Smittoidea propinqua (Smitt, 1868)

Serova, K. M., Belikova, E. V., Kotenko, O. N., Vishnyakov, A. E., Bogdanov, E. A., Zaitseva, O. V., Shunatova, N. N. & Ostrovsky, A. N., 2022, Reduction, rearrangement, fusion, and hypertrophy: evolution of the muscular system in polymorphic zooids of cheilostome Bryozoa, Organisms Diversity & Evolution (New York, N. Y.) 22 (4), pp. 925-964 : 940

publication ID

https://doi.org/ 10.1007/s13127-022-00562-y

persistent identifier

https://treatment.plazi.org/id/03AC87AF-FFA2-FFA4-FF20-CAED80799F84

treatment provided by

Felipe

scientific name

Smittoidea propinqua
status

 

Smittoidea propinqua View in CoL ( Figs. 1D View Fig , 10 View Fig , 17D View Fig )

Avicularium

Cystid and mandible The small suboral adventitious avicularium has an oval outline when viewed from above, with a crossbar ( Fig. 10A View Fig ). The avicularian chamber is immersed in the autozooidal frontal shield.

The mandible is hollow, semicircular with small denticles on the distal margin. Its lower wall bears two small depressions. The lower mandibular wall presumably bears an oval opening (visible as a dark area in our CLSM preparations, see e.g. Fig. 10D View Fig ) through which the mandible cavity communicates with the avicularian body cavity.

Polypide and muscular system The vestigial polypide is positioned between two large adductors. Few diaphragmatic muscles form a wide “ring” in the uppermost part of the tentacle sheath, which also possesses about 10 longitudinal muscle fibers ( Fig. 10D View Fig , inset). The upper ends of the longitudinal muscles intersect with the diaphragmatic muscles. Several thin retractors are attached to the lower part of the tentacle sheath.

Small, smooth, paired abductors are situated close to each other, forming a complete shallow arch of about 10 short bundles consisting of several muscle cells each, and distally attaching to the frontal membrane ( Figs. 10C View Fig , 17D View Fig ). Their lower wider ends are anchored at the proximal and lateral cystid walls.

Striated adductors, which are the largest muscles of the avicularium, occupy most of the cystid volume ( Figs. 10C, D View Fig , 17D View Fig ). They insert to the upper vestibular wall, whereas their lower ends are attached to the basal cystid wall.

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