First records and three new species of the family Symphytognathidae (Arachnida, Araneae) from Thailand, and the circumscription of the genus Crassignatha Wunderlich, 1995

Systematic notes on three troglobitic Anapistula (Araneae, Symphytognathidae) spiders from China, with the descriptions of two new species

Three cave-dwelling spider species belonging to the family Symphytognathidae Hickman, 1931, i.e., Anapistulasanjiao sp. nov. (♂♀), A.walayaku sp. nov. (♂♀), and A.panensis Lin, Tao & Li, 2013 (♂♀), are reported from southwest China. DNA sequences and detailed illustrations of the habitus, male palps and epigynes are provided, and their distributions are mapped. Their phylogenetic position within symphytognathids and relationships were tested and assessed using previously published phylogenetic analyses on symphytognathoids. The results showed that they form a clade with A.choojaiae Rivera-Quiroz, Petcharad & Miller, 2021 from Thailand.

Micro-CT visualization of the CNS: Performance of different contrast-enhancing techniques for documenting the spider brain

Spider brain and central nervous system (CNS) have remained unexplored, due in part to the difficulty of observing these organs, usually only possible through histological preparations. Recently, internal anatomy studies have been supplemented by the inclusion of X‐ ray micro‐CT. Unmineralized tissue such as the body of invertebrates requires a staining process to enhance tissue X‐ray absorption and improve contrast during observation. Many current protocols are based on iodine staining requiring critical point drying (CPD) of the sample for optimal contrast. This process induces shrinking of the soft tissue generating artifacts in the morphology, volume, and even position of internal structures. Phosphotungstic acid (PTA) is an alternative staining agent recently used in marine invertebrate and plant studies. Here, we used several specimens of the common spider Araneus diadematus to visualize the spider brain and compare both contrast‐enhancing ethanol‐based solutions. We assessed a gradient of staining times, observed and tested the repercussions of CPD, and examined the use of vacuum to accelerate PTA diffusion. We show that PTA provides the best contrast on micro‐CT scans in ethanol eliminating the need for CPD, and offering more realistic in situ visualizations of the internal organs. In combination with different scanning settings, PTA allowed observation of internal organs like the CNS, digestive system, muscles, and finer structures like the retina, visual nerves, and optic neuropiles. This fast and less invasive method could facilitate the proper documentation of the internal anatomy in the context of evolutionary, developmental and functional studies.

Taxonomic study on fourteen symphytognathid species from Asia (Araneae, Symphytognathidae)

Fourteen symphytognathid species belonging to three genera are examined, including the descriptions of eight new species and two new genera from China, Vietnam, Thailand and Myanmar: Patu Marples, 1951: P.catba S. Li & Lin, sp. nov. (♂, Vietnam), P.dakou S. Li & Lin, sp. nov. (♂♀, China), P.damtao S. Li & Lin, sp. nov. (♂, Vietnam), P.jiangzhou S. Li & Lin, sp. nov. (♀, China), P.jidanweishi Miller, Griswold & Yin, 2009 (♂♀, China), P.nagarat S. Li & Lin, sp. nov. (♂♀, Thailand), P.nigeri Lin & S. Li, 2009 (♀, China), P.putao S. Li & Lin, sp. nov. (♀, Myanmar), P.qiqi Miller, Griswold & Yin, 2009 (♀, China) and P.xiaoxiao Miller, Griswold & Yin, 2009 (♂♀, China); Kirinua S. Li & Lin, gen. nov.: K.maguai S. Li & Lin, sp. nov. (♂♀, China) and K.yangshuo S. Li & Lin, sp. nov. (♂♀, China); Swilda S. Li & Lin, gen. nov.: S.longtou (Miller, Griswold & Yin, 2009), comb. nov. (♂♀, China) is transferred from Crassignatha Wunderlich, 1995 and S.spinathoraxi (Lin & S. Li, 2009), comb. nov. (♂♀, China) is transferred from Patu. Diagnoses, descriptions and illustrations are provided for new taxa, as well as a distribution map. The males of P.xiaoxiao and S.longtou are described for the first time. Type specimens of P.jidanweishi, P.nigeri, P.qiqi, P.xiaoxiao, S.longtou and S.spinathoraxi are re-examined and photographed. All Asian Patu species are revised and two species, P.kishidai Shinkai, 2009 and P.bispina Lin, Pham & S. Li, 2009, are transferred to Crassignatha and proposed as new combinations: Crassignathakishidaicomb. nov. and C.bispinacomb. nov. In addition, DNA barcodes and genetic distances of ten species treated in this paper were obtained to confirm identification.

Old Brains in Alcohol: The Usability of Legacy Collection Material to Study the Spider Neuroarchitecture

Natural history collections include rare and significant taxa that might otherwise be unavailable for comparative studies. However, curators must balance the needs of current and long-term research. Methods of data extraction that minimize the impact on specimens are therefore favored. Micro-CT has the potential to expose new character systems based on internal anatomy to taxonomic and phylogenetic analysis without dissection or thin sectioning for histology. However, commonly applied micro-CT protocols involve critical point drying, which permanently changes the specimen. Here, we apply a minimally destructive method of specimen preparation for micro-CT investigation of spider neuroanatomy suitable for application to legacy specimens in natural history collections. We used two groups of female spiders of the common species Araneus diadematus—freshly captured (n = 11) vs. legacy material between 70 and 90 years old (n = 10)—to qualitatively and quantitatively assess the viability of micro-CT scanning and the impact of aging on their neuroarchitecture. We statistically compared the volumes of the supraesophageal ganglion (syncerebrum) and used 2D geometric morphometrics to analyze variations in the gross shape of the brain. We found no significant differences in the brain shape or the brain volume relative to the cephalothorax size. Nonetheless, a significant difference was observed in the spider size. We considered such differences to be explained by environmental factors rather than preservation artifacts. Comparison between legacy and freshly collected specimens indicates that museum specimens do not degrade over time in a way that might bias the study results, as long as the basic preservation conditions are consistently maintained, and where lapses in preservation have occurred, these can be identified. This, together with the relatively low-impact nature of the micro-CT protocol applied here, could facilitate the use of old, rare, and valuable material from collections in studies of internal morphology.