TRANSANDIPLANA GRAUI ALMEIDA & CARBAYO, 2023

Almeida, Ana Laura, Álvarez-Presas, Marta & Carbayo, Fernando, 2023, The discovery of new Chilean taxa revolutionizes the systematics of Geoplaninae Neotropical land planarians (Platyhelminthes: Tricladida), Zoological Journal of the Linnean Society 197 (4), pp. 837-898 : 854-859

publication ID	https://doi.org/ 10.1093/zoolinnean/zlac072
publication LSID	lsid:zoobank.org:pub:010109AB-79F5-4E6D-909B-08BB1803E589
DOI	https://doi.org/10.5281/zenodo.7797643
persistent identifier	https://treatment.plazi.org/id/03C49B73-6971-FFB6-FC30-7540B5227414
treatment provided by	Plazi
scientific name	TRANSANDIPLANA GRAUI ALMEIDA & CARBAYO
status	sp. nov.

Treatment

TRANSANDIPLANA GRAUI ALMEIDA & CARBAYO SP. NOV.

( FIGS 13–16 View Figure 13 View Figure 14 View Figure 15 View Figure 16 )

Zoobank registration: urn: lsid: zoobank. org:act: 9247667A-A4EE-4722-B935-7332CAA3F792

Holotype: MNHNCL PLAT-15049 (Field code, F4696). Huasco, Región de Atacama, Chile (28°27′′57.4′′S, 071°11′′09.5′′W), coll. F. Carbayo et al., 2 December 2010 GoogleMaps . Cephalic region: transverse sections on 13 slides; ovarian region: horizontal sections on 4 slides; prepharyngeal region: transverse sections on seven slides; pharynx and copulatory apparatus: sagittal sections on 13 slides.

Type locality: Huasco, Región de Atacama, Chile. The species is only known from this locality.

Etymology: The specific epithet pays homage to Dr José Horácio Grau, for his friendship and contribution to the knowledge of the Chilean planarians.

Description

External aspect: The live holotype ( Fig. 13A View Figure 13 ) is about 25 mm in length and 2 mm in width. The body margins are parallel. The anterior extremity of the body is rounded, while the posterior is pointed. The dorsal side is convex; the ventral one is flat. The dorsal colour is graphite-grey (RAL 7024) – slightly clearer on the body margins– and adorned with a median grey-white (RAL 9002) stripe ( Fig. 13A View Figure 13 ). The ventral surface is pure white (RAL 9010) – darker in the cephalic region – and exhibits a median, thin, whitish stripe throughout the body length ( Fig. 13B View Figure 13 ). The preserved holotype measured 25 mm long, 2.5 mm wide and 1 mm high.

The eyes are of a single-cup type measuring 35–38 µm in diameter. The anterior 2 mm of the body are encircled with a uniserial row of eyes. Behind this region, the eyes spread on to the dorsal surface to the extent of a band 40% of the body width on either side. This band is gradually thinner toward the posterior tip of the body, where the eyes are only marginally located.

Scarce sensory depressions are located ventromarginally in the anterior region of the body ( Fig. 13C–E View Figure 13 ). The depth of these depressions is equivalent to two-thirds of the height of the surrounding epidermal cells. The suboptimal quality of the sections of the cephalic region, which lacks part of the ventral portion, hindered a detailed description of their distribution. There are no sensory pits. The mouth is positioned at a distance from the anterior extremity equal to 67.6% of the body length; the gonopore is at 78.8%.

Internal morphology: The creeping sole occupies 85% of the ventral surface of the body. Rhabditogen cells, gland cells producing erythrophil granules and gland cells producing xanthophil amorphous secretion discharge their secretion through the dorsal epidermis of the pre-pharyngeal region. Gland cells producing cyanophil granules and gland cells producing amorphous erythrophil secretion discharge their secretion through the ventral epidermis. A glandular margin is absent. The gland cells exhibit the same distribution in the cephalic region, although they are scarcer. The main nervous system is organized in approximately 24 longitudinal nerve cords.The shape of each cord resembles a necklace of beads ( Fig. 14A, B, D View Figure 14 ). Cerebral ganglia could not be discerned.

The cutaneous musculature comprises three layers, namely, a subepidermal layer of circular muscle (2–3 µm thick), followed by a double layer with diagonal fibres (4 µm) and a third layer of longitudinal muscle (20–25 µm dorsally, 17–20 µm ventrally). Muscle fibres of the longitudinal muscle layer are arranged into bundles with six to 15 fibres each ( Fig. 14E, F View Figure 14 ). The cutaneous musculature thickness relative to body height at the pre-pharyngeal region is 6.7%. The musculature in the cephalic region maintains the organization observed in the pre-pharyngeal region.

The parenchymal musculature comprises three layers of scattered fibres, namely, a dorsal double layer (12–15 µm thick) of decussate fibres, a supraintestinal layer of transverse muscle (40–50 µm) and a subintestinal layer of transverse muscle (35–50 µm) ( Fig. 14C, D View Figure 14 ).

The mouth is situated at the end of the pharyngeal pouch ( Fig. 15A View Figure 15 ). A distinct oesophagus is present. The oesophagus to pharynx length ratio is 24%. The pharynx is cylindrical ( Fig. 15A View Figure 15 ). The oesophagic musculature consists of a subepithelial layer of circular muscle (40 µm thick), followed by a layer of longitudinal muscle (25 µm thick). Two types of gland cells discharge their erythrophil and cyanophil granules, respectively, through the covering epithelium of the distal portion of the pharynx. The outer pharyngeal musculature consists of a subepithelial layer of longitudinal muscle (2.5 µm thick), followed by a layer of circular muscle (7.5 µm thick). The inner pharyngeal musculature consists of a single muscle of circular and longitudinal fibres interwoven.

The testes range between club- and pear-shaped and are 180–230 µm in diameter. The testes are surrounded by a pigmented covering ( Fig. 14C, E, F View Figure 14 ), and are distributed into one to two rows at each side of the body. They are located dorsally, beneath the supraintestinal parenchymal muscle, and between the intestinal branches. The anteriormost testes lie at a distance from the anterior tip of the body equivalent approximately to 10% of the body length; the posteriormost testes are located 2 mm (8% of body length) anterior to the pharynx, i.e. at a distance from the anterior body tip equivalent to 52.4% of the body length.

The sperm ducts are located dorsally to the ovovitelline ducts. The distal portion of the sperm ducts is bent dorsally and medially to open into the mid-dorsal region of the prostatic vesicle ( Fig. 15C View Figure 15 ). The distal portion of one of the ducts is dilated to form a spermiducal vesicle filled with sperm. The anteriorhalf of the prostatic vesicle is extrabulbar, dilated and with a folded wall. The posterior-half is narrow and located within the penis bulb, whose dorso-anterior region is traversed by the prostatic vesicle ( Fig. 15B– D View Figure 15 ). The ejaculatory duct runs within the penis papilla to open at its tip ( Fig. 15C, D View Figure 15 ).

The prostatic vesicle is lined with a columnar epithelium in its proximal region; otherwise, the lining epithelium is cuboidal. Abundant gland cells discharge cyanophil granules into the prostatic vesicle ( Fig. 15B, D View Figure 15 ). The dilated portion of the prostatic vesicle is surrounded by a single muscle (10–65 µm thick) of intermingled fibres, while the canalicular portion is surrounded by a single circular muscle (15 µm thick).

The ejaculatory duct is lined with a cuboidal, ciliated epithelium, through which two types of gland cells discharge cyanophil and erythrophil granules, respectively. Muscle fibres surrounding this duct are not apparent.

The penis papilla is conical, with the dorsal insertion shifted backward and its basis somewhat bulged. This papilla occupies the entire length of the male atrium ( Fig. 15C, D View Figure 15 ). The epithelium of the penis papilla is cuboidal-to-columnar and is pierced by the openings of two types of numerous gland cells producing erythrophil and cyanophil granules, respectively. The epithelium is underlain by a single circular muscle (10 µm thick). Multiple radial and longitudinal muscle fibres are located in the stroma of the penis papilla.

The male atrium is smooth ( Fig. 15C, D View Figure 15 ) and is lined with a low epithelium (10 µm high) proximally and tall (30 µm thick) in the other regions. Two types of gland cells discharge their cyanophil and erythrophil granules, respectively, through the atrial epithelium. Cyanophil granules are particularly abundant in the proximal region of the male atrium. The atrial epithelium is underlain by a subepithelial layer of circular muscle (7.5 µm thick), followed by a layer of longitudinal muscle (5 µm thick).

The ovaries are ovoid, with 190 µm in maximum diameter ( Fig. 16A View Figure 16 ) and are located at a distance from the anterior body tip equivalent to about 11% of the body length. The ovovitelline ducts emerge from the dorsoposterior portion of the ovaries ( Fig. 16A View Figure 16 ). Laterally to the gonopore and the female atrium, the ovovitelline ducts ascend dorsoposteriorly, to subsequently bending anteriorly to communicate with the common ovovitelline duct. This unpaired duct runs dorso-anteriorly to join the posterodorsal region of the female atrium. In this joining point, a short diverticulum of projects anteriorly ( Fig. 15C View Figure 15 ).

The female atrium is spherical-to-ovoid. A dorsal fold located above the gonopore narrows the communication of the male and female atria. The female atrium is approximately as long as the male atrium and is lined with a columnar (150 µm high) epithelium provided with an irregular surface and stratified appearance. This epithelium has scattered and unevenly distributed cilia, presenting some spaces with a vacuolar aspect filled with cyanophil secretion ( Fig. 16B, C View Figure 16 ). This atrial epithelium is pierced by the necks of two types of gland cells producing erythrophil and cyanophil granules, respectively. The lining epithelium of the female atrium is underlain by a subepithelial layer of longitudinal muscle (2.5 µm thick), followed by a layer of circular muscle (7.5 µm thick); ectally to this muscle is a longitudinal loose muscle (20 µm) coating the atrium ( Fig. 16B View Figure 16 ).

Remarks on Geoplanini and the neae genus Transandiplana: Transandiplana is nested in Geoplanini in all molecular trees. This tribe also includes Amaga Ogren & Kawakatsu, 1990 , Bogga Grau & Sluys, 2012 , Barreirana Ogren & Kawakatsu, 1990 , Cephaloflexa Carbayo & Leal-Zanchet, 2003 , Choeradoplana Graff, 1896 , Cratera Carbayo et al., 2013 , Difroehlichia Leal-Zanchet & Marques, 2018 , Geobia Diesing, 1862 , Geoplana Schultze, 1856 , Imbira Carbayo et al., 2013 , Issoca Froehlich, 1954 , Luteostriata Carbayo, 2010 , Matuxia Carbayo et al., 2013 , Notogynaphallia Ogren & Kawakatsu, 1990 , Obama Carbayo et al., 2013 , Paraba Carbayo et al., 2013 , Pasipha Ogren & Kawakatsu, 1990 , Piima Carbayo, 2020 , Pseudogeoplana (collective genus) Ogren & Kawakatsu, 1990, Supramontana Carbayo & Leal-Zanchet, 2003 , Winsoria Negrete et al., 2020 and Xerapoa Froehlich, 1955 .

Geoplanini differ from the remaining tribes by a unique combination of characters, namely, dorsum convex (vs. carinate in Adinoplanini ), dorsal eyes (vs. only marginal in Haranini , Inakayaliini , Polycladini , Sarcoplanini and Timymini), dorsal longitudinal cutaneous muscle not sunken into the parenchyma (vs. sunken in Gusanini ; the Geoplanini Choeradoplana gladismariae Carbayo & Froehlich, 2012 is an exception), pharyngeal pouch anterior to the copulatory apparatus (vs. extending posteriorly over the copulatory apparatus in Haranini and Timymini), female atrium without musculoglandular organs (vs. with it in Adinoplanini and Sarcoplanini ) and female genital duct not dilated (vs. dilated in Inakayaliini ).

Thus, Geoplanini lack exclusive morphological characteristics. However, the eye distribution pattern might help to recognize most members of the tribe. Although some subcylindrical species of Geoplanini exhibit dorsal eyes, Geoplanini with a flattened body also present dorsal eyes. Exceptions to this pattern are some Geoplanini taxa such as Bogga and Amaga , which, while being flattened, have only marginal eyes. Nonetheless, the phylogenetic position of these two genera has not yet been assessed.

The new Geoplanini genus Transandiplana is represented by one single individual. It is retrieved as an ingroup of Geoplanini in all analyses, having an unstable position, either sister to Geoplana Stimpson, 1858 ( Fig. 2 View Figure 2 ; Supporting Information, Fig. S4 View Figure 4 ), to Paraba multicolor ( Graff, 1899) (Supporting Information, Fig. S3 View Figure 3 ) or it is a branch of a polytomy (Supporting Information, Figs S2 View Figure 2 , S 5 View Figure 5 , S 6 View Figure 6 ).

Transandiplana graui largely resembles some Geoplanini genera in the general shape of the copulatory apparatus, including the lack of structures such as musculoglandular organs. However, while it is similar to other Geoplanini, it also exhibits some features uncommon in Geoplanini, namely, sensory depressions, the main nervous system consisting of multiple longitudinal cords, testes provided with a pigmented covering, and the relatively large distance between the testes and the pharynx. With this combination of features, T. graui does not fit well in any of the Geoplaninae tribes. Sensory depressions are known from Sarcoplanini . The main nervous system in Geoplanini consists of either two longitudinal cords (usually in small and thin species such as Xerapoa ) or it exhibits the aspect of an even plate (especially in large and flat organisms such as Obama ). Transandiplana graui is an exception, as it presents both a slender body and a main nervous system consisting of multiple cords. These two latter features (dark spots covering testes and relative position of posteriormost testes) are underreported in most old species descriptions. Testes covered with dark spots were only reported for Obama ladislaƲii ( Graff, 1899) (in: Álvarez-Presas et al., 2015). Given the general morphological resemblance of T. graui with other Geoplanini taxa and the phylogenetic position as an ingroup of Geoplanini, we tentatively place the species and the genus within Geoplanini.

Transandiplana graui resembles ‘ Geoplana ’ caleta E. M. Froehlich, 1978 in the general aspect of the body and internal organs. However, important diagnostic traits (ventrolateral sensory depressions; main nervous system comprising multiple longitudinal cords; testes surrounded by a pigmented covering) and molecular data of G. caleta remain unknown. Thus, a systematic replacement would be speculative. Interestingly, both species occur in an adverse climatic region, namely, the Huasco river valley, in the arid Norte Chico zone (Atacama) of the Chilean Andes. Annual rainfall in the region is 42 mm /year, and the relative humidity ranges between 66–74% (see: Juliá et al., 2008).