Marcusia alba, Cuadrado & Rodríguez & Moro & Grande & Noreña, 2021

Cuadrado, Daniel, Rodríguez, Jorge, Moro, Leopoldo, Grande, Cristina & Noreña, Carolina, 2021, Polycladida (Platyhelminthes, Rhabditophora) from Cape Verde and related regions of Macaronesia, European Journal of Taxonomy 736, pp. 1-43 : 14-16

Marcusia alba sp. nov.

urn:lsid:zoobank.org:act:DE4AF1C8-D784-4AB7-B536-A1E88524115B

Figs 1C , 2

Etymology

The name of the new species, Marcusia alba , comes from the Latin ‘ albus ’ (white), and refers to the ivory white coloration this species shows.

Material examined (3 specs)

Holotype CAPE VERDE • São Vicente Island , Mindelo ; 16°53′46.54″ N, 24°59′32.93″ W ( Fig. 1C V1 ); 6 May 2017; Leopoldo Moro leg.; MNCN 4.01/2620 to 2683 (64 slides). One sagittally sectioned specimen stained with AZAN.

Additional material

CAPE VERDE • 2 specs; São Vicente Island , Baía das Gatas ; 16°54′09.33″ N, 24°54′25.25″ W ( Fig. 1C V 2 ); 6 May 2017; Leopoldo Moro leg.; RCCN .

Description

BODY. Shape oval. Length 2.6 cm. Smooth dorsal surface. Background pigmentation ivory white, darker along the middle dorsal region of the body. Amber dots and thin brushstroke-like lines garnish the dorsal surface. A thin, dark stripe, sometimes interrupted, extends along the central dorsal line ( Fig. 2A ). Two delicate marginal folds, separate and pointed, could be interpreted as pseudotentacles. Tentacular eyes scarce and widely dispersed over the tentacles. Cerebral eyes anterior drop-shaped and crossed by the central midline. Marginal eyes only at the anterior part ( Fig. 2B ). Ruffled pharynx, in the middle of the body with a central oral pore. Ventral sucker at the posterior part of the body. Male and female genital pore lead in a common genital atrium ( Fig. 2 D–E) that opens in the posterior body region after the pharynx ( Fig. 2C ).

MALE REPRODUCTIVE SYSTEM. Male copulatory organ backwards oriented, with a muscular penis papilla, very muscular seminal vesicle ( Fig. 2C, E ) and without a prostatic vesicle, instead a simple glandular epithelium leads into the penis papilla ( Fig. 2 D–E). Seminal vesicle rounded, frontal oriented and with thick muscular walls, opening into the ejaculatory duct. Short ejaculatory duct opens into the penis papillae. The male atrium is small and thin, connected to the common atrium.

FEMALE REPRODUCTIVE SYSTEM ( Fig. 2C, E ). The vagina runs from the common genital atrium and continues dorsally into a narrowed duct that widens into a chamber, the cement pouch. The vagina continues dorsally, then curves posteriorly and ventrally and ends with the entry of the oviducts.

Remarks

Marcusia alba sp. nov. belongs to the genus Marcusia due to the presence of cerebral, frontal and marginal eyes, male copulatory organ enclosed in a muscular bulb, the absence of prostatic vesicle and the common male and female atrium genital, as well as the common gonopore.

The genus Marcusia contained only one species, Marcusia ernesti Hyman, 1953 , known from the coast of the Gulf of California ( Hyman 1953). Marcusia ernesti and M. alba sp. nov. can be easily distinguished by their coloration patterns. Marcusia ernesti is black or grey with darker splotches and dotted with white spots, only visible in preserved individuals after Hyman (1953), M. alba sp. nov. is ivory white with brownish dots and stripes. The penis papilla is spherical in M. alba and elongated in M. ernesti , with the male atrium being tube-like and longer in the Californian species.

Another difference lies in the eyes’ presence and distribution. Marcusia ernesti presents marginal, frontal and cerebral eyes as well as two characteristic eye clusters with diagnostic value ( Hyman 1953). Marcusia alba sp. nov., on the other hand, has cerebral, marginal and tentacular eyes, but not frontal eyes or eye clusters.

The differences listed are enough to consider M. ernesti and M. alba sp. nov. as two different species of the same genus. Furthermore, the molecular analyses show the genus Marcusia (represented in this case by Marcusia alba sp. nov.) as a genus closely related to Pericelis Laidlaw, 1902 within the family Anonymidae Lang, 1884 , but as a clearly independent genus.

Figures

Fig. 1. Location of sampling points, distribution of the Macaronesian archipelagos and limitation of regions: Lauri-Macaronesia or Lusitanian Macaronesia (white); Central Macaronesia or Eumacaronesia (bordeaux) and Great Macaronesia (green). Abbreviations:A1 = San Miguel Island, Azores; C1 = Pasito Blanco, Gran Canaria, Canary Islands; C2 = Tenerife, Canary Islands; C3 = Garachico, Tenerife, Canary Islands; C4 = Amarilla Golf, Tenerife, Canary Islands; CV1 = Astillero Mindelo, S„o Vicente Island, Cape Verde; CV2 = Bahía das Gatas, S„o Vicente Island, Cape Verde; CV3 = Calheta Funda, Sal Island, Cape Verde; M1 = Ifni, South Morocco; M2 = Agadir, South Morocco.

Fig. 2. Marcusia alba sp. nov. (MNCN 4.01/2620 to 2683).A. Whole live animal, dorsal view.B. Anterior region with cerebral eyes cluster and pseudotentacles (white arrows). C. Histological section of the male copulatory organ stained with AZAN. D. Histological section of the female copulatory organ stained with AZAN. E. Sagittal reconstruction of the reproduction system. Abbreviations: see Material and methods.