Overview of South African Dendromonocotyle (Monogenea : Monocotylidae), with descriptions of 2 new species from stingrays (Dasyatidae) kept in public aquaria

Abstract

Two new species, Dendromonocotyle citrosa n. sp. off Dasyatis chrysonota (Smith) from Two Oceans Aquarium in Cape Town and off Himantura gerrardi (Gray) from uShaka Sea World in Durban and D. ukuthena n. sp. off H. gerrardi and H. uarnak (Forsskål) also from uShaka Sea World in Durban, are described. These can be distinguished from previously described Dendromonocotyle species by the morphology of the distal portion of the male copulatory organ and the proximal part of the vagina. Vaginal morphology is proposed as an important diagnostic character for species in the genus. Dendromonocotyle colorni Chisholm, Whittington & Kearn, 2001 which was originally recorded from H. uarnak in Israel, was discovered on H. uarnak sympatrically with D. ukuthena n. sp. and with D. citrosa n. sp. and D. ukuthena n. sp. off H. gerrardi. Minor differences in the number of papillary sclerites, the presence of septal tripartite sclerites and in the number of eyespots were seen between D. colorni collected from H. uarnak and H. gerrardi from uShaka Sea World and those originally described off H. uarnak from Israel. We demonstrate that the position of the marginal hooklets can be used to determine the orientation of the haptor of all representative Dendromonocotyle species with or without hamuli. We conclude that Dendromonocotyle species may not be as host-specific as previously believed and that minor differences in morphology are host or geographically induced.

Dendromonocotyle urogymni sp. nov. (Monogenea, Monocotylidae) from Urogymnus asperrimus (Elasmobranchii, Dasyatidae) off eastern Australia

“…The male copulatory organ of D. pipinna is a very short tube and there are small sclerotised ridges at the distal end. Vaughan et al (2008) found that the distal portion of the male copulatory organ of D. ukuthena Vaughan, Chisholm et Christison, 2008, which usually had an accessory filament, was missing in five of the 17 specimens they examined. The distal end of the spermatophore was identical to the distal portion of the male copulatory organ and they hypothesised that the male copulatory organ may have been severed to form part of the spermatophore (see Vaughan et al 2008).…”

“…Vaughan et al (2008) found that the distal portion of the male copulatory organ of D. ukuthena Vaughan, Chisholm et Christison, 2008, which usually had an accessory filament, was missing in five of the 17 specimens they examined. The distal end of the spermatophore was identical to the distal portion of the male copulatory organ and they hypothesised that the male copulatory organ may have been severed to form part of the spermatophore (see Vaughan et al 2008). The distal end of the male copulatory organ of D. urogymni is reminiscent of that seen in the five specimens of D. ukuthena with the missing distal end, but there are no indications that the male copulatory organ of D. urogymni has been severed and no spermatophores were observed.…”

“…Scale bars = 50 µm (A); 10 µm (B-E) acter to distinguish between species in this genus. Vaughan et al (2008) noted that the morphology of the vagina combined with the presence/absence of hamuli could also be used to assist in species identification. The male copulatory organ of D. urogymni is distinct having a spherical inflation mid-way along its length (Fig.…”

Heterocotyle tokoloshei sp. nov. (Monogenea, Monocotylidae) from the gills of Dasyatis brevicaudata (Dasyatidae) kept in captivity at Two Oceans Aquarium, Cape Town, South Africa: Description and notes on treatment

“…These were returned to freshwater before being stained with alum carmine, dehydrated in a graded ethanol series, cleared in cedarwood oil and individually mounted in Canada balsam. Some specimens preserved in absolute ethanol were subjected to proteolytic digestion (Vaughan et al 2008a) to provide clear definition of the sclerotised structures of the haptor and of the sclerotised male copulatory organ. This method was also used to provide further information on whether or not the sinuous ridges on the haptoral septa are sclerotised.…”

“…Monocotylid monogeneans are known to cause health problems in stingrays maintained in public aquaria (Chisholm and Whittington 2002, Janse and Borgsteede 2003, Chisholm et al 2004, Vaughan et al 2008a, Vaughan and Chisholm 2009). Monocotylids parasitising the skin surface of stingrays held in captivity have received the most attention because infections are more visible and physical damage associated with feeding worms typically presents itself as conspicuous tissue discolouration.…”