Philactinoposthia multipunctata, 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 : 9-11

Philactinoposthia multipunctata sp.nov.

( Figs. 3 , 7 , 8 , 9 )

Type material: Holotype: SMNH Type-8046. Paratype 1: SMNH Type-8047, Paratype 2: SMNH Type-8048.

Type locality. Punta Ala Torre Balbo in Italy (42° 48' 25" N, 10° 44' 34" E), at 3 m water depth in fine sand.

Other material examined. Living specimens in squeeze preparations; 1 set of 4–5 μm serial sagittal sections of paraffin-embedded specimen.

Etymology. Name refers to the numerous rhabdoid glands. Multi = many, punctum = dot, in latin.

Description. Active and fast swimmer. Living specimens ~ 3 mm long and ~340–500 μm wide. Body shape cylindric, both ends tapering. Epidermis completely covered with 5 μm long cilia. Numerous red-colored rhabdoid glands in body wall, uniformly scattered across body ( Fig. 7 BC). Each rhabdoid gland with up to 9 strokes and 10 μm long ( Fig. 7 A). Epidermis uncolored in transmitted light. Statocyst 8 μm in diameter, located anteriorly at level U7,5. Frontal organ well developed, cell bodies of frontal glands located posterior to statocyst, extending from U10 to U20. Mouth ventral, located in middle of body. Digestive central syncytium extends from U25 to U70.

Ovary unpaired, ventral, with up to 5 oocytes, extends posterior from level of testes, to bursal nozzle, U55–60 to U80. Female gonopore ventral, at level U85, opens directly to seminal bursa with wall and a fibrous disc in distal end; visible in pressed specimens ( Fig. 7 A). Seminal bursa connects anteriorly to well defined and clearly visible bursal nozzle with appearance like a stack of hats, with ventro-anterior direction ( Fig. 8 ABC). Bursal nozzle is long and slender, 60 μm long and consists of at least 13 “hats”.

Testes paired, lateral to ovary, extends anteriorly from level of mouth, to male copulatory organ posteriorly, U45 to U90. Male gonopore positioned in posterior end, ventral, at level U95, opens to male copulatory organ with v-shaped sclerotized penis-like structure built of 100 μm long stylet needles. Penis-like structure filled with spermatozoa, easily detected with moderate pressure. Needles weakly stained by eosin. Eosinophilic glands surround male antrum ( Fig. 8 C). False seminal vesicle located at proximal end of stylet-like structure.

Figures

FIGURE 3. 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. P. b re v i s sp. nov., P. ischiae sp. nov. and P. novaecaledoniae sp. nov. are placed in a clade composed of Philactinoposthia species with maximum support.

FIGURE 7. Philactinoposthia multipunctata sp. nov. Photomicrographs of living specimens. A. Dorsal view of whole squeezed specimen. Scale bar: 300 μm. B. View of posterior part of body. Scale bar: 90 μm. C. Female copulatory organ and rhabdoid glands. Scale bar: 110 μm.

FIGURE 8. Philactinoposthia multipunctata sp. nov. Photomicrographs of sagittal histological sections stained with hematoxylin-eosin. A. Section through body. Scale bar: 350 μm. B. Female copulatory organ. Scale bar: 30 μm. C. Section through posterior. Scale bar: 100 μm.

FIGURE 9. Philactinoposthia multipunctata sp. nov. Reconstructions show arrangement of organs. A. Dorsal reconstruction of whole living animal. B. Sagittal reconstruction of the whole animal. Scale bar: 500 μm.