Molecular approaches uncover cryptic diversity in intertidal Ligia isopods (Crustacea, Isopoda, Ligiidae) across the southern Africa coastline

Cryptic diversity and phylogeographic patterns of Deto echinata (Isopoda: Detonidae) in southern Africa

Recent phylogeographic studies of poorly-dispersing coastal invertebrates in highly biodiverse regions have led to the discovery of high levels of cryptic diversity and complex phylogeographic patterns that suggest isolation, geological, and ecological processes have shaped their biodiversity. Studies of southern African coastal invertebrates have uncovered cryptic diversity for various taxa and phylogeographic patterns that, although sharing some similarities across taxa, do differ. These findings underscore the need for additional studies to better understand the biodiversity levels, distributional patterns, and processes responsible for producing coastal biodiversity in that region. The coastal isopod Deto echinata is of particular interest, as its complex taxonomic history, poor dispersal capabilities, and broad geographic distribution suggest the potential for cryptic diversity. We use mitochondrial and nuclear sequences to characterize D. echinata individuals from localities ranging from northern Namibia to Glentana, about 2,500 km along the coastline on the south coast of South Africa. These are used to assess whether D. echinata harbors cryptic genetic diversity and whether phylogeographic distributional patterns correlate with those previously documented for other coastal isopods in the region. Analysis of mitochondrial and nuclear sequences revealed two deeply-divergent lineages that exhibit a distributional break in the Cape Peninsula region. These findings suggest D. echinata is a cryptic species complex in need of taxonomic revision and highlight the need for further taxonomic and phylogeographic studies of similarly poorly-dispersing coastal invertebrates in southern Africa.

Redescription of Tylos maindroni Giordani Soika, 1954 (Crustacea, Isopoda, Oniscidea) based on SEM and molecular data

The woodlouse species Tylos maindroni Giordani Soika, 1954 (Crustacea, Isopoda, Oniscidea) is redescribed from the Persian Gulf based on light and scanning electron microscopy. This species differs from the closely related T. exiguus Stebbing, 1910, from the Red Sea (coasts of Sudan and Eritrea), and Socotra Island, by pereopod 1 superior margin without a prominent projection and pleopod 2 endopod 2.3 times as long as exopod, vs. 3.6 in T. exiguus. A distribution map for T. maindroni is provided. In addition, we studied the molecular differentiation of five populations of T. maindroni from the Persian Gulf, based on partial cytochrome c oxidase subunit I (COI) gene sequences. The results revealed low levels of population structuring between the analyzed populations.

A comprehensive evaluation of the potential of semiterrestrial isopods, Ligia exotica, as a new animal food

The semiterrestrial isopod, Ligia exotica represents one of the oldest documented species introductions of marine organisms and is known as an intermediate form between marine and strictly terrestrial isopods. In order to explore the potential value of Ligia as an animal food source, this study focused on the growth rate under laboratory rearing conditions and conducted a detailed analysis of the overall nutrient content of the species in comparison to two other marine food media (krill and fish meal). Evaluation of the growth rate of juveniles suggests it is a relatively fast-growing species of the Ligiidae family. The essential amino acids content Ligia meal is the lowest amongst the three studied media but the proportion of flavor amino acids, and in particular taurine, was higher. The most restricted amino acids of isopod meal are methionine and cysteine. The significantly unbalanced amino acid composition of Ligia meal may affect the absorption and utilization by consumers. In terms of fatty acids, the total polyunsaturated fatty acids in the isopod is very low. A total of 12 vitamins were examined. The VK_1, VE, VB₂, VB₃, VB₅ content of isopod meal were significantly higher than those of krill meal and fish meal. Similarly, most of the 11 mineral elements are highest in the isopod meal. Ligia therefore offers potential as an alternative natural food source in animal given the growth rate under culture and the overall nutrient content. But Ligia collected in most of the field would be deemed unfit for human consumption because of the relatively low nutritional value and heavy metal content exceeding the provided standard. Further study is warranted to elucidate the biological characteristics of isopods and how its diet is reflected in its nutritional value to consumers.

Genetic and phylogenetic structure of Hynobius quelpaertensis, an endangered endemic salamander species on the Korean Peninsula

BACKGROUND

The Korean Peninsula is a small but unique area showing great endemic Hynobius diversity with H. quelpaertensis, H. yangi, H. unisacculus and three species candidates (HC1, HC3 and HC4). H. quelpaertensis is distributed in the southern part and in Jeju Island, while the remaining species have extremely narrow distributions.

OBJECTIVES

To examine the genetic structure of H. quelpaertensis and the phylogenetic placement in Hynobius.

METHODS

Three mitochondrial and six microsatellite loci were genotyped for 204 Hynobius quelpaertensis, three H. leechii, three H. yangi, three HC1, two H. unisacculus, three HC3, three HC4 and ten Japanses H. lichenatus.

RESULTS

A high level of mitochondrial diversity was found in H. quelpaertensis. Our mitochondrial data showed evidence of a historical link between inland and Jeju Island despite the signature of founder effect likely experienced by the early island populations. However, our microsatellite analysis showed the fairly clear signature of isolation history between in- and island populations. Upon phylogenetic analysis, H. quelpaertensis, H. unisacculus and HC1 formed a cluster, whereas H. yangi belonged to a separate cluster. HC3 and HC4 were clustered with either H. quelpaertensis or H. yangi depending on the locus used.

CONCLUSION

Our results show at least partially the historical imprints engraved by dispersal of Korean endemic Hynobius during Pleistocene, potentially providing a fundamental basis in determining the conservation units and finding management strategies for these species.

Molecular taxonomy of endemic coastal Ligia isopods from the Hawaiian Islands: re-description of L. hawaiensis and description of seven novel cryptic species

Past phylogeographic work has shown Ligia hawaiensis, a coastal isopod species endemic to the Hawaiian Islands, to be a paraphyletic complex of several highly genetically divergent yet morphologically cryptic lineages. Despite the need for a taxonomic revision of this species, the lack of morphological differentiation has proven an impediment to formally describe new Ligia species in the region. Molecular characters and species delimitation approaches have been successfully used to formally describe cryptic species in other crustacean taxa, suggesting they may aid taxonomic revisions of L. hawaiensis. Herein, various distance- and tree-based molecular species delimitation approaches are applied on a concatenated dataset comprised of both mitochondrial and nuclear gene sequences of L. hawaiensis and L. perkinsi, a terrestrial species endemic to the Hawaiian archipelago. Results of these analyses informed a taxonomic revision leading to the redescription of L. hawaiensis and the description of seven new cryptic species on the basis of molecular characters: L. dante, L. eleluensis, L. honu, L. kamehameha, L. mauinuiensis, L. pele, and L. rolliensis. These coastal Ligia species from the Hawaiian archipelago appear to be largely limited to single islands, where they appear largely constrained to volcanic rift zones suggesting allopatric events at local scales may drive diversification for poorly dispersing organisms in the Hawaiian coastlines. Additional work remains needed to fully assess the role of said events; however, the description of these novel species underscore their potential to aid in studies of local diversification of marine organisms in Hawai'i. Lastly, this represents the first application of molecular taxonomic approaches to formally describe genetic lineages found in Ligia isopods as species, underscoring the promise these methods hold to taxonomic revisions in other species in the genus shown to harbor cryptic genetic lineages.