Symphytognathidae, Hickman, 1931

Lopardo, Lara, Michalik, Peter & Hormiga, Gustavo, 2022, Take a deep breath … The evolution of the respiratory system of symphytognathoid spiders (Araneae, Araneoidea), Organisms Diversity & Evolution (New York, N. Y.) 22 (1), pp. 231-263 : 246

Symphytognathidae

Symphytognathidae , the traditionally called “lungless” spiders, currently comprise 90 described species in eight genera. The internal respiratory system has been described or depicted for only six species representing four genera: Symphytognatha globosa ( Hickman, 1931: fig. 6; Forster, 1959: fig. 144), Patu samoensis ( Marples, 1951) , Anapistula secreta ( Forster, 1958) Anapistula australia , Patu vitiensis ( Forster, 1959: figs. 158 and 146, respectively), and Curimagua chapmani ( Forster & Platnick, 1977: fig. 22). The respiratory system of Symphytognatha picta was neither described nor illustrated, but scored in the morphological matrix of Lopardo and Hormiga (2015: characters 21–33). In their revision of the family, Forster and Platnick (1977) provided a summary of the respiratory system, including internal respiratory structures, at the generic level (i.e., for Anapistula , Curimagua , Globignatha , Patu , and Symphytognatha ). Additionally, some information, mostly regarding external spiracle location, was provided for 15 additional species within the genera Anapistula (nine species; Harvey, 1998; Cardoso & Scharff, 2009; Lin et al., 2009, 2013), Patu (two species; Lin & Li, 2009; Lin et al., 2009) and Crassignatha (four species; Lin & Li, 2009). Finally, four undescribed Patu species were scored and/or depicted in Forster (1959) and Lopardo and Hormiga (2015: figs. 114C, 117B, F, 120C, E). Summarizing, Symphytognathidae seem to comprise three different tracheal arrangements (Fig. 5, Table 1, and supplementary material), the most common one (present in all but one of the examined genera) consisting of anterior tracheae connected by a rigid transverse duct and entering the prosoma, and an absent posterior respiratory system. Anapistula and an undescribed species of Patu (from Western Samoa; see Forster, 1959) comprise a peculiar posterior tracheal system, similar to that of Mysmeninae and/or Synaphridae (see above), i.e., a wide and advanced tracheal spiracle consisting of two distant openings connected by a thin furrow. Internally, the tracheal arrangement consists of two bundles of seemingly lateral tracheae connected by an atrium and entering into the prosoma. The median tracheae/ entapophyses of Anapistula have not yet been observed. Lastly, we report a third tracheal arrangement observed in an undescribed Patu species from Dominican Republic, with a posterior tracheal system consisting of a single narrow posterior spiracle adjacent to the spinnerets, small atrium leading to two single lateral tracheae and a single unbranched (i.e., fused) seemingly median entapophysis ( Fig. 4b ). The respiratory system remains unknown for the genera Anapogonia , Crassignatha , and Iardinis .

Figures

Fig. 4 The respiratory system of symphytognathoid spiders. Dor- sal view. a Tasmanapis strahan (Anapidae), ARS with uncon- nected reduced book lungs and tracheal tubes arising from the leaves. b Patu-SYMP-001-DR (Symphytognathidae), overview of ARS and PRS, which con- sists of numerous tracheae. Note the single median entapophysis. c Coddingtonia euryopoides (Theridiosomatidae), overview of ARS and PRS. d Cepheia longiseta (Synaphridae), ARS with few tracheae and promi- nent transverse duct. Abbre- viations: aTt, anterior tracheal tubes; mE, median entapophy- sis; plT, posterior lateral tra- chea; rBL, reduced book lung; Sp, spermatheca; TD, transverse duct; Tt, tracheal tube