The Southern California Bight covers a region of about 300 km of coastline from northern Baja California to Point Conception. The present study includes ascidian species abundance data from 1994 to 2000 from 29 sites within the 12 major harbors of the Bight north of the Mexico/US border, plus 2 sites in Ensenada (Baja California, Mexico) sampled in August 2000. Nonindigenous ascidians form a major part of the fouling community biomass on floating docks in these harbors. Nine solitary and 5 colonial species are present, 13 of them in San Diego Bay, the largest bay in this region. The most northerly and among the smallest bays, Santa Barbara, contains 8 nonindigenous species. This study reports additional surveys to our 1998 paper (Lambert & Lambert 1998, Mar Biol 130:675-688) for fall 1997, spring 1998 and summer 2000, documents the newly arrived Botrylloides perspicuum, and corrects the records of 2 species. A main focus is the listing and abundance of species at each survey site within each major harbor and an attempt to analyze the differences between sites and between seasons within a single harbor with reference to variations in water movement, temperature, salinity, pollution factors and competition. Several species appeared for the first time in southern California during 1994 to 1997, apparently correlated with the influx of warmer water during the El Nino of that time. Subsequent surveys show that all of these species have persisted, several have dramatically increased in abundance and distribution, and an additional species has successfully invaded.

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Persistence and differential distribution of nonindigenous ascidians in harbors of the Southern California Bight

The class Ascidiacea presents fundamental opportunities for research in the fields of development, evolution, ecology, natural products and more. This review provides a comprehensive overview of the current knowledge regarding the global biodiversity of the class Ascidiacea, focusing in their taxonomy, main regions of biodiversity, and distribution patterns. Based on analysis of the literature and the species registered in the online World Register of Marine Species, we assembled a list of 2815 described species. The highest number of species and families is found in the order Aplousobranchia. Didemnidae and Styelidae families have the highest number of species with more than 500 within each group. Sixty percent of described species are colonial. Species richness is highest in tropical regions, where colonial species predominate. In higher latitudes solitary species gradually contribute more to the total species richness. We emphasize the strong association between species richness and sampling efforts, and discuss the risks of invasive species. Our inventory is certainly incomplete as the ascidian fauna in many areas around the world is relatively poorly known, and many new species continue to be discovered and described each year.

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Global Diversity of Ascidiacea

The last comprehensive reviews of ecology and natural history of ascidians were included in the excellent 1971 publication by Millar on the biology of ascidians and the 1991 treatise on New Caledon...

Ecology and natural history of the protochordates

Ciona intestinalis is considered a widespread and easily recognizable tunicate, the sister group of vertebrates. In recent years, molecular studies suggested that C. intestinalis includes at least two cryptic species, named ‘type A’ and ‘type B’, morphologically indistinguishable. It is dramatic to certify that two different species may be hidden under the name of a species widely used as a model species in biological researches. This raised the problem of identifying diagnostic morphological characters capable of distinguishing these types. We compared the morphology of specimens belonging to the two types and found that only type A specimens possess tunic tubercular prominences, allowing unambiguous discrimination. Remarkably, these structures were already described as distinctive of the Japanese species Ciona robusta, Hoshino and Tokioka, 1967; later synonymized under C. intestinalis (sensu Millar, 1953). In this study, we have confirmed that C. intestinalis type A corresponds to C. robusta. Based on the geographic distribution of C. intestinalis type B, and considering that the original C. intestinalis species was described from North European waters, we determined that C. intestinalis type B corresponds to C. intestinalis as described by Millar in 1953 and possibly to Linnaeus’ Ascidia intestinalis L., 1767 for which we have deposited a neotype (from Roscoff, France) and for which we retain the name Ciona intestinalis (Linnaeus, 1767).

Morphological evidence that the molecularly determined Ciona intestinalis type A and type B are different species: Ciona robusta and Ciona intestinalis

We applied independent species concepts to clarify the phylogeographic structure of the ascidian Ciona intestinalis, a powerful model system in chordate biology and for comparative genomic studies. Intensive research with this marine invertebrate is based on the assumption that natural populations globally belong to a single species. Therefore, understanding the true taxonomic classification may have implications for experimental design and data management. Phylogenies inferred from mitochondrial and nuclear DNA markers accredit the existence of two cryptic species: C. intestinalis sp. A, genetically homogeneous, distributed in the Mediterranean, northeast Atlantic, and Pacific, and C. intestinalis sp. B, geographically structured and encountered in the North Atlantic. Species-level divergence is further entailed by cross-breeding estimates. C. intestinalis A and B from allopatric populations cross-fertilize, but hybrids remain infertile because of defective gametogenesis. Although anatomy illustrates an overall interspecific similarity lacking in diagnostic features, we provide consistent tools for in-field and in-laboratory species discrimination. Finding of two cryptic taxa in C. intestinalis raises interest in a new tunicate genome as a gateway to studies in speciation and ecological adaptation of chordates.

https://www.pnas.org/content/pnas/104/22/9364.full.pdf

Cryptic speciation in a model invertebrate chordate

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The Ascidians of the Japan Sea. I

The two species of the genus Ciona, C. robusta Hoshino et Tokioka and C. intestinalis (Linne) sensu Hoshino & Tokioka, 1967 from the Japanese waters are consistently distinguishable from each other by several minor but distinct features. On the other hand, the survey of literature and examination of many specimens collected from various localities in different years proved that European waters, the type locality of C. intestinalis, have been inhabited only by a single species indistinguishable morphologically from C. robusta. Thus, robusta should be regarded as a junior synonym of intestinalis. Further, it was also proved that C. intestinalis sensu Hoshino & Tokioka should be referred to C. savignyi Herdman originally collected off Kobe, Japan, during the Challenger Expedition, by reexamination of the type specimen of this species. In addition, brief references are made to other described species of the genus Ciona.

http://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/176100/1/fia0301-3_061.pdf

Taxonomic Studies of Ciona intestinalis (L.) and Its Allies

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Considerations on the taxonomic status of the lancelets of the genus branchiostoma from the japanese waters

The 59 species of known Japanese Spiuncula (hoshi-mushi) representing 14 genera are described. A general section on the morphology of these worms and comments on their collection, preservation, and identification is presented. There is a key to the genera and a key to each species designed for the nonspecialist. A brief biogeographical analysis concludes this work. The approximately 3200 specimens examined for this study came from many recent as well as historical collections, from depths ranging from intertidal to abyssal and from Hokkaido in the north to the Yaeyama Islands in the

https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/176092/1/fia0294-6_249.pdf

The sipuncula of japan : their systematics and distribution

/pdf/preliminary-report-on-the-biology-of-the-enteropneust-4rnnf2ilec.pdf

Teruaki Nishikawa

Papers

The Ascidians of the Japan Sea. I

Taxonomic Studies of Ciona intestinalis (L.) and Its Allies

Considerations on the taxonomic status of the lancelets of the genus branchiostoma from the japanese waters

The sipuncula of japan : their systematics and distribution

Preliminary report on the biology of the enteropneust, ptychodera flav a eschscholtz, in the vicinity of kushimoto, japan