Laxus oneistus

Pröts, Philipp, Novotny-Diermayr, Veronica & Ott, Jörg A., 2024, A novel three-part pharynx and its parallel evolution within symbiotic marine nematodes (Desmodoroidea, Stilbonematinae), Organisms Diversity & Evolution 24 (3), pp. 353-373 : 357

Laxus oneistus

The corpus has a vase-like shape and is about two to three times as long as wide, tapering gradually over a longer distance towards the anterior end. It is conspicuously large compared to the corpus of species in other genera and constitutes around 45–52% of the pharynx length ( Table 1). The myofilaments are only slightly directed forward and the anterior-most end and nearly perfectly perpendicular until 2/3 of the corpus length. From this point on, they are oriented slightly backwards. The density of myofilaments and intensity of the F-actin signal were equal in both corpus and the succeeding isthmus. Basally situated nuclei are positioned in between myofilaments in the corpus ( Figs. 1j , 4h, 5n and 7h ).

Figures

Fig. 1 Pharynx musculature of Stilbonematinae, CLSM optical sections. Anterior on the left side. a Eubostrichus topiarius, b Paralaxus cocos, c Catanema schiemeri, d Robbea lotti, e Robbea weberae, f Rob- bea judithae, g Cyathorobbea hypermnestra, h Cyathorob- bea ruetzleri, i Cyathorobbea agricola, j Laxus oneistus. Scalebars 20 μm. ap, anterior pharynx; b, bulbus; bd, buccal dilator muscle; c, corpus; da, dorsal ampulla; gd, gland duct; i, isthmus; sp, spiral muscle; spm, somato-pharyngeal mus- cle; sm, somatic muscle

Fig. 5 Dorsal and subventral gland ampullae. Anterior on the left side. a Catanema schiemeri, CLSM optical section, autofluorescence, corpus, b Catanema schiemeri, TEM micrograph, corpus c Catanema schiemeri, CLSM micrograph, isthmus, musculature in orange, nuclei in blue d Robbea lotti, CLSM optical section, musculature in orange, nuclei in blue, corpus e Robbea weberae, CLSM optical section, musculature in orange, nuclei in blue, corpus f Robbea judithae, CLSM optical section, musculature in orange, nuclei in blue, corpus g Cyathorobbea hypermnestra, CLSM optical section, musculature in orange, corpus h Cyathorobbea hypermnestra, TEM micrograph, corpus i Cyathorobbea hypermnestra TEM micrograph, anterior isthmus j Cyathorobbea ruetzleri, CLSM optical section, musculature

Fig. 7 Pharyngeal region, pharynx nuclei, CLSM opti- cal sections. Colors: a–c, e, f: musculature in red/orange, nuclei in blue; d: musculature in blue, nuclei in magenta; nuclei within the orange labelled area/ outline are pharynx nuclei. For some species the outline of the pharynx is further indicated with white dashed lines. a Catanema schiemeri, b Robbea judithae, c Robbea lotti, d Rob- bea weberae, e Cyathorobbea hypermnestra, f Cyathorobbea ruetzleri, g Cyathorobbea agri- cola, h Laxus oneistus. Dashed lines indicate the outline of the pharynx. Scalebars 20 μm. en, elongated nucleus inside the pharynx; n, nucleus inside the pharynx; ne, epidermal nuclei