The North Pacific nudibranch species Triopha catalinae (Cooper, 1863), also known as the clown nudibranch, includes two distinct morphotypes: the trans-Pacific morphotype, known from South Korea to Southern California, and the eastern Pacific-only morphotype from Southeast Alaska to Baja California. We tested the hypothesis that Triopha catalinae is a species complex by applying an integrative taxonomic approach that included (1) phylogenetic analyses of the mitochondrial 16S and COI, and the nuclear Histone H3 genes; (2) haplotype network analysis based on COI sequences; (3) Automatic Barcode Gap Discovery (ABGD) species delimitation analysis based on 16S and COI sequences; and (4) comparative internal and external morphological studies. Specimens of two morphotypes were found to be genetically distinct; they clustered into two well-supported clades in the phylogenetic analyses and two groups in the TCS haplotype network. Moreover, these two groups displayed morphological differences in the dorsal tubercles and radula structure: the trans-Pacific morphotype specimens possess relatively small and dendritic dorsal tubercles, two rows of arborescent tubercles on the dorso-lateral appendages of larger individuals, and radular formula 19–24 × (9–12.5–10.1.5–10.9–12). Specimens of the eastern Pacific-only morphotype have relatively large, conical or rounded dorsal tubercles, and radular formula 48–79 × (16–18.17–33.1.17–33.16–18). Finally, the ABGD analysis confirmed that these two morphotypes constitute different species. A review of the literature (including original descriptions) and available type material revealed that Triopha modesta Bergh, 1880 and T. catalinae are the valid names for the trans-Pacific and eastern Pacific-only morphotype, respectively.

北太平洋裸udi科物种Triopha catalinae（Cooper，1863），也被称为小丑裸udi科，包括两种不同的形态型：从南韩到南加州的跨太平洋形态型，以及从阿拉斯加东南到南太平洋到东太平洋的唯一形态型。下加利福尼亚州。我们检验了Triopha catalinae的假说是通过应用综合分类学方法（包括（1）对线粒体16S和COI以及核组蛋白H3基因的系统发育分析）而形成的物种复合体；（2）基于COI序列的单倍型网络分析；（3）基于16S和COI序列的自动条形码间隙发现（ABGD）物种定界分析；（4）比较内部和外部形态学。发现两种形态型的标本在遗传上是不同的。他们在系统发育分析中分为两个支持良好的进化枝，在TCS单倍型网络中分为两组。此外，这两组在背侧结节和小弓结构上显示出形态学差异：跨太平洋形态型标本具有相对较小的树突背结节，较大个体的背外侧附肢上有两排树状结节，胚根公式为19–24×（9–12.5–10.1.5–10.9-12）。仅东部太平洋形态型的标本具有相对较大，圆锥形或圆形的背侧结节，并且胚状公式为48–79×（16–18.17–33.1.17–33.16–18）。最后，ABGD分析证实这两个形态型构成不同的物种。查阅文献（包括原始描述）和可用的类型材料后发现，Triopha modesta Bergh，1880和T. catalinae分别是跨太平洋和仅东部太平洋形态型的有效名称。