Emprosthopharynx onubensis Pérez-García, Gouveia, Calado, Noreña & Cervera, 2024, sp. nov.

Emprosthopharynx onubensis sp. nov. Fig. 13 Holotype. • MNCN 4.01/2799 to 2819, Station 10, 21 February 2019, 25 mm, sagittal sectioned into 20 slides. Diagnosis. Elongated oval Stylochoplanidae with yellowish brown colour; tentacles absent; gonopores separated; with spermiducal bulbs and tubular seminal vesicle; interpolated prostatic vesicle pear-shaped, with smooth irregular epithelium; female apparatus with vagina bulbosa; without Lang’s vesicle. Description. Elongated oval body, with few marginal folds. Dorsal colouration yellowish-brown with a translucent appearance and intense pigmentation in the pharyngeal region (Fig. 13 A, B). Intestinal branches patent. Ventral side yellowish-brown. Without tentacles. Clusters of tentacular and cerebral eyes located anterior to the brain, with 19 tentacular eyes and 21 cerebral eyes per cluster (Fig. 13 C). Few cerebral eyes posterior to the brain. Pharynx ruffled in the first half of the body, and the oral pore in the second third of the pharynx. Gonopores separated (0.9 mm) and positioned immediately behind the pharynx. Reproductive system. Male copulatory apparatus comprises spermiducal bulbs (Fig. 13 D), an interpolated prostatic vesicle encircled by well-developed muscle layers and crossed by extravesicular glands, and a short penis papilla (Fig. 13 E, G). Vasa deferentia ventrally and dilated in spermiducal bulbs enter separated into the tubular seminal vesicle (Fig. 13 E). Prostatic vesicle elongated and oval, 1 mm in length, with a thick muscular wall (0.18 mm wide). Epithelial lining of the prostatic vesicle well-developed and irregular. Penis papilla short (0.2 mm long) and opens distally into a ciliated male atrium (0.18 mm wide and 0.36 mm deep), including a characteristic diverticulum just before the male pore (Fig. 13 E). The female reproductive system comprises a folded and ciliated external vagina and the vagina bulbosa (Fig. 13 F). The external vagina extends dorsally and then curves backwards, forming a narrower internal vagina. Without Lang’s vesicle. Type locality. El Portil, Huelva, Spain. Etymology. The specific name refers to Onuba, the Latin name of Huelva, the area where the holotype was collected. Remarks. The genus Emprosthopharynx was established by Bock in 1913 and classified within the family Stylochoplanidae. This family is characterised by a simple male copulatory apparatus, a small tubular seminal vesicle, a prostatic vesicle lined with irregular epithelium, and a female reproductive system lacking Lang’s vesicle (Fig. 13 D). In Table 4, it is evident that E. onubensis sp. nov. exhibits unique characteristics that distinguish it from other species within the genus, leading to the classification of a new species. Its external morphology includes yellow-brown dorsal pigmentation, numerous tentacular (19), and cerebral eyes (21). Furthermore, it shares common features with few species, such as an elongated-oval body shape, a larger body size (more than 20 mm), and a pyriform prostatic vesicle, characters found in E. rasae only. E. onubensis sp. nov. lacks tentacles, but the presence of this structure is not a very distinctive feature within the genus. For example, some species like E. gracilis and E. hancocki have tentacles, while others such as E. opisthoporus and E. vanhoffeni have a rudimentary form of tentacle. Of the nine species currently recognised in the genus (including E. onubensis sp. nov.), only E. opisthoporus, E. rasae, and E. vanhoffeni have marginal eyes. The other six species, including E. onubensis sp. nov., lack marginal eyes. Usually, the pharynx is centrally located in the Emprosthopharynx, but four species (E. opisthoporus, E. rasae, E. heroniensis, and E. lysiosquillae) share with E. onubensis sp. nov. an anterior pharynx position. E. onubensis sp. nov. has separate gonopores, a shared feature with E. pallida, E. opisthoporus, E. rasae, and E. lysiosquillae. The other species have closely located gonopores. The prostatic vesicle in E. onubensis sp. nov. is pyriform, similar to E. rasae. In other species, the prostatic vesicle is oval, rounded, or elongated. Despite most species having an oval, rounded, or elongated seminal vesicle, E. heroniensis has a pear-shaped seminal vesicle, and E. lysiosquillae has a bean-shaped vesicle. Furthermore, E. onubensis sp. nov. has a tubular seminal vesicle, a feature shared with E. vanhoffeni. The penis papilla of E. onubensis sp. nov. is short, like most of the species within the genus. This one is distinguished from the elongated papilla of E. pallida and E. heroniensis and the pointed papillae of E. hancocki and E. lysiosquillae as well. The genus Emprosthopharynx is known from the American Pacific coast (e. g., E. gracilis and E. hancocki are from California), Australia (E. heroniensis), Hawaii (E. rasae), Ecuador (E. opisthoporus), and Japan (E. lysiosquillae). On the other hand, E. pallida and E. vanhoffeni are known from the Cape Verde coast. E. pallida is also known from the Italian Mediterranean coast. E. onubensis sp. nov. represents the first record for the European and Iberian Atlantic coasts.