Oxydromus humesi is an annelid polychaete living as a strict bivalve endosymbiont (likely parasitic) of Tellina nymphalis in Congolese mangrove swamps and of Scrobicularia plana and Macomopsis pellucida in Iberian saltmarshes. The Congolese and Iberian polychaete populations were previously considered as belonging to the same species, the latter showing regular distribution, intra-specific aggressive behaviour, and complex hostentering behaviour. The fresh Iberian samples enabled us to undertake consistent morphometric analyses, as well as to further analyse the characteristics of the association and the population dynamics of the Iberian population hosted by S. plana. Among the morphological differences between the Congolese and Iberian specimens, leading to the description of the latter as Oxydromus okupa sp. nov., the most important are: 1) longer cephalic appendages, 2) greater distance between the eyes, 3) larger dorsal cirrostyle in relation to the corresponding dorsal lobe and cirrophore. Moreover, dorsal and ventral lobes are similar in length, with the tip of the former reaching the tip of the latter in O. okupa sp. nov., while the dorsal lobe is much shorter than the ventral one in O. humesi. Mature adults of O. okupa sp. nov. occurred during the whole study period, with a higher percentage of ripe females in spring and, particularly, in summer. Numerous host specimens showed the symbiont’s most preferred shell length (>26 - 36 mm). However, the prevalence was very low (usually <5%) and showed a clear seasonal pattern, being lower during spring/summer. This suggests that males are able to leave their hosts during this period, most likely to improve fertilization by directly entering or approaching a host occupied by a ripe female, while females usually remain inside. Based on the new results, the current knowledge of symbiotic Hesionidae and their relationships with invertebrate hosts is updated and discussed.
During a visit to polychaete-rearing facilities in the vicinity of Bay of Cá diz (SW Iberian Peninsula, Atlantic Ocean), we sampled two populations of Marphysa (Annelida, Eunicidae) originally occurring at nearby intertidal soft bottoms, one being more than twice as long as the other at the same age. We analysed them using partial sequences of two mitochondrial genes, 16S rDNA and Cytochrome Oxidase I, and classical morphological observations. Our molecular results confirmed that the two populations corresponded to two different species, with PTP species delimitation values ranging from 0.973 (long-bodied species) to 0.999 (short-bodied species). Morphologically, the short-bodied species resembles the recently redescribed M. sanguinea (Montagu, 1813), but differs mainly in having some parapodia with two subacicular hooks (one bidentate and one unidentate) and three types of pectinate chaetae, Two isodont present all along the body, and one particularly large anodont asymmetric appearing only from mid-posterior parapodia. The long-bodied species resembles Marphysa aegypti Elgetany, El-Ghobashy, Ghoneim and Struck, 2018 both in size and in having very robust, unidentate subacicular hooks (single in most parapodia, two-both similar in size and form-in some posterior parapodia), but differs, among other features, in the maxillary formula, the number of acicula per parapodia and the number and shape of pectinate chaetae. Accordingly, we are here fully illustrating and formally describing the two Iberian populations as Marphysa gaditana sp. nov. (short-bodied) and Marphysa chirigota sp. nov. (long-bodied) and we are emending the description of M. aegypti based on our revision of the type material. Also, we discuss on the distribution of the species of the sanguinea-group and on the relevancy of taxonomically robust studies when dealing with species of commercial interest having the potential of being globally spread through human activities, as well as on the misunderstandings caused by the incorrect use of the "cosmopolitan species" concept.
The family Flabelligeridae was previously represented in Tunisia by four genera including four species: Bradabyssa villosa (Rathke, 1843), Therochaeta flabellata (M. Sars in G.O. Sars, 1872), Pherusa plumosa (Müller, 1776), and Piromis eruca (Claparède, 1869). In this paper we report a fifth genus, Trophoniella, for the first time in Tunisia. The specimens were collected in Radés Station, Gulf of Tunis (Central Mediterranean) and belong to a new species, namely Trophoniella radesiensis n. sp., which is characterized by having: (1) a very smooth tunic, body covered dorsally, ventrally, and laterally by sediment grains (except in the posterior region), and (2) well-developed parapodia showing short neurohooks from chaetiger 6 to 19 and anchylosed neurohooks from chaetiger 20. Based on the 16S, the new species belongs to a low supported Piromis/Trophoniella clade and shows a 16.1% of genetic distance from Trophoniella hephaistos Jimi & Fujiwara, 2016, the single known species of the genus sequenced to date. [Zoobank lsid: urn:lsid:zoobank.org:act:D7C85C70-87FF-4AF4-8599-A8462B3FB8B1]
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