Leptoplanoidea Faubel, 1984

Superfamily Leptoplanoidea Faubel, 1984 View in CoL

Leptoplanoidea View in CoL is a heterogenous assemblage of 12 families. Several of these families ( Cestoplanidae View in CoL , Cryptocelidae View in CoL and Theamatidae View in CoL ) and individual genera (e.g. Phaenoplana View in CoL and Amemiyaia View in CoL ) have already been transferred to other groups ( Bahia et al., 2017; this study). Using two species representing Gnesiocerotidae View in CoL , we recovered the family as the first branching lineage in the superfamily. This is in contrast to Bahia et al. (2017), who found the gnesiocerotid Echinoplana celerrima Haswell, 1907 View in CoL embedded in a clade with Notoplana australis View in CoL and an unidentified species of Notocomplana View in CoL . We support the validity of Gnesiocerotidae View in CoL by including two separate genera ( Styloplanocera View in CoL and Gnesioceros View in CoL ). The family forms a basal lineage with Leptoplanoidea View in CoL and is morphologically united by a highly cuticularized cirrus that connects directly to the prostatic vesicle and is surrounded by a strongly developed, muscular bulb ( Fig. 2C).

Notoplanidae View in CoL is one of the most species-rich families in the superfamily and has been the focus of several classifications and revisions ( Bock, 1913; Marcus & Marcus, 1968; Faubel , 1983; Prudhoe, 1985). Given that Notoplana View in CoL represents the largest genus among acotyleans (60+ species), Bock (1913) subdivided Notoplana View in CoL into group A ( Notoplana evansi type), group B ( Notoplana atomata View in CoL type) and group C ( Notoplana alcinoi View in CoL type). In both group A and B, the penis is armed with a stylet, whereas some members of group C do not possess a stylet. Separation between groups A and B is based on the size of the male antrum and Lang’s vesicle: group A species are characterized by a large male antrum and a small, rudimentary Lang’s vesicle, and those in group B have a small male antrum and a large Lang’s vesicle ( Bock, 1913). This grouping was largely followed by Marcus & Marcus (1968), with the creation of additional subdivisions, some of which most probably represent unnatural groups by the authors’ own admission ( Marcus & Marcus, 1968).

In an extensive attempt at reorganizing Notoplanidae, Faubel (1983) View in CoL recognized ten genera, four of which were new. Half of these genera are monospecific and three others contain two species only ( Faubel , 1983). The two remaining species-rich genera are morphologically separated by the lack or presence of a penis stylet. In Notocomplana View in CoL , the penis is represented by a blunt or conical papilla, whereas in Notoplana View in CoL the penis is armed with a short stylet ( Faubel , 1983). Finally, Prudhoe’s (1985) attempt recognized four groups in Notoplana View in CoL , based on the presence or absence of a penis stylet and the presence or absence of a penis-pocket sheath. Prudhoe’s (1985) groups C and D (i.e. penis papilla without stylet or cuticular covering) corresponds to Faubel’s (1983) Notocomplana View in CoL and to Bock’s (1913) group C in Notoplana View in CoL .

Faubel (1983) also erected the new family Pleioplanidae View in CoL , using the number of tubular chambers formed by the lining of the prostatic vesicle as a distinguishing character (‘few’ in Notoplanidae View in CoL vs. ‘greater’ in Pleioplanidae View in CoL ; Faubel , 1983: 115). Such distinctions are subjective and are most likely to be heavily influenced by the angle of the plane of sectioning and the quality of fixation. He included the new genera Melloplana View in CoL and Pleioplana View in CoL in the family, both containing species formerly assigned to Notoplana View in CoL . According to Faubel (1983), Melloplana View in CoL possess an unarmed papillate penis, whereas species with a penis armed with a stylet are placed in Pleioplana View in CoL . Hence, the separation of the two new genera is based on the same trait used in his earlier separation of Notocomplana View in CoL (species without an armed penis) and Notoplana View in CoL (species with an armed penis) with the addition that Pleioplanidae View in CoL have a ‘greater number of tubular chambers’ in their prostatic vesicle.

Since Faubel’s (1983) revision, three additional genera have been placed into Pleioplanidae View in CoL : Izmira ( Bulnes, 2010) View in CoL , a monospecific Persica ( Maghsoudlou et al., 2015) View in CoL and Laqueusplana ( Rodríguez et al., 2017) View in CoL . Of these, Izmira View in CoL has a penis papilla, whereas the other two genera have a penis armed with a stylet. Our results revealed a paraphyletic Pleioplanidae View in CoL , in which Melloplana ferruginea ( Schmarda, 1859) View in CoL groups with Notocomplana lapunda ( Marcus & Marcus, 1968) View in CoL , which is characterized by an unarmed penis. Based on its clustering with other Notocomplana species in a phylogeny built on COI sequences, the only other species in Melloplana View in CoL , Melloplana japonica (Kato, 1937) View in CoL , has been transferred to Notocomplana View in CoL by Oya & Kajihara (2017). In addition to an unarmed penis papilla, our molecular results support the transfer of Melloplana ferruginea View in CoL to Notocomplana View in CoL to form Notocomplana ferruginea ( Schmarda, 1859) View in CoL comb. nov. Thus, all currently recognized species of Melloplana View in CoL are now included in Notocomplana View in CoL , in which the genus Melloplana View in CoL is synonymized.

To separate notoplanids with an unarmed penis papilla from those armed with a stylet, we erect the new family Notocomplanidae fam. nov. and formally designate Notocomplana as its type genus. Following the precedent of Faubel (1983) when he erected the genus, Notocomplana humilis (Stimpson, 1857) remains the type species. Notocomplanidae generally corresponds to Notoplanidae in Bock’s (1913) group C, Prudhoe’s (1985) groups C and D and Faubel’s (1983) Notocomplana . Morphologically, the family is defined as having the characters of Notoplanidae but possess an unarmed penis papilla. Thus, we place more importance on the armature of the penis than on more subjective traits associated with the lining of the prostatic vesicle.

Combining our molecular results with the character ‘armed penis’ also led us to return Pleioplana atomata (O.F. Müller, 1776) to its original genus, Notoplana . Clearly, in Notoplanidae , ‘presence or absence of a penis stylet’ must be considered of greater phylogenetic value than more plastic traits (e.g. degree of folding of prostatic vesicle lining, distance to which the ejaculatory duct enters the prostatic vesicle). Likewise, another pleioplanid, Persica qeshmensis Maghsoudlou et al., 2015 , grouped with Notoplana , all possessing a stylet. Consequently, we move Persica qeshmensis to Notoplana to form Notoplana qeshmensis comb. nov. We concur with Oya & Kajihara (2017) that the support for Pleioplanidae (even after removing Melloplana ) is questionable and that it most probably is synonymous with Notoplanidae . However, this hypothesis awaits testing by including sequences of Izmira and Laqueusplana in a future molecular phylogeny.

Similar to Notoplanidae , Stylochoplanidae is also a species-rich leptoplanoid family whose intrafamilial relationships are not resolved, despite several attempts at revisions ( Bock, 1913; Marcus & Marcus, 1968; Faubel , 1983; Prudhoe, 1985). Bock (1913), Marcus & Marcus (1968) and Prudhoe (1985) subdivided Stylochoplana into different groups, whereas Faubel (1983) removed species possessing a long, pointed stylet, a voluminous prostatic vesicle and a Lang’s vesicle into the new genus Armatoplana to distinguish them from other species that either lack a stylet, have a short stylet only or in which the stylet is only a thickened basement membrane. We included specimens of Armatoplana divae ( Marcus, 1947) and Armatoplana leptalea (Verrill, 1900) in our phylogeny. Armatoplana leptalea was originally described from Brazil ( Marcus, 1947) and its range has been extended to include Curaçao, Antigua, Barbuda and the Florida Keys ( Marcus & Marcus, 1968). We can add Panama, Colombia and Belize as additional localities (see Supporting Information, Appendix).

In their description of Armatoplana leptalea from Curaçao, Marcus & Marcus (1968: 25) mention that the specimens differ from the original ones collected in Brazil. These differences might explain why our Caribbean specimens cluster together, whereas the specimens from Brazil ( Bahia et al., 2017) form a distinctly separate group, albeit still within the species. However, the original species description of Armatoplana lactoalba (Verrill, 1900) included only a short account of the external morphology and lacked any details regarding the reproductive systems ( Verrill, 1902). Therefore, we cannot exclude the possibility that our specimens are Armatoplana lactoalba rather than Armatoplana leptalea , and species equivalence of Caribbean and Brazilian samples will require additional sampling, including careful reconstruction of the reproductive systems and molecular data.

Armatoplana divae has a distinct dorsal coloration, allowing for easy species identification based on external morphology alone. However, rather than clustering with Armatoplana leptalea , Armatoplana divae appears closer to Notoplana queruca . This is reflective of the unresolved classification of Stylochoplanidae and requires further study.

Finally, Amyris is characterized by a muscular penis papilla, called a cirrus. Marcus & Marcus (1968) considered the cirrus unarmed, because the cuticular lining of the ejaculatory duct appears smooth. However, we observed that the lining consists of numerous small, spine-like structures that overlap to give the appearance of a smooth lining. Upon eversion, the spines unfold, resulting in an armed penis papilla. Hence, our results showing the clustering of Amyris with other notoplanids possessing an armed penis are supported by morphology.

Marcus & Marcus (1968) recognized two species of Amyris , differentiated only by the size of the seminal vesicle, the degree of muscle development of the male organs, the depth of the male antrum and a wider and more folded vagina in Amyris ujara . All these traits are plastic and vary depending on fixation and age of the specimens. Based on identical sequences, our results indicate that Amyris ujara is a junior synonym of Amyris hummelincki .

RELATIONSHIPS IN COTYLEA

Six major clades were identified in Cotylea. The base of the tree is formed by taxa exhibiting acotylean- and cotylean-like traits; specifically, Cestoplanidae , Pericelidae + Diposthus popeae and a clade containing Boniniidae , Theamatidae and Amyellidae . Prosthiostomidae , Euryleptidae and Pseudocerotidae established the remaining three groups.

Given that the male reproductive systems of cotyleans are rather uniform, with few distinguishing characters (most have a free prostatic vesicle), characters associated with the digestive (pharynx) and sensory systems (pseudotentacles, eyes) and colour patterns are more commonly used for taxonomic identifications ( Newman & Cannon, 2003 and references therein). Faubel (1984) recognized three superfamilies in Cotylea. Opisthogenioidea is monospecific and was not included in our analysis. To classify the remaining two superfamilies, he placed a high taxonomic value on the shape of the pharynx. All families with a ruffled pharynx are placed into Pseudocerotoidea, whereas families with a cylindrical pharynx are placed into Euryleptoidea. The morphology-based cladistic analysis of Rawlinson & Litvaitis (2008) had already invalidated Faubel’s (1984) superfamilies, and our molecular analysis now reconfirmed that Boniniidae , Amyellidae , Diposthidae and Pericelidae are not members of Pseudocerotoidae (sensu Faubel , 1984) and that Prosthiostomidae should not be included in Euryleptoidea. Thus, the two superfamilies are not valid, and we urge the discontinuation of their use.