Scutiloricus hugoi, Neves & Kristensen & Møbjerg, 2021

Neves, Ricardo Cardoso, Kristensen, Reinhardt Møbjerg & Møbjerg, Nadja, 2021, New records on the rich loriciferan fauna of Trezen ar Skoden (Roscoff, France): Description of two new species of Nanaloricus and the new genus Scutiloricus, PLoS ONE (e 0250403) 16 (5), pp. 1-42 : 36-38

publication ID

https://doi.org/ 10.1371/journal.pone.0250403

DOI

https://doi.org/10.5281/zenodo.12630841

persistent identifier

https://treatment.plazi.org/id/0396B203-6934-5150-FDBF-F92CC5DDF9BB

treatment provided by

Felipe

scientific name

Scutiloricus hugoi
status

gen. et sp. nov.

Scutiloricus hugoi View in CoL gen. et sp. nov. can be distinguished from all other genera assigned to Nanaloricidae —namely Nanaloricus , Armorloricus , Phoeniciloricus , Spinoloricus , Culexiregiloricus and the recently described Fafnirloricus [ 8, 13, 28, 32 – 34]–by its possession of a unique combination of characters as outlined in Table 2. This table, moreover, provides further references to formal descriptions of additional species assigned to the various genera; [ 18, 19, 30, 35]. Australoricus , a genus that was discovered in sea caves off New South Wales in Australia, is not

included because its description is based solely on the larval stage [ 36]. Indeed, Scutiloricus hugoi gen. et sp. nov. can be distinguished from all other loriciferans by its possession of a combination of distinctive morphological features that includes: (i) fenestrated anterior spikes, (ii) linear arrangement of the dorsolateral flosculi, (iii) slightly invaginated anal field with a small anal cone flanked by a pair of small spurs, and (iv) females with a unique pair of seminal receptacles.

Two other morphological features attract special attention in Scutiloricus hugoi gen. et sp. nov., namely the arrangement of the dorsolateral flosculi and the peculiar anatomy of its invaginated anal field. The arrangement of dorsolateral flosculi has traditionally been used as a diagnostic character for comparative morphology of Loricifera. Among all genera assigned to Nanaloricidae , Scutiloricus hugoi gen. et sp. nov. is the only genus possessing linearly arranged dorsolateral flosculi. Specifically, all Nanaloricidae genera described so far possess either a rectangular or a triangular arrangement of dorsolateral flosculi. The linear pattern found in Scutiloricus hugoi gen. et sp. nov. is thus a unique feature described for the first time in Loricifera. The anal field with a small, protruding anal cone flanked by a pair of spurs that characterizes this new genus also represents a very peculiar combination of traits. Although a similar anal cone can be found in Culexiregiloricus [ 34], no other genus belonging to Nanaloricidae is characterized by an invaginated anal field with a pair of spurs, as observed in Scutiloricus hugoi gen. et sp. nov. In addition, there are almost no other similarities with Culexiregiloricus , a genus that is characterized by an oval lorica with intercalary plicae and dorsolateral flosculi arranged triangularly with a furrow located amid them. Overall, the external morphology of the new genus and species described here is not similar to any of the other generaassigned to Nanaloricidae (for a comparative analysis see Table 2). Indeed, only isolated features from each of the body sections are shared between Scutiloricus hugoi gen. et sp. nov. and other nanaloricid genera. For instance, both the new genus and species described here and Armorloricus possess a square lorica [ 28]; however, the latter genus has 15 anterior spikes (ventral plate has three), whereas Scutiloricus hugoi gen. et sp. nov. possesses only 14 (ventral plate has two).

Besides the external features, an aspect of the internal anatomy of Scutiloricus hugoi gen. et sp. nov. requires special attention. The finding of seminal receptacles in a female of this new genus and species is a first time observation for Loricifera, providing evidence for the existence of a female sperm-storage organ in this group of microscopic invertebrates. Moreover, the presence of mature sperm inside a paratypic female demonstrates that the seminal receptacles were functional at the time the specimen was preserved. Interestingly, though, ultrastructural observations of Armorloricus elegans provided evidence for the presence of spermatozoa inside a female specimen [ 37]. However, the presence of seminal receptacles in this species was never assessed. In the future, the study of this female organ is necessary to understand the functional morphology and ultrastructure of the newly described seminal receptacles, as well as to better comprehend the reproductive activity and sexual selection in Loricifera.

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