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Eulachon (Thaleichthys pacificus), a culturally and ecologically important anadromous smelt (Family Osmeridae), ranges from Northern California to the southeast Bering Sea. In recent decades, some populations have experienced declines. Here we use a contig-level genome assembly combined with previously published restriction site-associated DNA sequencing (RADseq)-derived markers to construct an amplicon panel for eulachon. Using this panel, we develop a filtered genetic baseline of 521 variant loci genotyped in 1989 individuals from 14 populations ranging from Northern California through central Alaska. Consistent with prior genetic studies, the strongest separation occurs among three main regions: from Northern California up to and including the Fraser River; north of the Fraser River to southeast Alaska; and within the Gulf of Alaska. Separating the Fraser River from southern US populations and refining additional substructure within the central coast may be possible in mixed-stock analysis; this will be addressed in future work. The amplicon panel outperformed the previous microsatellite panel and thus will be used in future mixed-stock analyses of eulachon to provide new insights for management and conservation of eulachon.

EulachonThaleichthys pacificus, a culturally and ecologically important anadromous smelt (Family Osmeridae), ranges from Northern California to the southeast Bering Sea. In recent decades, some populations have experienced declines. Here we use a contig-level genome assembly combined with previously published RADseq-derived markers to construct an amplicon panel for eulachon. Using this panel, we develop a filtered genetic baseline of 521 variant loci genotyped in 1,989 individuals from 14 populations ranging from Northern California through Central Alaska. Consistent with prior genetic studies, the strongest separation occurs among three main regions: from Northern California up to and including the Fraser River; north of the Fraser River to southeast Alaska; and within the Gulf of Alaska. Separating the Fraser River from southern US populations, and refining additional substructure within the central coast may be possible in mixed-stock analysis; this will be addressed in future work. The amplicon panel outperformed the previous microsatellite panel, and thus will be used in future mixed-stock analyses of eulachon in order to provide new insights for management and conservation of eulachon.

Pinto abalone (Haliotis kamtschatkana), the widest ranging abalone species in North America, occurs from Alaska, United States to Central Baja California, Mexico. The species has been observed in intertidal and subtidal habitats from 0 to 40mdepth. The best available data indicate that pinto abalone abundance has declined in many areas throughout the species' range due to fisheries harvest. Subsistence and personal use fisheries in Alaska and a commercial fishery in Mexico persist. Preliminary data from 2008 to 2016 indicate signs of recovery for some pinto abalone populations along the British Columbia coast due to multiple contributing factors including a reduction in illegal harvest, natural recovery following fishery closure, and low predation pressure. By contrast, pinto abalone populations at the San Juan Islands in Washington are experiencing recruitment failure and continuing to decline, despite closure of the fisheries and no evidence of poaching. Throughout the remainder of the species' range, trends are less clear, due to the lack of regular, long-term monitoring surveys for pinto abalone. The limited data from surveys and/or opportunistic sightings indicate that pinto abalone populations are small, patchily distributed, and/or fluctuate episodically in Alaska, California, and Mexico, with evidence of recent recruitment in a number of locations within these three areas. Baseline abundance and trend data for the species before the advent of commercial fisheries and, in some areas, the local extirpation of sea otters is lacking. Without a clear baseline with which to compare the current abundance levels and trend information, it is difficult to interpret what these levels mean for the status and viability of the species. Threats to pinto abalone were evaluated and characterized using a qualitative rating (i.e., low, moderate, high, very high) based on the threats' scope, severity, and persistence and the sufficiency of the data to support the rating. Several threats that posed a moderate level of risk to pinto abalone were identified including the following: low densities as a result of historical overfishing; the potential threat posed by ocean acidification; and illegal take because of poaching and inadequate law enforcement. The overall risk that pinto abalone face throughout their range was evaluated, and it was determined that they have a low to moderate level of extinction risk now and in the foreseeable future (over both the 30-y and 100-y time horizons). There is a high level of uncertainty regarding demographic factors, in particular regarding whether abundance and productivity levels are sufficient to support the persistence and recovery of the species in the face of continuing and potential future threats. Although recruitment failure may be occurring in some areas (e.g., San Juan Islands Archipelago), in other areas throughout the range recurring and/or recent recruitment events have been observed, despite low densities, and have even resulted in increased densities (across all size classes) at several index sites in British Columbia. Limitations in using demographic data to guide conservation actions and help ensure species persistence could be overcome by conducting consistent monitoring of pinto abalone populations throughout their range.

WOS:000435219000002; International audience; The identification of bivalve larvae and early postlarvae in plankton and benthic samples has long been a challenge, hampering both basic and applied research efforts in marine, estuarine, and freshwater environments. The usefulness of published optical micrographs of the early life-history stages of bivalves is limited because of the great morphological similarity of the imaged articulated shells, particularly at the early (straight-hinge) developmental stages. While a number of techniques have been refined in recent years and show promise for use in routine identifications of larval and post-larval bivalves (e.g., single-step nested multiplex polymerase chain reaction; in situ hybridization protocols through color coding with taxon-specific, dye-labeled DNA probes; coupled fluorescence in situ hybridization and cell sorting; and image analysis techniques using species-specific shell birefringence patterns under polarized light), no adequate comprehensive reference source exists that accurately depicts the morphology and morphometry of the shells of larval and post-larval stages of target bivalve species in a consistent format to assist in identification of such stages. To this end, scanning electron micrograph (SEM) sequences are presented of the disarticulated shell valves of laboratory-reared larval and post-larval stages of 56 species of bivalve molluscs from a wide spectrum of marine, estuarine, and freshwater habitats. Emphasis is placed on the usefulness of the morphology and morphometrics of consistently-oriented, disarticulated shell valves and associated hinge structures in discriminating the early life-history stages of these various bivalve species. Although the scanning electron micrograph sequences presented accurately depict the gross morphologies/morphometrics and hinge structures of the disarticulated shell valves of the larvae and/or postlarvae of the 56 species of bivalves, it is important to emphasize that a scanning electron microscope is not necessary to observe even fine hinge structures associated with the early ontogenetic stages of these species. Such structures are readily visible using a wide range of optical compound microscopes equipped with high-intensity reflected light sources, although the disarticulated shell valves must be viewed in several planes of focus to discern the often subtle details seen clearly in the scanning electron micrographs. These morphological characters provide researchers with invaluable aids for the routine identification of the early life-history stages of these species isolated from plankton and benthic samples.

This study presents the first microsatellite DNA study of population structure of Pacific hake, Merluccius productus (also known as Pacific whiting) within the Salish Sea, which has been identified as a distinct population segment under the US Endangered Species Act and is currently listed as a federal Species of Concern. In contrast, a separate coastal stock component of Pacific hake represents the most abundant commercial groundfish species on the US West Coast. We surveyed variation at 10 microsatellite DNA loci in a total of 655 individuals from three Salish Sea locations (Port Susan (PTS) and Dabob Bay in Washington and south-central Strait of Georgia (SOG) in British Columbia), three coastal locations (two off southern California and one in the Gulf of Alaska), and the Northern Gulf of California (GOC), México. No significant differences were detected among temporal samples from both PTS and SOG locations. Multilocus measures of population subdivision between coastal and Salish Sea populations (all pairwise FST ≥ 0.03) and between PTS and SOG populations (FST ≥ 0.01) suggest a moderate degree of demographic isolation among these spawning populations. No significant genetic differences were found among the three coastal Pacific hake samples; however, Pacific hake from the GOC were significantly differentiated from both coastal (FST > 0.05) and Salish Sea (FST ≥ 0.03) Pacific hake. Correlations between genetic and geographic distance showed that Pacific hake display a very strong isolation by distance signal, both over the whole study area (∼4500 km; r2 = 0.94) and within the Salish Sea (∼280 km; r2 = 0.72). This study suggests that PTS and SOG populations are to some extent demographically isolated from each other.

Archival scales from 603 sockeye salmon (Oncorhynchus nerka), sampled from May to July 1924 in the lower Columbia River, were analysed for genetic variability at 12 microsatellite loci and compared to 17 present-day O. nerka populations-exhibiting either anadromous (sockeye salmon) or nonanadromous (kokanee) life histories-from throughout the Columbia River Basin, including areas upstream of impassable dams built subsequent to 1924. Statistical analyses identified four major genetic assemblages of sockeye salmon in the 1924 samples. Two of these putative historical groupings were found to be genetically similar to extant evolutionarily significant units (ESUs) in the Okanogan and Wenatchee Rivers (pairwise F(ST) = 0.004 and 0.002, respectively), and assignment tests were able to allocate 77% of the fish in these two historical groupings to the contemporary Okanogan River and Lake Wenatchee ESUs. A third historical genetic grouping was most closely aligned with contemporary sockeye salmon in Redfish Lake, Idaho, although the association was less robust (pairwise F(ST) = 0.060). However, a fourth genetic grouping did not appear to be related to any contemporary sockeye salmon or kokanee population, assigned poorly to the O. nerka baseline, and had distinctive early return migration timing, suggesting that this group represents a historical ESU originating in headwater lakes in British Columbia that was probably extirpated sometime after 1924. The lack of a contemporary O. nerka population possessing the genetic legacy of this extinct ESU indicates that efforts to reestablish early-migrating sockeye salmon to the headwater lakes region of the Columbia River will be difficult.

Eulachon (Thaleichthys pacificus), an anadromous smelt in the Northeast Pacific Ocean was examined for listing under the USA’s Endangered Species Act (ESA). A southern Distinct Population Segment (DPS) of eulachon – that occurs in the California Current and is composed of numerous subpopulations that spawn in rivers from northern California to northern British Columbia – was identified on the basis of ecological and environmental characteristics, and to a lesser extent, genetic and life history variation. Although the northern terrestrial boundary of this DPS remains uncertain, our consensus opinion was that this northern boundary occurs south of the Nass River and that the DPS was discrete from more northern eulachon, as well as significant to the biological species as a whole and thus is a ‘species’ under the ESA. Eulachon have been nearly absent in northern California for over two decades, have declined in the Fraser River by over 97% in the past 10 years, and are at historically low levels in other British Columbia rivers in the DPS, and nearly so in the Columbia River. Major threats to southern eulachon include climate change impacts on ocean and freshwater habitat, by-catch in offshore shrimp trawl fisheries, changes in downstream flow timing and intensity owing to dams and water diversions, and predation. These threats, together with large declines in abundance, indicate that the southern DPS of eulachon is at moderate risk of extinction throughout all of its range. The southern DPS was listed as threatened under the ESA in May 2010 – the first marine forage fish to be afforded these statutory protections, which apply only to waters under U.S. jurisdiction.

This 20th Wakefield Symposium, ‘The genetics of subpolar fish and invertebrates’, is the successor of the 11th Wakefield Symposium, ‘Genetics of sub- arctic fish and shellfish’, which was held in Juneau, Alaska in 1993. In the introduction to that sympo- sium (Gharrett & Smoker 1994), it was noted that: ‘beginning in the 1960s, modern tools of genetic analysis began to be broadly applied in fisheries science’, and that ‘within the past decade (referring to the 1980s), fisheries genetics had entered the main- stream of fisheries resource utilization’. That obser- vation may be an understatement in today’s world of fisheries science. Once-vigorous fisheries in many parts of the world have failed, growing demand for fisheries products has led to full utilization of many remaining capture resources and is driving an increase in aquaculture productivity, and the role of aquacul- ture has increased dramatically ([FAO 2002]). Looming over concerns of lost stocks and persistent erosion of genetic variability are predictions of global warming, which may further tax genetic resources. One of the consequences of these developments is an increased interest in and reliance on genetic applications to many aspects of fisheries management, aquaculture, and conservation.

Information developed during recently completed evaluations of the status of seven species of anadromous Pacific salmonids (Oncorhynchus spp.) in the Pacific Northwest was used to characterize patterns of intraspecific diversity along three major axes: ecology, life history and biochemical genetics. Within the study area, the species' ranges, and therefore the number of distinct ecological regions inhabited differ considerably, with pink and chum salmon limited to the northern areas and chinook salmon and steelhead distributed over the widest geographic range. The species showed comparable differences in the patterns of life history and genetic diversity, with chinook and sockeye salmon and steelhead having the most major diversity groups and pink, chum and coho salmon having the least. Both life history and genetic diversity showed a strong, positive correlation with the extent of ecological diversity experienced by a species, and the correlation between the number of major genetic and life history groups within a species was even stronger (r=0.96; P

Phylogenetic relationships among vesicomyid clams (Bivalvia: Vesicomyidae) and their placement within the order Heterodonta were examined using mitochondrial encoded cytochrome oxidase subunit I (COI) DNA sequences. The presently analyzed vesicomyids represent a recent monophyletic radiation that probably occurred within the Cenozoic. Nucleotide phylogenetic analyses resolved discrete clades that were consistent with currently recognized species: Calyptogena magnifica, C. ponderosa, Ectenagena extenta, C. phaseoliformis, Vesicomya cordata, Calyptogena n. sp. (Gulf of Mexico), C. kaikoi, C. nautilei, C. solidissima and C. soyoae (Type-A). However, specimens variously identified as: V. gigas, C. kilmeri, C. pacifica, and V. lepta comprised two “species complexes”, each composed of multiple evolutionary lineages. Most taxa are limited to hydrothermal-vent or cold-seep habitats, but the “vent” versus “seep” clams do not constitute separate monophyletic groups. Current applications of the generic names Calyptogena, Ectenagena, and Vesicomya are not consistent with phylogenetic inferences.

A protein electrophoretic survey of mytilids inhabiting deep-sea hydrothermal vents and cold-water methane/sulfide seeps revealed electromorph patterns diagnostic of 10 distinct species. From hydrothermal vents located at sites on the Galapagos Rift, the Mid-Atlantic Ridge, and the Mariana Back Arc Basin, we detected four species of mytilids. Six additional species were detected from three cold-water seep sides in the Gulf of Mexico. The patchy distribution and temporal stability of seeps may provide a greater opportunity for mytilid diversification and persistence than vent sites Nei's genetic distances (D) between species were relatively large (range: 0.528 to ∞) both within and among habitat types. This pronounced degree of genetic differentiation suggests a relatively ancient common ancestor for the group. Phylogenetic trees were generated using distance Wagner and parsimony analyses of allozyme and morphological characters. The tree topologies obtained from both methods support: (1) the hypothesis that a seep ancestor gave rise to the deep-sea hydrothermal vent mytilids, (2) a historical progression from shallow-water to deep-water habitats, and (3) a co-evolutionary progression from external to internal localization of bacterial symbionts. Whether the seep mytilid taxa constitute paraphyletic or polyphyletic groups remains unresolved. Our phylogenetic hypotheses also provide a benchmark for the phylogeny of mytilid bacterial symbionts.

Archival scales from 603 sockeye salmon (Oncorhynchus nerka), sampled from May to July 1924 in the lower Columbia River, were analysed for genetic variability at 12 microsatellite loci and compared to 17 present-day O. nerka populations-exhibiting either anadromous (sockeye salmon) or nonanadromous (kokanee) life histories-from throughout the Columbia River Basin, including areas upstream of impassable dams built subsequent to 1924. Statistical analyses identified four major genetic assemblages of sockeye salmon in the 1924 samples. Two of these putative historical groupings were found to be genetically similar to extant evolutionarily significant units (ESUs) in the Okanogan and Wenatchee Rivers (pairwise F(ST) = 0.004 and 0.002, respectively), and assignment tests were able to allocate 77% of the fish in these two historical groupings to the contemporary Okanogan River and Lake Wenatchee ESUs. A third historical genetic grouping was most closely aligned with contemporary sockeye salmon in Redfish Lake, Idaho, although the association was less robust (pairwise F(ST) = 0.060). However, a fourth genetic grouping did not appear to be related to any contemporary sockeye salmon or kokanee population, assigned poorly to the O. nerka baseline, and had distinctive early return migration timing, suggesting that this group represents a historical ESU originating in headwater lakes in British Columbia that was probably extirpated sometime after 1924. The lack of a contemporary O. nerka population possessing the genetic legacy of this extinct ESU indicates that efforts to reestablish early-migrating sockeye salmon to the headwater lakes region of the Columbia River will be difficult.

A protein-electrophoretic analysis of six putative morphospecies in the bivalve family Vesicomyidae from eight deep-sea hydrothermal vent sites in the eastern Pacific, three cold-water seep sites in the eastern Pacific and the Gulf of Mexico, and one whale-carcass site off Southern California revealed electromorph patterns diagnostic of 10 vesicomyid species. Electrophoretic patterns for 14 enzymes encoded by 17 presumptive gene loci were scored in all 10 species. The pairwise genetic distances (Nei's D) for these 10 species ranged from 0.857 to 2.792, values within the range expected for distinct species and genera. However, the degree of genetic divergence among these taxa could not be used for phylogenetic inferences because allozyme differences had in many cases reached evolutionary saturation. Notwithstanding, the present results revealed a significant problem with current morphospecies identifications of these clams and with applications of the current generic names Calyptogena and Vesicomya. Given the cryptic nature of these taxa, we suggest that subsequent studies simply refer to these clams as “vesicomyids” until careful morphological analyses and molecular studies are completed and systematic relationships are clarified.

Early development in the north-west Atlantic awning clam, Solemya velum (Solemyoida: Solemyidae) was examined by light and scanning electron microscopy. Embryonic and pericalymma larval stages, typical of protobranch bivalves, developed within individual adhesive gelatinous egg capsules and offspring emerged at hatching as benthic crawl-away juveniles. Fertilized eggs were light orange in colour, spherical, and had a yolk-mass diameter of approximately 190 μm. Entirely ciliated cylindrical pericalymma larvae, with a length and width of 318 μm and 208 μn, respectively, were obtained within 24 h. These larvae lacked an apical ciliary tuft, possessed nine rows of calymma cells, and actively rotated within the egg capsule. During metamorphosis, which occurred within 48 h of fertilization, the transitory larval ectoderm was entirely ingested. The prodissoconch measured roughly 320 μm in length by 215 μm in height. The foot and ciliated gill buds were well developed by four days after fertilization and subsequent growth contributed to the dissoconch or adult shell. Hatching began at 13 d after fertilization when the shell measured approximately 402 μm in length by 251 μm in height. Actively crawling and burrowing juveniles were cultured for six months after fertilization and an ontogenetic sequence of encapsulated and juvenile shell morphology was obtained for identification purposes. Current contradictory hypotheses regarding the phylogeny of marine bivalve develop-mental types are reviewed in light of new information on the Order Solemyoida.

Widespread population extirpations and the consequent loss of ecological, genetic, and life-history diversity can lead to extinction of evolutionarily significant units (ESUs) and species. We attempted to systematically enumerate extinct Pacific salmon populations and characterize lost ecological, life history, and genetic diversity types among six species of Pacific salmon (Chinook [Oncorhynchus tshawytscha], sockeye [O. nerka], coho [O. kisutch], chum [O. keta], and pink salmon [O. gorbuscha] and steelhead trout [O. mykiss]) from the western contiguous United States. We estimated that, collectively, 29% of nearly 1400 historical populations of these six species have been lost from the Pacific Northwest and California since Euro-American contact. Across all species there was a highly significant difference in the proportion of population extinctions between coastal (0.14 extinct) and interior (0.55 extinct) regions. Sockeye salmon (which typically rely on lacustrine habitats for rearing) and stream-maturing Chinook salmon (which stay in freshwater for many months prior to spawning) had significantly higher proportional population losses than other species and maturation types. Aggregate losses of major ecological, life-history, and genetic biodiversity components across all species were estimated at 33%, 15%, and 27%, respectively. Collectively, we believe these population extirpations represent a loss of between 16% and 30% of all historical ESUs in the study area. On the other hand, over two-thirds of historical Pacific salmon populations in this area persist, and considerable diversity remains at all scales. Because over one-third of the remaining populations belong to threatened or endangered species listed under the U.S. Endangered Species Act, it is apparent that a critical juncture has been reached in efforts to preserve what remains of Pacific salmon diversity. It is also evident that persistence of existing, and evolution of future, diversity will depend on the ability of Pacific salmon to adapt to anthropogenically altered habitats.

Adults of the bivalve species Solemya velum live in symbiosis with chemoautotrophic bacteria in spe- cialized gill bacteriocytes. The bacteria play an essential nutritional role in the mature association, fixing CO2 via the Calvin cycle with energy obtained through the oxi- dation of reduced sulfur compounds. To understand how the continuity of this partnership is maintained between host generations, we investigated the mode of symbiont transfer in S. velum. A diagnostic assay using the poly- merase chain reaction and primers specific for the S. velum symbiont ribulose- 1 ,5-bisphosphate carboxylase (RubisCO) gene consistently detected bacterial sequence in female gonad tissue, suggesting the presence of sym- biont cells in host ovaries and a vertical mode of symbiont transmission from mother to offspring. Furthermore, in- tracellular bacteria were present in the developing gills of juveniles that had not yet hatched from the gelatinous capsule in which larval development occurs ( 11 days after fertilization). By 64 days postfertilization, the typical adult gill ultrastructure of alternating bacteriocytes and sym- biont-free intercalary cells was apparent. Knowledge about the mode of symbiont transfer in S. velum allows further study into the dynamics of host-symbiont interactions in chemoautotrophic associations.

Rapid evolution of reproductive isolation is proposed by A. Hendry and colleagues to be the cause of the genetic differences between two adjacent populations of Washington State sockeye salmon (Reports, 20 Oct., p. [516][1]). These two populations or “ecotypes,” one living in a tributary (Cedar River) and the other along a beach (Pleasure Point) of Lake Washington, are suggested to have evolved after introductions of sockeye into Lake Washington from Baker Lake between 1937 and 1945 (within about 13 generations) and in spite of high estimated migration rates. Hendry et al. 's conclusions, however, depend on several assumptions. First, they assume that the hatchery population used for the introductions was genetically homogeneous. However, the hatchery population, in fact, included both beach and river ecotypes (as well as other gene pools) in its ancestry in various proportions in the five brood years used for the introductions ([1][2]). Although some mixing of the ecotypes undoubtedly occurred in the hatchery, natural segregation based on different spawn times could have maintained much of the diversity between them until the time of the introductions. Therefore, the current diversity of ecotypes in Lake Washington, and any reproductive isolation, could reflect divergence much older than 13 generations. Another assumption the authors make is that the “beach immigrants” are derived from the Cedar River population, on the basis of temperature-sensitive otolith (a calcareous ear stone) banding patterns. However, some or all of these immigrants could have come from other beach-spawning sites in Lake Washington that have temperature profiles similar to that of Cedar River ([2][3]). 1. [↵][4]1. R. Rathbun , Rep. U.S. Comm. Fish Fisheries 25, 251 (1900) J. Kemmerich, “A review of the artificial propagation and transplantation of the sockeye salmon of the Puget Sound area in the State of Washington conducted by the federal government from 1896 to 1945” (U.S. Fish and Wildlife Service, Leavenworth, WA, 1945);R. G. Gustafson et al., NOAA Tech. Memo NMFS-NWFSC-33 (1997) (available at ). [OpenUrl][5] 2. [↵][6]1. J. G. Woodey , (1996) thesis, University of Washington(. # Response {#article-title-2} We reported that two new salmon populations within Lake Washington have diverged in response to natural selection and are now partially reproductively isolated. Gustafson and colleagues suggest some alternative scenarios. First, they point out that both beach and river ecotypes contributed to the initial Baker Lake hatchery stock used for introductions into Lake Washington. This is true, but, as we have discussed elsewhere ([1][7]), the hatchery propagated all (or nearly all) of the fish as a single mixed stock for up to eight generations. As a result, any preexisting genetic differentiation would have been homogenized before the introductions. Furthermore, salmon did not colonize Pleasure Point Beach until after the introductions from Baker Lake had ceased ([2][8]), suggesting that the Pleasure Point population was secondarily derived from the population of Cedar River. Reproductive isolation, therefore arose de novo and in situ. A mix of genes from beach and river ecotypes in the introduced group would simply have provided genetic variation to facilitate rapid divergence. Second, Gustafson et al. suggest that some of the Pleasure Point immigrants could have come from other beach populations. This is unlikely because the immigrants were genetically similar to Cedar River fish, and because most of the beach-spawners at the time of our study were at Pleasure Point. In shoreline surveys by boat, we found only five spawning pairs elsewhere. Third, they propose that the observed genetic differences could have resulted from founder effects. Although possible, this is unlikely, given the observed high rates of adult movement (any founder effect would be rapidly destroyed by gene flow unless reproductive isolation had evolved). The alternatives offered by Gustafson et al. are contradictory: they suggest that genetic differences were present before the introduction and then suggest that genetic differences arose in situ. In conclusion, our explanations remain the most consistent with the data. Although our study was the first to document the evolution of reproductive isolation on such a short time scale, we expect that other studies will reveal analogous situations. 1. [↵][9]1. A. P. Hendry, 2. T. P. Quinn , Can. J. Fish. Aquat. Sci 54, 75 (1997). [OpenUrl][10][CrossRef][11][Web of Science][12] 2. [↵][13]1. J. G. Woodey , (1966) thesis, University of Washington(. [1]: /lookup/doi/10.1126/science.290.5491.516 [2]: #ref-1 [3]: #ref-2 [4]: #xref-ref-1-1 "View reference 1 in text" [5]: {openurl}?query=rft.jtitle%253DRep.%2BU.S.%2BComm.%2BFish%2BFisheries%26rft.volume%253D25%26rft.spage%253D251%26rft.atitle%253DREP%2BUS%2BCOMM%2BFISH%2BFISHERIES%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [6]: #xref-ref-2-1 "View reference 2 in text" [7]: #ref-3 [8]: #ref-4 [9]: #xref-ref-3-1 "View reference 1 in text" [10]: {openurl}?query=rft.jtitle%253DCan.%2BJ.%2BFish.%2BAquat.%2BSci%26rft.volume%253D54%26rft.spage%253D75%26rft_id%253Dinfo%253Adoi%252F10.1139%252Fcjfas-54-1-75%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [11]: /lookup/external-ref?access_num=10.1139/cjfas-54-1-75&link_type=DOI [12]: /lookup/external-ref?access_num=A1997XB78600008&link_type=ISI [13]: #xref-ref-4-1 "View reference 2 in text"

Solemya reidi Bernard 1980 is a gutless protobranch bivalve known to possess intracellular chemoautotrophic bacterial symbionts in its gill. A light and electron microscope study on the embryology and larval development of S. reidi provides data for the bivalve Subclass Cryptodonta. S. reidi spontaneously spawned large eggs (271 μm in diameter), which developed within individual gelatious egg capsules. The first several cleavages were equal and a distinct molluscan cross was formed at the animal pole of the embryo, features previously unreported in bivalve development. Lecithotrophic pericalymma larvae (similar to the larvae of paleotaxodont protobranch bivalves and aplacophoran molluscs) hatched at 18 to 24 h and remained in the water column for a further 5 d at 10°C. At hatching, larvae measured from 360 to 440 μm in length and from 225 to 265 μm in cross-sectional diameter. Definitive adult structures developed within an epithelial locomotory test entirely covered with compound cilia. The test histolysed at metamorphosis and was ingested throught the mouth into the perivisceral cavity. Length and height of the shell following metamorphosis was 433 μm (±42 μm, n=16) and 282 μm (± 29 μm, n=13), respectively. Primary data and data from the literature show that the type of larval development in both paleotaxodont and cryptodont bivalves cannot be reliably estimated from egg or prodissoconch sizes.

Rod-shaped bacteria were consistently observed by transmission electron microscopy in the locomotory test of larvae and in the perivisceral cavity of post-larvae of Solemya reidi, a gutless protobranch bivalve known to possess intracellular chemoautotrophic bacterial symbionts in the adult gill. Bacteria develop within granular vesicles in the larval test, where they either remain to be ingested at metamorphosis, or are released into the space separating the test and embryo, to be subsequently ingested through the larval mouth. In either case, bacteria lie within the perivisceral cavity following metamorphosis. Bacteria were not seen either in or on gametes or in gills of juveniles. It is hypothesized that these bacteria represent a transmission stage of the gill symbionts present in adult S. reidi and are not evident in gametes or gills of juveniles due to cryptic packaging within granular vesicles. Perpetuation of this symbiosis would therefore be assured through vertical transmission, as is typical of other marine invertebrate-bacteria endosymbioses.

Structural changes occurring in the alimentary tract, perivisceral cavity, foot, hypobranchial gland, and gills of larval and post-larval Solemya reidi, a gutless protobranch bivalve, were examined using both light and electron microscopy at 1, 3, 5, 18, 34 and 42 d after fertilization. A fully developed mouth, esophagus, and anus, together with the rudiments of a stomach and rectum are present before metamorphosis. At metamorphosis, the cells making up the dorsal and lateral walls of the stomach dissociate, and by 18 d the mouth and anus are the only remaining portions of the alimentary tract. The larval test is ingested into the perivisceral cavity at metamorphosis and its autolysis continues through at least the 42nd day after fertilization. The foot, gills, and hypobranchial gland, poorly developed at metamorphosis, develop slowly and are still undergoing extensive morphogenesis at 42 d.

A minor spawning event by laboratory-held specimens of the septibranch bivalveCardiomyapectinatayielded approximately 40 developing embryos. Their early ontogeny was observed from the early gastrula stage of development until the developing shell had completely enclosed the embryos and had attained 90% of the prodissoconch size observed on juvenile shells. Available evidence indicates that this species undergoes a non-planktotrophic, direct pre-juvenile development. Support for this view includes the enclosure of the developing embryo in a negatively buoyant, adhesive capsule until an advanced stage of development; poorly developed velar ciliation and lack of prodissoconch II formation. Although incomplete, this, the first study on septibranch pre-juvenile development, reveals thatC. pectinataembryos form an external calcified shell in a manner homologous to the lamellibranch bivalves, and develop a velum modified for yolk storage, while lacking the epithelial test or pericalymma characteristic of protobranch bivalves. These data indicate that cuspidariid septibranchs are phylogenetically closer to the lamellibranchs than to the protobranch bivalves.

Egg capsules from three different prosobranch gastropods were retrieved from the Galapagos Rift and Juan de Fuca Ridge deep-sea hydrothermal vent fields. The morphology of these capsules and their excapsulated embryos and larvae are described and illustrated. Based on their capsule type and the protoconch morphology of their contained larvae, 29 lenticular capsules from the Galapagos Rift could be attributed to a provisionally described neogastropod turrid, Phymorhynchus sp. But 3 inflated, triangular capsules from the Galapagos Rift, and 56 different egg capsules from the Juan de Fuca Ridge, each shaped like an inflated pouch, could not be unambiguously assigned to a member of the known vent gastropod fauna. The mode of development and potential for dispersal is inferred from egg capsule type, the number of embryos per capsule, and protoconch characters comparable to those of confamilial shallow-water gastropods for which the type of development is known. These criteria and a comparison to the known juvenile shell morphology of Phymorhynchus sp., suggest that, after encapsulation, this species develops planktotrophically and is capable of long-range dispersal. Similar evidence suggests that the larvae contained in the inflated triangular capsules from the Galapagos Rift may also develop planktotrophically after hatching; but the larvae in the pouch-like egg capsules from the Juan de Fuca Ridge probably develop non-planktotrophically without a dispersal stage. These developmental patterns are characteristic of shallow-water members of the systematic groups to which these species belong, indicating, as previous studies have shown, that vent gastropods can persist in these patchy, ephemeral environments in the absence of unique adaptations allowing dispersal between active hydrothermal sites.