Siphonaria is a genus of panpulmonate marine limpets often mistaken for 'true' or patellogastropod limpets because of their remarkably convergent appearance. Among the c. 130 species of Siphonaria reported worldwide, S. japonica (Donovan, 1824) is the most commonly encountered species in the northwestern Pacific (NWP) region, including China, Japan and Korea. Siphonaria japonica shells are highly variable, leading to a prevalent view of a single species with considerable ecophenotypic variation. This study presents morphological (shell and radula) and molecular [sequence data for the mitochondrial gene cytochrome c oxidase subunit I (COI)] evidence leading to the discovery of a still undescribed species that has been previously mistaken for S. japonica in Korea and likely in other NWP localities. Our integrated analysis of shell and radula characters for selected sequenced Korean voucher specimens has revealed an overlooked species within the range of specimens considered to be S. japonica. The 'tall form' is distinguished from the 'short form' by a larger, oval shell with an elevated, posteriorly curved apex and a weakly undulated margin formed by alternating thick primary and thin secondary ribs, as well as a higher number of radula teeth per row with unicuspid and/or bicuspid mesocone in the innermost lateral teeth. In contrast, the 'short form' has a smaller, oval shell with a lower, flattened apex; a coarsely undulated margin due to strong primary ribs without secondary ribs; and fewer radula teeth per row, with a consistently bicuspid mesocone. Mitochondrial COI sequence analysis revealed a substantial genetic divergence (uncorrected p-distance 19.2-20.5%) between the two shell forms, exceeding intraspecific variation observed within each form. Phylogenetic analyses consistently recovered them as distinct, well-supported clades, indicating that they represent separate species. An extensive comparative analysis of both species across the NWP is required to investigate the distribution of the two shell forms and understand the ecological and phylogeographic factors influencing these co-occurring species.

The present contribution expands the family Nierstraszellidae Sirenko, 1992 from a pair of deepwater species assigned to Nierstraszella Sirenko, 1992, to eight deepwater extant species in three genera, two of them new to science. These species are typically found on deep-sea sunken wood, implying a homologous ecological specialization shared for all species within the family. This systematic revision reflects a new understanding of a distinctive and ancient lineage within the chiton order, Lepidopleurida Thiele, 1909, whose revision has been challenged by inaccessible deepwater habitat of its members. Here we integrate both SEM and molecular studies, and recast Nierstraszellidae as one of multiple, mostly still unresolved, monophyletic lineages within Lepidopleurida. The type genus, Nierstraszella, is newly restricted to its type species, N. lineata (Nierstrasz, 1905), and two new genera are introduced. Rissochiton gen. nov. includes five similar species found in the Indo-West Pacific Ocean, all once grouped uncomfortably as Leptochiton rissoi (Nierstrasz, 1905). We distinguish type species R. rissoi by morphology and DNA from four other similar species, including R. formosaensis sp. nov. and R. quincuncialis sp. nov. A second new genus, Astrochiton gen. nov., has a neotropical distribution that is disjunct from other Nierstraszellidae. The two species, our selected type species, Lepidopleurus binghami Boone, 1928, from the Caribbean Sea and Gulf of Mexico, and A. incongruus (Dall, 1908) from the tropical Eastern Pacific. The results of a phylogenetic analysis, based on combined mitochondrial cox1 and 16S gene regions and corresponding to morphological affinities, support all three genera as independent lineages. Together, Nierstraszellidae is strongly supported as monophyletic relative to multiple included outgroups from across and outside of Lepidopleurida. Within Nierstraszellidae, a geographic split is evident between Indo-West Pacific and neotropical species. The molecular analysis also reveals a strong phylogeographic pattern within N. lineata. that is inconsistent with regular gene flow, hinting at cryptic species diversity. Together, our analyses support three genera that are united by features of the girdle, radula, and patterns of strong variability in the number of pores of aesthetes in the aesthete group. In contrast to other Lepidopleurida, members of Nierstraszellidae have a surprising amount of intraspecific variability in their tegmental sculpture, with some individuals having tegmentum granules in rows, while others have no trace of granules. Based on the number and location of the pores of the aesthetes, the Jurassic species Leptochiton shapovalovi Sirenko, 2013 is provisionally assigned to Rissochiton, which has implications for the antiquity of the family.

The methane seeps on the Pacific margin of Costa Rica support extensive animal diversity and offer insights into deep-sea biogeography. During five expeditions between 2009 and 2019, we conducted intensive faunal sampling via 63 submersible dives to 11 localities at depths of 300–3600 m. Based on these expeditions and published literature, we compiled voucher specimens, images, and 274 newly published DNA sequences to present a taxonomic inventory of macrofaunal and megafaunal diversity with a focus on invertebrates. In total 488 morphospecies were identified, representing the highest number of distinct morphospecies published from a single seep or vent region to date. Of these, 131 are described species, at least 58 are undescribed species, and the remainder include some degree of taxonomic uncertainty, likely representing additional undescribed species. Of the described species, 38 are known only from the Costa Rica seeps and their vicinity. Fifteen range extensions are also reported for species known from Mexico, the Galápagos seamounts, Chile, and the western Pacific; as well as 16 new depth records and three new seep records for species known to occur at vents or organic falls. No single evolutionary narrative explains the patterns of biodiversity at these seeps, as even morphologically indistinguishable species can show different biogeographic affinities, biogeographic ranges, or depth ranges. The value of careful molecular taxonomy and comprehensive specimen-based regional inventories is emphasized for biodiversity research and monitoring.

Path dependence influences macroevolutionary predictability by constraining potential outcomes after critical evolutionary junctions. Although it has been demonstrated in laboratory experiments, path dependence is difficult to demonstrate in natural systems because of a lack of independent replicates. Here, we show that two types of distributed visual systems recently evolved twice within chitons, demonstrating rapid and path-dependent evolution of a complex trait. The type of visual system that a chiton lineage can evolve is constrained by the number of openings for sensory nerves in its shell plates. Lineages with more openings evolve visual systems with thousands of eyespots, whereas those with fewer openings evolve visual systems with hundreds of shell eyes. These macroevolutionary outcomes shaped by path dependence are both deterministic and stochastic because possibilities are restricted yet not entirely predictable.

The chiton genus Cryptoplax is widely distributed in the Indo-Pacific, extending to southern Australia and the northwestern Pacific (NWP), with 17 recognized species. Among these species, Cryptoplax japonica is commonly found on rocky intertidal and subtidal substrates in the NWP, whereas another species, C. propior, is rarely seen because of its cryptic subtidal habitat and limited distribution. In this study, we surveyed the genetic diversity of C. japonica populations based on 93 individuals from 24 sampling sites along the Korean and Japanese coastlines, including the type locality, using DNA sequences of the mitochondrial gene cytochrome c oxidase subunit I (COI). Haplotype network and phylogenetic analyses of COI sequences revealed two highly divergent genetic lineages of C. japonica separated by a large pairwise genetic distance (10.62%), which was comparable to the genetic difference when either of these two lineages (A or B) is compared with the co-occurring C. propior. In addition to COI sequences, average sequence divergence in 16S rDNA between these three lineages ranged from 2.0 to 3.3%. In contrast to this deep sequence divergence, both morphological examination of radula, girdle and articulamentum colouring, and morphometric analyses of shell measurements using principal component analysis and linear discriminant analysis revealed no diagnostic differences between the two C. japonica lineages. The co-occurrence of these two divergent lineages within most of our studied area, with no morphological differences, indicates cryptic divergence. More extensive sampling from the entire distributional ranges of these cryptic species, in combination with the use of additional molecular markers could shed light on the mechanisms underlying their divergence.

Transitions to terrestriality have been associated with major animal radiations including land snails and slugs in Stylommatophora (>20 000 described species), the most successful lineage of 'pulmonates' (a non-monophyletic assemblage of air-breathing gastropods). However, phylogenomic studies have failed to robustly resolve relationships among traditional pulmonates and affiliated marine lineages that comprise clade Panpulmonata (Mollusca, Gastropoda), especially two key taxa: Sacoglossa, a group including photosynthetic sea slugs, and Siphonarioidea, intertidal limpet-like snails with a non-contractile pneumostome (narrow opening to a vascularized pallial cavity). To clarify the evolutionary history of the panpulmonate radiation, we performed phylogenomic analyses on datasets of up to 1160 nuclear protein-coding genes for 110 gastropods, including 40 new transcriptomes for Sacoglossa and Siphonarioidea. All 18 analyses recovered Sacoglossa as the sister group to a clade we named Pneumopulmonata, within which Siphonarioidea was sister to the remaining lineages in most analyses. Comparative modelling indicated shifts to marginal habitat (estuarine, mangrove and intertidal zones) preceded and accelerated the evolution of a pneumostome, present in the pneumopulmonate ancestor along with a one-sided plicate gill. These findings highlight key intermediate stages in the evolution of air-breathing snails, supporting the hypothesis that adaptation to marginal zones played an important role in major sea-to-land transitions.

The calyptraeids Crepidula adunca and Crepidula norrisiarum, both direct developers, are abundant in the shallow waters of the northeastern Pacific. They have long been considered as two allopatric species that live on different hosts and differ in body size. In this study, we rigorously test this historical hypothesis by assessing molecular taxonomy, museum records, new morphological and host observations, and population genetic structure along the northeast Pacific coast. Results show that, contrary to previous understanding, the distributions of the two species largely overlap and that size does not effectively distinguish them, especially in the northern part of the range where the nominal “C. adunca” has been studied. Newly recognized northern occurrences of C. norrisiarum demonstrate that both species have similar, disrupted distributions that range from British Colombia through southern California. Neither species is reported to occur on the outer shores of southern Washington or Oregon, the exception being records of C. adunca at Cape Arago, Oregon. Despite this apparent geographic gap, neither species shows appreciable genetic differentiation between the northern and southern parts of its ranges. Despite body size having been used to distinguish these species, our observations do not support body size as a species-specific trait; rather, they support a new hypothesis that body size variation reflects regional differences in host use and host availability.

Metallothioneins (MTs) are proteins devoted to the control of metal homeostasis and detoxification, and therefore, MTs have been crucial for the adaptation of the living beings to variable situations of metal bioavailability. The evolution of MTs is, however, not yet fully understood, and to provide new insights into it, we have investigated the MTs in the diverse classes of Mollusks. We have shown that most molluskan MTs are bimodular proteins that combine six domains-α, β1, β2, β3, γ, and δ-in a lineage-specific manner. We have functionally characterized the Neritimorpha β3β1 and the Patellogastropoda γβ1 MTs, demonstrating the metal-binding capacity of the new γ domain. Our results have revealed a modular organization of mollusk MT, whose evolution has been impacted by duplication, loss, and de novo emergence of domains. MTs represent a paradigmatic example of modular evolution probably driven by the structural and functional requirements of metal binding.

The molluscan class Gastropoda includes over 5,000 parasitic species whose evolutionary origins remain poorly understood. Marine snails of the genus Caledoniella (Caledoniellidae) are obligate parasites that live on the abdominal surface of the gonodactylid mantis shrimps. They have highly modified morphological characteristics specialized to the ectoparasitic lifestyle that make it difficult to infer their close relatives, thereby posing a question about their current systematic position in the superfamily Vanikoroidea. In the present study, we performed molecular phylogenetic analyses using three nuclear and three mitochondrial gene sequences to unveil the phylogenetic position of these enigmatic snails. The resulting trees recovered Caledoniella in the superfamily Truncatelloidea and within a subclade of commensal species that live on the burrow wall of marine benthic invertebrates. More specifically, Caledoniella formed the sister clade to a commensal snail species living in mantis-shrimp burrows and they collectively were sister to Sigaretornus planus (formerly in the family Tornidae or Vitrinellidae), a commensal living in echiuran burrows. This topology suggests that the species of Caledoniella achieved their ectoparasitic mode of life through the following evolutionary pathway: (1) invasion into the burrows of benthic invertebrates, (2) specialization to mantis shrimps, and (3) colonization of the host body surface from the host burrow wall with the evolution of the parasitic nature. The final step is likely to have been accompanied by the acquisition of a sucker on the metapodium, the loss of the radula and operculum, and the formation of monogamous pair bonds. The present molecular phylogeny also suggested parallel evolution of planispiral shells in a subclade of Truncatelloidea and enabled us to newly redefine the families Caledoniellidae, Elachisinidae, Teinostomatidae, Tornidae and Vitrinellidae.

Continuing molecular and morphological investigations of a limpet recently reported as introduced to Sicily in the Mediterranean Sea have revealed it to be an undescribed species of Lottia Gray, 1833, a genus that is native to Sri Lanka and vicinity in the northern Indian Ocean. The genetic and morphological features of the limpets compared from Sicily and Sri Lanka correspond so closely that we do not hesitate to describe it collectively as Lottia iani n. sp., with type locality of Tangalle on the coast of Sri Lanka. Much is still unknown about its native range, when and how it arrived in Sicily, whether it is capable of impacting native species, and whether its introduction might be more widespread in the Mediterranean than just the particular eastern Sicilian localities where it has been observed. It is plausible that the introduction of L. iani to Sicily could have resulted from recent expansions to the Suez Canal, which is known to have led to other species introductions in recent years. Other possibilities include an introduction related to shipping or mariculture activities. However it managed to arrive, this limpet species has clearly been able to establish a self-recruiting local population at particular Sicilian localities with rocky volcanic shores.

John Stuart Pearse, Professor Emeritus in the Department of Ecology and Evolutionary Biology (EEB) at the University of California, Santa Cruz, died on July 31, 2020, at the age of 84. John was the consummate invertebrate biologist with far-reaching interests and expertise. He was also an amazing teacher and mentor to a cadre of postdocs and graduate students, and to the hundreds of undergraduates who took his courses in invertebrate zoology, intertidal biology, and kelp forest ecology. John was born in Boise, Idaho, on May 28, 1936. His father was an experimental agronomist with the U.S. Forest Service, and the family moved between assignments about every 5 years. They left Idaho and went to Ogden, UT, and then to Washington, DC, and lastly Tucson, AZ. While in Washington, DC, John spent time visiting museums and exploring the local forests. In Tucson, John became a budding herpetologist, and was befriended by a new University of Arizona faculty member, Charles Herbert Lowe, Jr., who later became a major force in desert ecology known for his studies on parthenogenetic whiptail lizards. John's father received a new assignment in Egypt, bringing the family there but leaving John behind in Tucson to finish his senior year in high school while staying with family friends George and Irene Olin. Besides George's job as a driver and dispatcher, John described him as a “fabulous desert naturalist” who later became the first botanist at the Arizona-Sonora Desert Museum. John volunteered there (1952–1954) installing trails, building the desert garden, and caring for the animals. After finishing high school, John joined his family in Egypt where his father was working with the U.S. AID program in Egypt's Western Desert on the coast of the Mediterranean Sea. John's education continued in his freshman year at the American University in Cairo, Egypt, where he was one of six American students (apparently all named John). John fell in love with marine life that summer after constant snorkeling in the Mediterranean, which opened up a new world to him. However, the American University of Cairo did not have a department or even courses in biology. John's father, despite having disliked living in Chicago while he was completing a master's degree at the University of Chicago, helped John get a scholarship there, and arranged for him to live with his aunt and uncle. After exploring the Gulf of Suez with friends, and traveling through Europe by himself, John arrived in 1955 at the University of Chicago, completing his BA in Zoology in 1958. It appears that John did not have a much better opinion of living in Chicago, although he enjoyed the summer of 1956 working as a forest fire fighter back in Idaho. However, his explorations of Mediterranean marine biology prompted him to seek out a summer of volunteering at the Marine Biological Laboratory in Woods Hole, MA. John attended graduate school at Stanford University in California; working with Arthur Giese, he earned his PhD degree in 1964. John was quick to praise Giese as a wonderful mentor, and likewise was especially appreciative of Stanford's Donald P. Abbott, whose influence, starting with his invertebrate zoology course at Hopkins Marine Station in 1959, had a life-long effect on John. John's research interests were broad and deep. We have compiled a nearly complete listing of 158 scientific publications, organized by topic and by geographic region, of which we have only cited select items here. The Web of Science algorithm categorizes John's publications indexed in that database into 25 non-exclusive categories, the top five being Zoology, Environmental Sciences, Ecology, Marine, Freshwater Biology, Reproductive Biology, and Physiology. These categories reflect John's passionate curiosity for a broad range of biological questions, his impressive mastery of experimental skills, his global experience studying polar, temperate, and tropical faunas, and his 60 years of scholarly contributions. John's formal research career began as a graduate student when he took advantage of an opportunity that brought him to McMurdo Sound in Antarctica for more than 14 months (1960–1962), as part of a program developed there by Donald Wohlschlag of Stanford with support from the US National Science Foundation. John and a team of other graduate students were given a rare opportunity to document a previously unexplored community of surprisingly diverse and abundant animals that lived under the ice sheet. While there, John's goal was to determine in as much detail as he could the temporal pattern of reproduction in representative Antarctic species. He wondered whether animals that lived in permanently cold and mostly dark waters under the ice sheet would have annual reproductive cycles similar to animals at better-studied latitudes, as pioneered by his advisor, Arthur Giese. At the time, John and his fellow graduate students would cut holes through the ice and then use traps to retrieve animals from the bottom. By far the most abundant animals trapped were amphipods (Orchomene spp.) and sea stars (Odontaster validus), and John collected data on both. Eventually, he chose to emphasize the data for the sea star, and thus began a life-long passion for the study of echinoderm reproduction. Over 20 years later, John would again return to Antarctica with his own graduate students to continue and expand his earlier studies, by then expanded to the Indo-Pacific and California. Much of John's diversity of research was united by his fascination with marine invertebrate reproduction, a topic that he continuously published on throughout his career. After he returned from Antarctica, he used his collected data to complete and publish the first part (Pearse, 1964) of a truly landmark PhD dissertation. Dr. John Pearse was then ready for a warmer setting and made plans to do comparative work in the tropics. He set out on a 3-month cruise on the Te Vega through the Southwest Pacific, where he sampled the sea urchin genus, Diadema (Pearse & Arch, 1969; Pearse & Phillips, 1968), then joined the faculty of the American University in Cairo, Egypt. Meanwhile, he continued to publish notable parts of his Antarctic research (Pearse, 1966, 1967, 1969a), and began to document the Egyptian fauna (James & Pearse, 1969; Pearse, 1967, 1968a, 1969b, 1969c; Pearse et al., 1970). However, John's efforts to build a program in Egypt were interrupted by the Arab–Israeli Six-Day War in June, 1967. Americans were expelled from Egypt and John next found himself in temperate southern California working on kelp forests with Wheeler North at the Kerckhoff Marine Lab of the California Institute of Technology. His early kelp forest studies were already revealing his emerging interests in community interactions (North & Pearse, 1970) and the broad quantitative sampling of the kelp forest community (Pearse et al., 1970). After several temporary teaching jobs on the West Coast, John accepted a faculty appointment at the University of California, Santa Cruz (UCSC), where he quickly established research in the local kelp forest and rocky intertidal habitats. An early paper from this work (Lowry & Pearse, 1973) established the habitat responses of abalones and sea urchins to the presence of sea otters, another featured his regular experimental approach to addressing questions (Towle & Pearse, 1973), and others were based on comprehensive documentation of a central California kelp forest community (Pearse & Lowry, 1974). In 1978, the construction of the Long Marine Laboratory at Terrace Point in Santa Cruz finally provided John with the facilities to begin his long-planned studies of the role of photoperiod cues in the timing of reproduction in echinoderms. At that time, it was widely accepted that marine animals must use annual fluctuations in temperature to control their reproductive cycle, but John suspected that photoperiod, not temperature, might provide animals with a more reliable natural cycle, especially in western North America where winter and summer differed only slightly in temperature. The first study, in what would become an influential series of experimental demonstrations of photoperiodism, was successful in demonstrating for the first time that a marine animal, the sea star Pisaster ochraceus, used changing photoperiod to set the timing of its annual reproductive cycle (Pearse & Eernisse, 1982). For these contributions, John received the Antarctic Service Award, Western Society of Naturalists' Naturalist for the Ages Award, Monterey Bay National Marine Sanctuary Award for Science, Monterey Bay National Marine Sanctuary Award for Education, Ricketts Memorial Lecture Award, and was elected a Fellow of the American Association for the Advancement of Science. Pearse Valley in Antarctica was named for John. Well over half of John's publications featured studies of reproduction in sea urchins (echinoids) or sea stars (asteroids). The highlights of his research on the reproductive biology of echinoderms and other marine invertebrates have been well summarized already in a 70th birthday tribute by Hadfield (2007), which should be consulted for details not presented here. Interested readers can also explore our more complete compilation of John's publications. His approach was consistently experimental, whether he and collaborators were teasing apart how these echinoderms used photoperiodic cues to time their reproduction, or testing hypotheses on larval feeding, or asking how adult feeding in the field or laboratory contributed to reproduction, growth, and skeletal biomineralization. John seemed to be equally at home with field work in Antarctica, on the temperate coast of California, or in the tropical Indo-Pacific. While he was primarily known, worldwide, for his echinoderm contributions, he also studied the reproduction and ecology of multiple other taxa, including molluscs ranging from chitons to limpets, snails, nudibranchs, and terrestrial slugs. This experimental approach had a deep influence on John's students, including both of us. We learned to consider the entire animal in its habitat, and over time, in order to appreciate how an animal managed to successfully reproduce. John was great at giving us the tools and enthusiasm for pursuing zoological questions, wherever they might lead, and he would encourage either single-author or collaborative projects, depending on how either might better help us address scientific hypotheses. Building on the already-noted efforts to characterize subtidal marine communities that he began even as an undergraduate student on the Mediterranean coast of Egypt, John continued to expand his commitment to long-term monitoring and surveys, both intertidal and subtidal. While the invertebrate holdings at the California Academy of Sciences were rich and diverse globally, they were short on local species and exemplars until the arrival of more than 780 specimen lots from the UCSC Intertidal Survey in the early 1970s. One of the survey sites was Pleasure Point in Santa Cruz (33rd Avenue), well known for its nearshore sewer outfall. In 1976, the outfall was shut down, and this spurred John's next major survey project looking at the recovery of the intertidal fauna and flora; the survey extended over four decades and was a predictable field trip for intertidal biology courses (Doyle & Pearse, 1972; Pearse et al., 2015). Concurrently, John also began a long-term study in the kelp forest off Hopkins Marine Station and included students from his Kelp Forest Ecology course. John also instigated and oversaw the first intertidal survey of the University of California Landels-Hill Big Creek Reserve in Big Sur (Pearse, 1984). After his retirement, these surveys and monitoring efforts continued but now as an outreach effort. In the second decade of his retirement, John and colleagues organized LiMPETS (Long-term Monitoring Program and Experiential Training for Students) for the National Oceanic and Atmospheric Administration's west coast National Marine Sanctuary program (Osborn et al., 2005, 2007). That program, conceived as an early citizen science program, today engages over 6,000 students, educators and volunteers who collect data at more than 60 intertidal sites over 600 miles of California coastline, and has been extended to a similar, also still ongoing, program in Hawaii (Zabin et al., 2013). After John’s return from Egypt and while he was a research fellow at Kerckhoff, Wheeler North left him free to take a number of temporary teaching positions. An early one was back at Stanford’s Hopkins Marine Station, where he met Vicki Buchsbaum (who became Vicki Buchsbaum Pearse in 1970). Others included teaching at Oregon State University’s marine lab in Newport, a second cruise on the Te Vega as faculty this time, the University of California San Diego, the University of Southern California’s marine lab on Catalina Island, and UCSC. From 1971, John pioneered combining teaching and research in his courses at UCSC. This included following changes in the intertidal community after the closure of the Pleasure Point sewage outfall with students in his Intertidal Organisms field course, and the long-term study in the kelp forest off Hopkins Marine Station that was a central part of his Kelp Forest Ecology course. In this way, John taught students marine ecology, as they helped him collect research data on marine organisms. Many of these students went on to careers in science. At UCSC, together with William Doyle, John was instrumental in establishing the marine science program and was a key person in the organizing of the Institute of Marine Sciences. John also served as the Associate Chair of Biology and oversaw the recruitment of EEB faculty members Grant Pogson, Terrie Williams, and Giacomo Bernardi. After retiring from UCSC, John became a significant contributor to the California Academy of Sciences, serving as Trustee July 1994–June 2003, as Vice President July 1996–June 1997, and President July 1997–June 2003. His leadership and guidance were pivotal during this time of planning the building replacement for the Academy. John helped shape the discussions that led to the initial vision and strategy for developing the world-class facilities which house the Academy today. In recognition of his scientific contributions and service to the Academy, John received the Academy's highest honor in 2011, The Fellows Medal. John also served as President of the Western Society of Naturalists, Santa Cruz City Museum Association, International Society of Invertebrate Reproduction, UCSC Chapter of Sigma Xi, and the Society for Integrative and Comparative Biology. He had editorships for Marine Biology, Invertebrate Reproduction and Development, Marine Ecology Progress Series, Science, and the Encyclopedia of Reproduction. With Arthur Giese, he was Co-Editor of seven volumes of the treatise Reproduction of Marine Invertebrates, with Vicki Pearse joining them as Co-Editor for the last two volumes. The home of John and Vicki, first in Santa Cruz and later in Pacific Grove, was always warm and welcoming. They followed the model of Don and Izzie Abbott in hosting after-seminar potlucks for students and speakers, visiting colleagues, and researchers from all over the world. A number of UCSC undergraduate and graduate students lived with John and Vicki for extended periods. And no gathering was complete without lively discussion and debate. Many of the international visitors came from contact with John and Vicki during their extensive traveling, which found them at natural history destinations, academic institutions, and marine laboratories throughout the world. Gracious, supportive interactions with John were the norm, a non-universal trait in academia. This was a trait John especially valued and practiced. At his 70th birthday talk in 2006, John took special note of his own mentors: he referred to George Olin of the Arizona-Sonora Desert Museum as a “…wonderful and influential role model;” his major professor, Arthur Giese, as “wonderful all around;” Wheeler North as a “wonderful role model of a truly decent human being and an excellent scientist;” and Don Abbott at Hopkins Marine Station as “the person who I tried to emulate throughout my career, especially in my teaching and how I treated students.” While John's students and colleagues all had unique and specific shared research interests with John, we all shared in common and benefited from John's benevolence as well. In June 2006, in celebration of his 70th birthday, John was honored with PearseFest, a memorable 2-day symposium and banquet on the UCSC campus. In July 2017, the 8th North American Echinoderm Conference held in Worcester, MA, was dedicated to John and Vicki for their long-standing love of echinoderms, for nurturing the careers of numerous students and colleagues (Langan, 2007), and for serving as strong role models for biologists at all stages of their careers. In 2020, about 3 months after his passing, a special memorial session with 28 contributed papers was arranged as a tribute to John for the 101st meeting of the Western Society of Naturalists, entitled Tidepooling with John: In honor of Dr. John Pearse. In all aspects of his scientific, public, and family life, John and Vicki were a team for the ages. Vicki is the daughter of the late Ralph and Mildred Buchsbaum, the authors of multiple editions of the best-selling Animals Without Backbones (Buchsbaum, 1938), and more recently revised as a family collaboration (Buchsbaum et al., 1987), and a more complete textbook full of zoological natural history, Living Invertebrates (Pearse et al., 1987). We include here an additional list of publications by Vicki Buchsbaum Pearse. Like John, Vicki also earned her PhD at Stanford (V. Buchsbaum, 1968). She continues to be a notable scientist in her own right, and her co-authored contributions with John represent an important part of their mutual legacy. Her studies of sea anemones and their symbionts, and expertise as a global authority on placozoans, are particularly notable. Vicki was also Founding Editor of Invertebrate Biology, and was closely associated with the name change (from Transactions of the American Microscopical Society) and the pivot toward publishing studies of the biology of invertebrate animals (Tyler & Carlton, 1995). Vicki served as editor-in-chief of the journal from 1995 (Volume 114) through 2003 (Volume 122), and deserves much of the credit for its ongoing success. In closing, we concur with David Epel (pers. comm. to DJE, 20 October 2020), a long-time Hopkins colleague, who noted that “Few people have the motivation to want to make their world a better place, the skills to do this, and the energy to take on these leadership activities.” John was one of these people. We know we speak for John's colleagues, students, associates, and admirers who experienced the benevolence of John and Vicki. Many of us are also thankful for Vicki's insightful and helpful mentoring and friendship. Speaking to individuals associated with this journal we also learned of John and Vicki's many contributions to the journal and its readership. Parts of John's history reassembled here came from Hadfield (2007) and from annotations by John himself of his 2006 Pearsefest presentation. Additional commentary and materials incorporated and summarized here were provided by Vicki Buchsbaum Pearse, Devon Pearse, Dan Costa, Rosemary Romero, Terrance Gosliner, Janet Leonard, Larry Basch, David Epel, Gary Griggs, Todd Newberry, and by speakers at the recent Western Society of Naturalists 2020 special tribute session for John. We thank everyone for their contributions and memories of John. Reproduction and ecology of Antarctic echinoderms Reproduction of temperate northeastern Pacific fauna Reproduction of temperate northwestern Atlantic fauna Reproduction of tropical eastern Pacific echinoderms Reproduction of tropical Indo-Pacific echinoderms General works on reproduction of marine invertebrates General works on echinoderm biology General works on invertebrate biology Politics

Additional file 1. Taxon sampling, locality and specimen vouches. Information on taxon sampling, locality and specimen vouchers.

Latitudinal diversity patterns in marine species are commonly estimated from literature records, which at times are incomplete and/or biased. Advances in molecular phylogenetics have contributed to avoid this bias, clarifying the identity of the species, improving our knowledge of species diversity and distribution. With the aim to identify biogeographic biases, we compiled and compared range distribution data of polyplacophorans along the South-eastern Pacific (SEP) coast (0°–56° S) generated from: (i) literature review (LIT dataset) and (ii) Operational Taxonomic Units (OTUs dataset), based on the analysis of 8949 individuals obtained from field sampling and biological collections. Cytochrome oxidase I (COI) and 16S rRNA of 104 specimens were used for genetic identification of conflictive morphospecies. Multivariate analysis (nMDS, PERMANOVA) were applied to test differences between datasets (LIT, OTUs) and also between biogeographic ecoregions. Just like prior studies based on literature reviews, the richness of LIT species showed an increase with latitude. Contrastingly, OTUs’ richness peaked at intermediate latitudes showing a bell-shaped distribution, indicating that the LIT dataset was flawed by inaccuracies in the identification and location of polyplacophoran species on the South-eastern Pacific, causing an overestimation of their geographic ranges. Our results contrast with the previous richness patterns described for the SEP polyplacophorans, where species richness was reported to increase with latitude. Both an overestimation of geographic ranges and inaccuracies in the identification of species cause these differences. Biogeographical studies should be conducted on the basis of a comprehensive review of specimens with verifiable occurrences, and incorporate as far as possible genetic analysis to define the identity of conflicting morphospecies, in order to improve the estimation of species richness and the understanding of marine biodiversity.

BACKGROUND:Polyplacophora, or chitons, have long fascinated malacologists for their distinct and rather conserved morphology and lifestyle compared to other mollusk classes. However, key aspects of their phylogeny and evolution remain unclear due to the few morphological, molecular, or combined phylogenetic analyses, particularly those addressing the relationships among the major chiton lineages.RESULTS:Here, we present a mitogenomic phylogeny of chitons based on 13 newly sequenced mitochondrial genomes along with eight available ones and RNAseq-derived mitochondrial sequences from four additional species. Reconstructed phylogenies largely agreed with the latest advances in chiton systematics and integrative taxonomy but we identified some conflicts that call for taxonomic revisions. Despite an overall conserved gene order in chiton mitogenomes, we described three new rearrangements that might have taxonomic utility and reconstructed the most likely scenario of gene order change in this group. Our phylogeny was time-calibrated using various fossils and relaxed molecular clocks, and the robustness of these analyses was assessed with several sensitivity analyses. The inferred ages largely agreed with previous molecular clock estimates and the fossil record, but we also noted that the ambiguities inherent to the chiton fossil record might confound molecular clock analyses.CONCLUSIONS:In light of the reconstructed time-calibrated framework, we discuss the evolution of key morphological features and call for a continued effort towards clarifying the phylogeny and evolution of chitons.