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Costasiella arenaria n. sp.: live animals in the field. A. Light green specimen with brown dorsal body and stripes on rhinophores (photo by J. Townsend). B. Dark brown specimen with dark pigment on cerata as well as body surface (photo by J. Townsend). C. Spawning specimen, light green colored with almost no brown pigment (photo by S. Edwards). D. Spawning specimen, pale with many red and white dots (photo by L. Ianniello).
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The history of the genus Costasiella is summarized. A new species of Costasiella, C. arenaria n. sp., from Lake Worth, Florida, USA is described. For comparative purposes specimens of C. formicaria (Baba, 1959) from Japan and serial sections of C. pallida Jensen, 1985 from Hong Kong have also been examined. These three species, like the type specie...
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... , referred to as C. ocellifera and C. cf. ocellifera . The latter had previously been called ‘ Costasiella n. sp.’ (Clark, 1994). However, both populations were collected from Avrainvillea and thus cannot be identical to the species here described. The egg mass of C. arenaria differs from both C. ocellifera and C. cf. ocellifera . The capsule diameter of C. ocellifera is about three times that of the egg diameter, and eggs of the planktotrophic C. cf. ocellifera are spirally arranged inside the egg mass (Miles & Clark, 2002), whereas capsules in C. arenaria are less than twice the egg diameter and appear to be irregularly arranged inside the egg mass (Fig. 1C, D). The eyes of C. arenaria do not appear particularly big in live specimens. However, they are bigger than those of C. nonatoi (65–100 m m vs . 70–80 m m) (Marcus & Marcus, 1960; present study). Costasiella arenaria was not seen associated with any recognizable algae in the field. Single strands of green siphonalean filaments appear on several photos (Fig. 1), but are not distinct enough to identify ...
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Citations
... Moreover, these findings highlight the shortcomings of traditional species discovery for yet another genus of heterobranch sea slugs, showing that one nominal species (historically, C. antillensis) comprises six distinct, unrecognized species. Comparable levels of cryptic diversity masked by one species name have been shown in other sacoglossan genera, including Plakobranchus and Elysia (Krug et al. 2013; Costasiella ( Jensen et al. 2014), Oxynoe (Berriman et al. 2018, Krug et al. 2018a, Sacoproteus (Krug et al. 2018b), Polybranchia (Medrano et al. 2019), Placida (McCarthy et al. 2019 and Thuridilla (Martín-Hervás et al. 2021). Notably, however, none of those prior cases included a Western Atlantic radiation as species rich as the C. antillensis complex, making Cyerce an important taxon for studying speciation in the context of Caribbean biogeography. ...
Integrative studies have revealed cryptic radiations in several Caribbean lineages of heterobranch sea slugs, raising questions about the evolutionary mechanisms that promote speciation within the tropical Western Atlantic. Cyerce Bergh, 1871 is a genus comprising 12 named species in the family Caliphyllidae that lack the photosynthetic ability of other sacoglossans but are noted for vibrant colours on the large cerata (dorsal leaf-like appendages) that characterize many species. Two species are widely reported from the Caribbean: Cyerce cristallina (Trinchese, 1881) and Cyerce antillensis Engel, 1927. Here, we present an integrative assessment of diversity in Caribbean Cyerce. Four methods of molecular species delimitation supported seven species in samples from the Caribbean and adjacent subtropical Western Atlantic. Six delimited species formed a monophyletic lineage in phylogenetic analyses but were > 9% divergent at the barcoding COI locus and could be differentiated using ecological, reproductive and/or morphological traits. We redescribe C. antillensis, a senior synonym for the poorly known Cyerce habanensis Ortea & Templado, 1988, and describe five new species. Evolutionary shifts in algal host use, penial armature and larval life history might have acted synergistically to promote the rapid divergence of endemic species with restricted distributions in this radiation, substantially increasing global diversity of the genus.
... A more precise correspondence is found among the uniseriate radulae of extant sacoglossan opisthobranchs (figure 3; [41][42][43][44][45][46][47][48]; fig. 2C-F of [49]). Among the Sacoglossa, blade-shaped teeth are arranged in an arc, and the teeth likewise possess a thinner, bladed keel on the dorsal or anterior (cusp) edge (see [43]; fig. ...
Molluscs have produced an extensive fossil record, owing to the prevalence of robust biomineralized shells among this clade. By contrast, most other components of molluscan anatomy are seldom preserved. Importantly, little is known of the evolutionary history of the unique molluscan feeding apparatus-the radula. A scarcity of fossil radulae has hampered our understanding of the ancestral condition, and of the dietary ecology of early molluscs. The handful of known fossil radulae all point to early molluscs as simple deposit feeders that obtained food via rasping or scraping. This study reports microscopic radulae preserved as 'small carbonaceous fossils' (SCFs) from Cambrian (Stage 4-Wuliuan, approximately 514-504.5 Ma) strata of Sweden. These rare fossil radulae offer novel insights into the feeding anatomy and ecology of early molluscs. Each radula comprises a uniseriate arc of (≤10) blade-shaped teeth, fringed by a slicing keel. This distinctive morphology is strikingly convergent with the radulae of extant sacoglossan heterobranch gastropods-such radulae are specially adapted for piercing the cell walls of green algal tissues to enable suctorial feeding on the cytoplasm contents. Discovery of analogous Cambrian radulae demonstrates this specialized form of herbivory had already evolved among molluscs more than half a billion years ago.
... does not cluster with any sequenced species ( Figure S6). Eight of the 17 currently accepted species and nine additional undescribed ones were recently sequenced and included in our phylogeny [67,68]. From those, C. fridae n. sp. is externally more similar to Costasiella sp. 2, cf. ...
... From those, C. fridae n. sp. is externally more similar to Costasiella sp. 2, cf. kuroshimae (Figure 8 in Jensen et al. [67]) and Costasiella sp. 1 ( Figure 1E in Christa et al. [68]), although genetically they present great divergence (COI similarity up to 79%). ...
... Figures S1-S6. COI gene tree for all barcoded specimens, and phylogenetic trees and species delimitation tests for the six newly described species [61,67,[91][92][93]. Data Availability Statement: Voucher information is fully available in MCZbase (https://mczbase. ...
Baseline biodiversity data are key for ecological and evolutionary studies and are especially relevant for areas such as the Maldivian Archipelago in the Indian Ocean, which can act as a stepping-stone for the transport of widely distributed marine species. We surveyed the islands and reefs of the Faafu and Malé Atolls with snorkeling and scuba diving, collecting the two gastropod subclasses, Heterobranchia and Vetigastropoda. Our inventory comprises 104 species photographed alive to create an identification guide. We also provide COI barcodes for most species, adding novel sequence data for the Maldivian malacofauna. Half of our species represent new records for the Maldives, emphasizing how much diversity remains to be discovered. Species distributions reflect ecological rarity, with almost 60% of taxa only found in one site. We also compiled a comprehensive checklist of heterobranchs and vetigastropods of the Maldives based on literature records, resulting in 320 species, which, together with barcoding data, indicate several potential cryptic species in the Indo-Pacific. Six new species are described, the nudibranchs Limenandra evanescenti n. sp., Eubranchus putnami n. sp., Sakuraeolis marhe n. sp., Moridilla maldivensis n. sp., Tergiposacca perspicua n. sp., and the sacoglossan Costasiella fridae n. sp.
... Distribution. Costasiella kuroshimae is currently known from the Indo-Pacific including the Red Sea (Yonow 2015), Singapore (Jensen 2009), Indonesia (Eisenbarth et al. 2018), Japan (Ichikawa 1993), Guam (Jensen et al. 2014b), Madagascar, Tanzania, Malaysia, Papua New Guinea, Palau, and Australia . Known from the Gulf waters of Thailand . ...
... Due to the original description of the species being entirely based on external features, the identity of numerous similar species and the extent of the variability of the species has remained unclear for several years. Molecular work (Jensen et al. 2014b) has shown that specimens identified as Costasiella kuroshimae or C. cf. kuroshimae actually make up numerous distinct species that currently await description. ...
Improved access to field survey infrastructure throughout South-East Asia has allowed for a greater intensity of biodiversity surveys than ever before. The rocky bottoms and coral reef habitats across the region have been shown to support some of the highest sea slug biodiversity on the planet, with ever increasing records. During the past ten years, intensive SCUBA surveys have been carried out at Koh Tao, in the Gulf of Thailand, which have yielded remarkable findings in sea slug biology and ecology. In this work a brief history of sea slug biodiversity research from Thailand is covered and a complete inventory of sea slugs from Koh Tao, Gulf of Thailand is provided. This inventory is based on surveys from 2012 to 2020, with previously unreported findings since 2016. Habitat specificity and species-specific ecology are reported where available with a focused comparison of coral reef habitats and deeper soft-sediment habitats. The findings contribute 90 new species records for Thai waters (92 for the Gulf of Thailand) and report a remarkable consistency in the proportional diversity found to be exclusive to one habitat type or another. Additionally, taxonomic remarks are provided for species documented from Koh Tao that have not been discussed in past literature from Thailand, and a summary of previous records in the Indo-West Pacific is given.
... These have subsequently been identified as belonging to the species complex named Costasiella cf. kuroshimae because of their similarity to C. kuroshimae Ichikawa, 1993 from Japan (Jensen 2009;2015;Jensen et al. 2014b;Krug et al. 2015). ...
... Its cerata have pale yellowish transparent tips, and its rhinophores appear relatively longer. It has been included in molecular analyses of sacoglossans (Jensen et al. 2014b;Krug et al. 2015) as Costasiella sp. 4, and it is possibly also this species that is listed as Costasiella sp. 2 by Christa et al. (2014). Because cryptic spe- at level of genital receptacle; D. at level of stomach; E. close-up of fertilization area; F. Light micrograph of penis of 0.8 mm specimen. ...
... She also suggested that Doto (?) ocellifera Simroth, 1895 was a Costasiella, later confirmed by Clark (1984) who synonymized it with C. lilianae. Clark (1984) also described a species from Bermuda, which he identified as C. nonatoi, and his description has been used to identify similar specimens from Florida, Panama, and the Bahamas (Rudman 2004;Jensen et al. 2014b;Christa et al. 2014;Espinoza et al. 2014;Krug et al. 2015). However, these records all refer to the species now known as Panderevela ipse. ...
The first species of the sacoglossan genus Panderevela from the Indo-Pacific region is described and named in honor of the late Prof. Jørgen Hylleberg. It is small, less than 2 mm long preserved, darkly pigmented, and associated with the green alga Avrainvillea. It was collected at Rawai Beach, Phuket Island, Thailand, in November 1986 and November 1990. Although searches have been made on several other occasions in the same location, the species has not been found since then, so it appears to be rare. The morphological characters defining the genus Panderevela are discussed and the anatomy is compared to other species of the family Costasiellidae. All specimens collected were fixed in formalin, so DNA analysis has not been possible.
... Sixteen Costasiella species are described worldwide, and a further eight undescribed species are documented in Gosliner et al. [11]. Jensen et al. [25] described and illustrated a specimen from Guam (preliminarily identified as Costasiella "kuroshimae") resembling our five specimens very closely, which were all collected together in Mantehage at Barracuda Point sitting close to a Flabellia alga in 14 m depth. The white head is typical for this species, which shows only a tinge of yellow in front and behind the eyes. ...
... The rhinophores are rather transparent and do not show any black. Based on the phylogeny of Costasiella species from around the world, Jensen et al. [25] considered identification of C. kuroshimae as very difficult, because of the similarity of non-related specimens and a lack of a proper description of the original material of this species. ...
... Sixteen Costasiella species are described worldwide, and a further eight undescribed species are documented in Gosliner et al. [11]. Jensen et al. [25] described and illustrated a specimen from Guam (preliminarily identified as Costasiella "kuroshimae") resembling our five specimens very closely, which were all collected together in Mantehage at Barracuda Point sitting close to a Flabellia alga in 14 m depth. The white head is typical for this species, which shows only a tinge of yellow in front and behind the eyes. ...
... The rhinophores are rather transparent and do not show any black. Based on the phylogeny of Costasiella species from around the world, Jensen et al. [25] considered identification of C. kuroshimae as very difficult, because of the similarity of non-related specimens and a lack of a proper description of the original material of this species. ...
Bunaken National Park has been surveyed for a fourth time in 14 years, in an attempt to establish the species composition of heterobranch sea slugs in a baseline study for monitoring programs and protection of this special park. These molluscs are potentially good indicators of the health of an ecosystem, as many are species-specific predators on a huge variety of marine benthic and sessile invertebrates from almost every taxonomic group. Additionally, they are known to contain bio-compounds of significance in the pharmaceutical industry. It is therefore of paramount importance not only to document the species composition from a zoogeographic point of view, but to assist in their protection for the future, both in terms of economics and aesthetics. These four surveys have documented more than 200 species, with an approximate 50% of each collection found only on that survey and not re-collected. Many species new to science have also been documented, highlighting the lack of knowledge in this field.
... (Malaquias and Reid 2008). Our approach compliments recent work in other sea slugs showing that nominal species may comprise five to 10 pseudocryptic taxa (Krug et al. 2013;Jensen et al. 2014). True species richness in sacoglossans has been systematically under-estimated by a conservative taxonomy overly reliant on characters of limited value (e.g., shell features) while overlooking key traits (e.g., colored mantle striations in Lobiger; radular tooth shape, mantle spotting in Oxynoe). ...
Predicting biotic resistance to highly invasive strains of "killer algae" (Caulerpa spp.) requires understanding the diversity and feeding preferences of native consumers, including sea slugs in family Oxynoidae. Past studies reported low algal host specificity for Oxynoe (6 spp.) and Lobiger (4 spp.), but these taxonomically challenging slugs may represent species complexes of unrecognized specialists that prefer different Caulerpa spp. Here, we assess global diversity of these genera by integrating gene sequences with morphological data from microscopic teeth and internal shells, the only hard parts in these soft-bodied invertebrates. Four delimitation methods applied to datasets comprising mtDNA and/or nuclear alleles yielded up to 16 species hypotheses for samples comprising five nominal taxa, including five highly divergent species in Lobiger and five in Oxynoe. Depending on the analysis, a further four to six species were recovered in the O. antillarum-viridis complex, a clade in which mitochondrial divergence was low and nuclear alleles were shared among lineages. Bayesian species delimitation using only morphological data supported most candidate species, however, and integrative analyses combining morphological and genetic data fully supported all complex members. Collectively, our findings double the recognized biodiversity in Oxynoidae, and illustrate the value of including data from traits that mediate fast-evolving ecological interactions during species delimitation. Preference for Caulerpa spp. and radular tooth characteristics covaried among newly delimited species, highlighting an unappreciated degree of host specialization and coevolution in these taxa that may help predict their role in containing outbreaks of invasive algae.
... With only six generally accepted previously described species, Oxynoe was considered to have low diversity compared with other sacoglossan genera (e.g. Costasiella, >20 spp., Jensen et al. 2014; Elysia, >90 spp.; Krug et al. 2015Krug et al. , 2016. Here, describing seven new species and suggesting an eighth be resurrected from synonymy, we more than double the known diversity in Oxynoe. ...
An integrative approach to investigate the species-level diversity in Oxynoe (Mollusca, Heterobranchia, Sacoglossa) revealed the existence of 11 distinct taxa. Oxynoe viridis (Pease, 1861) and Oxynoe antillarum Mörch, 1863 are redescribed Oxynoe natalensis E. A. Smith, 1903 and Oxynoe azuropunctata Jensen, 1980 are regarded as valid. Species originally described from empty shells are regarded as nomina dubia. Seven new species are described, four from the tropical Indo-West Pacific: Oxynoe kylei, sp. Nov., Oxynoe neridae, sp. Nov., Oxynoe jordani, sp. Nov. and Oxynoe jacksoni, sp. Nov. and two from the tropical Atlantic: Oxynoe struthioe, sp. Nov. and Oxynoe ilani, sp. Nov. The name Oxynoe panamensis Pilsbry & Olsson, 1943 has been applied to eastern Pacific specimens, but was introduced based on material collected from the Caribbean therefore, the new name Oxynoe aliciae, sp. Nov. is introduced for eastern Pacific specimens. Species are delineated using molecular and morphological traits, as well as algal host and reproductive biology. Results from morphological comparisons are concordant with molecular and integrative species delimitation analyses, providing robust evidence for species hypotheses. As Oxynoe is one of the few groups specialised to feed on the green algal genus Caulerpa, which includes highly invasive species, clarifying the taxonomy of Oxynoe may inform efforts to predict community response to disruptive algal invasions.
... Although also reported to feed on Cladophora (Clark 1975), no supporting data were published. At least three independent radiations onto Vaucheria have thus occurred in Sacoglossa: the genus Alderia, one lineage of Costasiella (2 spp.; Jensen et al. 2014), and E. chlorotica. Most Vaucheria spp. ...
The Caribbean is a biodiversity hotspot for photosynthetic sea slugs, with about 27 described species in the genus Elysia Risso, 1818. However, many species are poorly known or have complex taxonomic histories, complicating assessments of regional biodiversity and impeding studies of plastid symbiosis, speciation, and larval biology. Using an integrative approach, we address the taxonomy and systematics of Caribbean elysiids by performing robust tests of existing species hypotheses, and describe six new species. Species delimitation included DNA barcoding of up to 189 nominal conspecific specimens; nuclear gene sequences were then used to confirm that divergent lineages were genetically distinct candidate species. New synonymies and species descriptions are based on external anatomy, penial and radular morphology, developmental characters, and host ecology of all species described from the region, plus a critical review of the literature. We synonymized three species (Elysia annedupontae Ortea, Espinosa & Caballer in Ortea, Caballer, Moro & Espinosa, 2005, Elysia clarki Pierce et al. 2006, and Elysia leeanneae Caballer, Ortea & Espinosa in Ortea, Espinosa, Buske & Caballer, 2013), transfered one species from Bosellia (Elysia marcusi), and described six new species (Elysia pawliki n. sp., Elysia zemi n. sp., Elysia christinae n. sp., Elysia hamanni n. sp., Elysia taino n. sp., and Elysia buonoi n. sp.). We resurrected the name Elysia velutinus Pruvot-Fol, 1947, a senior synonym of Elysia tuca Ev. Marcus & Er. Marcus, 1967. Based on a four-gene phylogeny of 76 Elysia spp., we identified shifts in host use and penial armature that may explain patterns of endemic diversification in Elysia, invoking both ecological and non-ecological mechanisms. Non-monophyly of styletbearing species rejects previous attempts to classify species based on presence of a stylet (i.e., the genus Checholysia Or tea, Caballer, Moro & Espinosa, 2005). Our findings show how integrative approaches can resolve the taxonomic status of problematic species (e.g., Elysia papillosa Verrill, 1901) for soft-bodied marine taxa.
