Gieysztoria reta, Adami & Damborenea, 2024

Adami, Mariana Laura & Damborenea, Cristina, 2024, A new species of Gieysztoria Ruebush & Hayes, 1939 (Platyhelminthes, Rhabdocoela, Dalyelliidae) from Argentina with comments on geographical distribution of the genus in the Neotropical region, Zoosystema 46 (28), pp. 723-732 : 725-730

Gieysztoria reta n. sp.

( Figs 1-4 )

urn:lsid:zoobank.org:act:4822C132-297D-49A3-BC35-4D496B2481E2

TYPE LOCALITY. — Argentina, Buenos Aires Province, Reta.

TYPE MATERIAL. — Holotype. Argentina • Reta , Buenos Aires Province, natural wetland close to a dune field; 38°54’06”S, 60°21’4”W; 16 m a.s.l.; 2.II.2019; Adami M. L. leg.; 125 Μm plankton net, whole mount in polyvinyl-lactophenol; MLP-He, 8020.

Paratypes. Argentina • 8 whole mounts in polyvinyl-lactophenol; same data as for holotype; Adami M. L. leg.; MLP-He, 8021 .

OTHER MATERIAL. — Argentina • 2 specimens preserved in 100% ethanol; same data as for holotype; MLP-He, 8022 .

ETYMOLOGY. — Name refers to the geographic area where the species lives.

DIAGNOSIS. — A small, complex stylet, 50-75 Μm long, with a proximal fenestrate fibrous girdle and distally with four sets of spines: 1) the largest, robust, ventral fang-shaped spine slightly curved toward the center and proximately grooved; 2) a shorter ventral fang-shaped spine; 3) a dorsal group of seven to eight fine spines arranged as bristles; and 4) a group of 12 to 13 dorsal hollow, broad-based spines of different lengths, arranged in three rows, forming a fan shape. Copulatory bursa with two cavities separated by incomplete septum. Uterus with a conspicuous bend.

DESCRIPTION

Living adult specimens up to 500 Μm long and 260 Μm wide ( Fig. 2A ); mature fixed adult specimens approximately 336 Μm to 600 Μm (n =11) long, and 175 Μm to 234 Μm (n =11) wide ( Fig. 2B ). Body oval, rounded at the anterior end and tapering towards the posterior end. Overall colour light brown with two pigmented black eyes (ey). Pharynx doliformis (ph): 135 Μm to 150 Μm long and 112 Μm to 150 Μm wide (n= 10), with prepharyngeal cavity (pp) ( Fig. 2A, B ).

Body wall musculature with an outer layer of circular muscles fibers (cm) and diagonal muscles fibers (dm). Inner longitudinal muscle fibers not observed in the stacks. Cellular epidermis about 5 Μm, with cilia (c) of approximately 6 Μm ( Fig. 3A, B ).

Male reproductive system, testes (t) ventro-lateral, paired, 75 Μm long in caudal half of the body. Testes and copulatory organ connected by vasa deferentia (vd) ( Figs 3C ; 4A ). Copulatory organ on the middle axis in three individuals, and on the right side of the body in other specimens. Seminal vesicle (sv) oval, 57 Μm long and 36 Μm wide, with muscular wall (svm), posteriorly connected with prostatic vesicle (pv) ( Figs 2B, C ; 3C, D ). Prostatic vesicle 29 Μm long and 18 Μm wide, with at least four accessory glands (ag) arranged as elongated sacs reaching the stylet girdle ( Figs 2C ; 3D ). Prostatic vesicle anterior to ejaculatory duct (ed) which runs inside the sclerotic stylet ( Fig. 3F ).

Stylet (st) about 50-75 Μm (n= 11) long, and 40-69 Μm (n= 11) wide. Proximal portion: fibrous girdle 40-60 Μm (n= 4) wide and 17-21 Μm (n= 4) long, with dorsal discontinuity about 18 Μm wide, and circular fenestra (f) traversed by few fibers ( Fig. 2D ). Distal portion with four different sets of spines of variable shape and size. Two large, single ventral spines (s1 and s2). S1, on the ventral side of stylet, the largest, robust fang-shaped spine, 27-38 Μm (n=5) long, slightly curved toward male genital atrium. Proximally fibrous and grooved, and distally inserted in a cavity (ic) connected with male atrium ( Figs 2D ; 3E ; 4A, B ). S2 shorter than s1, also ventral, 20 Μm long, fang-shaped, similar to s1( Figs 2D ; 4B ). Opposite to s1 and s2, there is a dorsal group of seven or eight fine spines arranged like the bristles of a paintbrush (s3) ( Figs 2D ; 4B ). Also dorsal, but on the opposite side, group of 12 or 13 hollow spines with broad bases arranged in three rows, forming a fan shape (s4) with variable length: shorter at both ends, and longer in the center of the fan, 13 and 26 Μm long, respectively ( Figs 2D ; 3C, D ; 4B ). Distal part of stylet anterior to male genital atrium (ma), which enters the common genital atrium (cga) ( Figs 3 C-E; 4A).

Female reproductive system, ovary single (ov), at least 60 Μm long, posterior and dorsal to the intestine, located on the left side ( Fig. 3B, C ). Vitellaria (vi) extended dorsally in the center region of the body ( Figs 2A, B ; 3B ). Vitelloduct, female duct and seminal receptacle not observed. Single yellowish shelled egg (e) about 160 Μm long (n= 8) carried in uterus ( Figs 2A, B ; 3B, C ). Uterine bend (ub) caudal to uterus. Large, globular, conspicuous, 50 Μm long and 30 Μm wide, associated by means of muscle fibers with copulatory bursa (cb) ( Fig. 3B ), opening into common genital atrium (cga) ( Fig. 3D, E ). Common genital atrium surrounded by circular muscle fibers (cma) and to a lesser extent by longitudinal muscle fibers (lma) continuous with muscle fibers of male genital atrium ( Figs 3C, D ; 4A ).

Copulatory bursa 57 Μm long and 34 Μm wide (n= 2), dorsal to common genital atrium, opening into it through a ductus. Bursa with two cavities (b1 and b2) separated by an incomplete septum (s). Content observed inside both cavities ( Figs 2B ; 3C, D ). Proximal cavity (b1) with muscular wall with strong circular fibers (cmb1) ( Figs 3B ; 4A ). Single thick muscular fiber extending from b1 wall (sfb1) to anterior end ( Figs 3C ; 4A ). Distal cavity (b2) with strong outer circular muscle fibers (cmb2) and fine inner longitudinal muscle fibers (lmb2) connecting with ductus communis ( Figs 3C, D ; 4A ).

Common gonopore (gp) ventral, with four circular muscle fibers forming a sphincter (scm) ( Figs 3E, F ; 4A ).

REMARKS

Regarding stylet morphology, Gieysztoria reta n. sp. has spines of different shapes and sizes and a circular opening (fenestra) in the girdle, so it belongs to the Inaqueales Group, subgroup Fenestratae ( Luther 1955).

Considering stylet morphology, G. reta n. sp. resembles its Brazilian congeners G. hermes Reyes & Brusa, 2021 , G. therapaina Marcus, 1946 , G. complicata (Fuhrmann, 1914) , and G. intricata Marcus, 1946 ; and Argentinian congener G. matilde Brusa, Damborenea & Noreña, 2008 , G. namuncurai Damborenea, Brusa & Noreña, 2007 , and Peruvian congener G. kasasapa Damborenea, Brusa & Noreña, 2005 ( Table 1 ). The most similar stylet to that of G. reta n. sp. is that of G. hermes . However, the stylet is larger in Giesystoria reta n. sp. than in G. hermes (50-75 Μm and 34.2 Μm, respectively). Gieystoria reta n. sp. has four sets of spines (two single strong ventral spines, and two groups of dorsal spines), while G. hermes has three single ventral spines (the new species has one less ventral spine) ( Reyes et al. 2021: fig. 12C, blue). In G. reta n. sp., the two ventral spines seem not to be associated with the dorsal groups of spines, although Reyes et al. (2021) reported that in G. hermes , the two lateral ventral spines are associated with the dorsal groups of spines. Spine s 1 in the new species is larger than the largest fang-shaped spine in G. hermes ( Reyes et al. 2021: fig. 12C, red).

Like G. hermes , G. reta n. sp. has two groups of dorsal spines: a group of fine spines on one side, and a group of thicker hollow spines arranged in three rows on the other side. However, in G. reta n. sp., these three rows of spines are arranged forming a fan shape, while in G. hermes , this arrangement is not observed, and the number of rows of spines is not mentioned, though more than three rows are shown in the drawing of the holotype ( Reyes et al. 2021: fig. 12C). In G. hermes , the dorsal group of fine spines is arranged forming a comb-like structure in the stylet, whereas G. reta n. sp. has a single row of spines. Regarding the copulatory bursa, G. hermes has a single cavity with a thick wall, while G. reta n. sp. has two cavities with circular and longitudinal muscle fibers separated by an incomplete septum.

G. matilde and G. reta n. sp. have similar stylet lengths (54- 65 Μm and 50-75 Μm, respectively), but G. reta n. sp. has two ventral large spines, while G. matilde has a single large hollow blade-like spine. Like G. reta n. sp., G. matilde has two major groups of thin spines, one group with thicker spines than the other, though the original description does not specify their sizes. Gieystoria namuncurai and the new species share several stylet traits, but clear differences distinguish G. namumcurai from G. reta n. sp.: the lack of a circular opening (fenestra) in the girdle, a total stylet length of 100 Μm, and the presence of several rows of spines arranged in two groups, while in the new species there is only one group. Gieystoria kasasapa also shows differences from G. reta n. sp.: the stylet is larger in G. kasasapa than in G. reta n. sp. (75-85 Μm and 50-75 Μm, respectively). The Peruvian species has two groups of spines, both with less spines than the new species, and a single large hollow spine. Another species similar to G. reta n. sp. is G. therapaina , which has a stylet 33 Μm long, almost half the length of the stylet of the new species (50-75 Μm). Distally to the girdle, G. therapaina has four groups of spines ( Marcus 1946): three groups with several spines of different sizes and thicknesses, while the fourth group consists of a single large spine 20 Μm long, almost 2/3 of the total stylet size. Gieystoria reta n. sp. has two large ventral spines, and the largest spine is about half the length of the stylet.

Another species with similar stylet morphology to the new species is G. complicata , which has three groups of spines: one group with two strong parallel outward-curving spines (spines a), the second group with numerous spines in shape of a crown (spines b), and the third group with numerous spines arranged like a ‘brush’ (spines c), longer and broader than spines b ( Marcus 1946). However, in contrast to the new species, G. complicata does not have a fenestrated girdle, and the stylet is longer (100 Μm).

The stylet in G. reta n. sp. is also similar to the one in G. intricata , which has different sets of spines: single and clustered shorter spines, and a fenestrated girdle. However, it can be clearly distinguished from the new species because its stylet is longer (120 Μm) and has a single strong spine with cuticular hairs.

Figures

FIG. 1. — Study area:A, geographical location (● Reta locality);B, sampling site.

FIG. 2. — Gieysztoria reta n. sp.: A, C, D, specimens viewed under compound microscope: A, living specimen whole mount; B, fixed specimen viewed under a phase contrast light microscope; C, detail of seminal vesicle, prostate vesicle and additional glands; D, detail of stylet. Abbreviations: ag, accessory glands; cb, copulatory bursa; e, egg; ey, eye; f, fenestra; i, intestine; ph, pharynx; pp, prepharyngeal cavity; pv, prostate vesicle; st, stylet; sv, seminal vesicle; s1, largest spine; s2, large spine; s3, group of fine short spines; s4, group of shorter hollow spines; t, testes; ub, uterus bend; vi, vitellaria. Scale bars: A, B, 100 μm; C, 50 μm; D, 20 μm.

FIG. 3. — Gieysztoria reta n. sp. CLSM images of whole-mounts labeled with rhodamine-phalloidin showing the muscle arrangement: A, B, caudal body section from dorsal to ventral plane; C-F, caudal body section viewed from the right side toward the left side to sagittal plane. Images A, B and C-F correspond to two different specimens. Numbers 1-4 indicate circular fibers of gonopore sphincter; dashed lines outline the vitellaria area. Continuous arrow indicates strong muscle fiber of bursa cavity. Dashed arrow indicates muscle fiber that associates the uterus bend with the copulatory bursa. Abbreviations: b1, copulatory bursa cavity 1; b2, copulatory bursa cavity 2; c, cilia; cb, copulatory bursa; cga, common genital atrium; cm, circular muscle fibers of the body wall; cma, circular muscle fibers of common genital atrium; cmb1, circular muscles of the bursa cavity 1; cmb2, circular muscles of bursa cavity 2; dm, diagonal muscle fibers of the body wall; e, egg; ed, ejaculatory duct; ep, epidermis; gp, gonopore; i, intestine; ic, insertion cavity of s1 spine; ov, ovary; ph, pharynx; pv, prostate vesicle; s, septum; sv, seminal vesicle; svm, muscular wall of seminal vesicle; s4, group of dorsal hollow spines; t, testes; ub, uterus bend; vd, vasa deferentia; vi, vitellaria. Scale bars: A, B, 50 μm; C, D, E, F 40 μm.

FIG. 4. — Graphic reconstruction of the genital system of Gieysztoria reta n. sp.: A, genital reconstruction using confocal microscopy images; B, penis stylet from the holotype, blue (s1), pink (s2), yellow (s3) and green (s4). Abbreviations: ag, accessory glands; b1, copulatory bursa cavity 1; b2, copulatory bursa cavity 2; c, cilia; cga, common genital atrium; cma, circular muscle fibers of common genital atrium; cmb1, circular muscles of the bursa cavity 1; cmb2, circular muscles of bursa cavity 2; e, egg; ed, ejaculatory duct; f, fenestra; gp, gonopore; ma, male genital atrium; lma, longitudinal muscles fibers of common genital atrium; lmb2, longitudinal muscle of bursa cavity 2; ov, ovary; pv, prostate vesicle; sfb1, strong muscle fiber of bursa cavity 1; scm, muscle fibers of gonopore sphincter; sv, seminal vesicle; s1, largest spine; s2, large spine; s3, group of fine short spines; s4, group of hollow spines; t, testes; ub, uterus bend; vd, vasa deferentia; vi, vitellaria. Scale bars: A, 50 μm; B, 20 μm.