Abstract
The genus Leptochiton Gray, 1847 is a paraphyletic group of small, pale, and usually deepwater chitons. They lack some of the morphological shell characters that are important in the systematics of Polyplacophora, and species identification within this genus is challenging. One species complex in the North Pacific includes at least 11 species that were historically synonymized or confused with Leptochiton rugatus (Carpenter in Pilsbry, 1892). Scrutiny of ecological and biogeographical patterns has helped to separate species lineages within this clade and support morphological diagnoses. Based on morphological and molecular studies, a new species is described that was previously confused with both Leptochiton assimilis (Thiele, 1909) and Leptochiton rugatus. This new species is widely distributed in the summer-warmed bays of the southern Primorye, Moneron Island, Northern Japan, Kunashir, and the Yellow Sea. This species is at least ~8% different in the COI barcode region from Leptochiton rugatus s.s. Morphological differences between the new species and closely related species are presented.
Highlights
Polyplacophoran molluscs, chitons, represent around 1000 living species divided into two distinct orders: Lepidopleurida and Chitonida
Shallow-water lepidopleuran chitons may be tolerant of relatively wide ranges of temperatures in short-term exposure, such as Leptochiton asellus, maintained experimentally over a range from 10 to 20°C (Sigwart et al 2011); tolerance of extremes and overall temperature profile in the long term will control species ranges
The known localities for Leptochiton subrugatus sp. nov. range from –1.7 to 24°C and a salinity of 28–34, 5%. We consider this to be a relatively warmwater species. It is distributed in relatively high latitudes, the localities in the northern part of its range depend on the summer warming of shallow waters or the penetration of warmwater currents to the north
Summary
Polyplacophoran molluscs, chitons, represent around 1000 living species divided into two distinct orders: Lepidopleurida and Chitonida. Five species live in shallow water: Leptochiton assimilis (Thiele, 1909), L. alascensis (Thiele, 1909), L. hakodatensis (Thiele, 1909), L. lukini Sirenko, 1990, and L. rugatus (Carpenter in Pilsbry, 1892) Another six species live at great depths: Leptochiton batialis Sirenko, 1979, L. belknapi Dall, 1878, L. commandorensis Sirenko, 2017, L. fuliginatus (Reeve, 1847), L. incubatus Sirenko, 2017, and L. kaasi Sirenko, 1990.
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