Miamira striata

Autor: Tibiriçá, Yara, Gosliner, Terrence M., Bonomo, Lynn J., Cervera, Juan Lucas
Rok vydání: 2021
Předmět:
DOI: 10.5281/zenodo.5597061
Popis: Miamira striata (Eliot, 1904) (Figs. 2–7) Orodoris striata Eliot 1904: 268–270 (original combination); Eliot 1910: 532; Edmunds 1971: 390. Dendrodoris tuberculosa — Debelius & Kuiter 2007: 262 (misidentification) Asteronotus sp. — Tibiriçá et al. 2017: 46, figs 13L, 15 (misidentification) Type material. The holotype of M. striata was originally deposited in the Natural History Museum of London but could not be located and is probably lost (A. Salvador, pers. comm.). Here one specimen collected at the type locality is designated as neotype. Neotype (Figs. 2E, 6, 7D, 7E) (dissected and sequenced): 60mm long preserved, Cement Wall Dive Site, Zanzibar, Tanzania (6°18’36.00”S, 39°34’48.00”E), 34m depth, 20 Oct.2018, collected by T. M. Gosliner (CASIZ 227551). A neotype is hereby designated to clarify the taxonomic status of this much-confused species and enable further clarification of similar morphotypes with no available material at the present (e.g. from Réunion Island). The neotype closely resembles the original material described by Eliot (1904) in its external and internal anatomy, including the presence of the striated markings and brownish body that clearly distinguishes this species from other closely related congeners. Type locality. Pemba Island, Zanzibar Archipelago, Tanzania. Additional material examined. (all dissected and sequenced) Two specimens: 92mm long, 6m depth, Kwalala Reef Dive Site, Nacala, Nampula Province, Mozambique (14°11’13.42”S, 40°40’52.77”E), 13 Jun. 2014, collected by Y. Tibiriçá (MB28-004911); 150mm long, 9m depth, Fish Alley Dive Site, Nuarro, Memba Bay, Nampula Province, Mozambique (14°11’39”S, 40°41’16”E), 23 Aug. 2016, collected by Y. Tibiriçá (MB28-005043). Diagnosis. Body oval, undulate mantle margin. Circular, smooth dorsal mantle depressions. Numerous ridges form almost concentric circles that radiate from the dorsal mantle depressions; large single tubercle anterior to the gill pocket; secondary tubercles on ridges. Gill sheath irregular with lobes; tripinnate gill branches. Beige background; mantle depressions dark brown to greenish. Jaws bearing simple rodlets. Rachidian teeth absent, innermost tooth with small denticles on both sides, next few inner lateral teeth with denticles only on the outer side, outer lateral teeth without denticles, outermost teeth degenerated and smooth. Prostate very long, highly convoluted. External morphology (Figs. 2, 3). Body large (up to 150mm), rigid, oval, dorso-ventrally flattened. Mantle edge grooved, extending beyond foot on all sides; posterior edge of mantle may fold depending on animal activity (Figs. 2A, 2C and 2E). Six to eight smooth, low mantle depressions (Fig. 2B) present on each dorsum side. Mantle depressions surrounded by ridges that radiate concentrically. Tall dorsal tubercle anterior to gill pocket (Figs. 2A, 2C). Central ridge crest, running from tubercle to anterior rhinophores. Low lateral and mid-dorsal tubercles between mantle depressions. Rhinophores, retractable, thick, perfoliate, smooth at base, bearing 19–22 lamellae (Fig. 2B). Gill sheath raised with pointed scalloped margins (Fig. 2A). Eight gill leaves, tripinnate, around anal papillae; anal papillae, conspicuous, elevated (Fig. 2D). Foot elongated, narrow, shorter than mantle (Fig. 3A). Oral tentacle small, elongated (Fig. 3B). Coloration. Background color beige. Mantle edge whitish. Top of ridges translucent white to beige. Fine yellow lines on each ridge side (Fig. 2F). Lateral mantle depressions dark brown. Rhinophores light beige. Rhinophores sheath translucent white (Fig. 2B). Gill rachis pink with yellowish apical edges. Gill leaves greyish (Fig. 2D). Gill pocket wall beige, margin white. Anal papillae pink, anus internally white. Ventral mantle surface bluish white (Fig. 3A). Brown, elongate, oval spots on sides of foot (Fig. 3A). Foot whitish with thin creamy striations (Fig. 3B). Oral tentacles translucent white (Fig. 3B). Internal morphology. Anatomical overview (Fig. 4A). Oral tube anterior, smaller than buccal bulb. Large dorsally located blood gland. Reproductive system located in anterior two-thirds of body. Intestine lying freely on right side of digestive gland covering part of reproductive system. Buccal mass (Fig. 4B and Figs. 5–6). Buccal bulb muscular; radular sac short, ovulate. Two long salivary glands, wider at base, nnear each side of oesophagus (Fig. 4B). Radular formulae 110 x 102.0.102 (MB28-004911), 103 x 104.0.104 (MB28-005043), 115 x 97.0.97 (CASIZ 227551). Radula teeth numerous (Figs. 5A, 6A). Rachidian teeth absent. Inner 14–16 lateral teeth elongate, smooth on inner side, outside with a ridge shaped denticle divided in 2–7 poorly defined, irregular denticles (Figs. 5B, 6B). Remaining lateral teeth with a longer cusp, without denticles. Lateral teeth larger toward middle row and smaller toward edges (Figs. 5C, 5E, 6C, 6E). Outer teeth simple, degenerate, apex blunt (Figs. 5E, 6E). Armed jaws comprised of simple rodlets (Figs. 5F, 6F). Reproductive system (Fig. 4C). Hermaphroditic duct leads to thick, large ampulla. Ampulla branches into short, thin oviduct and prostate. Oviduct enters large female gland. Female gland smaller in CASIZ 227551 (not shown). Prostate very long, highly convoluted. Prostate leads to a long, thin and coiled deferent duct. Deferent duct expands into long muscular penial bulb, opening into common atrium with vagina. Vagina elongate, undulate; at about 2/3 of proximal end, vagina bifurcates into uterine duct. Uterine duct long, entering female mass near ampulla. Distal vagina enters bursa copulatrix, near long duct, which ends at pyriform receptaculum seminis. Vaginal gland, oval, ventral to female gland mass, near common atrium. Geographic distribution. Western Indian Ocean. Tanzania (Eliot 1904; Edmunds 1971; present study), Seychelles (Eliot 1910; Debelius & Kuiter 2007), Réunion (South-west Indian Ocean Seaslug site 2011), and Mozambique (Tibiriçá et al. 2017; present study). Habitat. Tropical coral reefs and sandy areas with patchy corals and seagrass, often crawling on sand. Remarks. Miamira striata was described (as Orodoris striata) from a specimen collected in Tanzania by Eliot (1904) with additional material later recorded from the Seychelles (Eliot, 1910). Our specimens were collected in Tanzania and northern Mozambique, further photographic records exist for Seychelles and Reunion with slight color variation (seaslugs.free.fr). Eliot’s descriptions (1904, 1910) were not accompanied by illustrations, but the general morphology of our specimens clearly matches the holotype description. The holotype was described by Eliot (1904) as such: approximately 150 mm; ground color greenish on dorsum, deep green and brown laterally; narrow prominent ridges on the dorsum, whitish with some greenish grey areas; fairly large tubercles, ridges passing over them; large tubercle behind the gill pocket; gill leaves ranging from seven to eight, anal papillae and main gill rachis pink; three circular deep green areas on each side where ridges are absent; gill sheath irregular lobed; underside white with a brownish line between the mantle and the foot side. Eliot (1910) continued the description providing details of the preserved specimen, which he mentioned was badly preserved, and the color has changed to “uniform yellowish white” and the “characteristic curved ridges” were barely visible and tubercles fairly disguised. The radular formula was 120 x 130.0.130; the jaws bore simple rodlets; the innermost teeth bore two denticles on each side, and the next 10 –15 inner lateral teeth bore a variable number of denticles on the outer side up to ten, but no denticles were present on the inner side. The outermost lateral teeth were smaller and devoid of denticles with irregular lobes. In particular, our specimens share the following external features: numerous lateral ridges on the dorsum with a circular distinct shape, ridges passing over the tubercles, oval body, large tripinnate gill branches, a raised irregular lobed gill sheath, the large tubercle anterior to the gills and pink colored anal papillae and main gill rachis. Unfortunately, the holotype of M. striata is likely lost. Nevertheless, the specimens collected during Gardiner’s Expedition and identified by Eliot (1910) are deposited in the Natural History Museum of London and despite being poorly preserved, the general shape, dorsal elevated lines and tubercles confirm that they belong to the same species. Small differences exist between the holotype and the specimens examined by us, which we consider as intraspecific variation. For instance, the circular areas on the side of the mantle are dark brown in our specimens, but deep green in the holotype. The ground color of our specimens is beige, but in the holotype, greenish centrally and green and dark brown laterally. Nonetheless, a specimen photographed in Réunion also shows such coloration (South-west Indian Ocean Seaslug site, 2011, as Dendrodoris sp.1) and in one of our specimens the dark brown depressions changed to a greenish color after preservation (Fig. 7). The holotype had a 2.5 cm white margin around the mantle, that could also be seen in the neotype from Tanzania, but not in the specimens from Mozambique, confirming a degree of intraspecific variation. Regarding the teeth, the number of denticles appears variable. This was also observed by Marcus & Marcus (1970), who suggested that shape and number of denticles within Orodoris spp. is inconstant. In our specimens, the innermost lateral teeth bear one or two denticles on each side, while the holotype bore two denticles on each side (Eliot, 1904). In the specimen from Seychelles examined by Eliot (1910) the innermost teeth bear two denticles on the inner side and three on the outer side. In all specimens examined by us, the inner side of lateral teeth lack denticles, but the outer side bears a varying number: up to 10 in the holotype and Seychelles specimen (Eliot, 1904, 1910), up to seven in the Tanzanian specimen (CASIZ 227551), and up to four in the Mozambique specimens (MB28-004911, MB28-005043). These denticles are irregular in shape and have a united base forming a ridge on the top of the cusp, as observed by Eliot (1910) rendering them nearly imperceptible. The ABGD analysis supports that M. striata is a different species from all other Miamira sequenced species. The closest related species to M. striata is M. miamirana with minimum p -distance of 4.1%. Similar uncorrected pairwise distances have been found between other species of Chromodorididae. For example, Ortigosa et al. (2014) found a p -distance of 5% between Felimida elegantula (Philippi, 1844) and Felimida luteorosea (Rapp, 1827); while Layton et al. (2018) found interspecific p -distance between putative Chromodoris spp. ranging from 2% up to 20.4% with an overall mean of 9.5%. Miamira miamirana is a highly variable and broadly distributed species in the Indo-Pacific, which itself requires further examination. Some differences between M. miamirana and M. striata are substantial. Firstly, M. miamirana bears deeper warts along the mantle edge than M. striata. Secondly, M. miamirana has compound tubercles forming ridges, while in M. striata the longitudinal and transverse ridges pass over the tubercles (Eliot, 1904). These ridges were described by Eliot (1904) as being numerous and prominent in the living organism, but somewhat faded in preserved species, a characteristic also observed in our specimens (Fig. 7). No other species of Miamira exhibit this characteristic, a complex ridge system.
Published as part of Tibiriçá, Yara, Gosliner, Terrence M., Bonomo, Lynn J. & Cervera, Juan Lucas, 2021, Redescription of a forgotten nudibranch Miamira striata (Eliot, 1904) and review of the taxonomic status of the genus Orodoris (Nudibranchia: Chromodorididae Miamirinae), pp. 151-165 in Zootaxa 4981 (1) on pages 155-162, DOI: 10.11646/zootaxa.4981.1.8, http://zenodo.org/record/4897719
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