Solenofilomorpha justinei, Nilsson, Karin Sara, Wallberg, Andreas & Jondelius, Ulf, 2011

Nilsson, Karin Sara, Wallberg, Andreas & Jondelius, Ulf, 2011, New species of Acoela from the Mediterranean, the Red Sea, and the South Pacific, Zootaxa 2867, pp. 1-31 : 25-27

Solenofilomorpha justinei sp.nov.

( Figs. 23 , 24 , 25 , 26 )

Type Material: Holotype: SMNH Type-8058. Paratype 1: SMNH Type-8059.

Type Locality. Amedée Island in New Caledonia, (22° 28' 40" S, 166° 28' 22" E), 15 m water depth in fine sand and Station 4, north side of Recif Tamanou, (22° 18.866 S, 166° 29.609 E), at 2 m water depth in fine sand.

Other Material examined. Living specimens in squeeze preparations.

Etymology. Species name honors professor Jean-Lou Justine.

Description. Living specimens up to 700 μm long and ~150 μm wide. Body shape variable, especially when compressed, but mainly cylindric, long and slender ( Fig. 23 A). Anterior end rounded, posterior end tapering. Specimens fixed for histological sectioning highly contracted.

Epidermis completely ciliated with 5 μm long cilia. Body mostly colorless by transmitted light, except some yellow to orange coloration, laterally, possibly food particles ( Fig. 23 ABC).

Numerous vacuoles located in posterior part of body, mostly posterior to ovary, small with little variability in size, ~20 μm in diameter ( Fig. 23 AC). Statocyst 5 μm in diameter, located 250 μm from anterior end, at U12. Frontal organ present, cell bodies of frontal organ extend from statocyst to posterior part of pharynx, U13 to U25. Mouth opening on ventral surface, posterior to statocyst, at U20, opens to ciliated pharynx with glandular epithelium, wavy or undulatory-shaped, extending from U20 to U30 ( Fig. 23 AB). Pharynx visible in compressed living specimens. Digestive central syncytium diffuse.

Ovary unpaired, ventral, with up to 4 oocytes, reaching posterior to male copulatory organ, extending from U50 to U90 ( Fig. 23 C). In sectioned specimens oocytes are located more anteriorly, this may be a fixation artifact. Seminal bursa absent in all specimens found. Sperm found posterior to antrum, dorsal to the oocytes, interpreted as allosperm. Testes unpaired, dorsal, separated from ovary, extending from seminal vesicle anterior to middle of body ( Figs. 23 A, 24AC), U35 to U60. Male gonopore located in posterior to mid-body, at U62, opens to ciliated antrum, 25 μm long. Proximal end of antrum opens to spherical seminal vesicle, at U62, 30 μm in diameter. Eosinophilic glands located in proximal part of antrum.

Remarks. The Bayesian analysis of nucleotide data places this species in the Solenofilomorphidae with maximum support, but there is limited resolution within this clade ( Fig 26 ). Morphological support for classifying this species in Solenofilomorphidae is derived from the unpaired testis and ovary located posterior to the male copulatory organ, which is positioned in the mid-body, and from its ciliated anterior pharynx.

Solenofilomorpha justinei can be identified as a member of the genus Solenofilomorpha due to its tubiform pharynx with glandular epithelium and the lack of rhammites and penis.

This species is distinguished from other species of Solenofilomorpha by the following characters: pharynx tubular with undulatory shape, body short (700 μm), and wide, (length /width about 5), lack of pigmentation, absence of seminal bursa, simple male copulatory organ consisting of seminal vesicle without well-developed penis, and massive testes reaching anteriorly to U35.

Solenofilomorpha longissima Dörjes, 1968 also lacks a seminal bursa, but there is a small muscular penis, the testis is much smaller and oocytes are larger and more numerous than in S. justinei . Moreover, the pharynx is more anterior in S. longissima , the body is much longer (1900 μm) and vacuoles are absent. In Solenofilomorpha guamensis Crezee, 1975 a seminal bursa is present, numerous glands surround the proximal part of the male antrum, the reproductive organs are more anterior and the pharynx is located more posteriorly in comparison to S. justinei . Solenofilomorpha funilis Crezee, 1975 has a seminal bursa, the pharynx is located more posteriorly than in S. justinei and the posterior vacuoles are much larger. Both S. guamensis and S. funilis swim with anterior part of the body straight and the posterior curved, whereas S. justinei swims with straight body.

Figures

FIGURE 23. Solenofilomorpha justinei sp. nov. Photomicrographs of living specimens. A. Dorsal view of whole specimen. Scale bar: 100 μm. B. View of posterior part of body. Scale bar: 50 μm. C. Showing pharynx. Scale bar: 40 μm.

FIGURE 24. Solenofilomorpha justinei sp. nov. Photomicrographs of sagittal histological sections stained with hematoxylineosin. A. Section through length of body. Scale bar: 60 μm. B. Section through posterior. Scale bar: 30 μm. C. Showing pharynx and testes. Scale bar: 30 μm.

FIGURE 25. Solenofilomorpha justinei sp. nov. Reconstructions show arrangement of organs. A. Dorsal reconstruction of whole living animal. B. Sagittal reconstruction of the whole animal. Scale bar: 100 μm.

FIGURE 26. Detail from the majority rule consensus tree summarizing the result of the Bayesian analysis of the combined 18 S rDNA, 28 S rDNA and COI dataset with the GTR + G substitution model after 10 million generations sampled every 1000 generations after a burnin of 5 million generations. Solenofilomorpha justinei n. sp groups with other Solenofilomorphidae species with maximum support, although there is low support for relationships within the clade.