Abstract
Atlantid heteropods are a family of holoplanktonic marine gastropods that occur primarily in tropical and subtropical latitudes. Atlantids bear a delicate aragonitic shell (<14 mm) and live in the upper ocean, where ocean acidification and ocean warming have a pronounced effect. Therefore, atlantids are likely to be sensitive to these ocean changes. However, we lack sufficiently detailed information on atlantid taxonomy and biogeography, which is needed to gain a deeper understanding of the consequences of a changing ocean. To date, atlantid taxonomy has mainly relied on morphometrics and shell ornamentation, but recent molecular work has highlighted hidden diversity. This study uses an integrated approach in a global analysis of biogeography, variation in shell morphology and molecular phylogenies based on three genes (CO1, 28S and 18S) to resolve the species boundaries within the Atlanta brunnea group. Results identify a new species, Atlanta vanderspoeli, from the Equatorial and South Pacific Ocean, and suggest that individuals of A. brunnea living in the Atlantic Ocean are an incipient species. Our results provide an important advance in atlantid taxonomy and will enable identification of these species in future studies of living and fossil plankton.
Highlights
The heteropods (Pterotracheoidea) are a superfamily of marine gastropods (Order Littorinimorpha) consisting of three families: Pterotracheidae, Carinariidae and Atlantidae (Lalli and Gilmer 1989; Bouchet et al 2017)
We formally describe the previously recognised A. turriculata form B, previously named A. brunnea form B (Wall-Palmer et al 2018b) as Atlanta vanderspoeli sp. nov. named after Professor Siebrecht van der Spoel who first recognised A. vanderspoeli but did not describe it as a new species (Van der Spoel 1972, 1976)
A total of 22 A. brunnea, 14 A. vanderspoeli and 55 A. turriculata were examined in this study
Summary
The heteropods (Pterotracheoidea) are a superfamily of marine gastropods (Order Littorinimorpha) consisting of three families: Pterotracheidae, Carinariidae and Atlantidae (Lalli and Gilmer 1989; Bouchet et al 2017). Atlantids are widespread and occur primarily in the epipelagic zone between the surface and 250 m, in tropical and subtropical latitudes (Wall-Palmer et al 2018a) They are highly modified for life in the open ocean with several striking morphological adaptions such as the development of complex image-forming eyes, a foot that has adapted into a single swimming fin, and the reduction in size (< 14 mm) and weight of the laterally compressed, thin-walled (3–40 μm) shell (Lalli and Gilmer 1989). The entire shell is moved back and forth rapidly during swimming, so that the swimming fin and shell work together as dissimilar paired swimming appendages (Karakas et al 2018). To gain deeper understanding of the consequences of a changing ocean, it is extremely important to resolve the species boundaries of holoplanktonic gastropods accurately, so that species-resolved environmental sensitivities can be determined
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