Subterminal Setae Research Articles

Two new species of the family Tobrilidae (Nematoda: Triplonchida) from West Bengal, India

The article presents the first records of the genera Epitobrilus Tsalolikhin, 1981 and Eutobrilus Tsalolikhin, 1981 (Triplonchida: Tobrilidae), along with the description of two new species, Epitobrilus brachystomus sp. nov. and Eutobrilus minutus sp. nov., from paddy fields in West Bengal, India. Epitobrilus brachystomus sp. nov. differs from the congeners in having a relatively shorter stoma, distinct crustaformeria cells at the oviduct–uterus junction, five to six setae including a subterminal one in the tail region, and a longer tail with a distinct cuticular protrusion at the tip. Eutobrilus minutus sp. nov. can be distinguished from Eu. husmanni (Altherr, 1958) by the differences in the body size, the distance between the stomatal pockets, the tail length, and the presence of a subterminal setae. From another closely related species, Eu. nothus Gagarin, 1989, it differs in the ratio of the body length to the tail length (c), the tail length relative to its diametre (c′), the distance from the vulva to the anterior body end (V %), and in the distance between the stomatal pockets.

A NEW FREE-LIVING NEMATODE GENUS TETRATOBRILUS GEN. NOV. (TRIPLONCHIDA: TOBRILIDAE) FROM WEST BENGAL, INDIA

A new free-living nematode Tetratobrilus dentatus gen. nov. sp. nov. under family Tobrilidae Filipjev, 1918 of the order Triplonchida Cobb, 1919 is described from a drowned paddy field soil (mud) in West Bengal, India. It is characterized by heavily sclerotized walls of anterior portion of the buccal cavity, a small dorsal tooth and two sub-ventral stomatal pockets longitudinally, one following another. The first pocket is fused with the posterior portion of the stoma, similar to the genus Epitobrilus, but differs in the presence of two adjacent teeth (vs. one) in the first pocket. The second pocket contains only one tooth. It also possesses smaller anterior setae (less than 40% of head diameter) and a subterminal setae. Males bear six characteristic pitcher-shaped supplements. Comprehensive details regarding the morphological structures, accompanied by figures and morphometric measurements, are presented in this report. An updated key to the genus and other genera of family Tobrilidae is also provided. Key Words: Stomatal pockets, sub-ventral teeth, Tobrilidae, new genus, new species

The first record larvae of the genus Peltogaster (Rhizocephala: Peltogastridae) with eyes and unilobed male aesthetasc

The complete larval development of Peltogaster lineata Shiino, 1943 (Rhizocephala: Peltogastridae), including five nauplii and one cypris stage, is described and illustrated using SEM. The development took 3.5–4 days at a water temperature of 22–23 °C. Peltogaster lineata has the peltogastrid type of development. Nauplii possess a large and clearly reticulated flotation collar, six pairs of dorsal shield setae with the U-shaped second pair, long segmented frontolateral horns each with two subterminal setae, and a long seta at the antennal basis. The attachment disc in female cyprids has a flap-like extension at the posterior margin. Cyprids of both sexes possess two sensory setae at the attachment disc. The large male aesthetasc is unilobed, the female subterminal aesthetasc terminates into two thin long filamentous processes. Larvae of P. lineata have distinctly visible nauplius eyes.

<i>Hofmaenneria baikalensis</i> sp. n. and <i>Paratrilobus longisomus</i> sp. n. (Nematoda) from Lake Baikal

Illustrated descriptions of two new species of free-living nematodes Hofmaenneria baikalensis sp. n. and Paratrilobus longisomus sp. n. found in the Lake Baikal (Russia) are given. Hofmaenneria baikalensis sp. n. is close to H. keoladeoensis Khan et al., 2005, H. niddensis (Skwarra, 1921) Schneider, 1940 and H. sitnikovae Gagarin, Naumova, 2010. It differs from these three species in a presence of crystals in the body cavity and presence of three oval cardial glands. Paratrilobus longisomus sp. n. is close in the body size to P. expugnator (Tsalolichin, 1976) and P. rapis Gagarin, 1991 but it has a relatively shorter and slenderer tail and presence of subterminal seta at the tail end.

Two new species, Parabathylaimus gracilis sp. nov. and Belbolla sinica sp. nov. (Nematoda: Enoplida), from Yangma Island of the Yellow Sea, China

Two new species Parabathylaimus gracilis sp. nov. and Belbolla sinica sp. nov. are described from Yangma Island, Yellow Sea. Parabathylaimus gracilis sp. nov. is characterized by six outer labial setae three-jointed, inner labial setae and cephalic setae unjointed, amphidial fovea unispiral with circular aperture and positioned at middle of buccal cavity, spicules paired and slightly curved, gubernaculum kidney-like and distal end heavily cuticularized with a pointed projection, tail conical without long subterminal setae. Belbolla sinica sp. nov. is characterized by short body length, posterior pharynx region with seven bulbs, spicules straight with proximal and distal end tapered and middle part thickened, gubernaculum short without apophysis, two small wing-shaped precloacal supplements well developed, tail conico-cylindrical with cylindrical portion short.

Leptostracans (Crustacea: Phyllocarida) from mud volcanoes at the Gulf of Cadiz (NE Atlantic) with description of a new species of Sarsinebalia Dahl, 1985

Three leptostracan species (Crustacea: Phyllocarida) are reported from mud volcanoes at the Moroccan margin of the Gulf of Cadiz (NE Atlantic). Nebalia strausi Risso, 1826 and N. abyssicola Fage, 1929 were found in experimentally deployed organic substrates in Mercator, Meknès and Darwin mud volcanoes; N. abyssicola was also found among bathymodiolin bivalves and is recorded for the first time in the Atlantic Ocean. The third species was collected from the Gemini mud volcanoes and is described herein as Sarsinebalia ledoyeri sp. nov. The new species is characterised by having the eyes provided with ommatidia and lacking pigment, the ventral margin of the eye is concave along distal half, the antennular scale is more than twice as long as wide, the second article of the mandibular palp bears one seta on lateral surface about 0.5 times as long as the article and one subterminal seta longer than the third article, the distal article of the maxilla II endopod is about 1.8 times as long as the proximal article, the maxilla II exopod is clearly longer than the endopod proximal article, the lateral margin of the pleopod I exopod lacks setae and the posterodorsal border of pleonites VI–VII is provided with rounded to pointed denticles.

Two new nematode species of the genus Paratrilobus Micoletzky, 1922 (Nematoda, Triplonchida) from the water area of Lake Baikal (Russia)

This paper describes and illustrates two new nematode species of the genus Paratrilobus Micoletzky, 1922. The species Paratrilobus tankhoyensis sp. nov. was found at the estuary of the Pereyomnaya River (water area of Lake Baikal, near the Tankhoy railway station). Paratrilobus tankhoyensis sp. nov. is most similar to P. expugnator (Tsalolichin, 1976) in the body size, but differs in the comparatively thin body, shorter and thicker tail, shorter stoma and spicules. Another new species, Paratrilobus aquaticus sp. nov., was found in Posolsk Bank (natural underwater elevation of the bottom between the southern and central basins of Lake Baikal). The species is similar to P. granulosus Gagarin & Naumova, 2011 and P. ultimus (Tsalolichin, 1977) in the structure of the precloacal supplements. It differs from the former in the absence of crystalloids, a comparatively longer pharynx, longer stoma and outer labial setae as well as the absence of subterminal seta. It differs from the latter in a longer pharynx, stoma and longer outer labial setae as well as a longer and more slender tail. We also discuss diagnostic features of the males of the genus Paratrilobus.

Spelaeobochica mahnerti, a new cave-dwelling pseudoscorpion from Brazil(Arachnida: Pseudoscorpiones: Bochicidae), with comments on thetroglomorphism of the Brazilian bochicid species.

Spelaeobochica mahnerti sp. n., found in a limestone cave located in the municipality of Monjolos (Minas Gerais state, Southeastern Brazil), is described. It differs from congeneric species mainly by the rallum with 3 apically dentate blades, the position of the trichobothrium ib in the far distal half of the hand dorsum (near the base of fixed finger), the smooth subterminal setae, and by the arolia that are a little longer than the claws. A key to the species of Spelaeobochica is provided, as well as information on the habitat and threats for this new species. We further discuss troglomorphic traits in Brazilian species of Bochicidae.

A new species of Notodiaptomus from the Amazon basin (Crustacea, Copepoda, Calanoida, Diaptomidae).

A new Diaptomidae species is presented from the Neotropical region. It was found in two Amazonian lakes, Ressaca and Arapujá, both in Pará State, Brazil. The lakes are 400 km apart and threatened by the building of reservoirs for hydropower generation and pollution by human settlements. The new species resembles N. paraensis Dussart & Robertson, 1984, but it can be distinguished from this species and other congeners in having a special process on the fifth leg basis of the male, by the place of insertion of lateral spine in the last segment of right P5 of male, the shape and relationship between length and width of segments of male and female P5 exopodite 2 with stout inner process bearing short setules and outer small spine, exopodite 3, with two terminal setae, outer smaller; endopodite 1-segmented with one subterminal seta and oblique comb of spinules, the presence of a line of dorsal spinules at the distal margin of thoracic somites in both sexes. A brief comparison with other Notodiaptomus species is presented in the discussion.

Description of first zoeal stage of Cardisoma crassum Smith, 1870 (Crustacea: Decapoda: Gecarcinidae)

ABSTRACTOf the four species of the genus Cardisoma, a larval description is available for three. A larval description of Cardisoma crassum is not available. The objective of this work was to describe the first zoea of C. crassum. Ovigerous females were collected from the El Salado Estuary, in Puerto Vallarta, Jalisco, México. The first zoeal stage of C. crassum shares the features typical of the Cardisoma: antenna with the exopod equal to 2/3 of the protopod length, maxilla endopod with terminal and two subterminal setae, first maxilliped basis with setae arranged 2, 2, 3, 3 and with 1,1,6 setae on the endopod of the second maxilliped. Also the telson of C. crassum has only a minute lateral spine. On the other hand, according to this study, it is possible to identify three species of gecarcinid present in the eastern tropical Pacific, using the length from the tip of the dorsal to the tip of the rostral spine, from tip to tip of the lateral spines of the carapace, and the setation pattern of the endopod of the maxilla.

Amended diagnosis of the genus Nannodiaptomus (Copepoda, Calanoida),based on redescription of N. phongnhaensis and description of a new species from caves in central Vietnam.

Nannodiaptomus phongnhaensis Dang & Ho, 2001, an endemic stygobiotic diaptomid from Vietnam and the type species of the genus Nannodiaptomus Dang & Ho, 2001, is redescribed on the basis of a new material from its type locality: Hang Phong Nha Cave, Quang Binh province, central Vietnam. We also designated a neotype, because the type material has been lost. The diagnosis of the genus is amended, based on the description of the neotype. The taxonomic position of the genus in the subfamily Speodiaptominae is proposed, and its relationships with other genera of this subfamily are discussed. A new cave-dwelling species Nannodiaptomus haii sp. nov., from a cave near the type locality of N. phongnhaensis, is also described and illustrated. The new species differs from the type species of the genus, among other things, by the structure of male's left swimming leg 5, where the inner margin of the apical process and the sub-terminal seta on the swimming leg 5 Exp-2 have small serrated membranes, but these bear 3-4 distinct denticular protrusions in N. phongnhaensis.

Tobrilus methanus sp. n. and Tripyla posolskii sp. n. (Nematoda, Triplonchida) from Lake Baikal, Russia.

Two new nematode species found in Lake Baikal (Russia) are described and illustrated. Tobrilus methanus sp. n. is morphologically close to T. modestus Gagarin, 1996 and T. incognitus Tsalolikhin, 1972. The new species differs from T. modestus by the thinner body (a = 20-29 vs a = 15.5-18.5), longer pharynx (b = 3.4-4.4 vs b = 5.0-6.2), comparatively longer tail (c' = 3.4-5.0 vs c' = 2.0-2.5), less number of supplementary organs (6 vs 7-8) and presence of subterminal seta. T. methanus sp. n. differs from T. incognitus by the thicker body (a = 20-29 vs a = 35-37), longer pharynx (b = 3.4-4.4 vs b = 5.1-5.8), shorter outer labial setae (3-4 µm long vs 10 µm long) and presence of crystalloids. Tripyla posolskii sp. n. is close to T. dybowskii Tsalolikhin, 1976, but differs by the shorter body (L = 1548-2078 µm vs L = 2400-3530 µm), shorter tail (c = 4.7-7.2, c' = 5.8-7.9 vs c = 2.8-4.8, c' = 7.3-11.9) and shorter spicules (47-57 µm long vs 85-92 µm long). A key for the identification of valid species of the genus Tobrilus from Lake Baikal is given.

<p class="title"><strong>New records of water mites (Acari, Hydrachnidia) from bromeliad phytotelmata in Brazilian Atlantic rainforest, with description of one new species</strong></p>

New records of water mites (Acari, Hydrachnidia) from bromeliad phytotelmata in the Brazilian Atlantic rainforest are presented. One species, Protolimnesia goldschmidti (Limnesiidae) is described as new for science. It differs from all other species of the genus by the sixth segment of fourth legs having two subterminal setae extending beyond tip of segment. A first description of the female, deutonymph and larva is given for Xystonotus phytotelmaticola Pesic, 2015 (Mideopsidae).

Scanning electron microscopy of the cypris larvae ofCapitulum mitella(Cirripedia: Thoracica: Scalpellomorpha)

Adult specimens ofCapitulum mitellawere collected in August 2011 in the intertidal zone of Dinghai, Fuzhou, Fujian, China (26°16′N 119°48′E). The morphology of the cypris larva reared under our conditions was determined using scanning electron microscopy (SEM). Special emphasis was given to the carapace, lattice organs, antennules, thoracopods and furcal rami. The whole carapace surface is sculptured by slender ridges demarcating rectangular or irregular polygonal areas with very fine pores. The cyprid possesses five pairs of lattice organs, arranged as two anterior and three posterior pairs. The second segment carries a preaxial seta 2 and a postaxial seta 2. The third segment carries a postaxial seta 3 outside the attachment disc, whereas a postaxial disc seta, an axial disc seta and two radial disc setae are located inside the attachment disc. The attachment disc is somewhat bell shaped. A series of slender cuticular flaps forms a distinct ‘velum’ around the base of the disc. The fourth segment carries four subterminal setae and five terminal setae. The cyprid bears six pairs of biramous natatory thoracopods consisting of a protopod (coxa + basis), a two-segmented exopod and a two-segmented endopod. The cyprid possesses a rudimentary abdomen and an almost completely cleaved telson with a pair of one-segmented furcal rami. The morphology and setation of the antennules ofC. mitellaresemble those ofBalanus amphitrite(=Amphibalanus amphitrite) andMegabalanus rosa, but differ in some morphological details.

Lutzomyia diamantinensis sp. nov., a new phlebotomine species (Diptera: Psychodidae) from a quartzite cave in Diamantina, state of Minas Gerais, Brazil

A new species of Brazilian phlebotomine sandfly found in Brazil, municipality of Diamantina, state of Minas Gerais, is described based on males and females collected in a quartzite cave. The body of spermathecae is continuous to the individual duct, lanky and tapering at the end, with conical shaped, not striated and presenting the head with dense setae. The male presents gonostyle with four spines and a small subterminal seta and gonocoxite with one group of persistent setae. The paramere is simple with a group of small setae on the dorsal apex. The morphological features of this new species permit its inclusion in the migonei group.

Observations on the settlement and cementation of barnacle (Balanus amphitrite) cyprid larvae after artificial exposure to noradrenaline and the locations of adrenergic-like receptors

Exploration of substrata prior to cementation and metamorphosis is a critical step in the life cycle of Cirripedes. To this end, barnacle cyprid larvae have evolved sophisticated sensory mechanisms to investigate chemical as well as topographical composition of the substratum. Since barnacles are major biofoulers, the sensory structures of Balanus amphitrite cyprids have been described in detail using ultrastructural techniques like SEM and TEM. Settlement assays have shown that cyprid settlement is deterred by adrenergic receptor agonists and antagonists, yet the exact location of these receptors on cyprid sensory structures is unknown. Here, using a fluorescent adrenergic receptor antagonist (Bodipy FL-Prazosin) with the aid of confocal microscopy we describe the putative locations of adrenergic-like receptors in B. amphitrite cyprids. Our results indicate that postaxial setae 2 and 3 of the 2nd and 3rd segments respectively, the sub-terminal setae of the 4th antennular segment and the cement gland secretory cells seem to bear the adrenergic-like receptors. Using optical and electron microscopy we further studied the effects of noradrenaline (NA), an adrenergic receptor agonist, on cyprid settlement and metamorphosis. NA treated cyprids forgo the typical settlement behavior and metamorphose into juvenile barnacles without cementing to the substratum. Cyprid-barnacle metamorphosis in NA treated cyprids is also prolonged as compared to untreated barnacles. The key role played by adrenergic-like receptors during surface sensing, cementation and metamorphosis is discussed.

Video observation of surface exploration in cyprids of Balanus amphitrite: the movements of antennular sensory setae

Video microscopy of cyprids of Balanus amphitrite was used to monitor the action of antennular setae during the exploratory behaviour prior to attachment. In addition, SEM was used to provide a revised description of all antennular setae for that species. The videos describe if a particular seta touches the substratum and the area it can cover during surface exploration. On the fourth segment, the plumose terminal setae A and B are never in contact with the substratum, lack a terminal pore and it is argued that they sense hydrodynamic forces. The aesthetasc-like terminal seta D is likewise held free in the water at all times and it is speculated that it senses dissolved substances, but, since it contains a scolopale rod, it must also have a mechano-receptive function. All remaining antennular setae on the second, third and fourth segments have a terminal pore and it is argued that these are bimodal receptors with both chemo- and mechano-receptive modalities. These setae are also at one time or another in contact with the substratum, except perhaps for the small preaxial seta 2 and terminal seta C. The first seta to contact the surface during a tentative step is radial seta 5, which is longer than all other radial setae. All other setae on the second and third segment are only in contact after a step is completed. When the attachment disc touches the surface (=a step completed) the long and curved postaxial seta 2 (on the second segment) and postaxial seta 3 on the third segment are both flexed to either side of the antennule. This lateral displacement ensures that these two setae can touch large surface areas to either side of the appendage. The four subterminal setae on the fourth segment contact the surface both immediately before and after a step has been completed, and the constant flicking of the segment significantly increases the surface area tested by both these chemoreceptors and by terminal seta E, which can sweep up to 60 μm laterally from the attachment disc. The flicking of the fourth segment may also serve to dilute the boundary layer of chemoreceptors on the fourth segment such as the aesthetasc-like terminal seta D and thus facilitate the detection of new stimuli.

Antennular morphology of the cypris larvae of the mangrove barnacle Fistulobalanus albicostatus (Cirripedia: Thoracica: Balanomorpha)

Previous studies on the ultrastructure of barnacle cypris larvae suggest that cypris morphology, especially the antennules which play a key role in selecting the final substratum for settlement, may show variations between species existing in different habitats. In the present study, the cypris morphology of the barnacle Fistulobalanus (Balanus) albicostatus, which predominantly lives on trunks of mangrove trees was investigated using scanning electron microscopy and compared with that of species from other habitats that have already been described. The antennular segments II and III of F. albicostatus each bear one post-axial seta. The third segment consists of an attachment disc surrounded by a thin cuticular velum and the fourth segment exhibits four sub-terminal setae and five terminal setae. The morphology of the cypris antennules of F. albicostatus is similar to other balanomorph barnacles which inhabit hard shores, revealing that the antennular morphology does not have diagnostic variations between species from the different intertidal habitats. The morphology of the caudal rami (used in the evaluation of the substratum microtopography), however, appears to vary among barnacles living on different substrata.

The first-stage zoeas of Carpilius convexus (Forskal, 1775) and Carpilius maculatus (Linnaeus, 1758) (Crustacea: Decapoda: Brachyura: Xanthoidea: Carpiliidae): an example of heterochrony

The first-stage zoeas of Carpilius convexus (Forskål, 1775) and Carpilius maculatus (Linnaeus, 1758) are described and fully illustrated. Both these Indo-West Pacific species exhibited a unique xanthoidean character for the basis of the second maxilliped, which possesses five (arranged 1,1,1,2) setae instead of the expected four (arranged 1,1,1,1). A comparison with the zoeal stages of Carpiliuscorallinus (Herbst, 1783) as reported by Laughlin et al. (Laughlin et al., 1983) revealed marked differences including the possession of carapace lateral spines (v. absent in C. convexus only), the subterminal setation of the distal maxillule endopod segment with two subterminal setae (versus one subterminal seta in Indo-West Pacific species), the terminal setation of the distal maxillule endopod segment with four setae (versus three setae in C. convexus only), two lateral spines on the telson (versus three in Indo-West Pacific species) and the number of zoeal stages. The first-stage zoeas of the two Indo-West Pacific species appear to have hatched in a more advanced state of development than those of C. corallinus, and the expression of a number of characters has been accelerated (early onset). In fact, the zoeal stages of both Indo-West Pacific species and carpiliid species appear to be abbreviated because the first zoeas are considered to be equivalent to the third-stage zoeas of C. corallinus.

Notes on the ultrastructure of the setae on the fourth antennulary segment of the Balanus amphitrite cyprid (Crustacea: Cirripedia: Thoracica)

This study presents electron microscopy (SEM, TEM) observations on the putative settlement receptors of the fourth antennulary segments. The TEM data from all nine setae are from the outer dendritic segment. Eight of them have morphological characteristics, indicating bimodal sensory properties while one seta (sE) is presumed to be a unimodal mechanoreceptor. We suggest that setae A and B are stimulated by the water flow, seta D is olfactory, seta E detects the topography of the substratum by touch, and the subterminal setae are touch chemoreceptors. No function is suggested for seta C.