Choeradoplana claudioi Lago-Barcia & Carbayo, 2021

Lago-Barcia, Domingo, Silva, Marcos Santos & Carbayo, Fernando, 2021, Revision and description of six species of Choeradoplana (Platyhelminthes, Tricladida), with an emendation to the genus, ZooKeys 1016, pp. 1-48 : 1

Choeradoplana claudioi Lago-Barcia & Carbayo sp. nov. Figures 14 , 15

Material examined.

Both specimens were collected in Reserva Biológica Augusto Ruschi, Santa Teresa, State of Espírito Santo, Brazil (-19.8891, -40.5459) by F. Carbayo and co-workers, May 27-29th, 2008; Holotype MZUSP PL 1156 (field code, F2424), sexually mature: transverse sections of the cephalic region on 6 slides; horizontal sections of a portion behind the cephalic region on 4 slides; sagittal sections of the ovarian region on 4 slides; transverse sections of the pre-pharyngeal region on 4 slides; sagittal sections of the pharynx and copulatory apparatus on 11 slides. Paratype MZUSP PL 1157 (field code, F2510), sexually mature: sagittal sections of the pharynx and copulatory apparatus on 10 slides. The ovarian region was lost.

Distribution.

Only known from the type locality, Reserva Biológica Augusto Ruschi, Santa Teresa, State of Espírito Santo, Brazil.

Etymology.

The specific epithet honors Prof. Claudio Gilberto Froehlich for his contributions to the knowledge of the Neotropical land planarians.

Diagnosis.

Choeradoplana species with a golden yellow background color, with scattered sepia brown speckles on the whole dorsal surface, except for the anterior, greyish extremity. The extrabulbar portion of the prostatic vesicle is dish-like. The female genital atrium is compressed dorso-ventrally and partially positioned below the distal section of the male atrium.

Description.

Preserved specimens measure 24.0-36.5 mm in length and 2.5-3.0 mm in width (n = 2). The body is slender and subcylindrical. The cephalic region is differentiated from the remaining body by a ‘neck’, laterally dilated and rolled up so that the ventral surface provided with glandular cushions faces out; the posterior extremity is pointed. The creeping sole is as wide as 75% (F2424) of the body width at the pre-pharyngeal region. The mouth is positioned at a distance from the anterior extremity equal to 50% of the body length, and the gonopore is at 60%.

The dorsal coloration of the live specimens consists of a golden yellow (RAL 1004) background color, with scattered sepia brown (RAL 8014) speckles on the whole dorsal surface, except for the anterior, greyish extremity (Fig. 14A ). The ventral coloration is golden yellow.

Its eyes are devoid of halos and are formed by a one-pigmented cup of 60 μm in diameter. Eyes are absent in the very anterior extremity of the body equivalent to more or less 1% of the body length. The eyes are distributed marginally in a row of two or three eyes along the first 4.5 mm (or 12% of body length), then they are arranged in a single marginal row until the posterior end.

The sensory pits are 15 µm deep, and are distributed ventro-laterally in a uniserial row, only starting at approximately the equivalent to 1% of body length. The ventral epithelium of the ovarian region was lost and sensory pits are absent in the pre-pharyngeal region.

The cutaneous musculature of the pre-pharyngeal region consists of a subepithelial circular muscle followed by a diagonal layer with decussate fibers, and a strong longitudinal muscle organized in bundles (Fig. 14B ). This longitudinal muscle is 95 μm thick dorsally; it is ventrally divided into a 15 μm-thick muscle organized in bundles with 5-12 fibers each, and a 45 μm-thick muscle sunken into the parenchyma constituted of bundles with 6-17 fibers each. The thickness of the cutaneous muscle coat is 16% of the body height. (measurements from animal F2424 which has the best histological sections).

In the pre-pharyngeal region, a dorsal decussate muscle (25 μm thick), transverse supra-intestinal muscle (25 μm); and transverse subintestinal muscle (15 μm) (n = 1) (Fig. 14B ).

The cutaneous and parenchymal musculature is organized in the cephalic region as in Ch. iheringi . The muscle retractor of the head is delta-shaped in a cross-section along 1.8 mm (or 5% of body length, F2424) from behind, 1.3 mm (or 4%, F2424) of the anterior extremity of the body (Fig. 14C ), and its thickness equals 36% of the height of the cephalic region. The Muskelgeflecht is 190 μm thick (32% of body height). The subneural parenchymal muscle consists of scattered transverse fibers. The glandular cushions are composed of numerous rhabditogen cells (Fig. 14C ).

The mouth is located in the middle of the pharyngeal pouch (Fig. 14D ). The pharynx is cylindrical-to-bell-shaped, with its dorsal insertion approximately at the mouth level. An esophagus is absent. The pharyngeal pouch is lined with a non-ciliated, low epithelium underlain by a thin layer of circular muscle with interspersed longitudinal fibers (11-12 μm thick, n = 2). The outer pharyngeal epithelium is flat, ciliated and underlain by circular muscle (40-48 μm thick, n = 2) with interspersed longitudinal fibers ectally. The inner pharyngeal epithelium is flat, ciliated, and underlain by a thin circular muscle (48-50 μm, n = 2). The pharynx presents numerous xanthophil, erythrophil and cyanophil gland cells.

The testes are mature, dorsal, arranged in four paramedian rows between the supra-intestinal transverse parenchymal muscle and the intestinal diverticula (Fig. 14B ). They extend from the level of the ovaries (i.e., 7.7 mm behind the anterior extremity of the body, or 21% of body length, holotype) to the root of the pharynx (48%). Sperm ducts run immediately above the subintestinal parechymatic muscle layer. In their distal portion, they open into the respective branch of the prostatic vesicle (Fig. 15A-C ). The prostatic vesicle is divided into two differentiated halves (Fig. 15A-D ). The proximal half is extrabulbar and constituted by the two widened and rounded branches opening into a broadened, dish-shaped section located above the paired portion. The distal half is intrabulbar, dilated canal oriented dorso-posteriorly. The paired portion is lined with a cuboidal-to-columnar, ciliated epithelium, which is pierced by numerous gland cells producing fine erythrophil granules. The columnar epithelium of the dish-shaped portion is pierced by very numerous gland cells producing erythrophil gross granules (1-2 μm); and by two types of scarce gland cells producing fine, erythrophil and xanthophil granules, respectively (Fig. 15D ). The distal half is lined by a columnar, ciliated epithelium with a sinuous surface which is pierced by gland cells producing erythrophil granules along its whole length, and additionally a low number of gland cells producing xanthophil granules in its distal portion. The lining epithelium of the proximal half of the prostatic vesicle is coated by a 28-30 µm-thick (n = 2) circular muscle; the distal half is coated by a 1 µm-thick circular muscle, followed by a 22-25 µm-thick (n = 2) longitudinal muscle. The extrabulbar portion of the prostatic vesicle is coated by additional muscle fibers attaching it to the common muscle coat (Fig. 15A-C ). The opening of the prostatic vesicle into the antero-dorsal region of the male atrium is wide, without an ejaculatory duct or penis papilla (Fig. 15A-C ).

The male atrium is 5-6 × longer than the female atrium, and divided into a dorsal, proximal narrow third, slightly folded, and a distal two-thirds portion with some smaller folds. A main, very large, oblique fold on each side of the body extends behind the gonopore level and over the female atrium (Fig. 15E ). The male atrium is lined by a cuboidal, non-ciliated epithelium, and is underlain by a 30-60 µm-thick mixed layer of circular muscle with numerous interspersed longitudinal fibers (n = 2). The whole atrium receives two types of abundant gland cells producing erythrophil and cyanophil fine granules, respectively, and a third type of gland cells producing amorphous xanthophil secretion in the proximal third of the atrium.

The ovaries are mature, very elongated and placed above the ventral nerve plate at a distance from anterior tip of the body equal to 21% of body length (7.7 mm from anterior tip) (holotype). They present an anterior, ovoid section, 300 μm in length (F2424), and a posterior, 600 µm (F2424) long narrow section (Fig. 15E ). Ovovitelline ducts emerge from the lateral aspect of the ovoid section of the ovaries and run ventrally. Lateral to the posterior section of the female atrium, the ovovitelline ducts run medially and dorsally, then unite posteriorly to the female atrium (Fig. 15C ). The common glandular ovovitelline duct is 45-50 μm in length (n = 2) and runs ventro-anteriorly to communicate with the female genital canal. This canal runs slightly downwards and anteriorly, subsequently penetrates the common muscle coat to open into the female atrium. The female genital canal is lined by a cuboidal, ciliated epithelium.

The female atrium is dorso-ventrally compressed and wider towards the gonopore canal. It is placed below the posterior section of the male atrium (Fig. 15F ), and is lined with a cuboidal non-ciliated epithelium. This epithelium is pierced by gland cells producing fine xanthophil granules. The lining epithelium of the female atrium is underlain by a 37 μm-thick layer of mixed circular and longitudinal muscle fibers (n = 2).

The common muscle coat is a very dense layer composed by variously oriented muscle fibers. The length:height ratio of the copulatory apparatus enveloped by the common muscle coat ranges between 2.5-2.8:1.

Remarks.

Ch. claudioi Lago-Barcia & Carbayo, sp. nov. externally differs from most congeners in that the dorsum is composed of a light background color evenly covered with brown spots. However, this color pattern is so similar to Ch. abaiba , Ch. agua , Ch. banga , Ch. iheringi , and Ch. pucupucu that Ch. claudioi Lago-Barcia & Carbayo, sp. nov. cannot be confidently distinguished from them.

With respect to the internal morphology, Ch. claudioi Lago-Barcia & Carbayo, sp. nov. can be differentiated from most Choeradoplana species by the dish-shaped portion of the extrabulbar region of the prostatic vesicle. This attribute is only shared with Ch. onae Lago-Barcia & Carbayo, sp. nov., Ch. riutortae Lago-Barcia & Carbayo, sp. nov., and Ch. bocaina . However, the female genital atrium is compressed dorso-ventrally and partially positioned below the distal section of the male atrium, which readily distinguishes Ch. claudioi Lago-Barcia & Carbayo, sp. nov. from these three other species.

Figures

Figure 14. Choeradoplana claudioi Lago-Barcia & Carbayo, sp. nov., holotype A dorsal view of the creeping live animal B photomicrograph of a transverse section of the pre-pharyngeal region C photomicrograph of a transverse section of the cephalic region D photomicrograph of a sagittal section of the pharynx. Abbreviations: cm common muscle coat, co common glandular ovovitelline duct, dd decussate dorsal cutaneous muscles, dm diagonal decussate muscles, e eye, ej ejaculatory duct, ep esophagus, er erythrophil secretion, fa female atrium, fd female genital duct, g gonopore, i intestine, lc longitudinal cutaneous muscles, ma male genital atrium, mk Muskelgeflecht (Graff, 1899), mo mouth, o ovary, ov ovovitelline duct, ph pharyngeal pouch, pp penis papilla, pv prostatic vesicle, px pharynx, rg rhabditogen glands, r retractor muscle, sb subintestinal transverse muscles, sd sperm duct, sg shell glands, sk sunken longitudinal cutaneous muscles, sm spermatophore, sn subneural transverse muscles, sp supra-intestinal transverse muscles, t testis, vi vitellaria, vn ventral nerve plate.

Figure 15. Choeradoplana claudioi Lago-Barcia & Carbayo, sp. nov. A photomicrograph of a sagittal section of the copulatory apparatus of holotype B photomicrograph of a sagittal section of the copulatory apparatus of paratype F 2510 C diagrammatic representation of the copulatory apparatus of holotype D photomicrograph of a sagittal section of the prostatic vesicle of holotype E photomicrograph of a sagittal section of the ovarian region of holotype F photomicrograph of a sagittal section of the female atrium of holotype. Abbreviations: cm common muscle coat, co common glandular ovovitelline duct, dd decussate dorsal cutaneous muscles, dm diagonal decussate muscles, e eye, ej ejaculatory duct, ep esophagus, er erythrophil secretion, fa female atrium, fd female genital duct, g gonopore, i intestine, lc longitudinal cutaneous muscles, ma male genital atrium, mk Muskelgeflecht (Graff, 1899), mo mouth, o ovary, ov ovovitelline duct, ph pharyngeal pouch, pp penis papilla, pv prostatic vesicle, px pharynx, rg rhabditogen glands, r retractor muscle, sb subintestinal transverse muscles, sd sperm duct, sg shell glands, sk sunken longitudinal cutaneous muscles, sm spermatophore, sn subneural transverse muscles, sp supra-intestinal transverse muscles, t testis, vi vitellaria, vn ventral nerve plate.