Malacology/ Marine Invertebrates

A new Phyllodesmium species, P. jakobsenae nov. sp., is described from North Sulawesi, Indonesia. The new species is associated with the octocoral Xenia sp. Its external morphology is similar to other Phyllodesmium species inhabiting Xenia colonies, especially to P. hyalinum Ehrenberg, 1831, but cerata morphology and color, tooth and jaw morphology as well as the digestive glandular branching system within the cerata clearly distinguishes this new species. Behavioural notes are given and spawning is described. Active photosynthesis due to zooxanthellae (Dinophyceae of the genus Symbiodinium) in the digestive gland was measured in situ with a Diving-PAM (Pulse Amplitude Modulated Fluorometer). Experiments with P. jakobsenae indicate a symbiotic relationship with zooxanthellae at least for some days. These results are discussed in comparison to another Xenia inhabiting species, Phyllodesmium crypticum Rudman, 1981. Histological investigation of the digestive diverticula within the cerata of the new species also indicate a high effectiveness of the symbiosis.

Previous studies on kleptoplasty in sacoglossans have used different methodology to investigate how long the sacoglossans are able to keep photosynthetically active (functional) chloroplasts. In this study we have used Pulse Amplitude Modulated Fluorometry to measure the quantum yield of charge separation in photosystem II in dark acclimated cells (F IIe ) to detect the status of photosynthetic activity. Seven species of sacoglossa, Plakobranchus ocellatus, Elysia timida, Elysia sp, Elysia tomentosa, Thuridilla carlsoni, T. lineolata and Elysiella pusilla, were investigated regarding their ability to retain functional chloroplasts (RFC). The results show three different levels of RFC's where P. ocellatus has the longest RFC for more than 11 months, E. timida with a RFC 1/4 than P. ocellatus (almost 3 months) and the rest with RFC's down to 1/22 of P. ocellatus (up to 15 days). Based on these results, and compared to previous studies, eight different levels of retention abilities of non-functional and functional chloroplasts in sacoglossans are proposed. As far as we know, this is a novel method studying chloroplast functionality in sacoglossans.

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Long-term retention of zooxanthellae in five different species belonging to two different nudibranch groups (Aeolidoidea and Dendronotoidea) was investigated. Specimens belonging to the species Phyllodesmium briareum, Phyllodesmium colemani, Phyllodesmium longicirrum, Pteraeolidia ianthina and Melibe engeli were cultivated for 70-270 days under various feeding conditions, and photosynthetic activity was analysed by taking pulse amplitude modulated (PAM) fluorometer measurements. All five species showed stable symbiosis and long-term retention of zooxanthellae. Interspecific differences are discussed. Morphological adaptations for housing zooxanthellae in the digestive glandular system were investigated and documented by histological means.

Incorporation of photosynthetic units has been investigated under the assumption of them representing a key character that enhanced speciation and led to an adaptive radiation. Two independent opisthobranch systems were chosen to test this hypothesis: the nudibranch genus Phyllodesmium living in mutualistic symbiotic relationship with the dinoflagellate Symbiodinium, and the taxon Sacoglossa (herbivorous seaslugs) sequestering and partly incorporating healthy chloroplasts from chlorophytes. Photosynthetic activity of various members of both taxa was measured under starving conditions and efficiency of incorporation studied by analysing yield values of photosynthesis. For both systems, certain trends were observed: clades exhibiting a functional incorporation of photosynthetic units (i.e., these units were not digested after sequestration) are about five times more species rich than their sister taxon. When comparing the species, observed efficiency differed. Furthermore, morphological adaptations to higher efficiencies could be identified in long-term retention forms (e.g., Phyllodesmium longicirrum with a highly branched digestive gland in the dorsal appendages, and sacoglossan Plakobranchus ocellatus with special ridges on the dorsal side, housing most of the incorporated chloroplasts). Nevertheless, other factors driving evolution of these clades cannot be excluded; they might even be linked with the investigated key character. These are, e.g., food switch and/or incorporation of secondary metabolites for defense.

In this study, we examined two non-scleractinian taxa, the rare nudibranch Phyllodesmium lizardensis and Bayerxenia sp., the octocoral on which the nudibranch lives and feeds, to investigate the effect of experimental heat stress on their symbioses with Symbiodinium. Bleaching has not been studied in nudibranchs. Bayerxenia sp. belongs to the alcyonacea family Xeniidae, members of which are known to be heat sensitive, but the genus has never been subject to heat stress experiments or bleaching observations. While qPCR did not reveal any changes to the symbiont community composition, the two host species responded differently to increased temperature. There were changes in the relative proportion of tissue types in Bayerxenia sp., but these were not attributable to the temperature treatment. Bayerxenia sp. exhibited no changes in cellular structure (apoptosis or cell necrosis), or symbiont functioning, cell size, density, or cladal community structure. On the other hand, the host, P. lizardensis, experienced tissue loss and symbiont densities decreased significantly with the majority of the remaining symbiont cells significantly degenerated after the heat stress. This decrease did not influence symbiont community composition, symbiont cell size, or photosynthetic efficiency. While the bleaching process in nudibranchs was demonstrated for the first time, the physiological and molecular pathways leading to this response still require attention.

The genus Rhagada is the second most diverse camaenid genus in Australia. We examined anatomical and mitochondrial characters of previously unidentified material from the Kimberley that was earmarked to potentially represent new species in recently published molecular phylogenetic studies. Our comparisons revealed that specimens from Gibbings Island ('R. sp. Gibbings') were morphologically and genetically most similar to Rhagada cygna from the Dampier Peninsula. Hence, 'R. sp. Gibbings' is considered to be identical to R. cygna. In addition, we found that R. cygna as so delimited is not clearly distinguished from the second species on the Dampier Peninsula, Rhagada bulgana. Both species differ rather subtly in anatomical and mitochondrial characters, indicating their close relationships and potentially incomplete evolutionary differentiation. Furthermore, we describe two new species based on comparative morphology and mitochondrial sequences: Rhagada worora n. sp. from the Prince Regent Reserve in the Kimberley and Rhagada karajarri n. sp. from Dampierland. The present study confirms that species in Rhagada are best identified by means of both morphological and molecular data.

Article Two new sacoglossan sea slug species (Opisthobranchia, Gastropoda): Ercolania annelyleorum sp. nov. (Limapontioidea) and Elysia asbecki sp. nov. (Plakobranchoidea), with notes on anatomy, histology and biology Abstract Two new sacoglossan species, belonging to the genus Ercolania Trinchese, 1872 (Ercolania annelyleorum sp. nov.) and the genus Elysia Risso, 1818 (Elysia asbecki sp. nov.) are described from Lizard Island, Great Barrier Reef, Australia. Anatomy of both species was reconstructed by analyzing histological serial sections. Radula morphology was investigated by using light microscopy and scanning electron microscopy. Sequence analyses (NeighborNet; sequence divergence) and tree reconstructions showed for both species their distinction from con-generic species, but also two distinct mitochondrial lines in the new Ercolania species. Adults as well as freshly hatched juveniles of E. annelyleorum sp. nov. have been found in clusters of the ulvophycean alga Boodlea sp.,...

Vast parts of the monsoon tropics of Australia feature semi-arid habitats, which are generally thought to harbour a depauperate land snail fauna as compared to the mesic continental fringes, in particular the Australian wet tropics. However, our knowledge of land snails inhabiting these often remote environments is still very patchy. In order to improve the understanding of land snail diversity in the monsoon tropics, we revised the camaenid land snail genus Exiligada based on comprehensive collections, undertaken by use of helicopters on remote limestone outcrops in the Northern Territory and in Western Australia. Based on comparative analyses of shell and genital morphology and patterns of molecular differentiation, we recognize 15 species within Exiligada, 13 of which are newly described. In addition, we suggest a revised delimitation of the type species Exiligada negriensis, as compared to the latest available revision, by removing Exiligada qualis from its synonymy and recognizing it as a distinct species. A key for species identification is also provided. Molecular phylogenetic analyses strongly supported the monophyly of Exiligada with respect to other confamilial genera known to occur in the same geographical region. Most Exiligada species are narrowly endemic to restricted limestone outcrops that cover areas with a diameter of about 20 to 150 km. Within the distributional range of Exiligada, the ranges of up to seven species overlap but we never found more than three species to occur in sympatry at a given sampling site. We propose that species originated by allopatric differentiation, followed by secondary range expansion, leading to sympatric distributions. Our study confirms that less complex rock habitats in more xeric environments support no more than three sympatric species, this being likely to be a result of ecological exclusion.

The present work revises the taxonomy of one group of camaenid gastropods from Timor-Leste based on the study of a large number of recently collected ethanol preserved samples as well as historic museum material, including types. By employing comparative analyses of the variation in morphological features (shell, penial anatomy) and the differentiation in mitochondrial DNA sequences of the cytochrome c oxidase subunit 1 gene (COI) and the 16S rDNA (16S), altogether nineteen species are recognized from Timor-Leste and adjacent areas in the Lesser Sunda and Moluccas, such as West-Timor, Adonara, Leti and Sermata Islands (Indonesia). Four of these species were described previously and have mostly been placed within the genus Chloritis Beck, 1837 in the few historic treatments available. Fifteen species found to be new are formally described. In contrast to the previous taxonomic treatment, placement in the genus Parachloritis Ehrmann, 1912 is proposed on grounds of comparative shell mo...

This procedure has been continued into recent times. For example, Brandt (1968, 1974) described several new Brotia taxa from Thailand. However, the validity of these morphospecies remained enigmatic resulting until today in a most confusing usage of species names in biological and palaeontological accounts. In addition, due to the lack of detailed systematic and phylogenetic studies of Brotia, there is confusion as to the limits of this genus as well as its generic and familial affinities. What today is considered to constitute the genus Brotia has been subsumed, to various extents, under Melania Lamarck, 1799, an invalid generic name for

A new species, Brotia praetermissa, is described from Borneo. The type material was found unidentified in the spirit collection of the Natural History Museum, London. It was collected by A. Everett in the nineteenth century. Using morphological characters, the new species is affiliated with the Brotia pagodula species group. Representatives of this group can easily be recognized by the wrinkled apical shell of their protoconch. The species described herein is the only known representative of the likely monophyletic B. pagodula group in Borneo, while all other Brotia species known from this island are assigned to the Brotia testudinaria group. This finding renders it most likely that Borneo has been colonized twice by species of the genus Brotia, by the ancestor of B. praetermissa and that of the Brotia testudinaria group.

Kimberleytrachia Köhler, 2011 is a genus of camaenid land snail endemic to the Western Australian Kimberley region. It comprises twelve previously recognised species, all of which occur within the high precipitation zone along the north-western coast between the Admiralty Gulf and King Sound and within less than about 50 km distance from the coast. By evaluating the variation in shell and genital anatomy as well as the differentiation in the mitochondrial markers 16S and COI, we assess the monophyly of Kimberleytrachia with respect to other camaenid genera from north-western Australia. In addition, we newly describe six species (K. jacksonensis n. sp., K. leopardus n. sp., K. nelsonensis n. sp., K. serrata n. sp., K. setosa n. sp. and K. silvaepluvialis n. sp.) based on comparative morphology and mitochondrial DNA differentiation. We found that a rather smooth, weakly elevated shell and, in particular, the complex penial anatomy are key morphological characteristics of Kimberleytrac...

Speciation in the context of adaptive radiation is regarded as a key process in the creation of biodiversity. While several lacustrine species flocks provide ideal models for elucidating the underlying evolutionary mechanisms, riverine radiations are both rarely known and studied. The Kaek River, a third-order tributary of the Nan River and Chao Praya drainage in central Thailand, harbours an exceptional endemic species assemblage of morphologically distinct, viviparous pachychilid gastropods. Our systematic revision, combining a morphological and molecular genetics approach, reveals the sympatric existence of at least seven species of the genus Brotia that is widespread in rivers of South-east Asia where usually only two species at the most coexist. At eight locations along a 100-kilometre stretch of the Kaek River, we found the syntopic occurrence of two to three species that are separated by specific habitat preferences and exhibit trophic specialization in their radula morphology. Phylogenetic analyses (using MP, NJ, ML and Bayesian inference statistics) of partial COI and 16S sequence data of 17 samples from six species occurring sympatrically and parapatrically, respectively, in the Kaek River drainage (plus the type species B. pagodula as outgroup) indicate monophyly of all these endemic species. Brotia solemiana, which also occurs in the Loei River, a tributary of the Mekong drainage system, was found to be sister to all other Kaek River pachychilids. The distinctive morphotypes, proposed here to represent biospecies, do not show high levels of genetic variation consistent with long periods of reproductive isolation. This suggests a relatively recent origin of this intrariverine radiation and rapid morphological divergence in the Kaek River Brotia. Recent diversification combined with ecological separation and trophic specialization parallels conditions found, albeit on a more specious level, in the lacustrine species flock of the closely related pachychilid genus Tylomelania, which is endemic to ancient lakes on the Indonesian island of Sulawesi. We discuss and compare the allopatric and ecological aspects of speciation in this unique riverine radiation and outline a putative historical biogeography of the Kaek River species, employing the most recent geological and palaeohydrological data for Thailand.

Pachychilidae are distributed in the tropical regions of the southern continents implying a Gondwanan history. In the present study, we investigate the phylogenetic relationships of the freshwater pachychilid gastropod Paracrostoma endemic to Southern India using molecular genetic and morphological data, including the first examination of soft body material of the type species, Paracrostoma huegelii . In addition, two new species, Paracrostoma tigrina sp. nov. and Paracrostoma martini sp. nov. , are described. Our systematic revision shows that former taxonomic concepts of Paracrostoma were misleading. We demonstrate that the monophyletic Paracrostoma is restricted to Southern India and nested within a clade of South-east Asian taxa composed of Brotia and Adamietta . The mitochondrial phylogeny is corroborated by the presence of a subhaemocoelic brood pouch that represents a synapomorphy shared by members of only this group of taxa from the Asian mainland and India. Thus, in contrast to several other zoogeographical model cases, our study suggests that pachychilid freshwater gastropods colonized India out of South-east Asia, probably after the collision of both landmasses during the Eocene. By contrast, a simple vicariance scenario involving the Mesozoic raft of originally Gondwanan elements on the drifting Madagascar-India plate and later colonization of Asia from India fails to explain this distributional pattern. Therefore, Pachychilidae do not follow the predictions of the vicariant biotic ferry hypothesis, which has been suggested for a number of other organisms. We conclude that the origins of the Indian biota are more complex and diverse than assumed under the standard Mesozoic vicariance model.

This study aims at a better understanding of the evolutionary significance of viviparity in some freshwater gastropods. We use a phylogeny based on partial sequences of the mitochondrial 16S gene of representatives of the limnetic and pantropical Pachychilidae to infer the relationships within this particular group of cerithioideans and the evolution of reproductive strategies. The phylogeny presented herein implies a new systematization and suggests that viviparity has appeared three times among the Pachychilidae. This is supported by the finding of very distinct reproductive morphologies in different lineages of viviparous taxa that are exclusively found in Southeast Asia. Based on the observation that oviparity is the ancestral character state in this freshwater family, we conclude that viviparity has evolved subsequent to the exploration of freshwater. We present data showing that all Pachychilidae produce considerably larger but fewer egg capsules compared to most marine snails. In other studies on freshwater gastropods, this has been discussed as an adaptation to freshwater environments. In this context we hypothesize that the increased parental investment involved in the enlargement of eggs in concert with the reduction of clutch sizes was the driving factor that ultimately lead to the evolution of viviparity in the Asian taxa. Consequently, although not directly correlated with the colonization of the new adaptive zone, viviparity is strongly favored by other consequences of this step. Hence, we hypothesize that the production of large eggs, which is necessitated by the exploration of freshwater, represents a preadaptation existing in those ancestors from which viviparous pachychilid lineages eventually evolved in Southeast Asia.