New data on tardigrades of the genus Milnesium (Tardigrada, Eutardigrada, Milnesiidae) from the Russian Far East, obtained using the method of molecular barkoding

A study of terrestrial tardigrades of the genus Milnesium Doyère, 1840 collected in Russky Island (Primorsky kray, Vladivostok) was carried out using the methods of integrative taxonomy, including the analysis of morphological and molecular biological data. Three species are recorded from this island, of which M. inceptum Morek, Suzuki, Schill, Georgiev, Yankova, Marley et Michalczyk, 2019 is new for the fauna of Russia. New data were obtained on the distribution and genetic diversity of M. tardigradum Doyère, 1840. The third species, Milnesium sp., is similar to M. tardigradum but differs from latter in the presence of a characteristic thickened cuticle zone at the base of the claws of the fourth pair of legs and is probably a new for science species.

Changes in Winter Squash Fruit Exocarp Structure Associated with Age-Related Resistance to Phytophthora capsici

Phytophthora capsici is a destructive pathogen of cucurbits that causes root, crown, and fruit rot. Winter squash (Cucurbita spp.) production is limited by this pathogen in Michigan and other U.S. growing regions. Age-related resistance (ARR) to P. capsici occurs in C. moschata fruit but is negated by wounding. This study aimed to determine whether structural barriers to infection exist in the intact exocarp of maturing fruit exhibiting ARR. Five C. moschata cultivars were evaluated for resistance to P. capsici 10, 14, 16, 18, and 21 days postpollination (dpp). Scanning electron microscopy imaging of Chieftain butternut fruit exocarp of susceptible fruit at 7 dpp and resistant fruit at 14 and 21 dpp revealed significant increases in cuticle and epidermal thicknesses as fruit aged. P. capsici hyphae penetrated susceptible fruit at 7 dpp directly from the surface or through wounds before 6 h postinoculation (hpi) and completely degraded the fruit cell wall within 48 hpi. Resistant fruit remained unaffected at 14 and 21 dpp. The high correlation between the formation of a thickened cuticle and epidermis in maturing winter squash fruit and resistance to P. capsici indicates the presence of a structural barrier to P. capsici as the fruit matures.

Traumatic insemination and female counter-adaption in Strepsiptera (Insecta)

Traumatic insemination in Strepsiptera is a disputed issue. To clarify this question the mating of Stylops ovinae (Stylopidae) was documented in detail using a combination of different techniques. A major issue is the specific mode of sperm transfer, either as a traumatic penetration of the body wall, or alternatively an insertion of the penis into the brood canal without penetration of the body wall of the female. In contrast to previous studies, we used an integrative approach. In addition to video recordings of the mating, the duration and frequency of copulation were assessed. Histological sections of virgin females and females fixed shortly after copulation were made. Micro-CT scans of fixed copulae of S. ovinae were taken and the involved structures were studied with scanning electron microscopy and reconstructed three dimensionally. We could demonstrate that an invagination with a thickened cuticle is present, directly in front of the birth opening of the female. The male inserts his penis in this invagination and its apical part perforates the ventral cuticle. Thereafter the sperm is injected into the hemocoel of the female and reaches the oocytes via the hemolymph. The invagination is a secondary genital structure, similar to the spermalege of the common bedbug Cimex lectularius (Heteroptera).

Description of Aphelenchoides rotundicaudatus n. sp. (Nematoda: Aphelenchoididae) found in packaging wood from South Korea

Aphelenchoides rotundicaudatus n. sp. was isolated from packaging wood from South Korea imported to Ningbo harbour, China. Specimens were collected directly from wood samples using the Baermann method. Multiplication on Botryotinia fuckeliana failed. The new species has a body length of 364-509 μm (males) and 371-493 μm (females). The cuticle is weakly annulated and there are four lines in the lateral field. The stylet is 8-9 μm long and has small basal swellings. The excretory pore is located ca one body diam. anterior to median bulb. Spicules are small (10-13 μm), apex and rostrum rounded and only slight offset. The male tail has six (2 + 2 + 2) caudal papillae. Both male and female tails are cylindrical with a broadly rounded terminus, often with a small region of thickened cuticle or a blunt peg ca 1 μm long, particularly in the female. The new species belongs to the Group 1 category of Aphelenchoides species. Phylogenetic analyses based on full length ITS, partial LSU and SSU of rDNA confirmed its status as a new species.

The fine structure and function of the cephalic appendages of the branchiuran parasite, Argulus japonicus Thiele

The fish parasite Argulus japonicus Thiele (Crustacea: Branchiura) has recently been introduced into Britain and is now established in the wild. A. japonicus , an ectoparasite attaching to, and feeding on, the skin of its host, is a potentially serious pathogen of native freshwater fishes. The anatomy of the attachment and feeding structures is described using light and electron microscopy. The primary attachment organs are the suckers derived from the maxillules. The extrinsic musculature of the suckers comprises two major muscle groups: the suction muscles which insert on the floor of the sucker and generate suction, and the cup muscles which control the orientation and movement of the sucker as a whole. The inner wall of the sucker cup comprises two hoops of thickened cuticle and provides the rigidity necessary to prevent the sucker from collapsing. These hoops are hinged to allow extra movement of the distal hoop plus its marginal m em brane when forming a seal onto the surface of the host. Numerous mucous glands are present in the floor of the sucker. The elongate mouth tube represents a ventral outgrowth of the head bearing a small labrum and labium distally. The homology of the labium is confirmed by the arrangement of its paired muscles, which originate on the undersurface of the ventral cephalic tendon and pass down through channels in the suboesophageal ganglion. The labrum lacks muscles. The ontogeny of the mouth tube, the adult m andibular musculature and the possible feeding mechanism are described. The preoral spine lies in the ventral midline of the body anterior to the mouth tube. It consists of a tapering spine carried on a long eversible sheath. When fully retracted the spine and sheath virtually disappear into the body. As the spine retracts the cuticle of the proximal sheath becomes inverted. The epithelium beneath this sheath cuticle is syncytial and is separated from the cuticle-lined, central duct of the spine by a fluid matrix which can be displaced as the spine is retracted. The fluid matrix appears to be secreted by the epithelial cells of the sheath cuticle. Retraction is by means of paired retractor muscles which originate dorsal to the midgut and pass down through the nerve ring. These muscles shorten to about 25% of their maximum length during extreme retraction.

Canadian species of Merlinius Siddiqi, 1970 and a diagnosis and description for Mulveyotus hyalacus n. gen., n. sp. (Nematoda: Tylenchorhynchidae)

Three new bisexual species of Merlinius Siddiqi, 1970, characterized by apically flattened heads and elongate–conoid tails with narrowly rounded or pointed ends, and a new genus and species (Tylenchorhynchidae) in Canada are described and illustrated. The distinguishing female characters of Merlinius plerorbus n. sp. are the constricted head, 16- to 17-μm-long stylet, 45- to 54-μm-long tail with 38–40 annules and a smoothly rounded terminus, and lobed spermathecae. Diagnostic for females of Merlinius circellus n. sp. are the continuous low head, 9- to 10-μm-long stylet, tail with 72–75 annules and a pointed terminus, and spherical spermathecae. The female of Merlinius tetylus n. sp. has a stylet length of 14 μm, a 98-μm-long tail with about 100 fine annules, and lobed spermathecae. Supplemental descriptive data for M. processus Siddiqi, 1979, a new species record for Canada, is provided, and included in a key to the species of Merlinius. Merlinius laminatus (Wu, 1969) Siddiqi, 1970 is transferred as a new combination to Scutylenchus Jairajpuri, 1971. Differential characters of Mulveyotus hyalacus n. gen., n. sp., are a body length of over 1 mm, alow, flattened continuous head, an areolated lateral field of three incisures, and a conoid tail over 100 μm long with a tapered smooth terminus of thickened cuticle comprising 24% of the tail length.