Dendrobeania fruticosa (Packard, 1863)
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publication ID |
https://doi.org/ 10.1007/s13127-022-00562-y |
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persistent identifier |
https://treatment.plazi.org/id/03AC87AF-FFBF-FFB9-FF20-CC3680149B64 |
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treatment provided by |
Felipe |
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scientific name |
Dendrobeania fruticosa |
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Dendrobeania fruticosa View in CoL ( Figs. 1F View Fig , 12 View Fig , 18C)
Avicularium
Cystid and mandible The adventitious “bird’s head”-shaped avicularia of two size categories are situated on the proximal gymnocyst of autzooids. Larger avicularia develop on marginal autozooids, and smaller ones on central autozooids. Both types are similar in shape and structure ( Fig. 12A, B View Fig ).
The avicularian cystid has a swollen oval main part (“head”) and a distal, elongated “beak”—a pointed and curved rostrum hosting a mandible ( Figs. 12B View Fig , 18C). The postmandibular area is semi-oval. Both rostrum and postmandibular area bear cryptocystal shelf. The avicularian cystid is attached to the autozooid by a flexible cylindrical stalk (peduncle). It is an outgrowth of the maternal autozooid connected with avicularian “head” cavity through communication pores closed by a pore-cell complex ( Fig. 12C View Fig ). The funicular cord was detected in one peduncle in our sections.
The narrow, lanceolate mandible has an internal cavity lined by epidermal cells. It communicates with the body cavity of the avicularium through the small opening in the proximal transverse wall connecting the upper and lower walls ( Fig. 12D, H View Fig ). The distal tip of the sclerite is thickened and curved ( Fig. 12B View Fig ); its lateral edges are denticulated. The proximal margin of the upper mandibular wall is connected to the non-calcified frontal wall of the avicularium ( Fig. 12E View Fig ). Most of the lower wall of the mandible is internal, with the upper vestibular wall lying beneath. This wall runs proximally towards the mandible base and continues to the palate ( Fig. 12D, E View Fig ).
Polypide and muscular system The elongated oval vestigial polypide consists of a rudimentary ciliated lophophore enveloped by a tentacle sheath, and a round cerebral ganglion. The latter is situated below the lophophore “separated” from it by a narrow constriction ( Figs. 12D, E View Fig , 18C). The uppermost part of the tentacle sheath, when approaching the wall of the palate, is surrounded by a nipple-shaped papilla. Inside it, the wall of the tentacle sheath bears a diaphragm—a “cone” of the annular muscles, loose in the upper part and forming a dense, wide ring in the lower part. Below the diaphragm, the wall of the tentacle sheath has at least seven longitudinal muscle fibers ( Fig. 12F View Fig ). The upper ends of at least two of them run along most of the diaphragm ( Fig. 12G View Fig ). The polypide retractors consist of about 10 striated muscle fibers, some of which are attached to the polypide constriction, while the rest insert in the wall of the tentacle sheath above it ( Fig. 12D–F View Fig ). The proximal ends of the retractors are attached to the basal wall at the base of the rostrum.
The smooth abductors are represented by two proximal and one unpaired distal median muscle bundles. The proximal pair of abductors is anchored to the cystid proximal and lateral walls, above the proximalmost parts of the adductors ( Figs. 12E, H View Fig , 18C). Distally, the paired abductors attach to the frontal membrane within short zones approximately in its middle part. Each proximal abductor consists of more than 15 tightly packed, long and thin muscle fibers of about the same width and length. Some of them are grouped in “bundles”. The unpaired abductor arises from the basal cystid wall between adductors and extends towards the frontal membrane, where it attaches to it close to the proximal margin of the mandible. It is comprised of four muscle bundles of about the same length, each consisting of several thin muscle cells ( Fig. 12F, H View Fig ).
The large striated adductors occupy most of the volume of the avicularian cystid cavity, attaching to the basal wall and lower portions of the lateral walls of the avicularium ( Figs. 12C, E, F, H View Fig , 18C). Distally, each muscle bundle continues to a tendon; both tendons together insert in the upper vestibular wall ( Figs. 12C–E View Fig , 18C). Although Fig. 12E View Fig seemingly shows the tendon contacting the lower mandibular wall, in fact, it illustrates the sagittal section in which the tendon distal end is out of the section plane.
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