Molecular and anatomical analyses reveal that Peronia verruculata (Gastropoda: Onchidiidae) is a cryptic species complex

Abstract

Recent years have seen an increase in the number of studies that use DNA sequence information in addition to morphological methods, as the latter alone can be inadequate for morphologically similar, cryptic species. Marine onchidiid slugs (Mollusca: Gastropoda: Onchidiidae), which commonly inhabit intertidal environments and have a near-global distribution, comprise 11 genera and 86 described species. Singapore has 19 recorded species of onchidiids with Peronia verruculata (Cuvier, 1830) being the most abundant. Here we present mitochondrial DNA sequence data from 63 P. verruculata-like specimens to show that they constitute two closely-related clades with distinct sequence signatures and a clear barcode gap. Intraclade distances are 0–1.8% while interclade distances range from 4.7 to 6.0%. Scanning electron microscopy of internal copulation organs reveals that the two clades have distinct penial and accessory gland spine structures, which also differ in size. Using an integrative taxonomic approach, we propose that what was initially thought to be P. verruculata in Singapore, actually are two different species of Peronia.

Systematic revision of the genus Peronia Fleming, 1822 (Gastropoda, Euthyneura, Pulmonata, Onchidiidae)

“…(MH002570) for an individual identified as Peronia sp. and collected from Singapore (Chang et al 2018). This individual as well as others referred to as "Peronia sp.…”

“…Eleven COI sequences obtained from Gen-Bank (10) and BOLD (1) were added to our own data set (179 COI sequences) for a total of 190 sequences. Four COI sequences are from China (Sun et al 2014), two from Singapore (Chang et al 2018), two from Japan (Takagi et al 2019), one from the Persian Gulf (unpublished), one from Gujarat, western India (unpublished), and one from Iran (Maniei et al 2020a). All those sequences were merely referred to as Peronia sp., except for the specimens from China (referred to as Peronia verruculata), the specimen from western India (referred to as Onchidium verruculatum), and the specimen from Iran (recently described as P. persiae, a name regarded here as a synonym of P. verruculata, unit #4).…”

“…Note that in the case of duplicate sequences available in GenBank, only one representative was selected. So, for instance, Chang et al (2018) published many Peronia COI sequences that cluster in two mitochondrial units which they refer to as "Singapore clade" and "Peronia sp. 2 clade."…”

“…Sequences marked with an asterisk (*) are from our former publications (Dayrat et al 2011(Dayrat et al , 2016(Dayrat et al , 2018(Dayrat et al , 2019a; Goulding et al 2018a, b, c). In addition, 11 COI sequences also marked with an asterisk (*) were obtained from GenBank (GB) and BOLD: four sequences from China (Sun et al 2014), two from Singapore (Chang et al 2018), two from Japan (Takagi et al 2019) Vouchers used in Dayrat et al (2011). Ten of our Peronia specimens were tentatively identified by Dayrat et al (2011) at a time when nothing was known about the onchidiid species diversity in general and most especially in the genus Peronia.…”

Takeaways from Mobile DNA Barcoding with BentoLab and MinION

“…The practice of DNA barcoding—involving the generation of standardized genetic markers that, when matched to databases, allow for species identification—was first popularized by Hebert et al (2003) [ 1 ]. Since then, the field of DNA barcoding has evolved and expanded considerably beyond just species identification [ 2 , 3 , 4 , 5 ] to include species discovery, population genetics, and phylogenetics [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. This rapid growth in DNA barcoding capabilities has occurred as a result of advancements in sequencing technologies.…”