Cratera taxiarcha ( Marcus, 1951 )

Lago-Barcia, Domingo & Carbayo, Fernando, 2018, Taxonomic revision of four species of the Neotropical land planarian genera Cratera and Geoplana (Platyhelminthes, Tricladida) with a description of two new species and an emendation of Cratera, Zootaxa 4500 (4), pp. 517-542 : 528-533

Cratera taxiarcha ( Marcus, 1951)

Synonymy

Geoplana taxiarcha Marcus, 1951

Material examined. Holotype ( MZUSP PL 2135 ). Horto Florestal, State of São Paulo, Brazil, (-23.46, -46.63) (coordinates provided by the authors of the present study). Unknown coll. between August and November, 1950, sagittal sections of copulatory apparatus on 2 slides (S247-S248). F3518 ( MZUSP PL 2136 ): Parque Estadual da Serra da Cantareira , São Paulo, State of São Paulo. Brazil, (-23.43, -46.63). F. Carbayo et al. coll., 26 March 2009, transverse sections of cephalic region on 28 slides; transverse sections of ovaries region on 25 slides; horizontal sections of region behind ovaries on 12 slides; transverse sections of pre-pharyngeal region on 26 slides; sagittal sections of pharynx on 28 slides; sagittal sections of copulatory apparatus on 23 slides.

Distribution. Horto Florestal and Parque Estadual da Cantareira, São Paulo, State of São Paulo, Brazil.

Diagnosis. Species of Cratera with 70 mm in maximum length. Dorsal coloration comprises a white median line, two paramedian black lines and two marginal yellow lines. Dorsal eyes initiating in cephalic region. Proximal portion of prostatic vesicle bifurcated, extrabulbar, detached from penis bulb. Penis bulb well developed, extending 0.5 millimeters anteriorly to penis papilla. Diameter of muscular cylinder surrounding ejaculatory duct strong, two times the diameter of this duct. Dorsal portion of male atrium pierced by numerous cyanophil glands. Female:male atrial length ratio, 0.5-1. Common glandular ovovitelline duct absent.

Description. External aspect. Body wide, slightly lanceolate, with anterior tip rounded and posterior tip pointed. Size of preserved animal (F3518) is 52 mm long and 6 mm wide. Dorsum slightly convex, ventral side flat.

Dorsal coloration consists of a median white line with scattered black spots, flanked by two paramedian black lines with irregular margins, comprising a high concentration of black spots. Laterally to paramedian black lines, two yellow marginal lines, having black spots scattered along its length, especially in the anterior third of the body, where the spots create a thin marginal black line ( Fig. 7A ). Ventral surface whitish.

Sensory pits are 30 µm deep. They are arranged in a single row contouring the anterior end and extending backwards to at least a length equal to 27% of body length. Relative mouth:body length, 71%; relative gonopore:body length, 87% (specimen F3518).

Internal morphology. Creeping sole occupies entire body width. Glandular margin relatively less developed, comprising xanthophil glands. Cutaneous musculature with the usual three layers present in Geoplaninae : subepithelial circular (5 µm thick), diagonal with decussate bundles (10 µm thick) and an innermost longitudinal layer (50 µm thick), the latter more conspicuous and arranged in bundles. Cutaneous musculature as thick as 7% of body height. Parenchymal musculature composed of three muscular layers: a dorsal layer with diagonal decussate fibers (15 µm thick in paratype F3518), a supraintestinal transverse layer (40 µm thick), and a subintestinal transverse layer (50 µm thick). Ventral nerve plate present.

Relative position mouth:pharyngeal pouch length, of 69%. Pharynx cylindrical ( Fig. 7B ), with dorsal insertion slightly posteriorly to the ventral one; esophagus present, with 27% of pharynx length. The outer epithelium of the pharynx is underlain by a thin layer (5 µm thick) of circular muscle, followed by a thin layer of longitudinal fibers (8 µm thick), this layer only present in the proximal section of the pharynx. Inner pharyngeal epithelium underlain by a thick circular muscle (40-120 µm thick), followed by a longitudinal muscle (15 µm thick).

Testes dorsally located between supraintestinal parenchymal muscle layer and intestine. They extend from the level of the ovaries (equal to 25% of the body length in specimen F3518) to closely the root of the pharynx (equal to 61% of the body length in specimen F3518). Sperm ducts run laterally and, anteriorly to the penis bulb, subsequently bend medially to open into the short branches of the proximal portion of the prostatic vesicle. The proximal two thirds of the prostatic vesicle, extrabulbar, is C-shaped in lateral view. The prostatic vesicle penetrates dorso-anterior aspect of penis bulb, subsequently running ventro-posteriorly to communicate with the ejaculatory duct within the penis papilla. The entire prostatic vesicle is lined by a cuboidal-to-columnar ciliated epithelium and is pierced by glands producing fine erythrophil granules. This epithelium is surrounded by a 20 µm thick circular muscle layer. Penis bulb well developed, extending 0.5 mm anterior to the penis papilla. Ejaculatory duct crosses the center of the penis papilla. This duct is 50 µm in diameter proximally, and 25 µm distally. The ejaculatory duct opens to male atrium through a widening 150 µm in diameter ( Fig. 7 C-D). The ejaculatory duct is lined by a cuboidal ciliated epithelium and is underlain by a circular muscle 10 µm thick. The penis papilla is conical, horizontally located, with dorsal and ventral insertions at the same transverse plane and approximately as long as the male atrium ( Fig. 8A and 9A, B ). The papilla is lined with a cuboidal epithelium, which is underlain by a 10 µm thick circular muscle, followed by a 5 µm thick longitudinal muscle. The male atrium is broad, not folded, and mostly occupied by the penis papilla. Dorsal portion of male atrium pierced by abundant cyanophil glands. The muscularis of the male atrium consists of a thin 10 µm thick circular muscle, followed by a thinner longitudinal muscle.

Ovaries ovoid, 300 µm in diameter, placed above the ventral nerve plate, and at a distance from anterior end equal to 25% of body length. Ovovitelline ducts emerge from dorso-lateral aspect of ovaries. Laterally to the female atrium, ovovitelline ducts ascend to communicate with each other above dorsal section of female atrium. Distal ascending section of ovovitelline ducts receive shell glands. No common glandular ovovitelline duct present. Female genital duct as an anteriorly oriented projection from postero-dorsal region of female atrium.

The female atrium is a cavity partially narrowed by a lateral fold. It is continued with the male atrium; female:male atrial length, 2:3.5. The female atrium is lined by an epithelium with stratified appearance and internal gaps, and is underlain by a 5 µm thick circular muscle, followed by a 5 µm thick longitudinal muscle.

Common muscle coat composed of scattered fibers, and is more apparent around female atrium.

Remarks. The type material consisted of five adult specimens and an immature one, collected in Horto Florestal, São Paulo, State of São Paulo and Mogi das Cruzes, State of São Paulo, in 1950. Marcus described a very variable chromatic pattern of the specimens: “The species color varies. The venter may be white or greyish-yellow. The ground color is white, though the dorsum may be completely black. Other individuals present a median white line and two clear yellow lateral lines (Fig. 310). These lines may be different or allusive; in the last instance, the median line appears only in the anterior region (Fig. 261). In the clearer worms (Fig. 259), the white and yellow lines turn into wide bands, restricting the black pigment to two paramedian bands, the body margins and spots on the yellow zones, being more numerous in the posterior region” ( Marcus, 1951, p. 101; original in Portuguese).

It is striking that Marcus considered animals with so different color patterns as conspecific. Based on our experience, such great variation of the chromatic pattern of the body most likely reflects non-conspecificity.

Later, Marcus seems to have noticed that he misidentified the species and that it was a junior synonym of Geoplana ferussaci Graff, 1899 (E. M. Froehlich, pers. comm.). However, he did not address this issue. Jokingly, he simply recorded his suposedly misidentification by glueing a newspaper clipping on an illustration of hatchlings of ‘taxiarcha’ and ‘ferussaci’ types, hatched in the laboratory in 1951 as a metaphor: the clipping briefly reports the wreck of a Greek ship called ‘Taxiarchis’ on the English coast ( Fig. 10 ) (E. M. Froehlich, pers. comm.).

We believe that Marcus dealt with representatives of G. taxiarcha and at least a second species, possibly G. ferussaci . The taxonomic problem here presented is to pair one of the chromatic patterns of the body described by Marcus with the internal organs described and illustrated by him. Marcus’s notebooks, retained by Eudóxia, did not help solve this enigma. There are four entries for G. taxiarcha for the year 1950 in a notebook. None of these entries refers to a specimen with a color pattern like that of Fig. 310.

Even more striking is that only one (on slides S247-S248) of the three copulatory apparatuses he sectioned has survived in Eudóxia’s collection. In this collection, there are no additional slides of this species collected in 1950. Also there are no specimens from the Horto Florestal or Mogi collected in 1950 in the wet collection of E. M. Froehlich.

We believe that Marcus’ Fig. 310 of the dorsal color pattern is from a specimen conspecific with the one -if not the same specimen- whose copulatory apparatus is on the histological slides S247-S248. Our belief is based on that (a) our specimen F3518 presents a dorsal color pattern and a copulatory apparatus fully comparable with Marcus’s Fig. 310 and with the copulatory apparatus on slides S247-S248, respectively; and (b) specimen F3518 was collected in the Horto Florestal, as the holotype was.

Each of the slides S247-S248 bears a label handwritten by Marcus reading “ G. taxiarcha ”. The same handwriting is on the labels of slides S246 and S257, including transverse sections of the pre-pharyngeal region and sagittal sections of the pharynx, respectively. However, none of the two pharynges drawn by Marcus in his paper was based on the slide S257. We are unable to confirm that these sections are part of the specimen sectioned on slides S247-S248. Hence, herein we suggest as holotype of C. taxiarcha only the body parts mentioned in Material examined.

The holotype and specimen F3518 exhibit the ejaculatory duct with distal widening.

Finally, Froehlich (1956) also studied a specimen collected in 1951 in Ubatuba, 150 Km East from the type locality. Froehlich described the body color pattern of this specimen as slightly different from that of the type material, but he stated that eyes distribution, relative position of mouth and gonopore, and anatomy of pharynx and copulatory apparatus conform to the original description. We did not find histological sections of any specimen collected in Ubatuba in Eudóxia's collection and hence, are unable to check identity of this specimen.

Figures

FIGURE 7. Cratera taxiarcha (Marcus, 1951). (A): dorsal view of specimen F3518. (B): photomicrograph of a sagittal section of the pharynx of specimen F3518. (C): photomicrograph of a sagittal section of the tip of papilla of the holotype, showing the distal cavity of the ejaculatory duct. (D): photomicrograph of a sagittal section of the tip of papilla of specimen F3518, showing the distal cavity of the ejaculatory duct.

FIGURE 8. Cratera taxiarcha (Marcus, 1951). Photomicrograph of a sagittal section of the copulatory apparatus of the holotype.

FIGURE 9. Cratera taxiarcha (Marcus, 1951). (A) diagrammatic representation of the copulatory apparatus of specimen F3518 from sagittal sections. (B): photomicrograph of a sagittal section of the copulatory apparatus of specimen F3518.

FIGURE 10. Hand drawings, probably by E. M. Froehlich, of two hatchlings, one with the body color pattern of C. taxiarcha (left), another with the pattern of G. ferussaci (right) in Marcus’s opinion. Note the newspaper clipping glued on bottom left corner, reporting the wreck of a ship called ‘Taxiarchis’. See text for details.