The Discovery of the Mediterranean Echinorhynchus abissicola Dollfus, 1931 (Acanthocephala: Echinorhynchidae) From a New Host in the Persian Gulf

Collections

Originally, the intestine of one leather jacket from the Persian Gulf was found infected with 2 worms on 15 April 2023. These worms were later identified by OMA after processing and whole mounting for microscopic examination. New collections included 19 leather jackets (Fig. 1) of which 5 were found infected with many acanthocephalans (Fig. 2) but these will not be included in this presentation.

Methods for Microscopical Studies

Two female worms were punctured with a fine needle and subsequently stained in Mayer’s acid carmine, destained in 4% hydrochloric acid in 70% ethanol, dehydrated in ascending concentrations of ethanol (24 hr each), and cleared in 100% xylene then in 50% Canada balsam and 50% xylene (24 hr each). Whole worms were then mounted in Canada balsam. Measurements for diagnostic verification were made in micrometers, unless otherwise noted. Specimens are kept in the senior author's collection.

Optical Microscopy

Images created for this presentation were acquired using a Zeiss Axioskop Transmitted Nomarski DIC Phase Contrast Microscope Trinocular (Munich, Germany) and a Canon T3i EOS 600D DSLR Camera (Melville, New York).

Images from the microscope were transferred from the laptop to a USB and stored for subsequent processing on a computer. Measurements are in micrometers unless otherwise noted; the range is followed by the mean values between parentheses when appropriate.

A brief Description of the Persian Gulf Females (Figs. 3-8)

With characters of the genus Echinorhynchus Zoega in Müller, 1776. Measurements in Table 1. Main longitudinal lacunar canals lateral. Lemniscal and hypodermal nuclei fragmented (Fig. 7). Trunk long, cylindrical with parallel sides (Fig. 5). Proboscis cylindrical joined basally with receptacle, with 12-13 rows of 10 hooks each, smallest anteriorly and basally (Fig. 3). Hooks dorso-ventrally differentiated with the ventral hooks being relatively longer and more robust than dorsal hooks (Fig. 4) and with simple shorter truncated roots directed posteriorly (Fig. 4, arrows). Proboscis receptacle more than twice the length of the proboscis, double- walled, with undecided position of the cephalic ganglion and retinacula. Lemnisci shorter than receptacle (Fig. 5). Retractor muscles emerge from receptacle and extend into body cavity posteriorly (Fig. 6). Body wall covered with fragmented hypodermal nuclei (Fig. 7). Gonopore terminal and vagina relatively short with reduced sphincter (Fig. 8).

Taxonomic summaryType host: Snubnose eelpout, Pachycara obesa Zugmayer (synonym of Pachycara bulbiceps (Garman) (Zoarcidae). Other hosts: leather jacket filefish, Aluterus monoceros (Linn.) (Monacanthidae).

Type locality: The Mediterranean at Monaco at depth of 4,785 m. Other locality: The Persian Gulf off the Iranian coast. Site of infection: Intestine. Specimens: In first author’s collection.

Remarks

While the differences between the two sets of females from the Mediterranean and the Persian Gulf appear unremarkable (Table 1), our additions to the original description are significant enough to warrant a special note. For instance, we observed the sexual differentiation in hook sizes being more robust and longer ventrally than dorsally (Table 2, Fig. 4). Dollfus (1931) only measured the emerging parts of the hooks at 70 μm. The cephalic ganglion and the retinacula remain unrecognizable. We noted prominent elements of the retractor muscles (Fig. 6) and the hypodermal nuclei (Fig. 7). We also marked the terminal position of the gonopore and noted the short vagina (Fig. 8). The lessepsian distribution of fish and their parasites across the Suez Canal in the Mediterranean and the Red Sea/Persian Gulf may account for the finding of E. abissicola in A. monocerus in the Persian Gulf. There are at least 63 Lessepsian fish species that are known to have penetrated the Suez Canal either way since its opening in 1869 [7, 8]. If this was the case, then we would not have known if E. abissicola was originally a Mediterranean parasite that spread into the Red Sea and the Persian Gulf or was it the other way around. This Lessepsian migration has been more often documented from the Red Sea to the Mediterranean which may have been the direction of the movement of parasites [9].