Dorsal Margin Research Articles

MORPHOLOGICAL VARIATIONS IN MUD CLAM Polymesoda erosa (Lightfoot) USING FLUCTUATING ASYMMETRY ANALYSIS IN LA UNION, CABADBARAN CITY, AGUSAN DEL NORTE, PHILIPPINES

A geometric morphometric study was conducted on the population of Polymesoda erosa in La Union, Cabadbaran City, to investigate the morphological variations using fluctuating asymmetry (FA) analysis. FA acts as a reliable indicator of ecological stress and developmental instability since it detects genetic or environmental changes that an organism experiences. A total of ninety (90) individual mud clams were randomly collected and analyze. Water and soil samples were also collected to gather data on the degree of body variations and the impact of external factors on P. erosa. The result of the analysis using the SAGE software revealed a highly significant fluctuating asymmetry (P 0.0001). Significant variations in individuals, sides, and the interaction between individuals and sides symmetry were mostly responsible for the substantial variances seen in mud clam species. Particularly, landmarks 10 (dorsal margin maxima) and 13 (anterior margin maxima) exhibited notable variations. For the water quality results, the mud clam's internal valve was likely to be relatively unaffected or minimally impacted, but the level of nickel was high. In conclusion, the fluctuating asymmetry of P. erosa can be attributed to a stressed environment. Unfavorable environmental factors cause an organism's morphology to change, affecting its symmetry.

Molecular phylogeny reveals a new genus and species of freshwater mussel (Bivalvia, Unionidae, Gonideinae) from Jiangxi, China

Freshwater mussels of the tribe Gonideini (Bivalvia: Unionidae: Gonideinae) constitute one of the most taxonomically diverse groups and serve as keystone species in riverine and lacustrine ecosystems across East Asia. A new genus and species of Gonideini (Bivalvia: Unionidae) is described from Jiangxi, China, as Pseudopostolata angulagen. et sp. nov. based on an integrative analysis of shell morphology and molecular data. The validity of the new genus and species is supported by distinct conchological features: a short, rounded anterior; a long, wide posterior; a slightly downward-curved dorsal margin; and a distinctly obtuse angle at the center of the posterior margin. The multi-locus (COI + 16S rRNA + 28S rRNA) phylogeny showed that the species formed a monophyletic group in the tribe Gonideini of the subfamily Gonideinae. Pseudopostolata angulagen. et sp. nov. is identified as the sister group to a clade comprising the genera Postolata, Cosmopseudodon, Obovalis, Ptychorhynchus, Parvasolenaia, and Koreosolenaia. We emphasize the significant morphological convergence in freshwater mussels, particularly within Gonideini, highlighting the necessity of an integrated taxonomic approach for accurate generic classification of this group.

Studies on Neotropical Pseudophyllinae: Integrative description of Dentotibium gen. nov., and of a toothed foretibia katydid (Orthoptera: Tettigoniidae) that sings from burrows in branches

Herein, we describe the genus Dentotibiumgen. nov. and the species D. ramucantorissp. nov, a toothed foretibia katydid within the subfamily Pseudophyllinae from Colombia. This new katydid is a forest dweller inhabiting oak woodlands between 1600 and 2300 m above sea level, only found in the western slopes of the Eastern Andes of Boyacá Department, Colombia. This new species burrows in woody branches and shows big heads in both sexes. The appearance of Dentotibiumgen. nov. is similar to that of Trichotettix Stål, 1873 but differs in having tubercles over the dorsal margin of the foretibiae. It is also close to Nastonotus Bolívar, 1890, but differs from in lacking the three black stripes in the vertex and having a less marked frontal suture and smoother face. Males sing all night long, and their calling song consists of periodic syllables with three differentiable phases. Seasonal calling activity lowers remarkably during the dry season (Jun–Aug). DNA barcoding sequences for the paratypes made available in a previous study are included here.

Reassessment of a theropod ilium from the Kem Kem beds of Morocco and the evolution of ilia in Spinosauridae

A theropod ilium MHNM KK04 from the Kem Kem Beds (Cenomanian) of Morocco was originally described as an abelisaurid. It is here reinterpreted as a spinosaurine spinosaurid. The phylogenetic relationships of MHNM KK04 were analyzed. A thorough and careful comparison between spinosaurids and abelisaurids was made. The Kem Kem ilium was identified as a spinosaurid based on the similarity to the Spinosaurus aegyptiacus neotype and the MSNM V6900 specimen (i.e., the lateral wall of brevis fossa is taller than the medial wall, the ventral margin of the postacetabular blade is straight, and the ventral margin of postacetabular process is posteroventrally oriented). However, MHNM KK04 is slightly different from the ilium of the Spinosaurus aegyptiacus neotype (i.e., the ilium dorsal margin is sub-horizontal to slightly anteriorly inclined, the dorsoventral height of the iliac blade at the postacetabular portion is approximately the same size as the blade height above the acetabulum, and the postacetabulum length is slightly longer than the ischial peduncle length). MHNM KK04, together with previous studies, shows that there were at least two morphotypes of spinosaurines in the Late Cretaceous of Kem Kem beds. Nevertheless, taphonomy, intraspecific or ontogenetic variation cannot be ruled out in the present work. This reclassification adds to the number of juvenile spinosaurines from the Kem Kem beds and provided evidence on the evolution of ilia in spinosaurids.

Patellar Tendon Debridement and Reconstruction With Hamstring Tendon Autografts in the Setting of Severe Patellar Tendinopathy

Background: Patellar tendinopathy is a multifactorial condition characterized by micro-degenerative changes in the patellar tendon. This results from repeated stress to the knee extensor mechanism from explosive movement, axial malalignment, and/or abnormal patellar height. Currently, there is no standard surgical procedure for the treatment of severe patellar tendinopathy. Indications: Patellar tendon reconstructions for patellar tendinopathy may be indicated when >50% of the tendon attachment is degenerative and detached from the distal patella and non-operative treatment, like physical therapy, bracing, and injections, have not relieved symptoms. Debridement may not offer long-term viability against augmentation of the patellar tendon with autografts, with a risk of recurrent breakdown of the patellar tendon attachment with resumption of previous activities that initially lead to overload. Technique Description: An anterior incision was made from the superior pole of the patella to the tibial tubercle. Then, dissection was performed medially to harvest the gracilis and semitendinosus tendons. Open harvesters were used, and the hamstring tendons were released proximally, keeping the tibial insertions attached. A horizontal pin was drilled across the tibial tubercle and reamed with a 4.5 mm reamer. A passing stitch was fed through the tunnel. The proximal and distal margins of the patella were localized with spinal needles and a pin was drilled across its midportion, 5 mm deep to the dorsal cortical margin, and then rearmed. Degenerative tissue at the patellar tendon was excised. The gracilis tendon was passed medial to lateral through the tibial tubercle, and a Q-Fix anchor anchored the grafts medially and laterally. The semitendinosus graft was passed medial to lateral through the patella followed by the gracilis tendon lateral to medial. Appropriate reconstruction graft tension was confirmed and grafts were whipstitched together. Results: Clinical outcomes for the debridement of severe patellar tendinopathy report 77% symptomatic relief. With many unable to return to activity, patellar tendon reconstruction can be indicated. Outcomes for reconstructions for severe patellar tendinopathy are not reported. Discussion: Patellar tendon reconstruction with hamstring autografts for the treatment of severe patellar tendinopathy can provide a strong reconstruction graft to allow for the resumption of high-level activities. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

A new genus of Gyponini (Hemiptera, Cicadellidae, Iassinae) with description of two new species from Brazil and key to genera of the Hecalapona complex

Gracilipona gen. nov. is described and illustrated based on males and females of two new species from Brazil: G. tetrarama sp. nov. (type-species) from the states of Minas Gerais, Paraná, Rio de Janeiro, and Rio Grande do Sul, and G. birama sp. nov. from Bahia State. The new genus differs from other genera of the Hecalapona complex as follows: antennal ledge extending anteriorly below anterior margin of crown, forming an arched carina that connects the antennal ledges medially; pronotum moderately declivous; forewing with extra crossveins on distal third; protibia with dorsal surface flattened but not expanded, with lateral margins carinate; aedeagus with dorsal apodemes strongly developed and divergent and shaft with lateral processes arising from basal third; ovipositor with valvulae expanded subapically; first valvula with dorsal sculptured area short, mostly strigate, areolate near dorsal margin; and second valvula with a few rounded denticles subapically on dorsal margin. An updated key to genera of the Hecalapona complex and a discussion comparing Gracilipona gen. nov. with other related genera are provided.

Cymbella stomachsis sp. nov. (Bacillariophyta; Cymbellaceae), a new species from Guangdong Province, China

A new diatom species from the genus Cymbella C. Agardh is described from samples collected during a survey of freshwater diatoms from Modaomen Channel, Guangdong Province, China. With the aid of light microscopy (LM) and scanning electron microscopy (SEM), we give a detailed morphological description of Cymbella stomachsis sp. nov., which is placed in the genus Cymbella according to the shared features of asymmetry about the apical axis, deflection of the external terminal raphe fissures towards the dorsal margin, and the presence of apical pore fields and stigmata. Although it shares some similar structural features with C. tumida, C. stuxbergii, C. stuxbergioides, C. pesudostuxbergii, C. mexicana and C. australica, C. stomachsis sp. nov. is easily distinguished by the valve outline, the shape and density of areola, and the appearance of a lack of an intermissio at the central nodule. Especially, the structure of the intermissio is absent in similar taxa. This work is important for its enrichment of our understanding of the genus Cymbella and improvement of the database of diatom biodiversity and distribution in China.

Actumnus ngankeeae sp. nov. and Pilumnus swajayai Ng & Rahayu, 2021, pilumnid crabs from Japan (Crustacea: Decapoda: Brachyura)

New and rare crab species of the family Pilumnidae, Actumnus ngankeeae sp. nov. and Pilumnus swajayai Ng & Rahayu, 2021, are reported from Japan. Actumnus ngankeeae from the Ogasawara (Bonin) Islands is characterized by the following features: the carapace is transversely ovate and strongly convex longitudinally and transversely; the dorsal surface is uniformly covered with small granules and sparse short setae, with the regions defined by narrow furrows; the anterolateral margin is narrowly crested along its whole length and separated into four convex lobes by three V-shaped notches. Both chelipeds are stout, with short, strongly curved fingers. Its specific affinity to A. obesus Dana, 1852, is briefly discussed. Pilumnus swajayai from the Ryukyu Islands is wholly covered with tomentum; the carapace anterolateral margin is armed with three sharp teeth directed obliquely forwards, the second of which is the largest; the subhepatic tooth is distinct, but smaller than the carapace anterolateral teeth; the hepatic region is armed with a dentiform lobe; both chelipeds are armed with scattered conical granules on the carpi and palms; and the ambulatory legs are armed with some spinules on the dorsal margins of the carpi and propodi. The generic affiliation to Pilumnus is acceded to the original description after discussion on the related genera. The present record of P. swajayai from the Ryukyu Islands is the second since the original description from Indonesian waters.

Lebbeus dentatus n. sp. (Decapoda, Thoridae) described from a seamount of the Caroline Plate, NW Pacific

Based on the female specimen collected from an unnamed seamount on the Caroline Plate in the NW Pacific, a new species of the thorid genus Lebbeus White, 1847, L. dentatus n. sp., is described and illustrated. The new species belongs to a species group characterized by the possession of epipods on the pereopods 1 and 2, but is characteristic in the carapace having a strong supraorbital tooth extending to 0.3 length of the rostrum and largely unarmed dorsal margin of the rostrum. Integrative approach using morphological comparison and genetic analyses with the mitochondrial COI and 16S rRNA genes is taken to clarify the specific identities of the new taxon. An identification key to species belonging to the species group of Lebbeus characterized by the possession of epipods on the pereopods 1 and 2 is presented.

First Report of Tetranychus truncatus Ehara (Acari: Tetranychidae) Infesting Groundnut (Arachis hypogaea L.) in India through Morphological and Molecular Insight

Background: Red spider mite, Tetranychus truncatus Ehara (Acari: Tetranychidae) infests many agriculture and horticulture crops in India, but to date it had not been found damaging cultivated groundnut. During 2022-23, the incidence of this species was high in many groundnut growing regions of Tamil Nadu. Identification of the species is highly essential for effective management of the particular pest. Hence, the aim of this research was to identify the mite species infesting groundnut crop and describe the damage caused. Methods: Survey was carried out all over Tamil Nadu and samples of mite infested groundnut leaves were collected from field based on damage symptoms, observed and examined under Stereo zoom microscope, microslides were prepared using Hoyer’s medium and taxonomic characters were studied under phase contrast microscope. Molecular analysis was done by genomic DNA isolation, PCR amplification, sequencing and BLAST performed to check the identity with GenBank Sequences. ITS2 primer was used. Result: Red spider mite species, T. truncatus was identified first time in groundnut through both morphological characters and molecular tools. Female: Idiosomal setae longer than the interval between their longitudinal bases and gradually tapers distally. Diamond- shaped pattern of striae between e1 and f1 setal bases. Tarsus I with 4 tactile setae proximal to proximal duplex setae. Male: Aedeagus with tiny terminal knob, apparently truncate with a slight indentation on the dorsal margin.

Diversity of Pleurostomatid Ciliates: Morphology, Taxonomy and Molecular Phylogeny of Freshwater Isolates Found in a Northern China Wetland, with a Description of Two New Species

Ciliates of the order Pleurostomatida play essential functions in microbial food webs from a variety of habitats and have been thought to possess a high level of diversity. Due to undersampling and often absent molecular data, the actual diversity and phylogenetic relationships within this group remain unclarified. To help address this deficiency, a survey of freshwater pleurostomatid ciliates was undertaken in Lake Weishan Wetland, northern China. Here, two new Amphileptus species, Amphileptus sinicus sp. nov. and Amphileptus piscinarius sp. nov., were investigated using modern morphological and molecular techniques. Amphileptus sinicus sp. nov. is characterized by possessing a comparatively large cell size of 330–490 μm, contractile vacuoles on both ventral and dorsal margins, and 8–10 left and 42–61 right kineties. Amphileptus piscinarius sp. nov. is characterized by possessing a cell size of 140–210 μm, a large distinctly developed apical extrusome group, 3–4 contractile vacuoles on the ventral margin, and 6–8 left and 24–28 right kineties. Phylogenetic results based on the 18S rRNA gene data of these two species group them with other congeners, with these data suggesting the genus Amphileptus is paraphyletic.

Taxonomic notes on the genus Baetiella Uéno, 1931 (Ephemeroptera, Baetidae), with description of three new species from Thailand.

Based on material recently collected in northern Thailand, the present study provides an updated of the genus Baetiella, including Gratia. It comprises six species in Thailand, three of them being new species: Baetiella (Gratia) narumonae, Baetiella (Gratia) sororculaenadinae, Baetiella (Baetiella) bispinosa, Baetiella (Baetiella) baeisp. nov., Baetiella (Baetiella) lannaensissp. nov. and Baetiella (Baetiella) bibranchiasp. nov.Baetiella (Baetiella) baeisp. nov. can be distinguished from other species by the reduction of the posteromedian protuberances on abdominal tergites I-III, the asymmetrical coniform terminal segment of labial palp, the distal margin of abdominal sternites VII-X each with a row of long, spatulate setae, the dorsal margin of femur with two long, robust setae distally. Baetiella (Baetiella) lannaensissp. nov. is diagnosed by the posteromedian protuberances present on tergites I-VIII, dorsal margin of femur with a regular row of long, rounded, ciliated setae and body surface covered with numerous, dense, rounded scale-like setae. Baetiella (Baetiella) bibranchiasp. nov. can be separated from other species by coxal gills present at the base of forelegs and midlegs. The molecular study based on the mitochondrial gene COI and a larval key to species of Thai Baetiella are also provided.

The lionfishes: Comparative development of Pterois volitans, Dendrochirus barberi, and D. hemprichi (Scorpaeniformes: Scorpaenidae: Pteroinae) and discrimination of their early life stages from non-pteroine scorpaenid genera in the Western North Atlantic

Despite the threat that lionfishes pose to non-native marine ecosystems worldwide, their early life stages (ELS) remain difficult to distinguish from morphologically similar taxa due to inadequate descriptions and poorly defined taxonomic characters. Two members of the Indo-Pacific marine assemblage commonly known as lionfishes, zebrafishes, firefishes, turkeyfishes, and butterfly-cods (Scorpaeniformes: Scorpaenidae: Pteroinae) are invasive in the Western North Atlantic (WNA). Here, we describe the ELS of Pterois volitans, Dendrochirus barberi, and two transforming larvae and an early juvenile of D. hemprichi; review the early development of D. zebra and a larva described as D. bellus; identify characteristics that distinguish P. volitans from the four members of Dendrochirus; and compile meristic and distribution data for all currently valid species of lionfishes worldwide based on recent revisions and updated nomenclature. We also briefly describe a small juvenile of two poorly known non-pteroine deep-water scorpaenids, and discuss characteristics that distinguish the five pteroines from non-pteroine scorpaenid genera in the WNA. Differences in relative length and elevation of the parietal and nuchal spines, and in pigmentation patterns distinguish P. volitans from the four members of Dendrochirus. Pterois volitans has parietal spines two or more times longer than the nuchals with both sets of spines oriented about 30° above the longitudinal axis of the head, whereas the four members of Dendrochirus have relatively short parietal and nuchal spines subequal in length that lay flatter against the cranium (i.e., elevation ≤15° above longitudinal axis of head). Transforming larvae of the four members of Dendrochirus also develop saddles of pigment along the dorsal and ventral margins of the body that P. volitans lacks at the sizes examined. One or more of the following suite of traits distinguish larvae of the five pteroines from those of non-pteroine scorpaenids and other morphologically similar taxa: the presence or absence of a “shield” of pigment over the dorsolateral margin of the visceral mass (may be reduced or augmented with scattered blotches of pigment in larger larvae of some taxa); the relative length, elevation, and placement of the parietal and nuchal spines; the presence or absence of a small slit behind the fourth gill arch; differences in pectoral-fin length, shape, and extent of pigmentation; the relative size, length, and placement of spines along the posterior shelf of the preopercle (PPO); and the presence or absence, number, and placement of spine(s) along the opercle.

Defining distal splenopancreatectomy by the mesopancreas.

The implementation of the pathologic CRM (circumferential resection margin) staging system for pancreatic head ductal adenocarcinomas (hPDAC) resulted in a dramatic increase of R1 resections at the dorsal resection margin, presumably because of the high rate of mesopancreatic fat (MP) infiltration. Therefore, mesopancreatic excision (MPE) during pancreatoduodenectomy has recently been promoted and has demonstrated better local disease control, fueling the discussion of neoadjuvant downsizing regimes in MP + patients. However, it is unknown to what extent the MP is infiltrated in patients with distal pancreatic (tail/body) carcinomas (dPDAC). It is also unknown if the MP infiltration status affects surgical margin control in distal pancreatectomy (DP). The aim of our study was to histopathologically analyze MP infiltration and elucidate the influence of resection margin clearance on recurrence and survival in patients with dPDAC. Furthermore, the results were compared to a collective receiving MPE for hPDAC. Clinicopathological and survival parameters of 295 consecutive patients who underwent surgery for PDAC (n = 63 dPDAC and n = 232 hPDAC) were evaluated. The CRM evaluation was performed in a standardized fashion and the specimens were examined according to the Leeds pathology protocol (LEEPP). The MP area was histopathologically evaluated for cancerous infiltration. In 75.4% of dPDAC patients the MP fat was infiltrated by vital tumor cells. The rates of MP infiltration and R0CRM- resections were similar between dPDAC and hPDAC patients (p = 0.497 and 0.453 respectively). MP- infiltration status did not correlate with CRM implemented resection status in dPDAC patients (p = 0.348). In overall survival analysis, resection status and MP status remained prognostic factors for survival. In follow up analysis. surgical margin clearance in dPDAC patients was associated with a significant improvement in local recurrence rates (5.2% in R0CRM- resected vs. 33.3 in R1/R0CRM + resected, p = 0.002). While resection margin status was not affected by the MP status in dPDAC patients, the high MP infiltration rate, as well as improved survival in MP- dPDAC patients after R0CRM- resection, justify mesopancreatic excision during splenopancreatectomy. Larger scale studies are urgently needed to validate our results and to study the effect on neoadjuvant treatment in dPDAC patients.

New and Interesting Diatoms from the Shiwan Wetwalls, Yunnan Province, China. III. Valve ultrastructure of four new species of Eunotia (Bacillariophyceae: Eunotiales)

Four new Eunotia (Bacillariophyceae: Eunotiales) species are described from the Shiwan Wetwalls in Yunnan Province, China, based on light and scanning electron microscopy. The four species all share the features that assign them to the genus, including asymmetry about the apical axis, raphe predominantly on the valve mantle, and presence of one or more rimoportulae, and they all possess pseudosepta. They differ from one another in several attributes, however. Three of the species possess striae contained in internal troughs, two have spines (either one stout spine at each apex or blunt spines along the dorsal margin) and one has thickened ridges between the striae. These observations of four new Eunotia species further demonstrates the diversity and uniqueness of this wetwall community in Yunnan.

Dorsal approach in laparoscopic extended left hemi-hepatectomy: A case series.

The utility of the dorsal approach has been reported for laparoscopic left hemi-hepatectomy. The aim of the present study is to show the usefulness of the dorsal approach for laparoscopic extended left-hemi-hepatectomy while ensuring safe identification of hepatic veins and dissection of the dorsal tumor margin. Tumors requiring extended left hemi-hepatectomy. After mobilization of the lateral sector and division of the Arantius plate, parenchyma above the Arantius plate is removed to expose the root of the middle hepatic vein and left hepatic vein. Each of these veins can be isolated separately either intra- or extra-hepatically. After removing the parenchyma on the cranial side of the left Glissonean pedicle continuous with the exposed hepatic veins, the left Glissonean pedicle is isolated using the Glissonean pedicle transection method. After division of the left hepatic vein and Glissonean pedicle, segment 4 (in which the main part of the tumor is commonly located) is dissected from the anterior plane of the paracaval portion of the caudate lobe by the dorsal approach, along with the hepatic hilum. Following dissection of the dorsal side of the tumor, and division of parenchyma from the anterior edge of the liver, the anterior Glissonean branches and middle hepatic vein are divided safely and the specimen is resected. Three patients underwent laparoscopic extended left hemi-hepatectomy, with no open conversions. Operative time and blood loss were 331 (concomitant with another partial hepatectomy), 277, and 315 minutes; and 200, 100, and 100 g, respectively. The postoperative courses were uneventful. The dorsal approach maximizes the advantages of laparoscopic extended left hemi-hepatectomy and can be performed safely.

Description of a new species of Aegla (Decapoda, Anomura) from the Paran 3 hydrographic basin, Brazil.

Freshwater crustaceans of the genus Aegla are endemic to southern South America, and present greater richness in the river basins of the state of Rio Grande do Sul, Brazil. However, recent studies have shown the enormous potential for discovering new species of Aegla in the state of Paran. In the last six year the number of species recorded has almost doubled, increasing from 9 to 16. In the present work, we expand the current knowledge about the diversity of Aegla in a set of poorly explored drainage basins in the western region of the state and describe a new species, Aegla urussanga n. sp., based on morphological and molecular evidence. A combination of morphological characters supports the new species: orbital spine absent, non-elevated epigastric prominences, robust protogastric lobes with scales, anterior dorsal margin of epimeron 2 armed and with pronounced concavity, sub-rectangular palmar crest of chelipeds, internal margin of the ventral face of the ischium of the cheliped with a proximal stout spine, a distal stout spine, and up to three tubercles with spiniform scales. The molecular data, based on partial COI sequences, also support the distinction of the new species from others that occur in adjacent river basins. The species with the smallest genetic distance from A. urussanga n. sp. is Aegla castro Schmitt, 1942 which occurs in the Iguau River basin. The new species occurs in distinct streams, probably interconnected in the past and currently isolated by the Itaipu reservoir and is the second species of Aegla described from the complex of drainage basins called Paran 3 basin.

The Crocodylian proatlas functions to redistribute venous blood and cerebrospinal fluid.

The proatlas, a bone located between the skull and the neural spines of the cervical vertebrae, is best known from reptiles. Most previous studies of the proatlas have centered on its developmental, debating the relationship between the proatlas and the cervical neural arches. The present study was intended as a description of the proatlas in the American alligator (Alligator mississippiensis) and an experimental test of its hypothesized role in venous blood and cerebrospinal fluid (CSF) distribution. In Alligator, the proatlas is chevron-shaped; ventrally it has a loose connection to the dorsal surface of the first cervical vertebrae, dorsally it has a robust elastic tissue tether on the otoccipital and supraoccipital bones. The ventral surface of the proatlas parallels the dorsal margin of the foramen magnum and rests on the dorsal surface of the spinal venous sinus. Experimental manipulation of the proatlas demonstrated that displacement of the proatlas causes pressure changes in both the spinal venous sinus and the enclosed spinal CSF. The results of this study represent the first demonstration of an explicit functional role for the proatlas, the circulation of fluids between the cranial and spinal compartments of the central nervous system.

Halichoeres sanchezi n. sp., a new wrasse from the Revillagigedo Archipelago of Mexico, tropical eastern Pacific Ocean (Teleostei: Labridae).

A new labrid fish species, Halichoeres sanchezi n. sp., is described from eight specimens collected in the Revillagigedo Archipelago in the tropical eastern Pacific Ocean, off the coast of Mexico. The new species belongs to the Halichoeres melanotis species complex that is found throughout the region, differing by 2.4% in the mtDNA cytochrome c oxidase I sequence from its nearest relative, H. melanotis from Panama, and 2.9% from Halichoeres salmofasciatus from Cocos Island, off Costa Rica. The complex is distinguished from others in the region by having a black spot on the opercular flap and a prominent black area on the caudal fin of males. The juveniles and initial phase of the new species closely resemble those of H. salmofasciatus and Halichoeres malpelo from Malpelo Island of Colombia, differing in having an oblong black spot with a yellow dorsal margin on the mid-dorsal fin of initial-phase adults as well as on juveniles. In contrast, the terminal-phase male color pattern is distinct from other relatives, being vermilion to orangish brown with dark scale outlines, a white patch on the upper abdomen, and a prominent black band covering the posterior caudal peduncle and base of the caudal fin. The new species adds to the list of endemic fish species for the isolated archipelago and is an interesting case of island endemism in the region. The discovery was made during the joint 2022 collecting expedition to the archipelago, which featured a pioneering collaborative approach to an inventory of an island ichthyofauna, specifically including expert underwater photographers systematically documenting specimens in situ, before hand-collection, and then photographed fresh, tissue-sampled, and subsequently vouchered in museum collections.

Cymbella liangyanlingii sp. nov. (Bacillariophyta, Cymbellaceae), a new diatom species from the upper tributary of Liujiang River, Guangxi Zhuang Autonomous Region, China

Cymbella liangyanlingii sp. nov. was collected from epilithic samples in the Liujiang River, Guangxi Zhuang Autonomous Region, China. Light microscopy (LM) and scanning electron microscopy (SEM) were used to describe the morphology of the new species, and in addition we provided detailed ecological information about this species. C. liangyanlingii sp. nov. has the features that assign it to the genus Cymbella, including the terminal raphe fissures deflected toward dorsal margin, apical pore fields present at each end on the valve and, for most taxa in the genus, one or more stigmata on the ventral side of the central area. The key diagnostic features that easily distinguish the new species from other similar species: 1) the inconspicuous central area, 2) three slit-like stigmata on the ventral margin, 3) the striae have no interruption on the valve margin, and 4) striae that are mostly uniseriate in the middle and biseriate (5–7) in the ends. This combination of features distinguishes C. liangyanlingii sp. nov. from congers such as C. liyangensis, C. distalebiseriata, C. alexandrovichii and C. hubeiensis. These findings can help us further understand the morphological and ecological information of the genus Cymbella in China.