THALASSICOLLIDAE Müller, 1859

Suzuki, Noritoshi, Caulet, Jean-Pierre & Dumitrica, Paulian, 2021, A new integrated morpho- and molecular systematic classification of Cenozoic radiolarians (Class Polycystinea) - suprageneric taxonomy and logical nomenclatorial acts, Geodiversitas 43 (15), pp. 405-573 : 532-533

Family THALASSICOLLIDAE Müller, 1859

Thalassicollae Müller, 1859a: 28 [as a family].

Thalassicollida – Haeckel 1862: 237, 246 [as both family and tribe]; Haeckel 1882: 469 [as a family]; Haeckel 1884: 28 [as a family]; Haeckel 1887: 10-12 [as a family]. — Lankester 1885: 849 [as a family]. — Bütschli 1889: 1946 [as a family]. — Ludwig 1908: 17 [rank unknown].— Anderson 1983: 23. — Boltovskoy 1998: 30 [as a family].

Thalassicollidae – Wallich 1869: 97-99. — Claus 1876: 158. — Delage & Hérouard 1896: 177 [as a suborder]. — Brandt 1902: 82. — Popofsky 1908: 203. — Lankester et al. 1909: 144. — Enriques 1932: 983. — nec Aberdeen 1940: 132-133. — Hollande & Enjumet 1953: 107, 108, 136-144. — Campbell 1954: D44. — Chediya 1959: 65. — Cachon & Cachon 1985: 284. — Anderson et al. 2002: 1000.

Brachiata Mivart, 1878: 179 [unavailable name, as a subsection] (including Myxobrachia).

Thalassophysidae Brandt, 1902: 82 [nomen dubium]. — Lankester et al. 1909: 144. — Hollande & Enjumet 1953: 108, 130-131, 144-150. — Cachon & Cachon 1985: 285.

Thalassophysiden – Huth 1913: 25 [nomen dubium, as a family].

Thalassicolliden – Huth 1913: 25-26 [as a family].

TYPE GENUS. — Thalassicolla Huxley, 1851: 433 [type species by subsequent designation ( Haeckel 1887: 18): Thalassicolla nucleata Huxley, 1851: 435 ].

INCLUDED GENERA. — Myxobrachia Haeckel, 1870: 519. — Procyttarium Haeckel, 1879: 705 (= Actissa with the same type species). — Thalassicolla Huxley, 1851: 433 (= Thalassicollidium with the same type species). — Thalassicollarium Haeckel, 1887: 18 . — Thalassolampe Haeckel, 1862: 253 . — Thalassopila Haeckel, 1882: 469 .

NOMINA DUBIA. — Actidiscus , Actilarcus , Actiprunum, Monocarion , Thalassophysa .

DIAGNOSIS. — Thalassicollidae consists of solitary Collodaria without a siliceous skeleton. A single large nucleus is present in the center and is surrounded with the endoplasm. Huge number of algal symbionts are present.

STRATIGRAPHIC OCCURRENCE. — Living.

REMARKS

“ Thalassicolla ” is scattered among the Sphaerozoidae and Collosphaeridae clades in molecular phylogenetic studies ( Biard et al. 2015). A life stage shift from “ Thalassophysa ” to Collozoum was reported by Hollande & Enjumet (1953: 136-144). Morphologic changes among Myxobrachia, Thalassicolla and Thalassolampe are ordinarily observable in a single cell within a several-day laboratory observation. In addition, many undescribed “genera” in Thalassicollidae are commonly found in plankton samples. The Thalassicollidae are an artificial group but should be maintained as a morphological family for convenience because “solitary collodarians” are abundantly and regularly found in plankton samples. Thalassicolla has long been regarded as a model organism of Spumellaria , but it is now understood that Thalassicolla has extremely endemic characters in terms of cytology, ecology, morphology and taxonomy ( Suzuki & Aita 2011; Biard et al. 2015; Suzuki & Not 2015). The ultrafine cytologic structure is also quite different between Collodaria and spherical Spumellaria ( Hollande & Enjumet 1960; Cachon & Cachon 1972b; 1972c; 1984). However, the protoplasmic illustrations in textbooks of Radiolaria, were referred to Thalassicollidae with or without certain modifications. Thus, they are useless in acquiring a basic knowledge of the majority of spherical Radiolaria ( Campbell 1954: D12; Chediya 1959: 10; Orlev 1959: 376; Nakaseko et al. 1975: fig. 95; Nakaseko & Sugano 1976: fig. 7.1; Kling 1978: fig. 3.B; Margulis & Schwartz 1988; Nazarov 1988: figs 1, 2; Cachon et al. 1989: fig. 2). In particular, the bubble-like structure (named “glycocalyx” in Hollande & Hollande 1975) is a character unique to some members of the Thalassicollidae and Thalassosphaeridae . Due to its historic reputation as “a model Spumellaria ”, the biological knowledge of Thalassicollidae is substantial. “Living” images were illustrated for Thalassicolla ( Huth 1913: figs 1-7; Anderson 1978b: fig. 1; 1983: fig. 1.1.A; Anderson & Botfield 1983: fig. 1: Caron & Swanberg 1990: fig. 3.D; Probert et al. 2014: S1, PAC 1, 3-6, 10-15; Suzuki & Not 2015: fig. 8.13.1; Biard et al. 2016: figs 3.a, 3.b, 3.e; Matsuoka et al. 2017: appendix A; Liu et al. 2019: fig. 1), Thalassolampe ( Hollande & Enjumet 1953: fig. 8; Anderson 1993: fig. 4; 1996: fig. 1.F), Thalassopila ( Biard et al. 2016: fig. 3.c) and “ Thalassophysa ” ( Hollande & Enjumet 1953: figs 12-14, 37). The biology and ecology of Thalassicolla has been profusely documented with studied dealing with: ultrafine cellular structure ( Hollande & Hollande 1975; Anderson 1976a, 1978b; Cachon & Cachon 1976; Anderson & Botfield 1983); feeding behavior, nutrition and reproduction ( Anderson 1978b); optimal pH for enzyme activity and cellular specialization ( Anderson & Botfield 1983); food preference in laboratory culture ( Anderson 1980); 14C isotopic evidence for assimilation of organic substances from algal symbionts (Anderson et al. 1983; 1985); and interaction of holobionts by transcriptome ( Liu et al. 2019). The ultrafine cellular structures of Thalassolampe ( Hollande & Cachon-Enjumet 1959; Cachon & Cachon 1977) and “ Thalassophysa ” ( Hollande & Cachon-Enjumet 1959; Hollande et al. 1970) were also reported. Algal symbionts of Thalassicolla were identified as Brandtodinium nutricula by Probert et al. (2014). Fatal symbiosis by Solenodinium and Caryotoma bernardi was also documented in Thalassicolla ( Hollande & Enjumet 1953: 166-173; Hollande & Corbel 1982). However, molecular studies concerning the morphological taxonomy for these fatal symbionts were not conducted.

VALIDITY OF GENUS

Procyttarium

Procyttarium has the same type species as Actissa . However, the practical definitions of these two genera were based on different species. Procyttarium is based on Procyttarium primordial , whereas Actissa is based on Actissa princeps . The definition of Procyttarium in Haeckel (1879: 705) is: “ globular cell (central capsule) with a central oil sphere surrounded by numerous small ‘yellow vacuoles’ radiating fine pseudopodia ” (translated from German by J.-P. Caulet). SinceHaeckel (1887: 12) established Actissa , only Ludwig (1908) has studied Actissa . Ludwig (1908: 28) revised the definition of Actissa as: “ Thalassicollidae usually without spicules, usually without or with rare vacuoles in the extracapsular gelatinous sheath, which is more compact. Often very numerous algal symbionts. Smaller than Thalassicolla . Pigmented in red, yellow, or black. The central capsule wall is usually thick. In the vegetative stages, the chromatin usually borders a sphere built from ‘ground matter’. The centrosome is observed at the beginning of anisospore formation. The macro- and microspores are usually inside the nucleus ” (translated from German by J.-P. Caulet). As these definitions show, these two “genera” differ. A new genus is needed for Actissa sensu Ludwig (1908) .