Three New Species of Placoneis Mereschkowsky (Bacillariophyceae: Cymbellales) with Comments on Cryptic Diversity in the P. elginensis—Group

Using genetic markers 18S V4 rDNA and rbcL and morphological investigation of the diatom genus Placoneis, we described three new species. The new species, Placoneis baikaloelginensis sp. nov., Placoneis subundulata sp. nov., Placoneis neohambergii sp. nov. were isolated from Russia (Lake Baikal) and Vietnam (waterbodies of Cát Tiên National Park (Đồng Nai Province) and Khánh Hòa Province). We examine relationships within the Cymbellales and show that the genera Placoneis, Paraplaconeis and Geissleria are phylogenetically independent. We discuss the importance of careful identification of strains used for phylogenetic analysis and we show the history of identification of several different Placoneis elginensis strains. After careful identification of Placoneis elginensis vouchers, we found that we have a few independent species. The question of cryptic or pseudocryptic species in this context is discussed.

Sleuthing cryptic Chromodorids (Mollusca, Nudibranchia): adding to Philippine marine biodiversity

The Verde Island Passage of the Philippines is renowned for its rich marine biodiversity and heterobranch mollusks are demonstrable models of that species richness of the region. Chromodorid nudibranchs represent a particularly rich taxon, with species of Chromodoris being one of the most iconic and abundant taxa in shallow water coral reef environments. Despite being one of the best-documented clades of nudibranch mollusks, recent work has shown that numerous cryptic and pseudocryptic species are abundant in the waters of the Coral Triangle region. This paper reviews the species richness and distribution of Chromodoris species in the Philippines and provides a description of a new species of Chromodoris from the region. Chromodoris alcalai Gosliner, n. sp. is named to honor Dr. Angel Alcala’s 90th birthday and his pioneering contributions to preserving the marine biodiversity of the Philippines. This species is most similar externally to C. dianae Gosliner and Behrens, 1998, with which it was erroneous lumped. Distinctness of molecular data, external morphology and coloration, and internal anatomical features clearly distinguish these two species. KEYWORDS: systematics, Nudibranchia, coral reefs, Indo-Pacific, Coral Triangle

How Many Sipunculan Species Are Hiding in Our Oceans?

Sipuncula, long considered a separate phylum, are now commonly included in the Annelida based on phylogenomic analyses. The sipunculan body consists of an unsegmented trunk and a retractable introvert, usually with a set of tentacles at its anterior end. Unlike other annelids, they have no chaetae, but the introvert is often adorned with proteinaceous hooks that can be important taxonomic characters. Other external taxonomic characters include the tentacles (number, shape and arrangement), body papillae and, in some cases, hardened shields, as well as length ratios. Many species require dissection for correct identification to reveal internal characteristics, such as introvert retractor muscles, nephridia and contractile vessels. Here we summarize the state of the current knowledge of species diversity in sipunculans. We emphasize molecular studies, conducted over the past two decades, that have revealed multiple complexes of cryptic or pseudocryptic species. It has become obvious that diversity is significantly higher than the current taxonomic scheme accounts for, but formal species descriptions are lagging behind. Although the major branches in the sipunculan phylogeny have become increasingly consolidated, the internal relationships within most branches are still in flux.

Integrative taxonomy resuscitates two species in the Lasioglossum villosulum complex (Kirby, 1802) (Hymenoptera: Apoidea: Halictidae)

Morphological and allozyme analyses suggested the occurrence of a pseudocryptic species in the Lasioglossum villosulum (Kirby, 1802) species complex (Hymenoptera: Halictidae). We analysed the morphology of more than 1500 specimens and the DNA barcode fragment of the cytochrome c oxidase subunit I (COI) of 102 specimens of this species complex from several Palaearctic countries. Our phylogenetic tree reconstructions, based on maximum likelihood and Bayesian inference revealed one clade corresponding to all specimens morphologically identified as Lasioglossum medinai (Vachal, 1895) and one divergent specimen morphologically identified as Lasioglossum berberum (Benoist, 1941). The other specimens, morphologically identified as L. villosulum, aggregated into at least three other lineages in our phylogenetic trees. The tree-based species delineations methods based on the Generalized Mixed Yule Coalescent (GMYC) model and the Bayesian Poisson Tree Process (bPTP) identified five to ten candidate species within the L. villosulum species complex, with L. medinai and L. berberum consistently recognized as separated from all other candidate species. Diagnostic morphological differences were found among L. medinai, L. berberum and the remaining specimens identified as L. villosulum. No diagnostic morphological differences were found to distinguish the different phylogenetic candidate species or lineages found within L. villosulum and L. medinai. Thus, both genetic and morphological approaches support the existence of L. medinai and L. berberum as distinct species from L. villosulum.

Batillipes pennaki Marcus, 1946 (Arthrotardigrada: Batillipedidae): deciphering a species complex

Batillipes pennaki has been considered a common and a cosmopolitan marine tardigrade species. However, the original diagnosis of this species is very incomplete, and consequently there is a high probability of incorrect records. Therefore, a comparative analysis of quantitative and qualitative morphological characters among eight different populations from the Atlantic basin was done in this study to investigate if B. pennaki is a complex of similar species, each with a restricted distribution range. The result of discriminant analyses showed clear morphometric differences between populations that were arranged into three main groups, distinguishing Western Atlantic populations, Eastern Atlantic populations and a Mediterranean population. Furthermore, the result of analyses of morphological structures revealed peculiarities of some traits with taxonomic relevance, such as leg IV sensory organs and primary clavae, consistent with the clusters revealed by quantitative data, allowing us to distinguish three different pseudocryptic species and supporting the hypothesis that B. pennaki is a species complex.

Morphological Distinction of Three Ammonia Phylotypes Occurring Along European Coasts

The high morphological variability observed in the genus Ammonia, together with its global distribution, led to the description of a plethora of species, subspecies, and varieties. Until now, many researchers used a limited number of (morpho-)species, and considered the numerous varieties as ecophenotypes. Recently, molecular studies show that these putative ecophenotypes are, in reality, well-separated genetically and should rather be considered as separate species. This study aims to investigate the morphological characteristics of three phylotypes (T1, T2, and T6) belonging to the genus Ammonia, encountered along European coasts. For this purpose, Ammonia specimens were sampled at 22 locations between 2014 and 2016 and were imaged using an environmental SEM (Scanning Electron Microscope). For 96 specimens, images of the spiral, umbilical, and peripheral sides were obtained and pore features were investigated using 1000x magnified images of the penultimate chamber on the spiral side. Sixty-one morphometric parameters were measured for each individual. To assign specimens to their respective phylotypes, we employed molecular analyses using SSU (Small Sub-Unit) rDNA fragments. A multivariate approach (Factorial Analysis of Mixed Data, FAMD), allowing the joint analysis of quantitative and qualitative measurements, was used to determine the most reliable morphometric parameters to discriminate the three phylotypes. Our results show that the use of only two morphological characteristics is sufficient to differentiate the three pseudocryptic species: the raised or flush character of the sutures on the central part of the spiral side and the mean pore diameter. These two criteria, which can be observed with a standard stereomicroscope, provide an efficient method to discriminate T1, T2, and T6 with at least 90% accuracy. We consider that there is still insufficient information to reliably assign previously defined formal scientific names to the three phylotypes, and therefore we recommend the continued use of phylotype designations T1, T2, and T6. Our results make it possible to study the distribution of these three pseudocryptic species (T1, T2, and T6) on the basis of stereomicroscope examination alone, which means these species can also be more easily recognized in dead/fossil assemblages. Among other things, this will allow verification in sediment cores of the putative recent introduction in European coastal areas of T6, which is often considered an exotic species originating from East Asia.

Revision of the Parasesarma guttatum species complex reveals a new pseudocryptic species in south-east African mangroves

Parasesarma De Man, 1895 is the most speciose genus in the family Sesarmidae (Decapoda: Brachyura: Thoracotremata). In the western Indian Ocean, Parasesarma is represented by five species only, although some genetic evidence suggests that P. guttatum could be a species complex comprising two cryptic species. Accordingly, P. guttatum is here split into two pseudocryptic species, and a new species, Parasesarma capensis, sp. nov., is described. P. capensis, sp. nov. fills the same ecological niche as P. guttatum south of the Mozambique Channel. While variation in mitochondrial DNA and morphological differences clearly distinguish the two species, there is no nuclear genetic variation. This may reflect a short history of reproductive isolation. The distinguishing morphological characters of the new species are the 13–15 rounded tubercles on the movable finger, the upper surface of the palm with three transverse crests (one regularly tuberculate and two pectinated), and the shape of the first gonopod. Phylogenetic inference analyses show a sister-species relationship between P. guttatum and P. capensis, sp. nov., and strongly suggest that at least two East African Parasesarma species need a taxonomic revision. The description of this new sesarmid species from the south-eastern African coast sheds new light on the overall biogeographic patterns and general biodiversity of this taxon within the western Indian Ocean.

Range extension for the region of sympatry between the nudibranchs Hermissenda opalescens and Hermissenda crassicornis in the northeastern Pacific

The mollusc nudibranch genus Hermissenda Bergh, 1879 was recently discovered to include three pseudocryptic species, dividing a single species H. crassicornis (sensu lato) into H. crassicornis Escholtz, 1831, H. opalescens J.G. Cooper, 1863, and H. emurai Baba, 1937. The species were distinguished by both genetic and morphological evidence, and the distribution of sampled animals suggested the three species had mostly distinct geographical ranges. Here, we report the presence of both H. crassicornis and H. opalescens in Barkley and Clayoquot Sounds, British Columbia, Canada, based on diagnostic characters and molecular data congruent with the differences described for these two species. This result extends the region of sympatry for the two species from northern California, USA, to, at least, Vancouver Island, British Columbia in 2016. Depending on how long this overlap has occurred, the possible northward expansion of H. opalescens would have implications for understanding the effects of short- or long-term environmental changes in ocean temperatures as well as complicating the interpretation of past neurobiological studies of H. crassicornis (sensu lato).