Polybranchia, PEASE, 1860

GENUS POLYBRANCHIA PEASE, 1860 View in CoL

Polybranchia Pease, 1860: 141 View in CoL . Type species: Polybranchia pellucida Pease, 1860 (by monotypy).

Phyllobranchus Alder & Hancock, 1864: 145 View in CoL . Type species: Proctonotus orientalis Kelaart, 1858 (by monotypy), not in homonymy with Family Phyllobranchus Girard, 1851 View in CoL [Annelida].

Lobifera Pease, 1866: 206 View in CoL , unnecessary replacement name for Polybranchia Pease, 1860 View in CoL .

Polybranchus O’Donoghue, 1929: 737 View in CoL , unjustified emendation for Polybranchia Pease, 1860 View in CoL .

Phyllobranchillus Pruvot-Fol, 1933: 93 View in CoL , replacement name for Phyllobranchus Alder & Hancock, 1864 View in CoL .

Branchophyllum Pruvot-Fol, 1947: 101 View in CoL , replacement name for Phyllobranchus Alder & Hancock, 1864 View in CoL .

Diagnosis

Body oval, broader anteriorly, tapering posteriorly. Head with short, enrolled oral tentacles. Rhinophores bifurcated, papillate or smooth. Eyespots at base of rhinophores. Pericardium large, papillate or smooth. Anal papilla on right lateral side of body, at same level as heart, below ceratal bases. Numerous pedunculated, leaf-like cerata surround lateral sides of body, each penetrated with branches of digestive gland. Dorso-lateral cerata larger, smaller cerata on lateral sides. Cerata evenly papillated along dorsal surface vessels; two or three large papillae on dorso-medial surface of cerata, all other papillae of similar size; ventral surface of cerata often papillated. Small lateral cerata either lack digestive gland branches or have dense network of digestive gland extensions. Ceratal penduncles with small distal depressions. Body colour variable from translucent pale olive-green to brown or salmon pink. Cerata colour from translucent olive-green, light to medium brown, red or purple. Radula with single row of teeth forming an ascending and a descending limb; descending limb protruding off right side of pharynx. Ascus with teeth organized into single row. Teeth short and stout, each with hollow depression on dorsal side, half the length of a single tooth; depression interlocks with neighbouring teeth. Teeth cusp thick, resembling a rounded ‘dull blade.’ Penis long, typically smooth, occasionally with numerous warty papillae, in one species armed with a minute stylet.

Remarks

Pease (1890) introduced the genus name Polybranchia Pease, 1890 for the new species Polybranchia pellucida Pease, 1860 , collected in the Hawaiian Islands. The diagnosis of the genus is short, but provided several important details that allow its identification: body with several rows of ‘deciduous’ (=autotomizable) ‘lobes’ (=cerata), with the branchiae (=digestive gland branches) embedded in the cerata; ‘cephalic tentacles’ (=rhinophores) bifurcate. Four years later, and apparently unaware of Pease’s (1860) paper, Alder & Hancock (1864) introduced the new genus name Phyllobranchus Alder & Hancock, 1864 for the species Proctonotus orientalis Kelaart, 1858 , originally described from India ( Kelaart, 1858). The diagnostic characteristics of Phyllobranchus include bifurcate ‘tentacles’ (=rhinophores) and ‘branchial leaves’ (=cerata) with distinct footstalks arranged in several rows; ‘tongue’ (=radular teeth) similar to that of Hermaea Lovén, 1844 ( Alder & Hancock, 1864). All these characteristics, in addition to the features of the type species (see remarks on Polybranchia orientalis below) confirm that the name Phyllobranchus corresponds to the modern usage of Polybranchia Pease, 1860 and, therefore, is a junior synonym. Two years later, Pease (1866) also unaware of Alder & Hancock’s (1864) work, recognized he was mistaken about the identity of the ‘radiating lines’ enclosed in the ‘lobes’ he called ‘branchiae’ in his original description of Polybranchia , and consequently considered that the name Polybranchia (=multiple branchiae) was not descriptive of the characteristics of this group. Therefore Pease (1866) introduced the new name Lobifera Pease, 1866 to replace Polybranchia and included two additional new species, Lobifera nigricans Pease, 1866 and Lobifera papillosa Pease, 1866 (the former is currently considered a member of Cyerce Bergh, 1870 ). This act constitutes an unnecessary replacement of an available name ( ICZN, 1999: Article 10.6), thus Lobifera maintains the same type species as Polybranchia ( ICZN, 1999: Article 67.8) and becomes an objective junior synonym. Subsequently, Pease (1871) became aware of the description of Phyllobranchus by Alder & Hancock (1864) and concluded it has the same characteristics as Polybranchia and Lobifera . Pease (1871) also indicated that Alder & Hancock (1864) considered the ‘radiating lines enclosed’ in the ‘lobes’ (=cerata) to be true branchiae and consequently reverted to use the name Polybranchia instead of Lobifera .

Trinchese (1896) noted that Phyllobranchus Alder & Hancock, 1864 is preoccupied by Phyllobranchus Girard, 1851 (Annelida) but continued using the former name as valid. O’Donoghue (1929) misspelled Polybranchia as Polybranchus (unjustified emendation) and considered that this name has priority over Phyllobranchus Alder & Hancock, 1864 .However, Thiele (1931) indicated that Polybranchia Pease, 1860 was preoccupied by Polybranchia Latreille, 1825 (Insecta) and considered Polybranchia (as Lobifera Pease, 1866 ) a subgenus of Caliphylla A. Costa, 1867. Pruvot-Fol (1933) argued that because both Polybranchia Pease, 1860 and Phyllobranchus Alder & Hancock, 1864 are preoccupied, and Lobifera was introduced for species with a transverse groove on the foot, none of those names are available/appropriate for this group. Therefore, Pruvot-Fol (1933) proposed the replacement name Phyllobranchillus Pruvot-Fol, 1933 for both Polybranchia Pease, 1860 and Phyllobranchus Alder & Hancock, 1864 . However, Polybranchia Latreille, 1825 was introduced as a family-level name and consequently cannot enter in homonymy with a genus-level name ( ICZN, 1999: Article 53.2). Additionally, as indicated above, Lobifera is an unjustified substitute name for Polybranchia and also an objective junior synonym as it retains the same type species ( ICZN, 1999: Article 67.8). Pruvot-Fol (1947), after apparently forgetting her previous proposal to replace Polybranchia Pease, 1860 with Phyllobranchillus Pruvot-Fol, 1933 , again reiterated that Polybranchia was preoccupied and proposed the new name Branchophyllum Pruvot-Fol, 1947 to replace it. Later, Pruvot-Fol (1954) recognized that Polybranchia Latreille, 1825 was a family-level name and, therefore, Polybranchia Pease, 1860 remained available.

A revision of the literature thus confirms that Polybranchia Pease, 1860 is a valid name and includes species of Sacoglossa with bifurcate rhinophores, cerata with branches of the digestive gland and a complete foot, lacking a transversal groove. Below we describe seven distinct species recovered in phylogenetic and species delimitation analyses, as well as two additional morphologically distinct taxa not studied herein, providing justifications for the usage of available names or the introduction of new ones.