Mesochirozetes, , Heller, 1931

Tseng, Wei-Zhe, Hsiao, Yun, Cabras, Analyn & Cheng, Ren-Chung, 2024, Positive association between PTN polymorphisms and schizophrenia in Northeast Chinese Han population., Zoological Studies 63 (49), pp. 141-149 : 10-11

Mesochirozetes is raised to full generic level

Our phylogenetic analyses reveal a polyphyletic relationship between two subgenera of Chirozetes (the nominal subgenus and Mesochirozetes ), and support a sister affinity between Mesochirozetes and Pempheres ( Fig. 1 ). This result highlights the need for a proper taxonomic treatment of Mesochirozetes to ensure the monophyly of genus Chirozetes . Mesochirozetes is a monotypic subgenus of Chirozetes established based on its type species, Chirozetes (Mesochirozetes) formosanus Heller , collected in Kosempo, Southern Taiwan. In the original description of Mesochirozetes, Heller (1931) designed an identification key to distinguish this subgenus from the nominal subgenus Chirozetes and the genera Daedania and Pempheres . According to his classification, Daedania and Pempheres exhibit obtuse, wedge-shaped elytra [Flügeldecken stumpf keilförmig], whereas Chirozetes and Mesochirozetes have elytra that are somewhat cylindrical with obtusely-rounded apex [Flügeldeckenziemlich walzenförmig, hinten stumpf verrundet]. However, some Chirozetes species also exhibit a wedge-shaped elytra (e.g., C. lineolatus as shown in the figure 1 of Heller 1924), suggesting that elytral shape may not be suitable for distinguishing Chirozetes from Daedania and Pempheres .

Furthermore, the sexually dimorphic characteristics of Mesochirozetes are distinct from Chirozetes but similar to Pempheres . Specifically, males of Mesochirozetes and Pempheres , except for P. picta Heller (known from a single female specimen), do not exhibit prosternal spines ( Fig. 3B–D ) and hairs on the ventral side of protarsi, which are present in the males of Chirozetes species ( Fig. 3A ). The sexual dimorphism of both taxa present in the abdomen, where males of Mesochirozetes and Pempheres species have canaliculate structures in the middle of ventrites ( Fig. 4B–D ), whereas Chirozetes lacks such abdominal canaliculate structures ( Fig. 4A ). Heller described this character in Pempheres ( Heller 1894: 12) and Mesochirozetes ( Heller 1931: 109) , but never recognized it as a diagnostic characteristic for either taxon. However, despite the morphological similarity between Mesochirozetes and Pempheres , we still observed characteristics that differ between Mesochirozetes and Pempheres species. For example, Mesochirozetes has two canaliculate structures in ventrites I and V ( Fig. 4B ), while Pempheres species have a single structure in ventrite I ( Fig. 4C–D ). The relative length of the first two antennomeres also differs, which Pempheres species exhibit antennomere 2 twice as long as 1, while antennomere 2 of Mesochirozetes is as long as, or slightly longer than 1. Based on the results of phylogenetic analyses and morphological examinations, we propose raising the subgenus Mesochirozetes to full generic level to maintain the monophyly of Chirozetes .

Additionally, we modified the diagnoses of Pempheres and Mesochirozetes , after Pascoe (1871) and Heller (1894 1931). The sexually dimorphic characteristics are important diagnoses for both genera, including the males without prosternal spines and hairs on the ventral side of protarsi, and with canaliculate structures on ventrites. The number of canaliculate structures can further distinguish Pempheres and Mesochirozetes , where Pempheres has a single structure on ventrite I while Mesochirozetes has two on ventrites I and V. Antennal funicles are also crucial to distinguish both genera. Pempheres species have antennomere 2 twice as long as 1, while the antennomere 2 of Mesochirozetes is equal to, or slightly longer than 1. Two diagnostic characteristics for Pempheres , namely the sinuated protibia and proximity of antennal scape to rostral base, are not suitable for distinguishing this genus. We find that the protibia is straight in all described species ( Fig. 2A–C ) and the proximity between scape and rostral base is common in mecopine genera, such as Mecopus , Mecopomorphus Hustache, 1920 and Neomecopus Hustache, 1921 . Therefore, we propose excluding these characters from the diagnosis of Pempheres .

Figures

Fig. 1. Phylogenetic tree based on four molecular markers. The node support is presented with bootstrap values (left) and posterior probability (right) under each branch. Mecopine species are highlighted, and the head morphologies of three species are illustrated on the right.

Fig. 3. Comparison of male prosternum of Chirozetes, Mesochirozetes and Pempheres spp. Males of Chirozetes exhibit distinct prosternal spines, where Mesochirozetes and Pempheres do not. A, Chirozetes arotes Heller, 1915; B, Mesochirozetes formosanus (Heller, 1931); C, Pempheres habena Pascoe, 1871; D, Pempheres trilineata Pascoe, 1871. Photo credits: D, Keita Matsumoto (NHMUK).

Fig. 4. Comparison of male abdomens of Chirozetes, Mesochirozetes and Pempheres spp. Males of Mesochirozetes and Pempheres exhibit distinct canaliculate structures, where Pempheres occurs on ventrite I, while Mesochirozetes on ventrite I and V. A, Chirozetes arotes Heller, 1915; B, Mesochirozetes formosanus (Heller, 1931); C, Pempheres habena Pascoe, 1871; D, Pempheres trilineata Pascoe, 1871. Photo credits: D, Keita Matsumoto (NHMUK).

Fig. 2. Type specimens of Pempheres and Mesochirozetes in dorsal view. A, lectotype of Pempheres trilineata Pascoe, 1871; B, lectotype of Pempheres habena Pascoe, 1871; C, holotype of Pempheres picta Heller, 1894; D, lectotype of Chirozetes (Mesochirozetes) formosanus Heller, 1931. Photo credits: A–B, Keita Matsumoto (NHMUK); C, Roberto Poggi (MSNG).