Contributions to the taxonomy of the long-jawed orb-weaving spider genus Tetragnatha (Araneae, Tetragnathidae) in the Neotropical region, with comments on the morphology of the chelicerae

Abstract

We newly diagnose, illustrate, and clarify the distribution ranges of six of the most common and broadly distributed species of Tetragnatha Latreille, 1804 found in the Neotropical region. Twenty new junior synonyms from around the world are included, nine for T. bogotensis Keyserling, 1865, four for T. mandibulata Walckenaer, 1841, three for T. keyserlingi Simon, 1890, three for T. nitens (Audouin, 1826), and one for T. elongata Walckenaer, 1841. Tetragnatha vermiformis Emerton, 1884 is newly recorded from South America. The Argentine T. major Holmberg, 1876 and T. riparia Holmberg, 1876 are considered nomina dubia. Finally, we discuss the terminology of the structures of the chelicerae to establish a coherent nomenclature for teeth and fang cusps.

Do exaggerated chelicerae function as weapons or genitalia in a long‐jawed spider? Functional allometric analysis yields an answer

“…Illustration of cheliceral embrace with female on the left and male to the right side (b) and chelicerae for female (c) and male (d). Male fang (mf), female fang (ff), dorsal male apophysis (a), elongated tooth (T), auxiliary guide tooth lower surface (AXl), auxiliary guide tooth upper surface (AXu), guide tooth lower surface (Gl), guide tooth upper surface (Gu), first denticle after guide tooth upper surface of females (U2), first denticle after guide tooth upper surface of males (sl), nomenclature after Castanheira, Baptista, Pizzetti, & Teixeira (2019). Black arrow shows major curve in female fang.…”

“…The male fang clasps the basal segment of the female chelicera and rests alongside guide (Gl) and auxiliary guide (AXl) teeth (Castanheira, Baptista, Pizzetti, & Teixeira, 2019) which are stubby denticle‐like projections on the distal portion of the basal segment of the female chelicera near the fang base (Figures 1e and 2c–d). The curve in the male fang is much less pronounced than that observed in females; consequently, less of the male fang contacts the basal segment of the female chelicera.…”

“…Specimens used in the figures were photographed under a Zeiss Stemi‐2000 dissecting microscope and were used to determine the parts of the chelicerae that made contact during mating. The description of the chelicerae follows Castanheira, Baptista, Pizzetti, and Teixeira (2019) and we use the same terminology here to describe the male dorsal apophysis, guide teeth, auxillary guide teeth, and other cheliceral traits.Behavioral measures of mechanical mesh were analyzed with the help of a natural mutant who had malformed chelicerae. In the summer of 2011, we collected a male whose basal segment of the chelicera bore a stunted and malformed version of the large dorsal apophysis (that engages the female's fang) found on the dorsal surface of the basal segment of the chelicera in adult males.…”

“…On the opposite side of the basal segment of the male chelicera there is an elongated tooth (T) in the upper row of denticles that touches the distal part of the basal segment of the female chelicerae located opposite from the fang base ( Figures 2b-d and 3c). The T structure The male fang clasps the basal segment of the female chelicera and rests alongside guide (Gl) and auxiliary guide (AXl) teeth (Castanheira, Baptista, Pizzetti, & Teixeira, 2019) which are stubby denticle-like projections on the distal portion of the basal segment of the female chelicera near the fang base (Figures 1e and 2c-d). The curve in the male fang is much less pronounced than that observed in females; consequently, less of the male fang contacts the basal segment of the female chelicera.…”

“…Tetragnatha species with short chelicerae (e.g., T. vermiformis in Castanheira, Baptista, Pizzetti, & Teixeira 2019). This fang foreshortening may allow the female to more speedily open the basal segment of her elongated chelicera and swing out her fangs to capture prey.…”