Herdmania Momus Research Articles

The distribution of the red-throated ascidian Herdmania momus shifts northwards in association with ocean warming in the Korean Peninsula

Abstract Climate change poses a major threat to marine ecosystems, with its effects felt worldwide. A major effect of climate change on marine ecosystems is the rise in water temperature, leading to a northward expansion of habitats for marine organisms. Herdmania momus, a species of ascidians (sea squirts), originally found in tropical and subtropical regions, was introduced to the Korean Peninsula. In this study, we examined the habitat of H. momus along the southeastern coast of the Korean Peninsula between 2016 and 2022. We found that H. momus settlements were observed across the entire survey area, with confirmed habitation in Busan in 2016, Ulsan in 2021, and Gyeongju (the northernmost location) in 2022. The observed habitation trend indicates a rapid geographical expansion, occurring approximately 79 years earlier than previously predicted. These observations demonstrate that marine organisms are undergoing a more rapid geographical expansion than previously projected. These unexpected findings should inform government policies related to proactive measures and strategies for managing the impact of climate change on marine ecosystems.

Proteomic changes in the solitary ascidian Herdmania momus following exposure to the anticonvulsant medication carbamazepine.

The increasing use of pharmaceuticals in human and veterinary medicine, along with their poor removal rates at wastewater treatment facilities is resulting in the chronic release of pharmaceutically-active compounds (PhACs) into the marine environment, where they pose a threat to non-target organisms. A useful approach, as applied in the current study for assessing the effects of PhACs on non-target organisms, is the proteomic approach: the large-scale study of an organism's proteins. Using 'shotgun' proteomics, we identified differentially-expressed proteins based on peptide fragments in the solitary ascidian, Herdmania momus, following a 14-day laboratory experimental exposure to the PhAC carbamazepine (CBZ), an anticonvulsant and antidepressant medication, frequently detected in the aquatic environment. Individuals were exposed to environmentally relevant concentrations: 5 or 10µg/L of CBZ, in addition to a control treatment. Out of 199 identified proteins, 24 were differentially expressed (12%) between the treatment groups, and thus can potentially be developed as biomarkers for CBZ contamination. Ascidians' phylogenetic position within the closest sister group to vertebrates presents an advantage in examining the pathological effects of PhACs on vertebrate-related organs and systems. Together with the world-wide distribution of some model ascidian species, and their ability to flourish in pristine and polluted sites, they provide a promising tool through which to study the extent and effects of PhAC contamination on marine organisms.

High mucous-mesh production by the ascidian Herdmania momus

Suspension feeders, including ascidians (Phylum Chordata, Class Ascidiacea), experience a dilute prey field composed of extremely small particles. The filtration apparatus of ascidians is based on a mucous-mesh that is continuously secreted and ingested. The rate and metabolic cost of this mesh secretion has not been quantified to date. We used video boroscopy to quantify the mucous-mesh production rate of the solitary ascidian Herdmania momus under different food and temperature treatments. H. momus individuals with an average (±95% CI) biomass of 30.7 ± 1.1 mg and a branchial sac area of 10.3 ± 1.2 cm2 produced an average of 276 ± 33.5 cm2 of mucous-mesh h-1, corresponding to a median turnover rate of 625 ± 82 mesh d-1. Since the mean mesh mass was 2.44 ± 0.58 mg, this production rate corresponds to roughly 50 ± 8 times the individual’s biomass per day. Food concentration had no detectable effect on mesh production rate, whereas a temperature difference of ~9°C (20 vs. 29°C) moderately increased mesh production by 30-50%. The current study reveals that the feeding process of H. momus involves a high expenditure on mucous-mesh synthesis that, combined with low food availability, may limit its growth in oligotrophic waters and under changing climate regimes.

Effects of temperature and salinity on egg development and larval settlement of an invasive ascidian species, <i>Herdmania momus</i> (Savigny, 1816)

The effects of temperature and salinity on egg development and settlement of the ascidian Herdmania momus were investigated. Adult specimens were collected from the Dodu Yacht facility in Jeju Island, Korea (33°30′30.54″N, 126°27′55.46″E) in August 2018. Egg development and larval settlement were observed and recorded at 8 h intervals using a stereomicroscope, under nine temperature (10, 13, 16, 19, 22, 25, 28, 31, and 34°C), and four salinity regimens (28, 30, 32, and 34 psu). The highest hatching rate (82.8±7%) was observed at 32 psu and 25°C and the lowest hatching rate (1.0±2%) was at 34 psu and 13°C. The developmental rate (0.222±0.0994) was highest at 28 psu and 28°C, and lowest (0.016±0.008) at 30 psu and 13°C. The highest settlement success rate (77.1±5%) was at 32 psu and 25°C and the lowest (0.1±1.0%) was at 30 psu, and 13°C. The rate of settlement (0.080±0.000) was highest at 28 psu and 28°C, and lowest (0.013±0.000) at 30 psu and 13°C. Both hatching and settlement success rates increased as temperature increased and tended to decrease beyond an optimal temperature range. Herdmania momus preferred 30-34 psu salinity and 22-25°C temperature. This study provides baseline information about the life history of H. momus, and important data to control the damage caused by the increase in number and distribution of this invasive ascidian.

Potential effects of biodegradable single-use items in the sea: Polylactic acid (PLA) and solitary ascidians

With conventional plastics posing a great threat to marine organisms, and potentially also to humans, bio-based, biodegradable plastics are being offered as an ecological solution by which to reduce the environmental impact. Inside compost facilities, bioplastics that comply with the EN 13432:2000 international standard biodegrade almost completely within 180 days. However, outside compost facilities, and specifically in marine environments, these bioplastics may have a similar effect to that of fossil-fuel based plastics. Here we investigated the effects of polyethylene terephthalate (PET) and polylactic acid (PLA) single-use cups and plates on a solitary ascidian’s biological and ecological features. Both PET and PLA microparticles reduced the fertilization rate of Microcosmus exasperatus, with no significant difference between materials. Accumulation rates in adult M. exasperatus exposed to micronized PET and PLA particles at two concentrations were similar for both the bioplastic material and the conventional plastic particles, with no significant difference between the two materials. A microbial-based digestive protocol was developed in order to recover the bioplastic material from ascidian tissue and reduce any material-loss caused by the known digestion protocols. Finally, PET plates submerged for three months in the Red Sea exhibited a significantly higher community richness and cover area in comparison to PLA plates, which did not provide a firm substrate for settlers. Indeed, coverage by the solitary ascidian Herdmania momus was significantly higher on PET plates. The current study demonstrates that discarded bioplastic products may have similar effects to those of conventional plastics on marine organism fertilization and biological accumulation, emphasizing the need to revise both the production and marketing of “biodegradable” and “compostable” plastics in order to prevent a further negative impact on ecosystems due to the mismanagement of bioplastic products.

A revision of the family Archinotodelphyidae Lang, 1949 (Copepoda: Cyclopoida: Oithonida), with the recognition of 15 new species.

The family Archinotodelphyidae Lang, 1949 is reviewed. Only the type genus, Archinotodelphys Lang, 1949, is accepted as valid and the genus Pararchinotodelphys Lang, 1949 is recognized as its junior subjective synonym. The two species formerly placed in the latter genus are transferred to the type genus as Archinotodelphys gurneyi (Illg, 1955) comb. nov. and A. phallusiae (Hansen, 1923) comb. nov. The species A. polynesiensis Monniot, 1986 was regarded as highly variable by Monniot (1986) but here we separate out his material from the host Herdmania momus (Savigny, 1816) which we recognise as a distinct species, A. momus sp. nov. Another 14 new species are described for the first time, from material collected at numerous localities across the global ocean. The new species are: A. curtus sp. nov. from Styela sp., A. illgi sp. nov. from an unknown host, A. hexasetosus sp. nov. from Molgula platybranchia Monniot C., 1970, A. cinctus sp. nov. from Bathystyeloides enderbyanus (Michaelsen, 1904), A. antarcticus sp. nov. from Molgula pedunculata (Herdman, 1881), A. monnioti sp. nov. from Pareugyrioides galatheae Millar, 1959 (type host) and P. digitus Monniot C., 1997, A. bimerus sp. nov. from an unidentified species of the family Molgulidae, A. longiseta sp. nov. from Styela sigma Hartmeyer, 1912, A. reductus sp. nov. from Pyura gangelion (Savigny, 1816), A. elegans sp. nov. from Polycarpa argentata (Sluiter, 1898), A. rostralis sp. nov. from Polycarpa nigricans Heller, 1878, A. longicaudatus sp. nov. from Microcosmus longicloa Monniot C. Monniot F., 1991, A. nudus sp. nov. from a Polycarpa sp., and A. unisetosus sp. nov. from an unidentified phlebobranch ascidian host. A key to species is provided.

Prediction of potential habitats and distribution of the marine invasive sea squirt, <i>Herdmania momus</i>

The influx of marine exotic and alien species is disrupting marine ecosystems and aquaculture. Herdmania momus, reported as an invasive species, is distributed all along the coast of Jeju Island and has been confirmed to be distributed and spread to Busan. The potential habitats and distribution of H. momus were estimated using the maximum entropy (MaxEnt) model, quantum geographic information system (QGIS), and Bio-ocean rasters for analysis of climate and environment (Bio-ORACLE), which can predict the distribution and spread based only on species occurrence data using species distribution model (SDM). Temperature and salinity were selected as environmental variables based on previous literature. Additionally, two different representative concentration pathway (RCP) scenarios (RCP 4.5 and RCP 8.5) were set up to estimate future and potential habitats owing to climate change. The prediction of potential habitats and distribution for H. momus using MaxEnt confirmed maximum temperature as the highest contributor (77.1%), and mean salinity, the lowest (0%). And the potential habitats and distribution of H. momus were the highest on Jeju Island, and no potential habitat or distribution was seen in the Yellow Sea. Different RCP scenarios showed that at RCP 4.5, H. momus would be distributed along the coast of Jeju Island in the year 2050 and that the distribution would expand to parts of the Korea Strait by the year 2100. RCP 8.5, the distribution in 2050 is predicted to be similar to that at RCP 4.5; however, by 2100, the distribution is predicted to expand to parts of the Korea Strait and the East Sea. This study can be utilized as basic data to effectively control the ecological injuries by H. momus by predicting its spread and distribution both at present and in the future.

A study on codon usage bias in cytochrome c oxidase I (COI) gene of solitary ascidian Herdmania momus Savigny, 1816.

Synonymous codon usage bias is an inevitable phenomenon in organismic taxa, where synonymous codons occur at uneven frequencies in gene. Synonymous codon usage pattern differs between species and also among the genes of a genome. Codon usage bias is determined under various degrees by mutational bias, natural selection and other factors. In this study codon usage pattern of cytochrome c oxidase I (COI) gene of a solitary ascidian Herdmania momus was determined by analyzing the nucleotide content, codon distribution frequency, hydrophobicity, Relative Synonymous Codon Usage (RSCU), Effective Number of Codons (ENC), GC3 and Codon Adaptation Index (CAI) values. Results presented low GC content and higher ENC values indicating less bias in codon usage preference. The Grand Average of Hydropathicity (GRAVY) values and hydropathy plot confirmed the hydrophobic nature of COI the protein.

Regeneration ability in four stolidobranch ascidians: Ecological and evolutionary implications

Owing to their impressive regeneration abilities and close phylogenetic relationship to vertebrates, ascidians (phylum: Chordata) are a key model system for regenerative and developmental studies. Nevertheless, ascidian regeneration research has been limited, to date, to only a few model species. In the present work, we investigated the ability of four solitary ascidians of the order Stolidobranchia, Polycarpa mytiligera, Herdmania momus, Microcosmus exasperatus, and Styela plicata, to regenerate their neural complex and siphons. Four treatments were used: a) amputation of the oral siphon, b) amputation of the atrial siphon, c) amputation of both siphons and the neural complex located between the siphons, and d) a control treatment with no amputations. All four species initiated regeneration of the amputated organs, with P. mytiligera demonstrating the most powerful regenerative ability, as it was the only species to survive all amputation procedures and have its neural complex fully regenerated. P. mytiligera's phylogenetic proximity to colonial species suggests that its remarkable regeneration abilities have been maintained as an ancestral feature, and that this species may constitute a unique phylogenetic transition between coloniality and a solitary life style. P. mytiligera's distinctive regeneration traits may have also provided this species with an ecological advantage, as evidenced by its abundance in the Red Sea. Our findings highlight P. mytiligera's potential to serve as a most valid model organism for research into the evolution of regeneration within chordates and into regenerative biology in general.

Using solitary ascidians to assess microplastic and phthalate plasticizers pollution among marine biota: A case study of the Eastern Mediterranean and Red Sea

The interaction of microplastic (MP) with marine organisms is crucial for understanding the significant effect that MP and its additives may have on marine environments. However, knowledge regarding the magnitude of these pollutants in the Eastern Mediterranean Sea and the tropical Red Sea is still scarce. Here we examined the levels of phthalate acid esters (PAEs) and MP in Herdmania momus and Microcosmus exasperatus sampled along the Mediterranean and Red Sea coasts of Israel. High levels of dibutyl phthalate (DBP) and bis (2‑ethylhexyl) phthalate (DEHP) were found in ascidians at the majority of sampling sites, and MP particles were found in ascidians at all sites. As efficient filter-feeders and being widely-distributed, invasive ascidians present fundamental opportunities for the environmental monitoring of microplastic and its additives worldwide. The high levels of pollutants revealed emphasize the need for further research into the magnitude and effects of MP and PAEs in these regions.

Core and Dynamic Microbial Communities of Two Invasive Ascidians: Can Host–Symbiont Dynamics Plasticity Affect Invasion Capacity?

Ascidians (Chordata, Ascidiacea) are considered to be prominent marine invaders, able to tolerate highly polluted environments and fluctuations in salinity and temperature. Here, we examined the seasonal and spatial dynamics of the microbial communities in the inner-tunic of two invasive ascidians, Styela plicata (Lesueur 1823) and Herdmania momus (Savigny 1816), in order to investigate the changes that occur in the microbiome of non-indigenous ascidians in different environments. Microbial communities were characterized using next-generation sequencing of partial (V4) 16S rRNA gene sequences. A clear differentiation between the ascidian-associated microbiome and bacterioplankton was observed, and two distinct sets of operational taxonomic units (OTUs), one core and the other dynamic, were recovered from both species. The relative abundance of the dynamic OTUs in H. momus was higher than in S. plicata, for which core OTU structure was maintained independently of location. Ten and seventeen core OTUs were identified in S. plicata and H. momus, respectively, including taxa with reported capabilities of carbon fixing, ammonia oxidization, denitrification, and heavy-metal processing. The ascidian-sourced dynamic OTUs clustered in response to site and season but significantly differed from the bacterioplankton community structure. These findings suggest that the associations between invasive ascidians and their symbionts may enhance host functionality while maintaining host adaptability to changing environmental conditions.

Temperature resilience facilitates invasion success of the solitary ascidian Herdmania momus

The tropical ascidian Herdmania momus (Savigny 1816) has been rapidly expanding its distribution in the Eastern Mediterranean Basin. To examine the role of temperature resilience on its invasion success, we conducted monthly field surveys for two years at Achziv (Israel) Marine Protected Area, and examined the survival of adult individuals from native (Red Sea) and invasive (Mediterranean) populations under different temperature treatments. In addition, temperature effects on fertilization and larval development were examined in controlled laboratory conditions. Results indicate that temperature has a significant effect on H. momus from its early life stages through adulthood. Field surveys revealed a significant decline in H. momus abundance in the Mediterranean with the decrease in seawater temperature. Low temperature inhibited development of early life stages, and individuals from both populations demonstrated low survivability under low temperature treatment. All the above may be derived from the tropical origin of H. momus, and may further limit its dispersal into colder areas. However, adult individuals from the invasive population demonstrated significantly higher survivability to the high temperature treatment in comparison to the native population from the Red Sea. Larvae development, metamorphosis and settlement were enhanced and with higher rates of success under the high temperature conditions. The high-temperature adaptation of the Mediterranean population of H. momus from fertilization to adulthood may thus contribute to its expanding distribution in the Eastern Mediterranean.

Reproductive Biology of The Solitary Ascidian, Herdmania momus (Ascidiacea: Hemichordta) from Hurghada Coasts, Red Sea, Egypt

The reproductive biology of the ascidian Herdmania momus (Savigny, 1816) was studied at anthropogenic impacted sites along Hurghada coasts, Red Sea, Egypt, during January - December 2013. The specimens of this species were collected monthly from the shallow subtidal zones, and varied from 1.20 to 7.0 cm in total length and from 1.28 to 50 g in total body weight. The results showed that, H. momus is hermaphrodite, carries ovaries and testes at the same individuals, but ovaries are larger in size and shapes than testes. The smallest immature individual has 1.2 cm in length; while the smallest mature individual measured 1.46 cm in length and 1.18 g in weight, with ovaries of 0.041g in weight. The sexually mature individuals of this species have ovaries containing oocytes varied in shapes and sizes, passing through four main stages of maturation reaching stage IV or late vitellogenic stage (ripe ova), with oocytes varied from 100 to 140 µm in diameter, characterized with deep orange color and dense accumulation of yolk granules. It was followed by stage V or spent stage of irregular resorbed eggs. The appearance of ripe ova at stage IV showed spatial and temporal variations. The monthly averages of gonadosomatic indices (GSI) exhibited that, the whole populations of this species at all sites have lengthy breeding season extends nearly all the year around and characterizes with high peaks in gonadal activity during January (6.21), April (6.15), June (6.47), July (6.28), declined slightly in May (5.86), and September (5.15), with remarkably spatial variations at the studied sites. The number of mature eggs or fecundity varied from 1481 to 3724 and averaged of 3082.96±769.96 eggs for all populations. These values exhibited greatly individual variations denoting to partially spawning for each individual. The relationship between total body length (cm) and mean the number of eggs (fecundity) showed an increase in egg number with an increase in animal length

Observations on the symbiotic relationship between the caridean shrimp Odontonia sibogae (Bruce, 1972) and its ascidian host Herdmania momus (Savigny, 1816).

Symbiotic relationships between shrimps and other invertebrates are a very common phenomenon in tropical environments. Although the caridean shrimp-ascidian association has been known for many years, the nature of this relationship is still unclear. The current study investigated the association between the caridean shrimp Odontonia sibogae (Bruce, 1972) and solitary ascidians. A combination of field work conducted along the Red Sea coast of Israel and laboratory experiments, conducted during 2015–2016, revealed a clear preference of the shrimps for the ascidian species Herdmania momus (Savigny, 1816), with a low survival ability of the shrimp outside their host's body. The shrimps usually inhabit their host as pairs of male and female or pair of females, but never as pairs of males. Out of the 53 studied females, 51% were observed to bear between 156–1,146 embryos, throughout the course of the year. As these ascidian hosts are known to create large aggregates, we suggest that males may possibly wander among the ascidians occupied by females in order to increase their reproductive success. To date, this is the first study to record the shrimp Dactylonia ascidicola (Borradaile, 1898) inhabiting the ascidian H. momus; and the first study to investigate in depth the ascidian-shrimp association in the Red Sea. It thus provides a platform for future research into the physiological and behavioral adaptations required for such a unique association.

Not-so-simple sieving by ascidians: re-examining particle capture at the mesh and organismal scales

The particle capture mechanisms of biological filters determine the particle spectrum that is ingested by filter-feeding animals. Although ascidian feeding has been extensively investigated, the organismal-scale fluid dynamics and mesh-scale particle-filter interactions are not fully characterized. Fluorescein dye visualization of flow through the branchial sac of the ascidian Ciona intestinalis showed organismal-scale flow was laminar and moved both parallel and perpendicular to the mucous mesh. Endoscopic investigations of Herdmania momus revealed the mesh-scale filtration process, including the pre-capture velocities, particle approach angles, and mesh behavior. The mesh speed was variable (range 0–0.4 mm s−1). To determine how particle shape affects hydrosol capture, Styela plicata was fed differently shaped polystyrene particles (ellipsoids and spheres); sampling the inhaled and exhaled water revealed that microellipsoids (0.3 × 0.7 µm) were captured at significantly lower efficiency (32%) than 1 µm microspheres (86%). The capture efficiency of microellipsoids resembled that of microspheres with a diameter similar to the microellipsoids’ minor axis (0.3 µm, 31%) suggesting that the minimum diameter of ellipsoidal particles determines the capture efficiency. Flow near the filter was parallel to the mesh even ~ 10 s of micrometers away, implicating a “crossflow” component to ascidian filtration, where the fluid being filtered is directed along the surface of the filter rather than exclusively perpendicular to it. Collectively, these results suggest that ascidian filtration acts as a hybrid-flow filtration system rather than a classical direct sieve.

Population dynamics of the solitary ascidian Herdmania momus (Savignyi, 1816) in Jeju Island, Korea

In 2007–2008, a population outbreak of the solitary ascidian Herdmania momus was observed along the coasts of Jeju Island and the ascidians became the top dominant species in macrobenthic communities. We conducted field experiments on population dynamics and demographic parameters including seasonal density fluctuation, vertical distribution, recruitment patterns, mortality, and growth rate. Recruitment continued year-round except in April following the lowest water temperature season in February. Population density was highest in August-October, concomitantly with the peak in recruitment, related to the highest water temperature. The lowest density was observed in February-April when the water temperature was lowest. In April all individuals disappeared from all permanent plots, resulting in a maximum life span of 10–12 months. Individuals of newly recruited H. momus grew to have an adult size of 4–6 cm in only 3–4 months. Higher densities were observed in the shallower areas (5 m) compared to the deeper zones. More recruitment occurred on vertical slopes than horizontal substrates, but substrate pre-occupancy caused no difference in recruitment. This is the first report on H. momus population-level investigation in Korea, which provides valuable baseline information on the current status of population demography and their potential community-level influence on Jeju coasts.

Trophic relationships between the farmed pearl oyster Pinctada margaritifera and its epibionts revealed by stable isotopes and feeding experiments

Bivalve cultures support a host of epibionts, mainly suspension feeders, which can compete for food resources with the cultivated bivalves. However, the magnitude of interspecific competition for food in bivalve aquaculture settings remains inconclusive, especially in tropical areas. We investigated the interactions for food between the farmed pearl oyster Pinctada margar- itifera and its epibionts, using stable isotope analysis and feeding experiments. Inter- and intra- specific variations of δ 13 C and δ 15 N stable isotope ratios (SIRs) were determined for oysters in the presence or absence of epibionts. The diet of the most abundant epibionts, Herdmania momus and Didemnum sp., was specified using isotope measurements and flow cytometry during feeding experiments, to determine the main phytoplankton groups consumed by these ascidians in natural conditions. The absence of intraspecific variation in SIRs among oysters with or without epibionts suggested that the diet of P. margaritifera was not affected by the presence of epibionts, indicating a reduced diet overlap and no food limitation. The δ 13 C signature of ascidians (�21‰) was lower than that of oysters (�18‰), indicating a difference in organic matter sources ingested by these filter feeders despite receiving the same food mixture. While the main carbon source of oysters came from large particulate organic matter (POM) >20 µm, our results showed that the diet of ascidians mainly came from smaller particles (POM <20 µm) and reflects the composition of ambi- ent water (mainly picophytoplankton <2 µm), which confirmed their lack of food selectivity. In the studied conditions, food competition between oysters and epibionts, specifically ascidians, was not a limiting factor, in spite of a diet overlap for nanophytoplankton.

Floating docks in tropical environments - a reservoir for the opportunistic ascidian Herdmania momus

The solitary ascidian Herdmania momus is considered native to the Red Sea, and invasive in the Mediterranean. Periodic surveys have revealed high recruitment and growth rates of this species on floating docks in the Gulf of Aqaba, Red Sea, following the annual vertical mixing event. In order to ascertain the length of time taken by H. momus individuals to settle on new artificial substrates, and the pace at which they grow and reach the reproductive stage, we monitored a newly-deployed floating dock for two years following its deployment. The number of individuals and their sizes were recorded weekly in March-June 2013 (spring-early summer), in June-August (summer), and re-visited each spring (April 2014, 2015). In addition, seven fixed quadrates were artificially cleaned and monitored in summer 2013. Ascidians were visible after eight weeks in the spring and five weeks in the summer. Growth rate in spring was twice as fast as in summer (0.275 and 0.106 cm/week respectively). Recruitment was higher during spring, reaching a density of 34.3 ± 7.1 in June, with fully reproductive individuals, dropping to 0.86 ± 0.46 individuals per quadrate in August. Field surveys of additional floating docks revealed significantly higher densities at the northern sites during spring. Following a nutrient enrichment event such an opportunistic filter-feeder can potentially release and distribute propagules to natural reefs, inducing a shift in community assemblage. In addition, its ability to colonize artificial substrates within its native range sheds light on its success as an invasive species in the Mediterranean.

Narrowly Distributed Crystal Orientation in Biomineral Vaterite

Biominerals formed by animals provide skeletal support and many other functions. They were previously shown to grow by aggregation of amorphous nanoparticles but never to grow ion-by-ion from solution, which is a common growth mechanism for abiotic crystals. We analyze vaterite (CaCO3) multicrystalline spicules from the solitary tunicate Herdmania momus, with polarization-dependent imaging contrast (PIC)-mapping and scanning and aberration-corrected transmission electron microscopies. The first fully quantitative PIC-mapping data, presented here, measured 0-30° angle spreads between immediately adjacent crystals. Such narrowly distributed crystal orientations demonstrate that crystallinity does not propagate from one crystal to another (0° angle spreads), nor that new crystals with random orientation (90°) nucleate. There are no organic layers at the interface between crystals; hence, a new, unknown growth mechanism must be invoked, with crystal nucleation constrained within 30°. Two observations are cons...

DNA barcoding of two solitary ascidians, Herdmania momus Savigny, 1816 and Microcosmus squamiger Michaelsen, 1927 from Thoothukudi coast, India

Morphology-based taxonomical studies of ascidians in India are meagre due to lack of ascidian taxonomist and limitations inherent in conventional system-based identification. The use of short fragment of mitochondrial DNA sequence is proving highly useful in identifying species in a situation where, the traditional morphology-based identification is difficult. In the present study, two adult solitary ascidians collected from the Thoothukudi coast were morphologically identified as Herdmania momus Savigny, 1816 and Microcosmus squamiger Michaelsen, 1927. The genomic DNA of these ascidians was isolated, COI gene was amplified, sequenced and submitted to the GenBank under the accession numbers KM058116, KM411616 and KJ944390. Homology search result using BLAST showed that H. momus showed 100% matched with other H. momus, while M. squamiger showed similarity with Pyura herdmani, a member of the same family Pyuridae. The phylogenetic and genetic distance was maximum in interspecies than in intraspecies. These COI sequences will allow the identification of the species through DNA barcoding technique. Here, we report for the first time the COI gene of H. momus, Savigny 1816 from the Indian coast.