Maritigrella fuscopunctata ( Prudhoe, 1978 ) Newman & Cannon, 2000

Velasquez, Ximena, Bolaños, D. Marcela & Benayahu, Yehuda, 2018, New records of cotylean flatworms (Platyhelminthes: Polycladida: Rhabditophora) from coastal habitats of Israel, Zootaxa 4438 (2), pp. 237-260 : 252-255

Maritigrella fuscopunctata ( Prudhoe, 1978) Newman & Cannon, 2000

( Fig. 9 )

Synonyms: Pseudoceros fuscopunctatus ( Prudhoe 1978) ; Eurylepta fuscopunctatus ( Gosliner et al. 1996) ; Eurylepta sp.3 ( Gosliner et al. 1996); Maritigrella makranica ( Maghsoudlou & Rahimian 2014) .

Material examined and locality: a) One mature specimen (12x 6 mm, live, ZMTAU-VR 25169 ) preserved in ethanol 70%. Collected at Nahariya, Israeli eastern Mediterranean Sea (33° 00' N, 35° 05’ E) on 12 October 2013 b) One specimen (14x 7 mm, live, ZMTAU-VR25170 ), preserved in ethanol 70%. Collected at Acre, Eastern Mediterranean Sea (32° 55' N, 35° 04’ E) on 16 June 2014 . c) One specimen (10x 4 mm, live, ZMTAU-VR25171 ; (GenBank ID: MH047290 ), preserved in ethanol 95%. Collected at Acre, Israeli eastern Mediterranean Sea (32° 55' N, 35° 04’ E) on 16 June 2014 .

Habitat: Specimens found subtidally in rocky reef habitats (4–5 m depth) and intertidally on the rocky shore, under rocks (1–2 m depth).

Distribution: Dunsborough and Broome, Western Australia (Type locality) ( Prudhoe 1978); Heron Island and Lizard Island, Australia ( Newman & Cannon 2000); Madang, Papua New Guinea; Maldives, Indonesia, Micronesia, Philippines, Marshal Island, Japan, Hawaii, Tanzania ( Gosliner et al. 1996; Newman et al. 2003; Newman & Cannon 2005); Kavaratti Island, India ( Apte & Pitale 2011); Gulf of Oman, Iran ( Maghsoudlou & Rahimian 2014); Malta, Italy ( Crocetta et al. 2015; Vella et al. 2016). In this study, the specimens were found along the Israeli Mediterranean coast.

External anatomy. Oval and elongated body with a ruffled margin ( Fig. 9A ). Dorsal background white-cream with black spots variable in size, forming irregular transverse rows perpendicular to and around the margin. Transverse rows surrounded by a greyish-black shade and stained with a vivid orange pigment at the margin. Few small, individual black spots scattered between the transverse rows. Large pale orange-brownish spots arranged in a honeycomb pattern in the midline running longitudinally from the level of the cerebral eyespot to the posterior edge of the body ( Fig. 9A ). The ventral side exhibits the same pattern as the dorsal surface with few black spots scattered in the median area instead of the honeycomb ( Fig. 9B ). Marginal tentacles with the same pattern of the body margin. Black spots surrounded by a black shadow and orange stains at the edge ( Figs. 9A, C ). Several eyes scattered between the marginal tentacles, cerebral eyes arranged in two elongated clusters ( Fig. 9C ). Small tubular pharynx located anteriorly ( Fig. 9B ). Separate male and female gonopores. The single male gonopore is located immediately after the pharynx and the female pore close to male gonopore. Conspicuous sucker located posteriorly and well separated from the female gonopore ( Fig. 9B ).

Taxonomic remarks. The genus Maritigrella includes ten valid species ( Newman & Cannon 2000; Tyler et al. 2006–2018) characterized by a tubular pharynx, well-developed marginal tentacles, and a conspicuous lined or striped pattern ( Newman & Cannon 2000). Originally described as Pseudoceros ( Prudhoe 1978) , then moved to Eurylepta ( Gosliner et al. 1996) , and finally placed within Maritigrella , this species is distinguished by the transverse rows formed by dots, the orange-brown honeycomb pattern along the midline, and the dark and purpleviolet pigment associated with the transverse lines ( Newman & Cannon 2000). The specimens found in Israel agreed with the general diagnostic pattern for the species but slightly differs in the color encircling the black spots, being dark grey close to the mid-body and orange at the margin ( Fig. 9 ). Crocetta et al. (2015) and Vella et al. (2016) reported M. fuscopunctata from another location in the Mediterranean, in which the orange pigment forms an interrupted marginal band. Although our specimens have orange pigment at the margin, a distinct band is not evident due to a more spaced grouping of the transverse rows.

A geographically more distant and morphologically different morphotype was described from India ( Apte & Pitale 2011), exhibiting a solid orange band at the margin instead of an interrupted band or separated orange stains as mentioned above for the Mediterranean worms. In addition, the Indian specimen has the margin bordered by regularly organized black dots with larger dots more scattered over the dorsal surface than forming well-defined transverse rows ( Apte & Pitale 2011). The same morphotype was also reported by Maghsoudlou & Rahimian (2014) for the Gulf of Oman in Iran. Differently, these authors considered such discrepancies significant enough for the creation of the new species Maritigrella makranica MAGHSOUDLOU & RAHIMIAN, 2014. While species identifications within the genus exclusively rely on color and pattern, variation also occurs in euryleptids ( Bahía et al. 2014) as it has also been largely discussed for pseudocerotids (See Bolaños et al. 2016). Despite color differences, the basic pattern remains nearly constant between these morphotypes.

Maghsoudlou & Rahimian (2014) stated as major differences between both species the presence of black spots scattered over the dorsal surface and the dark-grey hue surrounding the transverse black dots towards the midline, which is orange towards the margin in M. makranica , and the lack of a distinct orange submarginal band and the reticulated brownish honeycomb pattern extending over the entire dorsal surface in M. fuscopunctata . First, the specimens collected in our study and several web-based photographic records show that some morphotypes have black dots scattered over the dorsal surface ( Figs. 9A, B ; Newman & Cannon 2005: Photos 6-11; Cobb et al. 2003- 2017; Tan 2008; Ling 2009; Charpin 2004–2016; Crocetta et al. 2015: Fig. 7 a-c, p. 689; Vella et al. 2016: Fig. 2 ac, p. 123). In fact, it is commonly called punctuated worm or dark-spotted flatworm ( Tan 2008; Charpin 2004–2016; Vella et al. 2016). Second, it was possible to recognize variants for the pigment surrounding the black spots: a purple-violet ( Newman & Cannon 2000: Fig. 22, p. 203; Harasti 2003), brownish-orange ( Tan 2008; Charpin 2004–2016); brownish-orange medially and dark grey towards the margin ( Newman & Cannon 2005: Photo 9; Vella et al. 2016: Fig. 2a, p .123), dark grey-blackish ( Newman & Cannon 2005: Photo 10; Vella et al. 2016: Fig. 2a, b, p . 123; this study), in addition to the description for M. makranica . Third, the marginal band can be orange or purple as well as interrupted, solid or patchy (Duncan et al. 2015–2017; Harasti 2003; Cobb et al. 2003–2017; Newman & Cannon 2005: Photos 9, 10; Boyer 2009–2017; Crocetta et al. 2015; Aya 2015; Vella et al. 2016: Fig. 2a–e, p . 123). Finally, the honeycomb pattern is consistent in all the specimens and variation in length and width has no taxonomic significance. The rim delineated by more organized black spots observed in M. makranica is also observed in the specimens from Malta in the Mediterranean ( Vella et al. 2016), Indonesia ( Aya 2015), and Hawaii (Duncan et al. 2015–2017). The remarkable mixture of morphological characters observed in several formal and informally documented records for M. fuscopunctata clearly support the low taxonomic weight of the differential characters selected for M. makranica , and are considered insufficient for the creation of a new species. Therefore, it is highly likely that M. makranica represents a junior synonym of M. fuscopunctata .

A similar case is that of Maritigrella ocellata NEWMAN & CANNON, 2000 which differs from M. fuscopunctata mainly by the absence of the reticulated orange pigment along the midline region. Another difference mentioned by Newman & Cannon (2000) is the more abundant number of black spots surrounded by an orange hue instead of purple-violet as M. fuscopunctata . While we considered the presence of an orange pigment in a honeycomb pattern an important character for species distinction, number of dots and small differences in color are subjective and unreliable features for species distinction. Prudhoe (1978) presented a diagram of a cleared specimen of M. fuscopuntata ( Fig. 5a, p . 596) in which the pattern perfectly fits with the description for M. ocellata . In fact, the author stated that only by examining a color-transparency of the cleared animal when alive, allowed him to place both specimens under the same species. The foregoing opens the possibility of a potential synonymy between M. fuscopunctata and M. ocellata and raises the question if the lack of orange-brown pigment in the medial region is due to immaturity (juvenile worm) or the homeostatic condition (health, nutrition, reproductive success) of each individual. Additionally, several records for M. fuscopunctata have been sighted in different locations in the Indopacific unlike M. ocellata where no other reports exist since the creation of the species.

Finally, we compare available sequences in GenBank from the specimens found in Malta ( KU674837 -9) with the homolog sequence of our specimen from Israel ( MH047290 ). Our analysis revealed a close match of almost the full-length of the sequences (~984bp), which allowed us to confirm that these variants of M. fuscopunctata inhabiting different locations in the Mediterranean correspond to the same species ( Table 4). Additionally, our analysis validated the hypothesis that small color and pattern variations in M. fuscopunctata such as pigment around the black spots and a solid, interrupted or spotted orange margin may occur and are not sufficient for the creation of a new species. However, a more thorough molecular analysis is needed to determine if M. fuscopunctata is another species complex. M. fuscopunctata is recorded for the first time in the Israeli eastern Mediterranean Sea.

Figures

FIGURE 2. Pseudoceros duplicinctus. (A) Dorsal view, in vivo. (B) Ventral view of the live specimen showing the reproductive structures and sucker. (C) Close-up of the anterior region showing the pseudotentacles, pseudotentacular eyes and cerebral eyes. ce: cerebral eyes; fg: female gonopore; mg: male gonopore; pe: pseudotentacular eyes; pt: pseudotentacles; su: sucker.

FIGURE 5. Pseudobiceros murinus. (A, B) Dorsal and ventral view, in vivo. (C) Close-up of the anterior region of a preserved animal showing the pseudotentacles, pseudotentacular eyes, and cerebral eyes. (D) Close-up of the ventral side of a preserved animal showing the pharynx, reproductive structures, and sucker. ce: cerebral eyes; fg: female gonopore; mg: male gonopore; pe: pseudotentacular eyes; ph: pharynx; pt: pseudotentacles; su: sucker; u: uteri.

FIGURE 7. Thysanozoon brocchii. (A, B) Dorsal view, in vivo showing color variation. (C) Close-up of the anterior region showing the pseudotentacles and the pseudotentacular and cerebral eyes. (D) Close- up of the ventral view of a preserved specimen showing the pharynx, reproductive structures, and sucker. ce: cerebral eyes; fg: female gonopore; mg: male gonopore; pe: pseudotentacular eyes ph: pharynx; pt: pseudotentacles; su: sucker; u: uteri.

FIGURE 9. Maritigrella fuscopunctata. (A) Dorsal view, in vivo. (B) Ventral view of the live specimen showing the pharynx and sucker. (C) Close-up of the anterior region showing the marginal tentacles and cerebral eyes. ce: cerebral eyes; ph: pharynx; pt: pseudotentacles; su: sucker.