Elphidium is an abundant genus of foraminifera. Species can be found from coastal regions out to the continental slope, and in all temperature ranges. Like other forams, fossils from different species are used to date rocks. The taxonomy of the species within this genus is disputed due to the high variability of some species.
Description Elphidium is generally around 1 mm in size. The test is spiral-shaped, and can be red, orange, or brown. This shell is made up of calcium carbonate. Species of this genus have seven to twenty chambers in the final whorl, and may have an umbilical plug on each side. In some species the rim is sharp, while in others it is more rounded. Another distinctive feature is the retral processes (small backward extensions of the chamber walls) that cross the sutures, giving some the appearance of tiny rolled up glass baskets. Elphidium crawls using a type of pseudopod called reticulopodia.
Life cycle Elphidium shows dimorphism with alternating generations. The complete cycle for Elphidium crispum takes two years in the shallower marine regions, although it may be delayed at deeper stations. Asexual reproduction reaches a peak in spring of the first year. Sexual reproduction begins early in the second spring as temperatures begin to rise. The gametes conjugate outside in open sea to produce zygotes and the B form then develops and matures during the second summer. Lister (1895) observed Elphidium in two different forms as megalospheric form (sexual form) and microspheric form (asexual form). The megalospheric form was developed from the microspheric form. The gametes which gives rise to microspheric form by syngamy. Elphidium exhibits an alternation of generation in its life cycle. The megalospheric forms alternates with microspheric forms. The microspheric forms are developed by the conjugation or syngamy. It means there is always an alternations of asexual (microspheric) and sexual (megalospheric) generation in Elphidium. The microspheric form reproduces asexually by fission to produce a number of amoebulae. The inner cytoplasm mass containing several nuclei creeps out of the shell and remains as a lump around it. A small amount of cytoplasm collects around each nucleus. As a result, a large number of amoeboid cells are formed. Each amoebula secretes the proloculus, forms rhizopodia, then it grows and forms other chambers of the shell to become a megalospheric forms. The megalospheric form reproduces sexually by syngamy or conjugation. During sexual reproduction in megalospheric forms, nucleus first breaks up into many small nuclei and the cytoplasm collects around each of these nuclei. The nuclei divide twice giving rise to a large haploid and known as isogametes. Isogametes of two different individuals fuse in pairs to form zygotes. These are then develops into microspheric form. The life cycle of Elphidium may be summarized as follows: the microspheric forms produce amoebulae by asexual fission which develops into megalospheric forms. The megalospheric forms produce flagellated isogametes which after syngamy produce zygotes that develop into microspheric forms. Thus, its life cycle clearly exhibits the phenomenon of alternations of asexual microspheric generations with sexual megalospheric generations.
Subdivisions
Subgenus Elphidium (Parrellina) Carter, 1958 Elphidium (Parrellina) centrifugalis Carter, 1958 Subgenus Elphidium (Polystomella) Heron-Allen & Earland, 1932 Elphidium incertae sedis Elphidium abyssicola Ishiwada, 1964 Elphidium aculeatum (d'Orbigny, 1846) Elphidium adelaidense Howchin & Parr, 1938 Elphidium advenum (Cushman, 1922) Elphidium africanum LeRoy, 1953 Elphidium aguafrescaense Todd & Kniker, 1952 Elphidium alaskense Cushman & Todd, 1947 Elphidium albanii Hayward, 1997 in Hayward, Hollis & Grenfell, 1997 Elphidium alvarezianum (d'Orbigny, 1839) Elphidium ancestrum Le Calvez, 1950 Elphidium argenteum Parr, 1945 Elphidium armenium Saakyan-Gezalyan, 1957 Elphidium articulatum (d'Orbigny, 1839) Elphidium asagaiense Asano, 1949 Elphidium asanoi Kaiho, 1984 Elphidium asanoi Matsunaga, 1963 Elphidium asiaticum Polski, 1959 Elphidium asklundi Brotzen, 1943 Elphidium australis Cushman & Parker, 1931 Elphidium azerbaidjanicum Mamedova, 1966 Elphidium aznaburticum Pronina, 1964 Elphidium bartletti Cushman, 1933 Elphidium batavum Hofker, 1968 Elphidium batialis Saidova, 1961 Elphidium bhattacharyai Jauhri, 1994 Elphidium biperforatus (Whittaker & Hodgkinson, 1979) Elphidium bogdanowiczi Pronina, 1964 Elphidium bosoense Fujita, 1956 Elphidium botaniense Albani, 1981 Elphidium brooklynense Shupack, 1934 Elphidium californicum Cook Ms., 1959 Elphidium capelavelaense McCulloch, 1981 Elphidium carenerosensis Bermúdez & Fuenmayor, 1966 Elphidium cariacoense Bermúdez & Seiglie, 1963 Elphidium carpentariaense Albani & Yassini, 1993 Elphidium carteri Hayward, 1997 in Hayward, Hollis & Grenfell, 1997 Elphidium cercadense Bermúdez, 1949 Elphidium chapmani Cushman, 1936 Elphidium charlottense (Vella, 1957) Elphidium cherifi Anan, 2010 Elphidium chilenum Todd & Kniker, 1952 Elphidium clarki Graham, 1950 Elphidium clavatum Cushman Em. Loeblich & Tappan, 1953 Elphidium cochense McCulloch, 1981 Elphidium collinsi Hayward, 1997 in Hayward, Hollis & Grenfell, 1997 Elphidium colomboense McCulloch, 1977 Elphidium colomi Ferrer, 1971 Elphidium complanatum (d'Orbigny, 1839) Elphidium compressulum Copeland, 1964 Elphidium concinnum Khalilov, 1957 Elphidium concinnum Nicol, 1944 Elphidium consociatum Khalilov, 1957 Elphidium costiferum (Terquem, 1882) Elphidium crassatum Cushman, 1936 Elphidium crassimargo Shchedrina, 1984 Elphidium craticulatum (Fichtel & Moll, 1798) Elphidium crespinae Cushman, 1936 Elphidium crispum (Linnaeus, 1758) Elphidium cristobalense McCulloch, 1981 Elphidium cubaguaense McCulloch, 1981 Elphidium culebrense Cushman, 1936 Elphidium cuvillieri Levy, 1966 Elphidium cynicalis Jennings, 1936 Elphidium decipiens (O.G.Costa, 1856) Elphidium decorum Qiu & Lin, 1978 Elphidium deferrariisi Malumián, 1990 Elphidium delicatulum Bermúdez, 1949 Elphidium discoidale (d'Orbigny, 1839) Elphidium dominicense Bermúdez, 1949 Elphidium dopperti Daniels, 2001 Elphidium duzdagicum Pronina, 1964 Elphidium earlandi Cushman, 1936 Elphidium echinus Serova, 1955 Elphidium elegans Serova, 1955 Elphidium elegantum (Hofker, 1976) Elphidium ellisi Weiss, 1954 Elphidium eocenicum Cushman & Ellisor, 1931 Elphidium excubitor Nicol, 1944 Elphidium exoticum Haynes, 1973 Elphidium ezoense Asano, 1937 Elphidium fastigiatum Cushman, 1945 Elphidium fax Nicol, 1944 Elphidium fedorowi Bogdanovich, 1960 Elphidium felsense Papp, 1963 Elphidium ferrentegranulum Krasheninnikov, 1960 Elphidium fichtelianum (d'Orbigny, 1846) Elphidium fijiense Hayward, 1997 in Hayward, Hollis & Grenfell, 1997 Elphidium fimbriatulum (Cushman, 1918) Elphidium fissurisuturalum Wang, He & Lu, 1988 Elphidium flexuosum (d'Orbigny, 1846) Elphidium florentinae Shupack, 1934 Elphidium formosum Todd, 1957 Elphidium friedbergi Serova, 1955 Elphidium frigidum Cushman, 1933 Elphidium frizzelli Miller, 1953 Elphidium galvestonense Kornfeld, 1931 Elphidium georgianum Cushman, 1935 Elphidium georgium Venglinsky, 1958 Elphidium gibsoni Hayward, 1979 Elphidium glabratum Cushman, 1939 Elphidium granatum Gudina, 1964 Elphidium granti Kleinpell, 1938 Elphidium granulosum (Sidebottom, 1909) Elphidium grimensis Quilty, 1980 Elphidium groenlandicum Cushman, 1933 Elphidium guraboense Bermúdez, 1949 Elphidium haagensis van Voorthuysen, 1950 Elphidium hadleyana Smitter, 1955 Elphidium halickii Brodniewicz, 1972 Elphidium hallandense Brotzen, 1943 Elphidium hampdenense Finlay, 1939 Elphidium hauerinum (d'Orbigny, 1846) Elphidium hawkesburyense (Albani, 1974) Elphidium helenae Quilty, 1980 Elphidium hiltermanni Hagn, 1952 Elphidium hispidulum Cushman, 1936 Elphidium hokkaidoense Asano, 1950 Elphidium hornibrooki Srinivasan, 1966 Elphidium howchini Cushman, 1936 Elphidium hughesi Cushman & Grant, 1927 Elphidium humboldtensis Haller, 1980 Elphidium hungaricum Korecz-Laky, 1967 Elphidium hyalocostatum Todd, 1957 Elphidium ibericum (Schrodt, 1890) Elphidium icenorum Macfadyen, 1939 Elphidium inchonense Mcculloch, 1977 Elphidium inclarum Krasheninnikov, 1960 Elphidium indicum Cushman, 1936 Elphidium infrajuliense Bertels, 1977 Elphidium ingressans Dorreen, 1948 Elphidium inopinatum Khalilov, 1957 Elphidium iojimaense Asano & Murata, 1958 Elphidium iranicum (Yassini & Ghahreman, 1977) Elphidium ishikariense Kaiho, 1984 Elphidium izumoense Nomura, 1990 Elphidium javanum Yabe & Asano, 1937 Elphidium jiani Lei & Li, 2016 Elphidium johnstonae Mclean, 1956 Elphidium joukovi Serova, 1955 Elphidium kadilnicovi Semenov & Semenova, 1980 Elphidium kaicherae Mclean, 1956 Elphidium kaneharai Ishiwada, 1958 Elphidium kanoum Hayward, 1979 Elphidium karenae Asbjornsdottir, 1994 Elphidium karpaticum Myatlyuk, 1950 Elphidium kazmakrisense Mamedova, 1966 Elphidium kerguelenense Parr, 1950 Elphidium kobense McCulloch, 1977 Elphidium koberi Tollmann, 1955 Elphidium koeboeense LeRoy, 1939 Elphidium kozlowskii Brodniewicz, 1965 Elphidium kudakoense Bogdanovich, 1947 Elphidium kusiroense Asano, 1938 Elphidium laeve (d'Orbigny in Parker, Jones & Brady, 1865) Elphidium lagunense (Albani & Balbero, 1982) Elphidium laloviensis Venglinsky, 1948 Elphidium lanieri (d'Orbigny, 1839) Elphidium latidorsatum (Reuss, 1864) Elphidium latispatium Poag, 1966 Elphidium latusovum Krasheninnikov, 1960 Elphidium lauritaense Todd & Kniker, 1952 Elphidium lautenschlaegeri Voloshinova, 1952 Elphidium lene Cushman & McCulloch, 1940 Elphidium lens Galloway & Heminway, 1941 Elphidium leonensis Applin & Jordan, 1945 Elphidium lessonii (d'Orbigny, 1839) Elphidium ligatum Krasheninnikov, 1960 Elphidium limatulum Copeland, 1964 Elphidium limpidum Ho, Hu & Wang, 1965 Elphidium lobatum Galloway & Heminway, 1941 Elphidium ludbrookae Bhalla & Dev, 1988 Elphidium mabutii Asano, 1962 Elphidium macellum (Fichtel & Moll, 1798) Elphidium maioricense Colom, 1942 Elphidium manibulum Khalilov, 1957 Elphidium maorium Hayward, 1997 Elphidium margaritaceum Cushman, 1930 Elphidium marshallana Todd & Post, 1954 Elphidium matagordanum (Kornfeld, 1931) Elphidium matanginuiense Hayward, 1997 Elphidium matauraense Hayward, 1997 Elphidium matsuense Nomura, 1990 Elphidium matsukawauraense Takayanagi, 1955 Elphidium mawsoni Parr, 1950 Elphidium mexicanum Kornfeld, 1931 Elphidium microelegans Serova, 1955 Elphidium microgranulosum Galloway & Wissler, 1951 Elphidium miikense Murata, 1961 Elphidium millettiforme McCulloch, 1977 Elphidium minutum (Reuss, 1865) Elphidium mirandum Krasheninnikov, 1960 Elphidium mironovi Voloshinova, 1952 Elphidium morenoi Bermúdez, 1935 Elphidium mortonbayense Albani & Yassini, 1993 Elphidium multacamerum Krasheninnikov, 1960 Elphidium mundulum Todd & Low, 1960 Elphidium musselroeensis Quilty, 1980 Elphidium nagaoi Asano, 1938 Elphidium nakanokawaense Shirai, 1960 Elphidium nataliae Popescu, 1995 Elphidium nautiloideum Galloway & Heminway, 1941 Elphidium neocrespinae Gibson, 1983 Elphidium neosimplex McCulloch, 1977 Elphidium nigarense Cushman, 1936 Elphidium nipeense Keijzer, 1945 Elphidium noniformis Gerke in Voloshinova & Dain, 1952 Elphidium nonioniformis Smigielska, 1957 Elphidium norvangi Buzas, Smith & Beem, 1977 Elphidium notabilis Pishvanova, 1958 Elphidium novozealandicum Cushman, 1936 Elphidium obtusum (d'Orbigny, 1846) Elphidium oceanense (d'Orbigny in Fornasini, 1904) Elphidium oceanicum Cushman, 1933 Elphidium oligocenicum Khalilov, 1951 Elphidium ombetsuense Asano, 1962 Elphidium omotoensis Dorreen, 1948 Elphidium omuraense Shuto, 1953 Elphidium onerosum Bogdanovich, 1960 Elphidium orientale Voloshinova, 1952 Elphidium owenianum (d'Orbigny, 1839) Elphidium ozawai Uchio, 1951 Elphidium panamense Cushman, 1936 Elphidium papillosum Cushman, 1936 Elphidium paraense Petri, 1954 Elphidium paraskevaidisi Christodoulou, 1960 Elphidium parviforme McCulloch, 1981