Faerlea tyleri, Atherton & Jondelius, 2022

Atherton, Sarah & Jondelius, Ulf, 2022, Phylogenetic assessment and systematic revision of the acoel family Isodiametridae, Zoological Journal of the Linnean Society 194, pp. 736-760 : 743-745

FAERLEA TYLERI SP. NOV.

( FIG. 4 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: D7ACB50A-70AB-40E3-ADB7-86310945FB0F

Material examined: Holotype (SMNH-Type-9336) and paratypes (SMNH-Type-9337): serially sectioned specimens. Digital video and photographs of original specimens.

Type locality: USA, Hawaii, Waimanolo Beach. 21°19’8.23”N, 157°40’11.92”W .

Habitat: Marine sediments; mixed fine and medium sand with some organic content; 1.5 m deep.

Diagnosis: Species of Faerlea without pigmentation, glassy. Body up to 1 mm long, vermiform with rounded anterior and posterior. Large vacuoles in posterior and laterally. Smaller vacuoles in the anterior. Frontal glands well developed. Rhabdoids absent. Testes and ovaries paired. Male copulatory organ located close the posterior end. Small, round seminal vesicle present with a penis as a simple inpocketing of the epidermis. Bursa or female accessory organs absent.

Etymology: This species is named after Seth Tyler in recognition of his contributions to the taxonomy of Acoela .

Description

Living specimens up to 1 mm long. Glassy and without body pigmentation or eyespots. Body width ~67 µm at position of stylet and increasing toward posterior; ~100 µm at position of largest egg. Body shape vermiform with rounded anterior and posterior ends. Statocyst to 8 µm in diameter located 67 µm from anterior end. Frontal organ well developed. Large vacuoles present at the posterior end and extending laterally, decreasing in size toward the anterior; smaller vacuoles present in the anterior. Epidermis 4–5 µm thick, uniformly covered with cilia. Cilia 3–5 µm long. Rhabdoids absent. Mouth located at the second-quarter of the body. Ovaries paired, located in third-quarter of the body. Bursa or female accessory organs absent. Testes paired, located laterally approximately ~300 µm from the anterior end the body. Vas deferens more evident toward male copulatory organ, with clear sperm. Male copulatory organ small, ~20 µm long and ~25 µm deep in fixed specimens, spheroid. Present 55 µm from posterior end in living specimens. Penis present as a simple inpocketing of the epidermis, 9 µm long and projecting outward in fixed specimens. Male pore small, ~5 µm long, ciliated.

Remarks

Faerlea tyleri is the first species of its genus to be documented from Hawaii or the Pacific. In general, the species fits well with the other known species of Faerlea : Faerlea tyleri is fragile due to its heavily vacuolated parenchyma; the position of the testes is far toward the anterior; and the position and composition of the male copulatory organ is consistent with the other species. The species is most similar to F. fragilis and F. glomerata in that it is non-parasitic and does not possess female accessory organs. However, Faerlea tyleri differs from either species in its general body shape, which is more strap-shaped with rounded anterior and posterior ends than either F. fragilis or F. glomerata , and the small size of the male copulatory organ. Additionally, Faerlea tyleri can be distinguished from F.glomerata by the size of the frontal organ, which, although well developed, is smaller in comparison, the more distinctly paired ovaries and wide separation between the ovaries and the male copulatory organ. Faerlea tyleri can be distinguished from F. fragilis by the relatively few vacuoles and the position of the ovaries, which begin further toward the posterior end.

Figures

Figure 4. Faerlea tyleri. A, whole body drawing, sagittal view. B, whole body drawing, frontal view. C, micropictograph of whole body. D, sagittal section of posterior end stained with haematoxylin–eosin. eg, egg; f, frontal organ; I, intestine; m, mouth; mco, male copulatory organ; p, penis; st, statocyst; sv, seminal vesicle; t, testis; v, vacuole.