ABSTRACT Individual linear growth rates were studied in the freshwater pearl mussel Margaritifera margaritifera from the Vuokinjoki River. Growth deceleration coefficients were shown to vary widely and differ significantly among individuals. The average value of the growth deceleration coefficient for the population is 0.069. The growth of mussels in the Vuokinjoki River is accompanied by three regular biorhythms. These biorhythm periods were roughly constant both through an individual's ontogeny and among mussels. Their average periods were 13.3, 6.4, and 4.0 years. The growth deceleration coefficient a depends on the age of the mussels. We discuss the possibility that the hydrological regime disturbance caused by the Kem hydropower plants' cascade construction could influence the growth rate.
{"title":"Growth Parameters of the Freshwater Pearl Mussel Margaritifera margaritifera (Bivalvia, Margaritiferidae), Vuokinjoki River Population (Karelia)","authors":"A. Zotin, S. Murzina, K. A. Filippova, E. Ieshko","doi":"10.4002/040.063.0107","DOIUrl":"https://doi.org/10.4002/040.063.0107","url":null,"abstract":"ABSTRACT Individual linear growth rates were studied in the freshwater pearl mussel Margaritifera margaritifera from the Vuokinjoki River. Growth deceleration coefficients were shown to vary widely and differ significantly among individuals. The average value of the growth deceleration coefficient for the population is 0.069. The growth of mussels in the Vuokinjoki River is accompanied by three regular biorhythms. These biorhythm periods were roughly constant both through an individual's ontogeny and among mussels. Their average periods were 13.3, 6.4, and 4.0 years. The growth deceleration coefficient a depends on the age of the mussels. We discuss the possibility that the hydrological regime disturbance caused by the Kem hydropower plants' cascade construction could influence the growth rate.","PeriodicalId":49895,"journal":{"name":"Malacologia","volume":"63 1","pages":"67 - 75"},"PeriodicalIF":1.3,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45303478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT The radula is the anatomical structure used for feeding in most Mollusca species and is one important autapomorphy. Previous studies were focused on the radular teeth and their functional morphology, but their anchorage in the radular membrane and its function have never been examined. Here, we analyse the micro-structure of connecting chitinous fibres and its implication on the radular function in 13 closely related paludomid gastropod species from the so called “ancient lake” Tanganyika. This species flock shows a stunning interspecific diversity in their radular tooth morphology and tooth embedding in the membrane as well. The species studied here feed on organics from different substrates, both soft and solid, and are substrate-specific. Here, the morphological composition of the membrane is described in detail for the first time, it consists of parallel fibres that extend also within the teeth. We also show that morphologies of the anchorage correlated with the specific preferred feeding substrate can hence be identified as functional adaptation.
{"title":"Tightening it Up: Diversity of the Chitin Anchorage of Radular-Teeth in Paludomid Freshwater-Gastropods","authors":"W. Krings, Jan-Ole Brütt, S. Gorb, M. Glaubrecht","doi":"10.4002/040.063.0108","DOIUrl":"https://doi.org/10.4002/040.063.0108","url":null,"abstract":"ABSTRACT The radula is the anatomical structure used for feeding in most Mollusca species and is one important autapomorphy. Previous studies were focused on the radular teeth and their functional morphology, but their anchorage in the radular membrane and its function have never been examined. Here, we analyse the micro-structure of connecting chitinous fibres and its implication on the radular function in 13 closely related paludomid gastropod species from the so called “ancient lake” Tanganyika. This species flock shows a stunning interspecific diversity in their radular tooth morphology and tooth embedding in the membrane as well. The species studied here feed on organics from different substrates, both soft and solid, and are substrate-specific. Here, the morphological composition of the membrane is described in detail for the first time, it consists of parallel fibres that extend also within the teeth. We also show that morphologies of the anchorage correlated with the specific preferred feeding substrate can hence be identified as functional adaptation.","PeriodicalId":49895,"journal":{"name":"Malacologia","volume":"63 1","pages":"77 - 94"},"PeriodicalIF":1.3,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42822872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT Freshwater mussels have suffered a severe decline during the last century. Accurate description and identification of species have been an arduous and important task for the conservation of this group. Recently, with the promotion of molecular technology, especially mtDNA, many morphological species have been merged. In the genus Lamprotula, L. caveata, L. cornuumlunae and L. leaii are recognized as valid species. The complete mitogenome of. L. cornuumlunae was firstly sequenced in this study. By comparing mitochondrial genomics and phylogenetic analysis, the results showed that mtDNA cannot distinguish between L. caveata and L. cornuumlunae. We hypothesized that the deficiencies of mtDNA in species delimitation was caused by very recent speciation. Time-calibrated multilocus divergence time estimation revealed that L. caveata and L. cornuumlunae recently diverged in the Neogene Pliocene. This study presents the potential problems of relying on mtDNA sequences for delimiting recently diverged species. We emphasis that mtDNA cannot be used solely or dominantly to understand biodiversity. Instead, it is indeed an effective tool, combined with more data, such as shell morphology, reproductive characters and biogeography, to integrate species concepts.
{"title":"Comparative Analyses of the Complete Mitochondrial Genomes of Three Lamprotula (Bivalvia: Unionidae) Species: Insight into the Shortcomings of Mitochondrial DNA for Recently Diverged Species Delimitation","authors":"Ruiwen Wu, Xiongjun Liu, S. Ouyang, Xiaoping Wu","doi":"10.4002/040.063.0106","DOIUrl":"https://doi.org/10.4002/040.063.0106","url":null,"abstract":"ABSTRACT Freshwater mussels have suffered a severe decline during the last century. Accurate description and identification of species have been an arduous and important task for the conservation of this group. Recently, with the promotion of molecular technology, especially mtDNA, many morphological species have been merged. In the genus Lamprotula, L. caveata, L. cornuumlunae and L. leaii are recognized as valid species. The complete mitogenome of. L. cornuumlunae was firstly sequenced in this study. By comparing mitochondrial genomics and phylogenetic analysis, the results showed that mtDNA cannot distinguish between L. caveata and L. cornuumlunae. We hypothesized that the deficiencies of mtDNA in species delimitation was caused by very recent speciation. Time-calibrated multilocus divergence time estimation revealed that L. caveata and L. cornuumlunae recently diverged in the Neogene Pliocene. This study presents the potential problems of relying on mtDNA sequences for delimiting recently diverged species. We emphasis that mtDNA cannot be used solely or dominantly to understand biodiversity. Instead, it is indeed an effective tool, combined with more data, such as shell morphology, reproductive characters and biogeography, to integrate species concepts.","PeriodicalId":49895,"journal":{"name":"Malacologia","volume":"63 1","pages":"51 - 66"},"PeriodicalIF":1.3,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48924368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT Freshwater gastropods in the family Pleuroceridae are important components of North American freshwater ecosystems that can greatly influence ecological processes and biotic communities. Elimia is the most taxa rich among pleurocerid genera. Elimia comalensis Pilsbry, 1890, is the only pleurocerid species that occurs in Texas and is currently known to occupy artesian springs and spring-fed river systems associated with the Edwards Plateau region. Published literature on E. comalensis is limited, and little information is currently present regarding explicit patterns of distribution and abundance within most systems currently occupied. We examined temporal and spatial variation of E. comalensis densities in the upper San Marcos River from 2013 to 2016, as well as interspecific affinities between E. comalensis and two invasive thiarid snails. We observed significant annual differences in E. comalensis densities, with greater mean density occurring under low flow conditions in 2014. We also observed significant differences in densities among sites, with greater density occurring at sites with larger and more complex substratum particles. Elimia comalensis exhibited a strong positive relationship with the thiarid snail Tarebia granifera, although data suggest that interspecific competition is limited as these species co-occur at high densities. As anthropogenic impacts continue to impact Edwards Plateau spring systems, further research on the distribution and population dynamics of ecologically important pleurocerid snails, such as E. comalensis, is needed to aid in the conservation of these unique ecosystems.
{"title":"Spatiotemporal Variation in Elimia comalensis (Gastropoda: Pleuroceridae) Density and Interspecific Associations with Exotic Thiarid Snails in the Upper San Marcos River, Texas","authors":"Kyle T. Sullivan, Bradley M. Littrell","doi":"10.4002/040.063.0101","DOIUrl":"https://doi.org/10.4002/040.063.0101","url":null,"abstract":"ABSTRACT Freshwater gastropods in the family Pleuroceridae are important components of North American freshwater ecosystems that can greatly influence ecological processes and biotic communities. Elimia is the most taxa rich among pleurocerid genera. Elimia comalensis Pilsbry, 1890, is the only pleurocerid species that occurs in Texas and is currently known to occupy artesian springs and spring-fed river systems associated with the Edwards Plateau region. Published literature on E. comalensis is limited, and little information is currently present regarding explicit patterns of distribution and abundance within most systems currently occupied. We examined temporal and spatial variation of E. comalensis densities in the upper San Marcos River from 2013 to 2016, as well as interspecific affinities between E. comalensis and two invasive thiarid snails. We observed significant annual differences in E. comalensis densities, with greater mean density occurring under low flow conditions in 2014. We also observed significant differences in densities among sites, with greater density occurring at sites with larger and more complex substratum particles. Elimia comalensis exhibited a strong positive relationship with the thiarid snail Tarebia granifera, although data suggest that interspecific competition is limited as these species co-occur at high densities. As anthropogenic impacts continue to impact Edwards Plateau spring systems, further research on the distribution and population dynamics of ecologically important pleurocerid snails, such as E. comalensis, is needed to aid in the conservation of these unique ecosystems.","PeriodicalId":49895,"journal":{"name":"Malacologia","volume":"63 1","pages":"1 - 9"},"PeriodicalIF":1.3,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43075751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Denise Klinkenbuß, Olivia Metz, Jessica Reichert, T. Hauffe, T. Neubauer, F. Wesselingh, T. Wilke
ABSTRACT In recent years, 3D analyses, new indices to describe the complexity of morphological structures and sophisticated machine learning approaches have advanced morphometrical analyses to assist species determination. However, the applicability of these modern approaches to the determination of cryptic species or fossil taxa has rarely been investigated. In this study, fossil and subfossil specimens of the four modern Dreissena species in the Caspian Sea are used to test the performance of 3D-based morphological approaches for machine learning assisted species identification. Specifically, 3D scans of the shells were used to construct 3D models for calculating “traditional” shell dimensions and “modern” shell complexity parameters. Finally, two machine learning approaches were applied to test the determination performance of shell measurements vs. shell complexity and individual vs. combined shell parameters. The results show that (i) there is no superior machine learning approach to species determination based on shell characters, (ii) shell complexity parameters are not per se more suitable for species identification than shell dimensions, (iii) a combination of shell parameters increases determination performance and reduces their species dependence and (iv) shell characters alone do not allow precise determination of all Dreissena species studied. These findings suggest that the most appropriate machine learning approach, the most informative shell characters and the best combination of characters need to be tested individually for different data sets. However, considering that it is difficult even for experts to distinguish Dreissena species based on shell characters, the machine learning assisted classification in the current study has performed comparatively well. Future analyses based on machine learning may therefore help experts to process large sample sizes efficiently and non-specialists to assess species level information with reasonable certainty.
{"title":"Performance of 3D Morphological Methods in the Machine Learning Assisted Classification of Closely Related Fossil Bivalve Species of the Genus Dreissena","authors":"Denise Klinkenbuß, Olivia Metz, Jessica Reichert, T. Hauffe, T. Neubauer, F. Wesselingh, T. Wilke","doi":"10.4002/040.063.0109","DOIUrl":"https://doi.org/10.4002/040.063.0109","url":null,"abstract":"ABSTRACT In recent years, 3D analyses, new indices to describe the complexity of morphological structures and sophisticated machine learning approaches have advanced morphometrical analyses to assist species determination. However, the applicability of these modern approaches to the determination of cryptic species or fossil taxa has rarely been investigated. In this study, fossil and subfossil specimens of the four modern Dreissena species in the Caspian Sea are used to test the performance of 3D-based morphological approaches for machine learning assisted species identification. Specifically, 3D scans of the shells were used to construct 3D models for calculating “traditional” shell dimensions and “modern” shell complexity parameters. Finally, two machine learning approaches were applied to test the determination performance of shell measurements vs. shell complexity and individual vs. combined shell parameters. The results show that (i) there is no superior machine learning approach to species determination based on shell characters, (ii) shell complexity parameters are not per se more suitable for species identification than shell dimensions, (iii) a combination of shell parameters increases determination performance and reduces their species dependence and (iv) shell characters alone do not allow precise determination of all Dreissena species studied. These findings suggest that the most appropriate machine learning approach, the most informative shell characters and the best combination of characters need to be tested individually for different data sets. However, considering that it is difficult even for experts to distinguish Dreissena species based on shell characters, the machine learning assisted classification in the current study has performed comparatively well. Future analyses based on machine learning may therefore help experts to process large sample sizes efficiently and non-specialists to assess species level information with reasonable certainty.","PeriodicalId":49895,"journal":{"name":"Malacologia","volume":"63 1","pages":"105 - 95"},"PeriodicalIF":1.3,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44852059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Björn Stelbrink, B. K. Ellis, A. Paquet, C. Albrecht
ABSTRACT Acroloxus coloradensis is a rare and potentially glacial relict freshwater limpet species endemic to North America. However, despite its remarkable patchy distribution across the continent, only very few genetic data is available for the different populations. Here, we sequenced two standard barcoding markers for individuals from five populations to shed some light on the genetic population structure of this species. Overall, our genetic analyses revealed low genetic variation and identified three and two haplotypes for COI and 16S rRNA, respectively. The three Rocky Mountain populations differed only slightly for COI and shared the same haplotype for 16S rRNA. For both markers, no genetic variation was detected within the two populations sampled in Québec. The present genetic data suggest that A. coloradensis is indeed a relict species and that the distribution of this species was strongly affected by the last glacial retreat in North America.
{"title":"Low Genetic Diversity in a Potential (Glacial) Relict: The Rocky Mountain Capshell, Acroloxus coloradensis (Henderson, 1930) (Gastropoda: Acroloxidae)","authors":"Björn Stelbrink, B. K. Ellis, A. Paquet, C. Albrecht","doi":"10.4002/040.063.0110","DOIUrl":"https://doi.org/10.4002/040.063.0110","url":null,"abstract":"ABSTRACT Acroloxus coloradensis is a rare and potentially glacial relict freshwater limpet species endemic to North America. However, despite its remarkable patchy distribution across the continent, only very few genetic data is available for the different populations. Here, we sequenced two standard barcoding markers for individuals from five populations to shed some light on the genetic population structure of this species. Overall, our genetic analyses revealed low genetic variation and identified three and two haplotypes for COI and 16S rRNA, respectively. The three Rocky Mountain populations differed only slightly for COI and shared the same haplotype for 16S rRNA. For both markers, no genetic variation was detected within the two populations sampled in Québec. The present genetic data suggest that A. coloradensis is indeed a relict species and that the distribution of this species was strongly affected by the last glacial retreat in North America.","PeriodicalId":49895,"journal":{"name":"Malacologia","volume":"63 1","pages":"109 - 113"},"PeriodicalIF":1.3,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48867381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Matt J Nimbs, N. Wilson, G. Limmon, Stephen D. A. Smith
ABSTRACT The small, green sea hare, Phyllaplysia viridis, originally described from Indonesia in 1905, has rarely been recorded since. Because the taxonomic status of Phyllaplysia is uncertain, there remains a need for clarification of the currently accepted species. To do so, we used contemporary specimens from eastern Australia and Indonesia to redescribe P. viridis using photographs and scanning electron imagery of its external and internal morphology. Although all examined specimens were small, consistently green animals, images revealed some variation in colour and pattern among adults. Molecular data confirmed the presence of P. viridis in the Philippines, Indonesia and eastern Australia. A phylogenetic tree based on available COI barcode sequences illustrate a sister relationship with other Phyllaplysia. The construction of a haplotype network failed to show any marked geographic structure among specimens.
{"title":"Redescription of the Sea Hare Phyllaplysia viridis (Bergh, 1905) (Gastropoda: Heterobranchia: Aplysiida)","authors":"Matt J Nimbs, N. Wilson, G. Limmon, Stephen D. A. Smith","doi":"10.4002/040.063.0102","DOIUrl":"https://doi.org/10.4002/040.063.0102","url":null,"abstract":"ABSTRACT The small, green sea hare, Phyllaplysia viridis, originally described from Indonesia in 1905, has rarely been recorded since. Because the taxonomic status of Phyllaplysia is uncertain, there remains a need for clarification of the currently accepted species. To do so, we used contemporary specimens from eastern Australia and Indonesia to redescribe P. viridis using photographs and scanning electron imagery of its external and internal morphology. Although all examined specimens were small, consistently green animals, images revealed some variation in colour and pattern among adults. Molecular data confirmed the presence of P. viridis in the Philippines, Indonesia and eastern Australia. A phylogenetic tree based on available COI barcode sequences illustrate a sister relationship with other Phyllaplysia. The construction of a haplotype network failed to show any marked geographic structure among specimens.","PeriodicalId":49895,"journal":{"name":"Malacologia","volume":"63 1","pages":"11 - 20"},"PeriodicalIF":1.3,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48916557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. K. Sajikumar, R. Jeyabaskaran, C. P. Binesh, Kolliyil Sunilkumar Mohamed
ABSTRACT Two specimens of the mimic octopus Thaumoctopus mimicus were documented for the first time in the Arabian Sea during September 2018 off southern Kerala, India, from 15 m depth. The specimens had dorsal mantle lengths (DML) of 44 and 48 mm. Description and morphological measurements of the specimens are provided. The identity of the specimens was genetically supported by using cytochrome C oxidase I gene sequencing. This finding represents the first record of the species in the Arabian Sea, which signifies an extension of its known geographic distribution range.
{"title":"First Record of the Mimic Octopus Thaumoctopus mimicus (Cephalopoda: Octopodidae) from the Arabian Sea: Range Extension and Genotyping","authors":"K. K. Sajikumar, R. Jeyabaskaran, C. P. Binesh, Kolliyil Sunilkumar Mohamed","doi":"10.4002/040.063.0111","DOIUrl":"https://doi.org/10.4002/040.063.0111","url":null,"abstract":"ABSTRACT Two specimens of the mimic octopus Thaumoctopus mimicus were documented for the first time in the Arabian Sea during September 2018 off southern Kerala, India, from 15 m depth. The specimens had dorsal mantle lengths (DML) of 44 and 48 mm. Description and morphological measurements of the specimens are provided. The identity of the specimens was genetically supported by using cytochrome C oxidase I gene sequencing. This finding represents the first record of the species in the Arabian Sea, which signifies an extension of its known geographic distribution range.","PeriodicalId":49895,"journal":{"name":"Malacologia","volume":"63 1","pages":"115 - 122"},"PeriodicalIF":1.3,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41542355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jing Guo, Wu-Bing Xu, P. Martín, Chunxia Zhang, Jia-En Zhang
ABSTRACT Sex differences in stress responses may be a key factor that determines population structure. Sex ratios of Pomacea canaliculata populations usually average 1:1 at birth, but are often female-biased for adults. Low temperatures and drought are the main abiotic stresses affecting reproductive dispersal and population development. Therefore, we investigated whether Pomacea sp. (mainly P. canaliculata but might include P. maculata) exhibited sex differences in cold hardiness and desiccation tolerance. The results show that more females survived than males during cold-drought stress and overwintering. Following cold-drought stress, 58% of females and 40% of males survived at 3°C drought conditions for 6 days. With the development of cold-drought hardiness, increased amounts of bound water, glycerol and lipids were found in Pomacea sp. along with decreased free water levels. These physiological parameters exhibited sex differences in the snails, except for lipids, and the changes all showed tendencies favoring the survival of females under cold-drought stress. These results suggest that female Pomacea sp. may be more viable than males under cold and dry conditions.
{"title":"Sex Differences in Cold Hardiness and Desiccation Tolerance of Invasive Apple Snails in South China","authors":"Jing Guo, Wu-Bing Xu, P. Martín, Chunxia Zhang, Jia-En Zhang","doi":"10.4002/040.062.0202","DOIUrl":"https://doi.org/10.4002/040.062.0202","url":null,"abstract":"ABSTRACT Sex differences in stress responses may be a key factor that determines population structure. Sex ratios of Pomacea canaliculata populations usually average 1:1 at birth, but are often female-biased for adults. Low temperatures and drought are the main abiotic stresses affecting reproductive dispersal and population development. Therefore, we investigated whether Pomacea sp. (mainly P. canaliculata but might include P. maculata) exhibited sex differences in cold hardiness and desiccation tolerance. The results show that more females survived than males during cold-drought stress and overwintering. Following cold-drought stress, 58% of females and 40% of males survived at 3°C drought conditions for 6 days. With the development of cold-drought hardiness, increased amounts of bound water, glycerol and lipids were found in Pomacea sp. along with decreased free water levels. These physiological parameters exhibited sex differences in the snails, except for lipids, and the changes all showed tendencies favoring the survival of females under cold-drought stress. These results suggest that female Pomacea sp. may be more viable than males under cold and dry conditions.","PeriodicalId":49895,"journal":{"name":"Malacologia","volume":"62 1","pages":"215 - 224"},"PeriodicalIF":1.3,"publicationDate":"2019-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44183156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mariana Díaz-Santana-Iturrios, Andrés Granados-Amores, D. Palacios-Salgado, J. Granados-Amores
ABSTRACT Double hectocotylization in octopods has only been reported for some individuals of a few species, often affecting arms of the same pair. We herein report several cases of non-bilateral double hectocotylization in a single species collected in different locations of the Mexican Pacific coast. The octopuses were identified by morphological and molecular criteria as Hubb's octopus, Octopus hubbsorum. The “regular” and “accessory” hectocotyli were examined by histological analysis; in the latter, the calamus was present and no ligula was detected. Double hectocotylization can be an intrinsic character of the species.
{"title":"Double Hectocotylization in Hubb's Octopus, Octopus hubbsorum (Cephalopoda: Octopodidae)","authors":"Mariana Díaz-Santana-Iturrios, Andrés Granados-Amores, D. Palacios-Salgado, J. Granados-Amores","doi":"10.4002/040.062.0207","DOIUrl":"https://doi.org/10.4002/040.062.0207","url":null,"abstract":"ABSTRACT Double hectocotylization in octopods has only been reported for some individuals of a few species, often affecting arms of the same pair. We herein report several cases of non-bilateral double hectocotylization in a single species collected in different locations of the Mexican Pacific coast. The octopuses were identified by morphological and molecular criteria as Hubb's octopus, Octopus hubbsorum. The “regular” and “accessory” hectocotyli were examined by histological analysis; in the latter, the calamus was present and no ligula was detected. Double hectocotylization can be an intrinsic character of the species.","PeriodicalId":49895,"journal":{"name":"Malacologia","volume":"62 1","pages":"311 - 317"},"PeriodicalIF":1.3,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41641230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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