Data from: Description of two new species of Indo-Pacific Thylacoplethus and a new record of Thompsonia japonica (Rhizocephala: Akentrogonida: Thompsoniidae) from hermit, porcelain and mud crabs (Decapoda) based on morphological and molecular data

Rhizocephalans of the order Akentrogonida are parasitic barnacles that infest decapods, stomatopods, peracarids, and other cirripedes. Within this order, Thompsoniidae is found in decapods and stomatopods, and is a family comprised of species characterized by having multiple globular reproductive bodies (externae) erupting from the host’s extremities and abdominal surface, and connected internally by a root-like system. Two of the four genera currently accepted within Thompsoniidae, Thompsonia and Thylacoplethus, contain perhaps the most morphologically derived species within Akentrogonida. Herein we describe two new species of Thylacoplethus, T. porcellanus and T. umanguvatus, from the porcellanid and hermit crabs Petrolisthes scabriculus (Dana, 1852) and Calcinus morgani Rahayu and Forest, 1999, respectively. We also redescribe Thompsonia japonica Häfele, 1911 from a xanthid brachyuran crab based on morphological characters and DNA sequences of the nuclear 18S rDNA gene. The new species from the porcellanid crab comprises the first record of an akentrogonid rhizocephalan parasitizing a species of Porcellanidae. We reconstruct a molecular phylogeny of Akentrogonida using new and published DNA sequences, and we discuss our findings within an evolutionary context of host speciation. All species in the four thompsoniid genera are briefly reviewed, and a replacement name is proposed for the preoccupied Pottsia Høeg and Lützen, 1993.

无吻根头目（Akentrogonida）的根头类寄生藤壶，为寄生于十足目、口足目、囊虾类及其他蔓足类宿主的寄生性蔓足动物。该目下的汤普森科（Thompsoniidae）仅寄生于十足目与口足目宿主，其类群的典型特征为：多枚球状生殖外突（externae）从宿主肢体及腹部体表钻出，内部以根状系统相互连接。目前汤普森科（Thompsoniidae）公认的4个属中，汤普森藤壶属（Thompsonia）与囊梗藤壶属（Thylacoplethus）包含了无吻根头目（Akentrogonida）中形态特化程度最高的物种。本文记述了囊梗藤壶属（Thylacoplethus）的2个新种：T. porcellanus与T. umanguvatus，它们分别采自粗糙瓷蟹（Petrolisthes scabriculus，Dana, 1852）与摩根寄居蟹（Calcinus morgani，Rahayu & Forest, 1999），二者宿主分别为瓷蟹科与寄居蟹类物种。本研究还基于形态特征与核18S核糖体DNA基因的DNA序列，重新记述了采自斜纹蟹科短尾蟹宿主的日本汤普森藤壶（Thompsonia japonica，Häfele, 1911）。此次采自瓷蟹的新种，是无吻根头类寄生瓷蟹科（Porcellanidae）物种的首个正式记录。本研究利用本次新获得及已发表的DNA序列，重建了无吻根头目（Akentrogonida）的分子系统发育树，并结合宿主物种形成的演化背景对研究结果进行了讨论。本文对汤普森科（Thompsoniidae）4个属的所有物种进行了简要综述，并为被占用学名的Pottsia属（Høeg & Lützen, 1993）提出了替代学名。