Muscular system in the interna of Polyascus polygenea and Sacculina pilosella (Cirripedia: Rhizocephala: Sacculinidae)

Abstract

Rhizocephala is a group of unique and highly specialized parasitic crustaceans. Due to specialization in endoparasitism adult rhizocephalans have lost almost all the traits of free-living crustaceans. Despite large amount of data on different aspects of their biology there is still insufficient knowledge of their interna morphology. The muscular system in interna has been found and described only for Peltogaster paguri from the family Peltogastridae. The aim of our study is to visualize and describe muscular system in the interna of Polyascus polygenea and Sacculina pilosella (family Sacculinidae). Representatives of both species have similar type of muscular system, which is significantly different from that in P. paguri. The muscular system of the sacculinids consists of muscular rosettes located within the body wall of each rootlet. Muscle fibers in these rosettes are oriented in different directions. Tiny muscular processes connect the rosettes to each other. These contractile elements form a joint net-like muscular system. We suggest that this muscular system provides peristaltic movement of the roots and transports nutrients within the interna.

Specialized structures on the border between rhizocephalan parasites and their host’s nervous system reveal potential sites for host-parasite interactions

“…We hypothesize that they also have different functions. We did not find any synaptic contacts between the host tissue and the cells www.nature.com/scientificreports www.nature.com/scientificreports/ of goblet-shaped organs, which agrees with the fact that we never observed the nervous system inside parasitic interna 44 . This suggests that the interaction with the host nervous system may be mediated by soluble molecules produced by non-neural but nevertheless specialized tissue of the parasite.…”

“…Molecular mechanisms for these interactions might be a promising direction of future studies. Interaction with the nervous system of the host is all the more fascinating as rhizocephalan interna has never been shown to have its own nervous system 44,45 . At the same time, its muscular system is well-developed 45 but it is unclear how it is innervated.…”

Detection of immune‐related enzyme activity, gene expression and metabolomic profiling in Chinese mitten crab Eriocheir sinensis parasitized by Polyascus gregaria

“…The parasite is highly specialized and consists of internae and externae, which are used for nutrition and reproduction respectively. The internae form rootlets and spread like a tree through various host tissues, such as the hepatopancreas, gill and muscle to absorb the nutrition (Høeg, 1995; Miroliubov et al, 2019). The externae, which exert reproductive functions (Hsiao et al, 2016; Mouritsen et al, 2018), are attached to the host's abdomen.…”

The Innate Immune Response to Infection by Polyascus gregaria in the Male Chinese Mitten Crab (Eriocheir sinensis), Revealed by Proteomic Analysis

“…Due to the commercial value of this species, intensive cultivation became popular after the 1950s [3] from the Yangtze River. Along with the rapid development of the large-scale aquaculture of these crabs are frequent outbreaks of viruses, bacteria, rickettsia-like organisms, and parasites, all of which have led to catastrophic economic losses for Chinese mitten crab farmers [4,5]. These infections can also cause remarkable morphological, physiological, and behavioral changes in the host [6].…”

“…Recently, several studies were published on Sacculinidae ecology [30,31], the histopathology and immune response in Carcinus maenas [22], the effects on the muscular system in Hemigrapsus sanguineus [5], and the molecular mechanisms of infection in Scylla olivacea [32]. Studies have specifically addressed the disease ecology of P. gregaria [33], its phylogenetic relationships [19], as well as the description of its morphological adaptation to parasitism in Hemigrapsus sanguineus [34].…”