa in each sample (Penadés-Suay et al ., 2017). Differences of prevalence of specific taxa among localities were tested with exact Chi-square tests.…”

“…mean species richness, diversity indices, or mean abundance of each tapeworm species per host). Based on a limited dataset available, Penadés-Suay et al (2017) recently investigated to what extent the potential dilution' effects of infective stages of tapeworms in the pelagic-oceanic habitat could result in comparatively species-poor, low-abundance infracommunities in large oceanic sharks, regardless of the richness in the component community locally available. These authors failed to detect this specific host habitat effect, but their literature search incidentally revealed a striking finding, that is, there were just four species of sharks (for a global diversity of approximately 500 spp.)…”