Luteostriata subtilis Boll, Amaral & Leal-Zanchet, 2019

Boll, Piter Kehoma, Amaral, Silvana Vargas Do & Leal-Zanchet, Ana Maria, 2019, Two new land planarian species (Platyhelminthes: Tricladida: Geoplanidae) from protected areas in southern Brazil, Zootaxa 4664 (4), pp. 535-550 : 543-548

Luteostriata subtilis Boll, Amaral & Leal-Zanchet , sp. nov.

urn:lsid:zoobank.org:act:F03CBF98-3ADB-4666-ACDB-07BA27EED07F

Notogynaphallia sp. 1in Baptista et al. 2006

Notogynaphallia sp. 1 in Fick et al. 2006

Notogynaphallia sp. 1 in Leal-Zanchet & Baptista 2009

Etymology: The specific name is a Latin adjective and refers to the three subtle and discontinuous stripes present on the dorsum, usually not visible to the naked eye, as well as to the subtle internal differences between this species and Luteostriata ceciliae ( Froehlich & Leal-Zanchet, 2003) .

Type-material. Holotype: MZUSP PL.2159: leg. I. A. Fick, 11 December 2000, National Park of Aparados da Serra (29°05’ to 29°15’S, 50°00’ to 50°15’ W), Cambará do Sul, Rio Grande do Sul, Brazil—anterior tip: transverse sections on 23 slides; anterior region at the level of the ovaries: transverse sections on 25 slides; anterior region at the level of the testes: sagittal sections on 23 slides; pre-pharyngeal region: transverse sections on 5 slides; pharynx: sagittal sections on 12 slides; copulatory apparatus: sagittal sections on 15 slides.

Paratypes: Two specimens collected in the same locality of the holotype. MZU PL. 273: leg. I. A. Fick, 22 December 1999 —anterior tip: transverse sections on 15 slides; anterior region at the level of the ovaries: sagittal sections on 9 slides; pre-pharyngeal region: transversal sections on 9 slides; pharynx: sagittal sections on 14 slides; copulatory apparatus: sagittal sections on 18 slides; MZU PL. 274: leg. L. M. Campos, 21 August 2004 —whole animal preserved in 70% ethanol .

Diagnosis: species of Luteostriata with light-yellow dorsum and two well-marked longitudinal black stripes; pharynx bell-shaped; large fold in the male atrium located ventrally to the opening of the ejaculatory duct.

Type-locality: Cambará do Sul, state of Rio Grande do Sul, Brazil

Distribution: Known only from the type-locality.

Description. External features: Body elongate with parallel margins, anterior tip rounded and posterior tip pointed. The maximal length when creeping reaches 62 mm; 47 mm after fixation. Mouth located at the middle third of the body; gonopore at the posterior third ( Table 3 ).

Alive, dorsum light yellow with two well-marked black lateral stripes; cephalic region has an orange shade that gradually fades posteriorly into the yellow color of the dorsum. Under the stereomicroscope, three additional inconspicuous stripes can be seen, one median and two paramarginal stripes. These three stripes are very thin and discontinuous, usually not visible to the naked eye ( Fig. 13 ). Stripes begin behind the cephalic region and end abruptly before the posterior tip in preserved specimens ( Fig. 13 ). Lateral stripes correspond to about 1/12 of the body width each. Ventral surface pale yellow.After fixation, the pigmentation becomes paler, almost white after several months, with the lateral stripes not very well marked.

Eyes monolobate (with pigment cups of about 20–30 µm). They surround the anterior tip and are uniserial in the cephalic region (about 7% of the body length) ( Fig. 14 ). After that, eyes become pluriserial and spread dorsally up to the level of the lateral stripes. Towards posterior tip, they become less numerous and uniserial.

Sensory organs, epidermis and body musculature. Sensory pits as simple invaginations (about 20–30µm deep) that contour the anterior tip and occur ventromarginally in an irregular, single row until slightly after the cephalic region (about 12% of the body length).

Creeping sole occupying about 80% of the body width ( Table 1 ). A glandular margin is absent ( Fig. 17 ).

Secretory cells in the pre-pharyngeal region: abundant erythrophil glands with coarse granules, rhabditogen glands with xanthophil secretion (more abundant dorsally) and a few cyanophil glands with amorphous secretion (more abundant ventrally). Glands discharging through the cephalic region of the body are similar to those of the pre-pharyngeal region, but erythrophil glands with coarse granules greatly increase in number toward the anterior tip, especially ventrally.

Cutaneous musculature in the pre-pharyngeal region similar to other species of Luteostriata , having a longitudinal layer with very thick bundles, thicker ventrally than dorsally ( Figs. 17–19 ) between four and eight times that of epidermis. Musculature with about the same thickness across the dorsum, becoming lower at the body margins; ventral and dorsal musculatures with similar thickness at the sagittal plane. Mc:h 17–19% ( Table 4 ). The longitudinal muscle fibers of the ventral sub-epidermal musculature concentrate progressively in the median region at about the anterior 1/9 of the body, forming a rounded to lens-shaped cephalic retractor muscle ( Figs. 15, 16 ). Next to the anterior tip, bundles of 2–8 fibers detach from the retractor muscle and run forward towards the body margins and dorsal surface. The visualization of the musculature is hampered by the large number of erythrophil cells. Mesenchymatic musculature well developed with a similar arrangement to that described for other species of the genus ( Fig 17 ).

Pharynx. Pharynx bell-shaped, about 5% of the body length, occupying the first three quarters of the pharyngeal pouch ( Fig 20 ). Dorsal insertion approximately on the same transversal level as the mouth, at the beginning of the median third of the pharyngeal pouch; margins highly folded ( Fig. 20 ). Esophagus absent.

Reproductive system. The testes are arranged in one irregular row on either side of the body, beneath the dorsal transverse mesenchymal muscles and interstitially to the intestinal branches ( Figs. 17, 18 ). They begin in the anterior sixth of the body and extend to near the root of the pharynx ( Table 1 ). Sperm ducts, sometimes divided into ductules, dorsomedial to ovovitelline ducts, beneath fibers of the subintestinal transverse mesenchymal musculature in pre-pharyngeal region ( Fig. 19 ). They form spermiducal vesicles posteriorly to the pharynx and divide distally into five to seven branches which open separately in the second anteriormost quarter of the prostatic vesicle ( Fig. 22 ). The prostatic vesicle is very long, extrabulbar, and laterally sinuous; its anterior end is forked and continues laterally to the pharyngeal pouch ( Fig. 22 ). The distal part of the prostatic vesicle is directed ventrally among fibers of the common muscle coat, and then curves upward and slightly backward, entering the penis bulb ( Figs. 22 , 24 ). Inside the penis bulb, it continues as an ejaculatory duct, which proceeds dorsally in a sinuous path. The ejaculatory duct opens into the dorso-anterior wall of the male atrium ( Figs. 22–24 ). Male atrium folded and very long, having a main fold located ventrally to the opening of the ejaculatory duct ( Figs. 22–24 ). Few cyanophil and erythrophil glands discharge their fine granular secretion into the ejaculatory duct. Other aspects of the epithelium, musculature and secretions of the male copulatory apparatus are similar to those of other species of Luteostriata .

Vitellaria, situated between intestinal branches, well-developed in all observed specimens ( Figs. 17–19, 21 ). Ovaries oval-shaped, about 1.5 times longer than wide, measuring about 0.2 mm in their antero-posterior axis ( Fig. 21 ). They are located dorsally to the ventral nerve plate, slightly anteriorly to the anteriormost testes, approximately in the anterior sixth of the body ( Table 3 ). Ovovitelline ducts emerge dorsally from the median third of the ovaries and run posteriorly immediately above the nerve plate ( Figs. 17, 19, 21 ). Close to the gonopore, the ovovitelline ducts ascend posteromedially and unite dorsally at the level of the posterior third of the female atrium, forming a long common glandular ovovitelline duct ( Figs. 22 , 23 ). The common glandular ovovitelline duct opens into the female canal, dorsally oriented, that connects to the posterior end of the female atrium ( Figs. 22 , 23 ). The female atrium is ample, with folded walls, and has one third to one fourth of the male atrium length ( Table 3 , Figs. 22 , 23 ).

Ovovitelline ducts lined with at least partially cyanophil epithelium ( Figs. 17, 19 ). Other characteristics of the epithelium, musculature and secretions of the female copulatory apparatus are similar to those of other species in the genus.

Gonoduct slightly inclined backward. Male and female atria are separated at the level of the gonopore by oblique dorsal and ventral, laterally displaced folds ( Figs. 22 , 24 ). Gonoduct lined with tall columnar epithelium, ciliated, receiving the opening of abundant glands with fine erythrophil secretion, as well as few glands with amor- phous cyanophil secretion. Muscularis of the gonoduct consisting of a layer of circular fibers followed by a layer of longitudinal fibers.

Comparative discussion. The external morphology, marked by monolobated eyes and yellow dorsum with dark longitudinal stripes, and internal characteristics, such as the general morphology of copulatory apparatus, as well as the presence of a cephalic retractor muscle associated with glands, strongly support the inclusion of the new species into the genus Luteostriata .

Externally, the color pattern of L. subtilis is similar to that of L. graffi ( Leal-Zanchet & Froehlich, 2006) , although the median and paramarginal stripes are easily visible in the latter ( Leal-Zanchet & Froehlich 2006). In L. ceciliae the median stripe is well marked and continuous, while the lateral and paramarginal ones are discontinuous but highly conspicuous ( Froehlich & Leal-Zanchet 2003). Luteostriata ernesti ( Leal-Zanchet & Froehlich, 2006) has two well-marked paramarginal stripes and three narrower internal lines, sometimes discontinuous, while both L. caissara (Froehlich, 1955) and L. pseudoceciliae ( Lemos & Leal-Zanchet, 2008) have five equally marked and continuous stripes ( Leal-Zanchet & Froehlich 2006; Lemos & Leal-Zanchet 2008). In L. fita ( Froehlich, 1959) the median stripe is marked only in the first half of the body ( Froehlich 1959). The remaining species have a different number of stripes: L. abundans (Graff, 1899) has seven, L. muelleri (Diesing, 1861) , one or three, and L. arturi ( Lemos & Leal-Zanchet, 2008) , two lateral bands with dark inner and outer margins ( Leal-Zanchet & Froehlich 2006; Lemos & Leal-Zanchet 2008; Carbayo 2010).

The body shape, as well as several internal characters, such as the pharynx, the proximally-forked prostatic vesicle, the branched sperm ducts, and the long and folded male atrium, are similar to those of L. ceciliae . The main differences are related to the opening of the ejaculatory duct, which is displaced ventrally in L. ceciliae and dorsally in L. subtilis , the position of the main male atrium fold, which is dorsal to the ejaculatory duct in L. ceciliae and ventral in L. subtilis , and the distal portion of the prostatic vesicle, which is directed dorsally against the muscle coat in L. ceciliae and ventrally in L. subtilis ( Froehlich & Leal-Zanchet 2003) .

The combination of those characters of both external and internal morphology differentiates L. subtilis from L. ceciliae and from the other species of the genus.

Figures

FIGURE 22. Luteostriata subtilis sp. nov., composite reconstruction of the copulatory apparatus of the holotype from sagittal sections. Arrows indicate oblique folds at the level of the gonopore.

FIGURES 13–14. Luteostriata subtilis sp. nov. in dorsal view: (13) color pattern of holotype; (14) eye pattern at the anterior end of paratype MZU PL. 273.

FIGURES 15–21. Luteostriata subtilis sp. nov., holotype in transverse (15–19) and sagittal sections with the anterior to the left (20, 21): (15, 16) cephalic region; (17) pre-pharyngeal region; (18) detail of the dorsal surface in the pre-pharyngeal region; (19) detail of the ventral surface in the pre-pharyngeal region; (20) pharynx; (21) ovary.

FIGURES 23–24. Luteostriata subtilis sp. nov.: (23) copulatory apparatus of the holotype in sagittal section; (24) copulatory apparatus of the paratype MZU PL. 273 in sagittal section.