Systematic analysis of the caridean shrimp superfamily Pandaloidea (Crustacea: Decapoda) based on molecular and morphological evidence

Abstract

One of the systematically controversial superfamilies in Caridea is the predominately deep-sea or cold water Pandaloidea, largely because this species-rich group of nearly 200 species in 25 genera exhibits a very high diversity of body forms and ecology. Although the relationships amongst the taxa within Pandaloidea have been repeatedly discussed based on morphology, no comprehensive molecular phylogeny exists. In this study, we present the first molecular phylogeny of the group, based on a combined dataset of two mitochondrial (12S and 16S rRNA) and six nuclear (ATP synthase β-subunit, enolase, glyceraldehyde-3-phosphate dehydrogenase, histone 3, phosphoenolpyruvate carboxykinase and sodium-potassium ATPase α-subunit) markers, based on 62 species (about 1/3 of known biodiversity) in 22 genera (88% of genera) of two pandaloid families (Pandalidae, Thalassocarididae) and outgroups from seven other caridean families. With generally high support, the relationships within the clade are fully resolved. Pandalidae is shown to be paraphyletic with Thalassocarididae deeply nested within as a monophyletic group, and the latter is herein considered to be a synonym of Pandalidae. Five major clades are recovered, with the shallow water genera Anachlorocurtis, Chlorocurtis, Chlorotocella and Miropandalus forming a sister clade to the remaining genera. At the genus level, the phylogeny indicates Plesionika, Heterocarpus and Pandalus to be not monophyletic. The validity of Pandalopsis, Stylopandalus and Calipandalus is challenged and these genera are considered herein to be junior synonyms of Pandalus (Pandalopsis) and Plesionika (Stylopandalus and Calipandalus). Although not fully resolved, some evidence potentially considers Nothocaris to be a valid genus. Ancestral State Reconstruction successfully recovered 15 synapomorphies for the major clades, with 11 of them reported to be of systematic significance for the first time.

Molecular confirmation and description of the larval morphology of Thalassocaris lucida (Dana, 1852) (Decapoda, Caridea, Pandaloidea)

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Fig. 1.Maximum likelihood phylogenetic tree constructed by IQ-TREE analysis from mitochondrial 16S rDNA segment (484–546 bp) on the present two larvae (indicated by arrows) using the most comprehensive sequence dataset for Pandaloidea molecular phylogeny (Liao et al ., 2019), with the adding of another 16S rDNA sequence of T. crinita (EU868712) available in GenBank and a new sequence from T. lucida (MN150471). Ultrafast bootstrap support values (UFBS) are indicated at the branches.

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“…The sequences obtained from the two larvae were added to the 16S rDNA dataset of the most comprehensive molecular phylogeny analysis on Pandaloidea published recently and covering 88% of the genera and about one-third of the known species (Liao et al ., 2019). The present two larvae formed a robust clade with Thalassocaris crinita but do not have a positive match for the species.…”

“…The present two larvae formed a robust clade with Thalassocaris crinita but do not have a positive match for the species. GenBank only has two 16S rDNA sequences of T. crinita (the other sequence, not included in Liao et al ., 2019, is EU868712) for the genus Thalassocaris . Therefore, the 16S rDNA segment of a specimen of another species T. lucida from Japan (CBM-ZC 7772) was sequenced and added to the dataset for analysis.…”

“…The final analytic dataset of 16S rRNA gene thus includes 66 Pandaloidea sequences and one of the 12 outgroups used in Liao et al . (2019), namely Saron marmoratus , was used as an outgroup. The dataset included 560 bp nucleotide length after the sequence alignment by MAFFT v.7 (Katoh & Standley, 2013).…”

“…Bate, 1888 is generally recognized as an independent caridean family, placed within superfamily Pandaloidea Haworth, 1825 (De Grave et al ., 2009; De Grave & Fransen, 2011). However, a recent phylogenetic analysis does not support the family status of Thalassocarididae and indicates that it should be incorporated within Pandalidae (Komai et al ., 2019; Liao et al ., 2019). Members of Thalassocarididae are restricted to the Indo-Pacific and represented only by four species in two genera (Chace, 1985; De Grave & Fransen, 2011): Chlorotocoides spinicauda (De Man, 1902), Thalassocaris crinita (Dana, 1852), Thalassocaris lucida (Dana, 1852) and Thalassocaris obscura Gopala Menon & Williamson (1971).…”