Hoploplana elisabelloi, Noreña, Carolina, Rodríguez, Jorge, Pérez, Jacinto & Almon, Bruno, 2015

Noreña, Carolina, Rodríguez, Jorge, Pérez, Jacinto & Almon, Bruno, 2015, New Acotylea (Polycladida, Platyhelminthes) from the east coast of the North Atlantic Ocean with special mention of the Iberian littoral, Zootaxa 4039 (1), pp. 157-172 : 158-160

Hoploplana Laidlaw, 1902

Hoploplana elisabelloi n. sp. Figure 2

Material examined. Three specimens were captured in Ría de Arousa, Galicia, Spain. One from the Isle of Rúa (08/10/2011), 42°32.985'N; 8°56.470'W, another on an algae stalk from “O Camouco” (25/08/2013), 42º33.321'N; 08º58.019'W, and the last one between mussels from a dock of the Yacht Club of Ribeira (21/12/2012), 42° 33.776'N / 08° 59.339'W.

Holotype. One sagittally sectioned specimen stained with Azan and deposited in the Invertebrate Collections of the MNCN; Cat. No. MNCN 4.01/ 1096 to 1117 (22 slides).

Type locality. Isle of Rúa, Ría de Arousa, Galicia, Spain. Depth: 12 metres usually over bryozoans (specifically Membranipora membranacea ).

Etymology. The specific name is dedicated to the late Galician biologist Elisa Bello; an outstanding person and best friend of the first author, who left us prematurely.

Description. Oval-rounded worms, holotype 15 mm long and 12 mm wide. The another two specimens from the same size. Colouration, translucent in appearance, is beige with reddish brown spots and covered with a delicate, bright white network pattern ( Fig. 2 A, B, C); body margin transparent with white rods (rhabdites). Ventral surface pale yellow. With well developed conical nuchal tentacles. Tentacular eyes at the base and inside the tentacles ( Fig. 2 D), with a few inconspicuous cerebral eyes located slightly ventral and anterior to the brain. Brain just below the tentacles, well developed and almost ventrally positioned ( Fig. 2 E). Marginal and frontal eyes absent. Oral pore ventral, in the middle of the body; ruffled pharynx in the second body third and provided with deep folds. Male and female genital pores clearly separate but close to each other, opening at the anterior end of the last third of the body. Ovaries well developed, arranged between the intestinal branches. Testes not observed.

Reproductive system ( Fig. 2 F, G, J). Reproductive organs located in the last body third. Male copulatory organ consists of a true muscular prostatic vesicle lined with a well-developed glandular epithelium and stylet. Extravesicular glands and a true seminal vesicle are lacking. Vasa deferentia swollen in spermiducal bulbs that enter fronto-laterally into a paired muscular expansion that can be considered external seminal vesicles. Each seminal expansion leads to a long, winding ejaculatory duct. The two ejaculatory, or sperm, ducts join and enter the prostatic vesicle through a common duct. Prostatic vesicle small, lined with high glandular epithelium, and surrounded by a well-developed muscle layer. The stylet is short and curved (6Μm in the holotype), housed in a large male atrium (18.5Μm long) lined with a ciliated glandular epithelium. Just posterior to the male pore, the atrium forms a ventro-caudal diverticulum (4.5Μm long).

The small female system is composed of a wide atrium and an ascending female canal that shows a close backwards-directed curve before it joins the shell chamber. Abundant shell and yolk glands were observed in the studied exemplars. The female canal ends with the opening of the oviducts.

Biology. Hoploplana elisabelloi was found mainly on bryozoans (specifically Membranipora membranacea ) at depths between 1 and 12 metres. The network of trabeculae on the dorsal surface of H. elisabelloi allows it to mimic with the environment. Of the known Hoploplana species, some species (e.g. H. schizoporellae Kato, 1944 ; H. villosa ( Lang, 1884) and H.divae (Bahia et al. 2012)), similar to H. elisabelloi sp.n., are known to associate with the Bryozoa. Nonetheless, there is not enough evidence to affirm if bryozoans are shelters or prey for H. elisabelloi sp.n.

One exemplar was photographed during ovo-deposition during which egg plates were observed ( Fig. 2 A). Spawning masses are characterised by flat ribbons of a gelatinous consistency. These ribbons consist of white eggs arranged in a tight spiral that bind to the substrate, forming a rounded crust.

Discussion. The new species belongs to the genus Hoploplana based on the presence of conical nuchal tentacles, a small glandular prostatic vesicle, the lack of a true seminal vesicle and a hook-shaped stylet inserted at the base of the prostatic vesicle.

Of the 14 species comprising the genus Hoploplana ( Table 1), eight ( H. cupida Kato, 1938 , H. deanna Kato, 1939 , H. inquilina (Wheeler, 1894) H. insignis ( Lang, 1884) , H. luracola Smith, 1961 , H. ornata Yeri & Kaburaki, 1918 and H. rosea Prudhoe, 1977 , H. usaguia Smith, 1960 ) have a smooth body surface that lacks papillae, similar to H. elisabelloi ; all other species have papillose surfaces. Of the species with a smooth surface, only H. deanna presents a hooked stylet, but differs from H. elisabelloi by the presence of a long common sperm duct, very short by H. elisabelloi , and the presence of the reticulate white surface characteristic of this species. The stylet is slightly curved in H. cupida , H. insignis and H. usaguia and sinuate in H. inquilina . The other species of the genus show a straight stylet (see Table I for comparison).

As in H. elisabelloi , a short common sperm duct is observed in H. inquilina and H. rosea . Although different in stylet shape, H. elisabelloi (short and curved stylet), H. inquilina (sinuate) and H. rosea (straight) all have a short common sperm duct. In addition, H. inquilina and H. rosea have a shallow ciliated atrium masculinum. However, H. elisabelloi is characterised by a deep, strongly ciliated atrium masculinum ( Fig. 2 H, I).

Distribution ( Fig. 1 , orange dots). The genus Hoploplana is known mainly from the Pacific Ocean (7 species, see Table I), the coasts of the western Atlantic Ocean (e.g. Brazil, Panama and Florida) and the Mediterranean Sea (e.g. Italy and Egypt). Until now, this genus appeared to be restricted to the warmer waters of tropical or temperate regions. Regardless, this newly described species is the northern-most record to date.

Species Body Stylet Sperm Duct Male atrium Distribution Surface (SD)

Hoploplana californica papillate straight long common cilia not longer than the epithelial cilia California ( USA)

Hyman, 1953 SD

Hoploplana elisabelloi n. sp. smooth hook short with very long cilia North Atlantic (Iberian peninsula) reticulate common SD

Hoploplana cupida Kato , smooth slightly long common cilia not longer than the epithelial cilia Japan

1938 curved SD

Hoploplana deanna Kato , smooth hook common SD cilia not longer than the epithelial cilia Japan

1939

Hoploplana divae Marcus , papillate sinuate long common cilia not longer than the epithelial cilia Brazil, Curaçao (also found on Cheilostomata

1950 SD Bryozoan (Bahia et al. 2012) and algae (Marcus &

Marcus, 1968)

Hoploplana inquilina smooth sinuate short cilia not longer than the epithelial cilia USA Atlantic Coast (commensal of snails or

Wheeler, 1894) reticulate common SD gastropods)

Hoploplana insignis (Lang, smooth slightly long common cilia not longer than the epithelial cilia Mediterranean Sea

1884) (dots) curved SD

Hoploplana luracola Smith, smooth straight common SD with very large cilia Panama, Atlantic Coast (commensal of Nerita

1961 (Ritena) gastropods)

Hoploplana ornata Yeri & smooth straight common SD cilia not longer than the epithelial cilia Japan

Kaburaki, 1918

Hoploplana papillosa Lang , papillate straight long common cilia not longer than the epithelial cilia Capri (Mediterranean Sea)

1884 SD

Hoploplana rosea Prudhoe , smooth straight short common inconspicuous Australia

1977 SD

Hoploplana rubra Kato, 1944 papillate slightly common SD cilia not longer than the epithelial cilia Japan curved

Hoploplana schizoporellae papillate straight common SD cilia not longer than the epithelial cilia Japan (on Schizoporella oenochros (Bryozoa))

Kato, 1944

Hoploplana usaguia Smith, smooth slightly common SD cilia not longer than the epithelial cilia Brazil (commensal of gastropods)

1960 curved

Hoploplana villosa (Lang, papillate slightly long common cilia not longer than the epithelial cilia Japan (on Microporella ciliata (Bryozoa)), Naples

1884) reticulate curved SD ( Italia) (on Ciona intestinales (Ascidiacea))

Figures

FIGURE 1. Studied Acotylea species distribution. A, Acotylea distribution in Europe; B, Acotylea distribution in the Iberian Peninsula; C, Acotylea distribution in Galicia, Spain; D, Cryptocelis compacta (green dots); E, Hoploplana elisabelloi n. sp. (orange dots); F, Discocelis tigrina (purple dots); G, Armatoplana celta n. sp. (grey dots); H, Stylochus neapolitanus (blue dots).

FIGURE 2. Hoploplana elisabelloi n. sp. A – C, living specimens; D, histological section of a tentacle and tentacular eyes; E, histological section of the brain; F, histological section of the reproductive system (anterior to the left); G, sagittal reconstruction of a whole specimen; H, histological section of the cirrus; I, histological section of the stylet; J, sagittal reconstruction of the reproductive system. Abbreviations: b, brain; ce, cerebral eyes; cg, cement glands; ed, ejaculatory duct; esv, external seminal vesicle; fa, female atrium; fp, female pore; i, intestine; ma, male atrium; mp, male pore; op, oral pore; ov, ovaries; ovd, oviducts; ph, pharynx; pv, prostatic vesicle; sc, shell camera; spdb, spermiducal bulbs; st, stylet; t, tentacles; te, tentacular eyes; ve, vagina externa; vi, vagina interna.