The first complete mitochondrial genome of Actinopyga from Actinopyga echinites (Aspidochirotida: Holothuriidae)

Barcoding (COI) Sea Cucumber Holothuria mammata Distribution Analysis: Adriatic Rare or Common Species?

The overexploitation of the western Pacific Ocean has expanded the sea cucumber fishery into new regions to supply the Asian market. In 2013, sea cucumbers were removed from the Croatian marine protected species list, and commercial fishery took place for a short period (2017-2018) in the Eastern Adriatic Sea. However, holothuroid species are difficult to distinguish. Holothuria mammata is a species that has rarely been reported in this region and strongly resembles the common species Holothuria tubulosa. This is the first study to assess the genetic diversity of sea cucumbers in the Adriatic Sea using genetic barcoding of the mitochondrial gene cytochrome c oxidase subunit 1 (COI). Specimens for barcoding were collected from the northern and central Adriatic, along with a specimen that had been previously identified as H. sp. cf. mammata based on its morphological characteristics. While genetic analyses showed identified this specimen as H. tubulosa, 30% of the collected specimens were genetically identified as H. mammata. These results call into question the historically accepted sea cucumber assemblage in the Adriatic Sea, which regarded H. mammata as a rare species and generally disregarded its presence in large census studies. Such species distribution data are extremely important in developing and monitoring a sustainable fishery.

Analysis of Complete Mitochondrial Genome of Bohadschia argus (Jaeger, 1833) (Aspidochirotida, Holothuriidae)

Bohadschia argu is a kind of sea cucumber with high economic value; it is the only undisputed species in the genus Bohadschia. In this study, the complete mitochondrial genome (mitogenome) of B. argus was acquired through high-throughput sequencing. The mitochondrial genome of B. argus was 15,656 bp in total length and contained a putative control region (CR) and 37 typical genes of animal mitochondrial genomes, including 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (rrnS and rrnL) and 22 transfer RNA genes (tRNA). The sizes of the PCGs ranged from 168 bp to 1833 bp, and all PCGs except nad6 were encoded on the heavy chain (H). Both rrnS and rrnL were also encoded on the H chain. Twenty-two tRNA genes had positive AT skew and GC skew. All tRNAs had a typical cloverleaf secondary structure except for trnI, in which an arm of dihydrouridine was missing. B. argus shared the same gene arrangement order (the echinoderm ground pattern) as other species in Aspidochirotida. Phylogenetic analysis clearly revealed that B. argus belongs as a member of the Holothuriidae, and it is closely related to members of Actinopyga and Holothuria.

The first complete mitochondrial genome of Phyrella fragilis (Mitsukuri & Ohshima in Ohshima, 1912) (Dendrochirotida: Phyllophoridae)

Echinoderms (Echinodermata) are morphologically diverse and ecologically important groups of marine invertebrate, many of which are key components of local benthic ecosystem. However, due to morphological plasticity and limited molecular phylogenetic studies, the taxonomic histories in echinoderms have not been completely resolved. The phylogenetic relationships of Phyllophoridae genera and species remain controversial and many species are incorrectly assigned within genus Phyrella. In this study, we report the first complete mitochondrial genome of Phyrella from Phyrella fragilis. The mitogenome has 15,910 base pairs (64.32% A + T content) and is made up of a total of 37 genes (13 protein-coding, 22 transfer RNAs and 2 ribosomal RNAs), plus a putative control region. This study will provide useful genetic data for future phylogenetic and taxonomic classification of Phyllophoridae.

Characterization and phylogenetic analysis of the complete mitochondrial genome of Actinopyga lecanora (Jaeger, 1833) (Holothuriida: Holothuriidae)

The white-bottomed sea cucumber, Actinopyga lecanora, is a valuable inshore fisheries resource which is famous for its high nutrition and pharmacological compounds. However, due to morphological plasticity and limited molecular phylogenetic studies, the taxonomic histories in the genus Actinopyga have not been completely resolved yet. Moreover, there remains a complex of cryptic species within Actinopyga, many of which are incorrectly assigned within the family Holothuriidae. In this study, we report the complete mitochondrial genome of A. lecanora. The mitogenome has 15,568 base pairs (63.40% A + T content) and is made up of a total of 37 genes (13 protein-coding, 22 transfer RNAs and 2 ribosomal RNAs), plus a putative control region. This study offers useful mitogenome data for future phylogenetic and taxonomic classification of Holothuriidae.