A molecular phylogeny of the Indo-West Pacific species of Haloa sensu lato gastropods (Cephalaspidea: Haminoeidae): Tethyan vicariance, generic diversity, and ecological specialization

Systematic revision of the Indo-West Pacific bubble-snails of the genus

The genus Haloa includes dull-coloured species of haminoeid snails inhabiting tidal and shallow waters of the tropical and sub-tropical Indo-West Pacific. This paper reports on the diversity and systematics of Haloa based on the phylogenetic hypothesis generated by Oskars and Malaquias (2019) and on the morphological study of specimens. Shells, external features and anatomical characters from the jaws, radula, gizzard plates and male reproductive system were studied by optical and scanning electron microscopy. The molecular species delimitation method Automatic Barcode Gap Discovery, using DNA sequences of the cytochrome c oxidase subunit I gene, was implemented to aid delimiting candidate species. Thirteen species were recognised as valid, including two new to science, namely Haloa cobbi, sp. nov. and Haloa eora, sp. nov., and one unnamed species herein referred to as Haloa sp. 1. Species depict intraspecific variability in their colouration and little character displacement in their anatomy. Shells are of limited taxonomic use; only details of the male reproductive system (e.g. fundus) and the DNA were truly diagnostic. Three species have an Indo-West Pacific distribution and three are restricted to the Indian Ocean. The remaining seven species occur in the Western and Central Pacific Ocean, three of them having geographical ranges restricted to offshore islands.

A global phylogeny of the deep-sea gastropod family Scaphandridae (Heterobranchia: Cephalaspidea): redefinition and generic classification

We present the most comprehensive phylogeny of a globally distributed deep-sea group of gastropods published to date including over 80% of the recognized diversity of the family Scaphandridae. The definition and taxonomic composition of the Scaphandridae has been hampered by the lack of a sound phylogenetic framework and definition of synapomorphic traits. We used a combination of molecular phylogenetics (Bayesian Inference and Maximum Likelihood) based on five gene markers (cytochrome c oxidase subunit I, 12S rRNA, 16S rRNA, 18S rRNA, and 28S rRNA) and morpho-anatomical characters to redefine the Scaphandridae and its genera. A new classification is proposed with the three genera Nipponoscaphander, Sabatia, and Scaphander. Main differences between genera lie on the shells (shape, parietal callus, spire) and male reproductive system (prostate). The species Hamineobulla kawamurai is reassigned to the closely related family Eoscaphandridae, currently defined mostly based on pleisiomorphic traits. Biogeographically the genus Nipponoscaphander is restricted to the Indo-West Pacific; Sabatia is mostly circumscribed to the Indo-West Pacific, but has one lineage present in the north Atlantic Ocean. Polyphyly across ocean realms prevails in the specious and globally distributed genus Scaphander with multiple speciation events between Indo-Pacific and Atlantic lineages but also with several episodes of cladogenesis within realms. Two rare cases of species with a broad distribution spanning the Indo-West Pacific and Atlantic realms are confirmed (S. meridionalis and S. nobilis).

Global diversification and evolutionary history of onchidiid slugs (Gastropoda, Pulmonata)

Many marine species are specialized to specific parts of a habitat. In a mangrove forest, for instance, species may be restricted to the mud surface, the roots and trunks of mangrove trees, or rotting logs, which can be regarded as distinct microhabitats. Shifts to new microhabitats may be an important driver of sympatric speciation. However, the evolutionary history of these shifts is still poorly understood in most groups of marine organisms, because it requires a well-supported phylogeny with relatively complete taxon sampling. Onchidiid slugs are an ideal case study for the evolutionary history of habitat and microhabitat shifts because onchidiid species are specialized to different tidal zones and microhabitats in mangrove forests and rocky shores, and the taxonomy of the family in the Indo-West Pacific has been recently revised in a series of monographs. Here, DNA sequences for onchidiid species from the North and East Pacific, the Caribbean, and the Atlantic are used to reconstruct phylogenetic relationships among Onchidella species, and are combined with new data for Indo-West Pacific species to reconstruct a global phylogeny of the family. The phylogenetic relationships of onchidiid slugs are reconstructed based on three mitochondrial markers (COI, 12S, 16S) and three nuclear markers (28S, ITS2, H3) and nearly complete taxon sampling (all 13 genera and 62 of the 67 species). The highly-supported phylogeny presented here suggests that ancestral onchidiids most likely lived in the rocky intertidal, and that a lineage restricted to the tropical Indo-West Pacific colonized new habitats, including mudflats, mangrove forests, and high-elevation rainforests. Many onchidiid species in the Indo-West Pacific diverged during the Miocene, around the same time that a high diversity of mangrove plants appears in the fossil record, while divergence among Onchidella species occurred earlier, likely beginning in the Eocene. It is demonstrated that ecological specialization to microhabitats underlies the divergence between onchidiid genera, as well as the diversification through sympatric speciation in the genera Wallaconchis and Platevindex. The geographic distributions of onchidiid species also indicate that allopatric speciation played a key role in the diversification of several genera, especially Onchidella and Peronia. The evolutionary history of several morphological traits (penial gland, rectal gland, dorsal eyes, intestinal loops) is examined in relation to habitat and microhabitat evolutionary transitions and that the rectal gland of onchidiids is an adaptation to high intertidal and terrestrial habitats.

A DNA barcode library for mangrove gastropods and crabs of Hong Kong and the Greater Bay Area reveals an unexpected faunal diversity associated with the intertidal forests of Southern China

Background

Mangroves are tropical and subtropical intertidal forests colonising sheltered coasts across the world. They host a unique faunal community, dominated by brachyuran crabs and gastropods. These invertebrates strongly contribute to the functionality of the entire forest. The reliable assessment of mangrove faunal diversity is, thus, a crucial step for efficient management and conservation plans, but it is hindered by difficulties in species identification. Here we provide a verified DNA barcode library for brachyuran crabs and gastropods inhabiting the mangroves of the Greater Bay Area, Southern China. In particular, we collected and morphologically identified 1100 specimens of mangrove associated brachyuran crabs and gastropods. The partial sequences of the mtDNA cytochrome oxidase subunit I gene were obtained from 275 specimens. Barcode sequences were then used to delineate Molecular Operational Taxonomic Units (MOTUs), employing three different delimitation methods: the automatic barcode gap discovery (ABGD) method, the general mixed Yule coalescent (GMYC) model and a Bayesian implementation of the Poisson tree processes (bPTP) model.

Results

By integrating DNA barcodes with morphology, we identified 44 gastropod species and 58 brachyuran species associated with Hong Kong mangroves, with five and seven new records, for gastropods and crabs, respectively, for the Greater Bay Area. The delineation of MOTUs based on barcode sequences revealed a strong congruence between morphological and molecular identification for both taxa, showing the high reliability of the barcode library.

Conclusions

This study provides the first reference barcode library for mangrove-associated macrobenthic fauna in the Greater Bay Area and represents a reliable tool to management and conservation plans. Our molecular analyses resolved long lasting taxonomic misidentifications and inconsistencies and updated the knowledge on the geographical distribution of Asian mangrove associated fauna, ultimately highlighting a level of biodiversity higher than previously thought for Southern China.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-021-01914-6.

An annotated checklist of sea slug fauna of Gujarat coast, India

An annotated checklist of sea slugs from Gujarat coastal waters was prepared, based on published literature and field observations from 2014–2019.  Ninety-five species from 62 genera belonging to 29 families were recorded.  Species are listed with synonyms and distribution status.     

Systematic revision of the Indo-West Pacific colourful bubble-snails of the genus Lamprohaminoea Habe, 1952 (Cephalaspidea : Haminoeidae)

The genus Lamprohaminoea includes species of colourful haminoeid snails associated with coral reefs and rocky shores in the tropical Indo-West Pacific. In this work, we revise the diversity and systematics of Lamprohaminoea species based on a phylogenetic hypothesis and on a detailed morphological analysis of specimens. Shells, external features of the animals and anatomical characters from the jaws, radula, gizzard plates, and male reproductive system were studied by optical and scanning electron microscopy. Additionally, a molecular species delimitation analysis based on the Automatic Barcode Gap Discovery method using DNA sequences of the cytochrome c oxidase subunit I was implemented. Five species were recognised, three of them new to science, namely L. cymbalum, L. ovalis, L. vamiziensis sp. nov., L. evelinae sp. nov., and L. mikkelsenae sp. nov. Morphologically, these species can be separated by subtle differences of their external colouration and by features of the male reproductive system. Lamprohaminoea vamiziensis sp. nov. is known only from the western Indian Ocean and L. evelinae sp. nov., from the west Pacific, whereas the other three occur across the Indo-West Pacific realm.