Teratological changes in postembryos of Eratigena atrica obtained by the application of alternating temperatures on spider embryos

Abstract

Spider embryonic development depends on several factors, including temperature. Under optimum thermal conditions embryogenesis proceeds undisturbed and embryo mortality is low. On the other hand, dramatic shifts in incubation temperature may cause a range of developmental defects in embryos. It has been confirmed in numerous laboratory experiments that abrupt temperature changes can be a powerful teratogenic factor. Changes in the external structure are frequently reflected in the internal anatomy, and above all, in the central nervous system. In the present teratological study, by exposing spider embryos to the temperatures of 14 °C and 32 °C, changed every 12 hours for the first 10 days of their development, we obtained 74 postembryos of Eratigena atrica with body deformities such as oligomely, heterosymely, schistomely, bicephaly, complex anomalies and others. We selected six spiders to describe and analyze their morphological changes. In one case, that of a spider affected by polymely (the presence of a supernumerary appendage) combined with heterosymely (the fusion of walking legs), we also focused on the structure of the central nervous system. The analysis indicated that this complex anomaly was accompanied by only one change in the central nervous system: the presence of a supernumerary neuropil. Since no fusion of walking leg neuropils was observed, it was concluded that, in this instance, there was no relationship between the fusion of legs and the structure of the central nervous system.

Keywords: Deformities; Eratigena atrica; Incubation temperature; Spider; Teratology.

Figure 1. Eratigena atrica postembryo from control group.

(A) Ventral view: (C) chelicerae; P, pedipalps, L1–L4, walking legs; (B–D) horizontal sections through the prosoma, brain (B) and ventral nerve cord (C, D): n, neuropil; n1–n4, neuropils of walking legs; np, neuropils of pedipalps.

Figure 2. Eratigena atrica postembryos with teratogenic changes.

(A) Ventral view: postembryo with bilateral oligomely and a protuberance in place of the right chelicera; (B) dorsal view: postembryo with a protuberance in place of the right pedipalp; (C ) ventral view: postembryo with oligomely of the walking legs, schistomely of the left pedipalp, and a protuberance between the pedipalp and walking leg; (D) ventral view: postembryo with oligomely of the walking legs on the right side of the prosoma and schistomely of the first left walking leg; (E) dorsal view: bicephalous postembryo with additional, well-developed walking legs between two heads; (F) ventral view: bicephalous postembryo with additional, partially fused walking legs between two heads; A, protuberance; C, chelicera; L, L/L, L1–L4, walking legs; P, pedipalp; white lines indicate the heads of bicephalous postembryos.

Figure 3. Eratigena atrica postembryo with complex anomaly.

(A) Dorsal view: a, deformed appendage; L1, L2A/2B, free ends of fused walking legs; P, pedipalps; L1–L4, walking legs; (B–D) horizontal sections through the prosoma, brain (B) and ventral nerve cord (C, D) (right side abnormal, left side normal): a, fused part of the legs; n1, n2A (C) and n2B (D), neuropils of heterosymelic legs; n1–n4, neuropils of the well-formed walking legs; np, neuropils of pedipalps; n, neuropil.