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. 2020 Aug;86(3):186-200.
doi: 10.1093/mollus/eyaa001. Epub 2020 May 13.

An integrative approach to the systematics of the Berthella californica species complex (Heterobranchia: Pleurobranchidae)

Hessam Ghanimi  1 , Jeffrey H R Goddard  2 , Anton Chichvarkhin  3 , Terrence M Gosliner  4 , Dae-Wui Jung  1 , Ángel Valdés  1
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An integrative approach to the systematics of the Berthella californica species complex (Heterobranchia: Pleurobranchidae)

Hessam Ghanimi et al. J Molluscan Stud. 2020 Aug.

Abstract

Berthella californica (W. H. Dall, 1900) is a widespread species of heterobranch sea slug distributed across the North Pacific Ocean, from Korea and Japan to the Galapagos Islands. Two distinct morphotypes are observed in B. californica, which differ in external coloration, egg-mass morphology and geographic distribution (with the exception of a small range overlap in Southern California). Molecular and morphological data obtained in this study reveals that these two morphotypes constitute distinct species. The name B. californica (type locality: San Pedro, California) is retained for the southern morphotype, whereas the name Berthella chacei (J. Q. Burch, 1944) (type locality: Crescent City, California) is resurrected for the northern morphotype. Moreover, molecular phylogenetic analyses recovered B. californica as sister to Berthellina, in a well-supported clade separate from Berthella, suggesting that the classification of B. californica may need additional revision.

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Figures

Figure 1
Figure 1
Live animals and egg masses. A–D.Berthella californica. A. Specimen from Ventura, California (CPIC 1328). B. Specimen from Ventura, California (CPIC 1761). C. Two specimens with egg mass from San Diego County, California. D. Specimen from La Jolla, California. E–H.Berthella chacei. E. Specimen from Kamchatka, Russia. F. Specimen from Duxbury Reef, California (CASIZ 182207). G. Specimen from Sonyang-myeon, South Korea (CPIC 2119). H. Two specimens with egg mass from Point Lobos, California. Image credits: A, B, H, C. Hoover; C, K. Lee; D, J.R. Lance; E, A. Chichvarkhin; F, T. Gosliner; G, D.-W. Jung.
Figure 2
Figure 2
Map of the localities sampled for this study color coded by geographic region and morphotype (including final species names) of specimens collected. Type localities of the different species names indicated by shaded boxes.
Figure 3
Figure 3
A. Bayesian consensus tree of the concatenated 16S rRNA, COI, 18S rRNA and histone H3 dataset. Posterior probabilities from the Bayesian analysis and bootstrap values from the ML analysis are presented above and below each branch, respectively. B,C. Results of the ABDG analysis showing the distribution of pairwise p-distances (K2 model) between Berthella californica and B. chacei for COI (B) and 16S rRNA (C).
Figure 4
Figure 4
SEMs of the shells of Berthella californica and B. chacei. A,B. Specimen of B. californica from Ventura, California (CPIC 1761),. A. Dorsal view of the teleoconch. B. Detail of protoconch. C,D. Specimen of B. chacei from Cape Arago, Oregon (CPIC 1409). C. Dorsal view of the teleoconch. D. Detail of protoconch.
Figure 5
Figure 5
SEMs of the radular teeth and jaw elements of the specimen of Berthella californica from Ventura, California (CPIC 1328). A. Innermost teeth. B. Mid-lateral teeth. C. Outer teeth. D. Jaw elements.
Figure 6
Figure 6
Reproductive system of Berthella californica and B. chacei. A. Specimen of B. californica from Ventura, California (CPIC 1328). B. Specimen of B. chacei from Sonyang-myeon, South Korea (CPIC 2119).
Figure 7
Figure 7
Type specimens. A,B. Shell of a syntype of Pleurobranchus californicus (CASIZ 064302); dorsal view (A), ventral view (B). C,D. Shell of a syntype of P. californicus (USNM 107893); dorsal view (C), ventral view (D). E,F. Shell of a syntype of P. chacei (CASIZ 065576); dorsal view (E), ventral view (F).
Figure 8
Figure 8
SEMs of the radular teeth and jaw elements of the specimen of Berthella chacei from Sonyang-myeon, South Korea (CPIC 2119). A. Innermost teeth. B. Mid-lateral teeth. C. Outer teeth. D. Jaw elements.
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