2urn:lsid:arphahub.com:pub:45048D35-BB1D-5CE8-9668-537E44BD4C7Eurn:lsid:zoobank.org:pub:91BD42D4-90F1-4B45-9350-EEF175B1727AZooKeysZK1313-29891313-2970Pensoft Publishers10.3897/zookeys.619.1004310043Research ArticleAnimaliaGastropodaInvertebrataMolluscaThecosomataMolecular systematicsNomenclatureSystematicsTaxonomyOceansPacific OceanRevision of the genus Cuvierina Boas, 1886 based on integrative taxonomic data, including the description of a new species from the Pacific Ocean (Gastropoda, Thecosomata)BurridgeAlice K.akburridge@yahoo.co.ukhttps://orcid.org/0000-0002-9108-31171JanssenArie W.1PeijnenburgKatja T. C. A.1Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA Leiden, The NetherlandsNaturalis Biodiversity CenterLeidenNetherlandsInstitute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, P.O. Box 94248, 1090 GE Amsterdam, The NetherlandsNaturalis Biodiversity CenterLeidenNetherlands
Corresponding author: Alice K. Burridge (akburridge@yahoo.co.uk)
Academic editor: N. Yonow
201627092016619112FF963A17-FFF9-FFEE-FFB3-C6661804AD2D32AEE355-D6DA-45DE-98D8-C27654903E341558693007201610092016Alice K. Burridge, Arie W. Janssen, Katja T. C. A. PeijnenburgThis is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.http://zoobank.org/32AEE355-D6DA-45DE-98D8-C27654903E34
Shelled pteropods (Gastropoda, Thecosomata, Euthecosomata) are a group of holoplanktonic gastropods that occur predominantly in the surface layers of the world’s oceans. Accurate species identifications are essential for tracking changes in species assemblages of planktonic gastropods, because different species are expected to have different sensitivities to ocean changes. The genus Cuvierina has a worldwide warm water distribution pattern between ~36°N and ~39°S. Based on an integrative taxonomic approach combining morphometric, genetic, and biogeographic information, the two subgenera of Cuvierina, Cuvierinas. str. and Urceolarica, are rejected. A new species is introduced: Cuvierinatsudaisp. n., which has to date been considered the same species as Cuvierinapacifica. Cuvierinatsudaisp. n. is endemic to the Pacific Ocean and is characterised by a shell height of 7.2-8.0 mm, a moderately cylindrical shell shape, the absence of micro-ornamentation and a triangular aperture. Cuvierinapacifica is restricted to the centre of the oligotrophic southern Pacific gyre, has a shell height of 6.6-8.5 mm, a more cylindrical shell shape, no micro-ornamentation and a less triangular aperture than C.tsudaisp. n.
Burridge AK, Janssen AW, Peijnenburg KTCA (2016) Revision of the genus Cuvierina Boas, 1886 based on integrative taxonomic data, including the description of a new species from the Pacific Ocean (Gastropoda, Thecosomata). ZooKeys 619: 1–12. doi: 10.3897/zookeys.619.10043
Introduction
Pteropods are holoplanktonic heterobranch gastropods classified in a superorder comprised of the orders Thecosomata and Gymnosomata, commonly referred to as “sea butterflies” and “sea angels”, respectively (Lalli and Gilmer 1989, Pierrot-Bults and Peijnenburg 2015). The order Thecosomata consists of Euthecosomata that have sinistrally coiled or straight, bilaterally symmetrical shells, and Pseudothecosomata that have either sinistrally coiled shells, an internal gelatinous pseudoconch, or are shell-less in the adult stage (Meisenheimer 1905, Tesch 1913). Pteropods play an important role in marine food webs (Jörger et al. 2010), and although most species occur in warm tropical and subtropical waters, the highest abundances have been observed for some (sub)polar cold water species (Bé and Gilmer 1977, Van der Spoel and Heyman 1983, Bednaršek et al. 2012, Burridge et al. 2016). Because of their thin-walled, aragonite shells, euthecosomes are exceptionally vulnerable to the effects of ocean acidification (e.g., Fabry et al. 2008, Bednaršek and Ohman 2015, Gattuso et al. 2015, Moya et al. 2016).
The genus Cuvierina is a remarkable group of shelled pteropods with relatively large (5.1-11.1 mm), straight, bottle-shaped shells (Janssen 2005). Ever since Cuvierina was described as a mollusc genus (as Cuvieria Rang, 1827, emended by Boas 1886), it has often been considered to consist of a single species, C.columnella (Rang, 1827), the type species of the genus by monotypy. The first taxonomic division within the genus came with the description of a second Cuvierina species, introduced as Cuvieriaurceolaris (Mörch, 1850), but in later literature it was often interpreted as a form or subspecies of C.columnella (e.g., Tesch 1913, Van der Spoel 1967, Rampal 1975). A third form, Cuvierinacolumnellaf.atlantica, was described by Van der Spoel (1970), and validated as a taxon of the species group by Bé et al. (1972). Bé and Gilmer (1977) interpreted the morphological differences between the three taxa as infraspecific variability. Contrarily, Rampal (2002) distinguished these taxa as independent species but introduced the taxon C.spoeli to replace the taxonomically invalid Cuvierinacolumnellaf.atlantica. Because the holotype of C.spoeli was from the Indian Ocean, where C.atlantica is absent, it rather represented C.columnella and was rejected as a valid species by Janssen (2005). Two further extant species, C.cancapae and C.pacifica, were described by Janssen (2005).
According to the most recent taxonomic revision of Cuvierina, five extant species were assigned to two subgenera based on shell morphology and supposed lineages of fossil occurrences since the early Miocene (Janssen 2005, 2006). The subgenusCuvierinas. str. consisted of C.atlantica, C.columnella, and C.pacifica, which are characterised by relatively slender, cylindrical shells, triangular rather than kidney-shaped apertures and the presence (C.columnella) or absence (C.atlantica, C.pacifica) of micro-ornamentation. Two geographical varieties were recognised within C.pacifica, one from the North Pacific and the other from the South Pacific, but were not formally introduced as new species. The subgenusUrceolarica, containing C.cancapae and C.urceolaris, is characterised by more inflated, bottle-shaped rather than cylindrical shells, pronounced micro-ornamentation, and kidney-shaped rather than triangular apertures.
All extant Cuvierina species are restricted to the surface layers of tropical and subtropical waters from ~45°N to ~40°S. In the Atlantic Ocean, C.atlantica occurs in the subtropical gyres and C.cancapae is found in tropical waters. In the Indian Ocean, C.columnella is found in the southern subtropical zone and C.urceolaris occurs in tropical waters and further south along Madagascar towards South Africa. Cuvierinacolumnella and C.urceolaris also occur in the Pacific Ocean along with C.pacifica (Janssen 2005, Burridge et al. 2015).
Burridge et al. (2015) examined the diversity, distribution, and evolution of Cuvierina taxa using integrative geometric morphometric, molecular, and biogeographic methods. They confirmed that the five species described for Cuvierina species have significantly different shell shapes and that C.pacifica consists of two disjunct morphometric groups, registered as C.pacifica N and C.pacifica S in their study. Three genetic lineages were distinguished based on mitochondrial Cytochrome Oxidase I DNA: the Atlantic lineage with C.atlantica and C.cancapae, the Indo-Pacific lineage with C.columnella, C.urceolaris, and C.pacifica N, and the South Pacific lineage with C.pacifica S. A new taxonomic description of C.pacifica N is required because the holotype of C.pacifica has the shell shape of C.pacifica S.
Based on the findings of Janssen (2005) and the integrative approach of Burridge et al. (2015) the taxonomy of the genus Cuvierina is revised. The subgenera Cuvierinas. str. and Urceolarica are rejected, a new species, C.tsudai, is described from the Pacific Ocean, and the species description of C.pacifica is restricted to the South Pacific lineage. A taxonomic key is provided for the identification of Cuvierina species.
Methods
Two approaches were used to distinguish between C.tsudai and C.pacifica based on differences in shell shape. First, simple measurements of shell height and width, aperture diameters, and position of maximum shell width as applied to museum specimens by Janssen (2005) were used to distinguish between C.tsudai and C.pacifica. Second, geometric morphometric data of shell shapes in ventral and apertural orientations were used for 168 adult specimens of Cuvierina that were registered as C.pacifica N or C.pacifica S in Burridge et al. (2015). The specimens corresponded to museum specimens as identified and measured by Janssen (2005, N = 92), additional museum specimens (N = 24), and recently collected fresh specimens (N = 52). Geometric morphometric methods consisted of digitising shell outlines using tpsDig and tpsUtil (Rohlf 2006) to contain 76 ventral and 37 apertural semi-landmarks per shell, after which a generalised least square Procrustes superimposition was applied (GLS, Kendall 1977 in Zelditch et al. 2004) to rotate, translate, and scale the semi-landmark coordinates. A subsequent
thin-plate spline
(TPS) analysis (e.g., Zelditch et al. 2004) provided centroid sizes, a size measure depending on surface area, and multiple relative warp axes per specimen, containing information on shape. To describe the new species C.tsudai as well as to reject the validity of the Cuvierina subgenera,
Cytochrome Oxidase I mitochondrial
(COI) DNA and 28S ribosomal DNA sequence data from Burridge et al. (2015) were used.
Results and discussionDistinction between Cuvierinatsudai and C.pacifica
Cuvierinatsudai and C.pacifica are similar in size but have different shell shapes, COI mtDNA and 28S rDNA. Because of their Pacific distributions and similarities in shell size, C.tsudai and C.pacifica have to date been considered the same species. Although Janssen (2005) demonstrated their presence as morphological varieties within C.pacifica, the congruence between morphometric and genetic differentiation supports the separation into two species (Figs 1A–J and 2, fig. 4 in Burridge et al. 2015). Shell heights of C.tsudai specimens are between 7.2 and 8.8 mm, showing a large overlap with C.pacifica, which measures between 6.6 and 8.5 mm (Janssen 2005). However, in terms of shell shape, C.pacifica and C.tsudai are significantly different (fig. 29 lower left in Janssen 2005, Burridge et al. 2015). The shell of C.tsudai is wider (more inflated) than the slender and more cylindrical C.pacifica (Fig. 2). Cuvierinapacifica has a larger height/width-ratio between 3.25 and 3.96 (mean 3.50) compared to C.tsudai, which has a ratio between 2.77 and 3.46 (mean 3.14). The position of maximum shell width is located at 34-45% (mean 40%) of the shell height from the septum upwards for C.pacifica and at 33-42% (mean 37%) for C.tsudai (Janssen 2005). The aperture of C.tsudai is wider, more triangular and more concave on the ventral side than in C.pacifica. The overall shape variation is larger for C.tsudai than for C.pacifica (Fig. 2). The average pairwise genetic distance of COI mtDNA (658bp fragment) between C.tsudai (N = 16) and C.pacifica (N = 43) is 4.5%. The genetic variation of COI within C.tsudai is 1.6% compared to 0.8% within C.pacifica. The 28S rDNA fragment (965bp) of C.tsudai differs at least at one position compared with other Cuvierina species, except for C.columnella (Burridge et al. 2015).
Holotype and paratypes of C.tsudai and holotype of C.pacifica. A Holotype (RMNH.5004167) and B–I paratypes (RMNH.5004168-72) of C.tsudai and J holotype of C.pacifica (RGM 458.690) photographed in a ventral view. Photographs of RMNH.5004169-72 from Burridge et al. (2015); RMNH.5004167-68 taken by R. van der Hulst and RGM 458.692 taken by E.F. de Vogel, this study. RMNH = Naturalis Biodiversity Center, mollusc collection and RGM = Naturalis Biodiversity Center, fossil planktonic mollusc collection, Leiden.
Shape variation in C.tsudai and C.pacifica by means of
Relative Warp
(RW) data. Ordination of RW data of C.tsudai and C.pacifica for the first ventral and apertural RWs (N = 167 excluding 1 specimen with only one orientation). On the X-axis, RW1 depicts 78.26% of the total ventral shape variation. On the Y-axis, 69.43% of the apertural shape variation is explained by its RW1. Shape variations depicted by ventral and apertural RW1 (with subsequent RWs = 0) are shown.
https://binary.pensoft.net/fig/104313
The larger genetic and shell shape variation for C.tsudai compared to C.pacifica coincides with a much larger Pacific distribution and lower ecological specificity of C.tsudai. Cuvierinapacifica is restricted to the centre of the oligotrophic southern Pacific gyre and occupies a more specialised ecological niche based on
ecological niche modelling
(ENM) than C.tsudai (Burridge et al. 2015). This study used presence-only data and six uncorrelated environmental parameters, of which ocean surface temperature and chlorophyll a concentration were the most important. The distribution of C.tsudai was mostly explained by maximum monthly
sea surface temperatures
(SST) and near-surface chlorophyll a concentrations (both 30.8%). The distribution of C.pacifica was best explained by low maximum monthly chlorophyll a concentrations (57.1%).
Description of Cuvierinatsudai sp. n.
Superfamily Cavolinioidea Gray, 1840
Family Cuvierinidae Gray, 1840
Genus Cuvierina Boas, 1886 (= replacement name for Cuvieria Rang, 1827 non Lesueur & Petit, 1807, pl. 30 (Coelenterata)
Type species.Cuvieriacolumnella Rang, 1827, p. 323, pl. 45 figs 1–3, by monotypy.
AnimaliaThecosomataCuvierinidaeD8F17853-41CE-5311-B07C-CC36FA29D14BCuvierinatsudaihttp://zoobank.org/B33A28E9-BCDE-4F2B-9349-F3E18CCD87BEsp. n.CuvieriacolumnellaRang, 1827: 323 (partim).Cuvierinacolumnella: Boas 1886: 132, 217, pl. 6 fig. 95g (partim, non Rang); Rampal 2002: 214 (partim, non Rang).Cuvierinacolumnella(Rang, 1827)formacolumnella(Rang, 1827) – Van der Spoel 1967: 79 (partim, non Rang);Van der Spoel 1970: 120, fig. 19 (partim, non Rang).Cuvierina (Cuvierina) pacificaJanssen, 2005: 46 figs. 18-20 (partim, northern Pacific specimens only, non figs. 14-17 = C.pacifica).CuvierinapacificaN (Janssen, 2005): Burridge et al. 2015: 5, fig. 2.Holotype.
RMNH.5004167, also see Fig. 1A and Table 1.
Voucher and sampling information of type specimens of C.tsudai including the holotype of C.pacifica.
Museum voucher
Image voucher
Collection date
Latitude
Longitude
Cruise
Station
COI GenBank
28S GenBank
First studied
Holotype of C.tsudai
RMNH.5004167
C_PNE_SE1201_21_01
2012-05-15
8°47'N
158°49'W
SE1201
21
This study
Paratypes of C.tsudai
RMNH.5004168.1
C_PNE_SE1201_21_02
2012-05-15
8°47'N
158°49'W
SE1201
21
This study
RMNH.5004168.2
C_PNE_SE1201_21_03
2012-05-15
8°47'N
158°49'W
SE1201
21
This study
RMNH.5004168.3
C_PNE_SE1201_21_04
2012-05-15
8°47'N
158°49'W
SE1201
21
This study
RMNH.5004169.1
C_PNE_KH1110_08_01
2011-12-19
22°47'N
158°06'W
KH-11-10
8
KP292730
KP292636
Burridge et al. 2015
RMNH.5004169.2
C_PNE_KH1110_08_20
2011-12-19
22°47'N
158°06'W
KH-11-10
8
KP292748
KP292637
Burridge et al. 2015
RMNH.5004170
C_PNE_KM1109_02_02
2011-03-04
21°14'N
158°11'W
Kilo Moana 1109
2
KP292755
KP292639
Burridge et al. 2015
RMNH.5004171
C_PNE_KM1109_08_01
2011-03-06
21°20'N
158°22'W
Kilo Moana 1109
8
KP292759
KP292640
Burridge et al. 2015
RMNH.5004172
C_PNW_TMKT1020_05_01
2010-09-29
27°08'N
125°33'E
R/V Tansei-Maru KT-10-20
5
KP292766
KP292642
Burridge et al. 2015
ZMUC, not registered
Figure 18
1933-08-21
33°45'N
137°30'W
DANA
4794
Janssen 2005
ZMUC, not registered
Figure 19
1934-02-12
32°56'N
131°50'W
DANA
4807
Janssen 2005
ZMUC, not registered
Figure 20
1929-05-25
20°04'N
125°59'E
DANA
3718 V
Janssen 2005
Holotype of C.pacifica
RGM 458.692
Figure 15
1986-04/05
18°39'S
172°12'W
Manihiki Plateau Expedition
U351a
Janssen 2005
Type locality.
8°47'N, 158°49'W.
Paratypes.
See Fig. 1B–I and Table 1 for all specimen information. Three specimens from the type locality (RMNH.5004168); three specimens from the Zoological Museum of the University of Copenhagen, Denmark (ZMUC, not registered) illustrated by Janssen (2005, figs. 18–20); five specimens from four locations (RMNH.5004169–72) studied by Burridge et al. (2015, referred to as C.pacifica N therein). The latter five specimens have COI mtDNA and 28S rDNA sequences available at GenBank (see Table 1).
Additional material examined.
Specimens recorded as C.pacifica from the North Pacific Ocean in Janssen (2005: 49, 71), housed in the Muséum National d’Histoire Naturelle (MNHN, Paris, France) and ZMUC (Copenhagen, Denmark). Specimens from Burridge et al. (2015), referred to as C.pacifica N in Table S1 therein, with photographs deposited at the Dryad repository (https://doi.org/10.5061/dryad.7n1q4) and COI mtDNA (KP292730-72) and 28S rDNA sequences (KP292636-42) deposited at GenBank. These specimens are housed in Naturalis Biodiversity Center (Leiden, The Netherlands) and ZMUC (Copenhagen, Denmark). Registration numbers, if available, from Janssen (2005).
Diagnosis.
Shell moderately small, adult specimens 7.2–8.8 mm high, height/width-ratio 2.77–3.46 (mean 3.14), position of maximum shell width 33–42% (mean 37%) of shell height from septum upwards. Aperture triangular. No longitudinal micro-ornamentation.
Description.
The shell shape of Cuvierinatsudai differs from other Cuvierina species. Its shell height is smaller than in C.columnella, C.cancapae, and C.atlantica, but larger than in C.urceolaris, and of similar size compared to C.pacifica. The position of maximum shell width is distinctly higher than for C.columnella and C.atlantica and lower than for C.pacifica. It is more cylindrical in shape than the inflated (bottle-shaped) C.urceolaris but less cylindrical than C.atlantica and C.pacifica. It differs from C.urceolaris and C.cancapae by the absence of micro-ornamentation. It has a more triangular and wider aperture than C.urceolaris and C.pacifica (Fig. 3, Janssen 2005, Burridge et al. 2015).
Cuvierinatsudai has a wide, exclusively Pacific distribution between 36°N and 39°S, in which it co-exists with C.columnella, C.urceolaris, and C.pacifica. It has been found most often in the North Pacific, but also occurs in the South Pacific. It has not been found thus far in the central, oligotrophic parts of the South Pacific subtropical gyre, the southeast Pacific, the coral triangle west of the Philippines or southwest of Papua New Guinea.
Etymology.
Named after Atsushi Tsuda, professor in biological oceanography at the University of Tokyo, Japan, for sending us pteropod samples from the Pacific Ocean and in recognition of his services to the zooplankton research community.
Rejection of the subgenera in Cuvierina
Two subgenera of Cuvierina were described that supposedly evolved since the early Miocene (Aquitanian, 23 million years ago): Cuvierinas. str., with extant species C.atlantica, C.columnella, and C.pacifica, and Urceolarica with extant species C.cancapae and C.urceolaris (see Janssen 2005, 2006). They were based on distinguishing shell characteristics in fossil species such as the position of maximum shell width, aperture shape and presence or absence of micro-ornamentation. However, the morphology and molecular phylogenetic information of recent species are in conflict with this separation. Cuvierinacolumnella, typically a Cuvierinas. str. species, has distinct micro-ornamentation, which was considered one of the distinguishing characters of the subgenusUrceolarica. It was shown that there are three divergent and well-supported lineages based on genetic data: the Atlantic (C.atlantica and C.cancapae), Indo-Pacific (C.columnella, C.urceolaris and C.tsudai), and South Pacific (C.pacifica) lineages (fig. 4 in Burridge et al. 2015). Hence, we reject the two subgenera within Cuvierina.
Taxonomic key to Cuvierina pteropods
The following taxonomic key identifies adult Cuvierina pteropod species based on distinctive shell shape characteristics and shell sizes. Photographs of typical adult shells are shown in Fig. 3.
1
Micro-ornamentation present
2
–
Micro-ornamentation absent
4
2
Strongly inflated shell shape, shell height 5.1–6.7 mm
C.urceolaris
–
Moderately inflated or cylindrical shell shape, shell height 7.5–11.1 mm
3
3
Cylindrical shell shape, shell height 8.8–11.1 mm
C.columnella
–
Moderately inflated shell shape, shell height 7.5–9.3 mm
C.cancapae
4
Cylindrical shell shape and triangular aperture, shell height 6.7–10.5 mm
C.atlantica
–
Moderately inflated or cylindrical shell shape, triangular to kidney-shaped aperture, shell height 6.6–8.8 mm
5
5
Cylindrical shell shape and kidney-shaped aperture, shell height 6.6–8.5 mm
C.pacifica
–
Moderately inflated shell shape and triangular aperture, shell height 7.2–8.8 mm
C.tsudai
Conclusions
Morphometric, genetic, and biogeographic information has led to the introduction of a new species of the warm water pteropod genus Cuvierina and the rejection of its subgenera. We encourage a combined evidence approach of taxonomy to more accurately identify species boundaries and higher taxonomic relationships in planktonic gastropods. Accurate taxonomic identification is a prerequisite to assess to what extent species are affected by ocean changes and to potentially use them as bioindicators.
Acknowledgements
We thank A. Tsuda, H. Miyamoto, E. Goetze, D. Kobayashi, L. Giuseffi, and E. Norton for contributing specimens from the Pacific Ocean, R. van der Hulst and E.F. de Vogel for photographing the holotype and some paratypes of C.tsudai, and J. Goud and B. van der Bijl for adding the type material to the collections of Naturalis Biodiversity Center. Finally, we are grateful to Deborah Wall-Palmer, Maria Moreno-Alcántara and Nathalie Yonow for constructive comments on this manuscript.
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