Ultrastructure and distribution of the taste buds in the buccal cavity in relation to the food and feeding habit of a herbivorous fish: Oreochromis niloticus

The buccal cavity of an herbivorous fish Oreochromis niloticus was investigated by means of scanning electron microscopy. The buccal cavity distinguished into the roof and the floor. Three different types of taste buds (type I, II and III) are distributed in the buccal cavity. The proximal part of the buccal cavity bears relatively high epidermal papillae in which type I TBs was found. The middle region of the buccal cavity is mostly occupied by low epidermal papillae containing type II TBs. Type III TBs which are present within the metabranchial buccal cavity; never rise above the normal level of the epithelium.The different types of TBs are useful for ensuring full utilization of the gustatory ability of the fish. It is postulated that the TBs serve different functions: TBs type I and II may act as chemoreceptors and mechanoreceptors. TBs type III acts predominantly as a chemoreceptors. TBs of each type show two kinds of receptor villi within their receptor areas: tall villi and small villi. The surface of the lining epithelial cells shows a delicate microridge system. These structures protect against physical abrasion potentially caused during food maneuvering and swallowing. Furthermore, protection of the epithelium from abrasion is enhanced with goblet cells secretion.     

Comparison of the oral cavity architecture in surgeonfishes (Acanthuridae, Teleostei), with emphasis on the taste buds and jaw “retention plates”

The present study summarizes observations on the skin plates (“retention plates”) and taste buds (TBs) in the oropharyngeal cavity (OC) of 15 species of surgeonfishes (Acanthuridae), all of which are predominantly herbivorous. Two phenomena mark the OC of these fishes: the presence of skin-plates rich in collagen bundles at the apex of the jaws, and cornified papillae on the surface. It is suggested that these plates help in retaining the sections of algae perforated at their base by the fishe’s denticulate teeth. The TBs, especially type I, are distributed across the buccal valves, palate and floor of the OC, forming species–specific groupings along ridges established by the network of sensory nerves. The number of TBs in the OC increases with growth of the fish up to a certain standard length, especially at the posterior part of the OC, and differs among the various species: e.g., Zebrasoma veliferum possesses 1420 TBs and Parcanthurus hepatus 3410. Species of Naso show a higher number of TBs than most species of Acanthurus, possibly connected with their more diversified diet. The pharyngeal region of these fishes is expanded through lowering the base of the gill-arches, and together with the occurrence of high numbers of TBs in this region, indicates the importance of the posterior region of the OC in herbivorous fishes for identification of the engulfed food particles prior to swallowing. The discussed observations shed light on the micro-evolutionary developments of the OC within the family Acanthuridae and contribute to the taxonomic characterization of the various species.     

Will fluctuations in salt marsh–mangrove dominance alter vulnerability of a subtropical wetland to sea‐level rise?

To avoid submergence during sea‐level rise, coastal wetlands build soil surfaces vertically through accumulation of inorganic sediment and organic matter. At climatic boundaries where mangroves are expanding and replacing salt marsh, wetland capacity to respond to sea‐level rise may change. To compare how well mangroves and salt marshes accommodate sea‐level rise, we conducted a manipulative field experiment in a subtropical plant community in the subsiding Mississippi River Delta. Experimental plots were established in spatially equivalent positions along creek banks in monospecific stands of Spartina alterniflora (smooth cordgrass) or Avicennia germinans (black mangrove) and in mixed stands containing both species. To examine the effect of disturbance on elevation dynamics, vegetation in half of the plots was subjected to freezing (mangrove) or wrack burial (salt marsh), which caused shoot mortality. Vertical soil development was monitored for 6 years with the surface elevation table‐marker horizon system. Comparison of land movement with relative sea‐level rise showed that this plant community was experiencing an elevation deficit (i.e., sea level was rising faster than the wetland was building vertically) and was relying on elevation capital (i.e., relative position in the tidal frame) to survive. Although Avicennia plots had more elevation capital, suggesting longer survival, than Spartina or mixed plots, vegetation type had no effect on rates of accretion, vertical movement in root and sub‐root zones, or net elevation change. Thus, these salt marsh and mangrove assemblages were accreting sediment and building vertically at equivalent rates. Small‐scale disturbance of the plant canopy also had no effect on elevation trajectories—contrary to work in peat‐forming wetlands showing elevation responses to changes in plant productivity. The findings indicate that in this deltaic setting with strong physical influences controlling elevation (sediment accretion, subsidence), mangrove replacement of salt marsh, with or without disturbance, will not necessarily alter vulnerability to sea‐level rise.     

Ultrastructure of trichome of old world porcupine of Indian subcontinent

The present investigation is based on ultrastructural details of different types of quills of two species of old world porcupine (Hystrix indica and Hystrix brachyura) of Indian subcontinent using environmental scanning electron microscopy (ESEM). In H. indica, four types of quills have been detected – bristlelike spines, stilettolike spines, spikes and mane. The quills of H. brachyura are categorized into four types – broad, slender, hollow tail quill and quills of the anogenital region. The ESEM images of surface characteristic of different types of quills of both the species except the hollow tail quill showed usual scaly features without having any differences. The cross‐sectional images of quills of H. indica and H. brachyura show a narrow cortex and a broad medullary region with a network of anastomosing channels. The cortical layer is comparatively thicker in mane hairs of H. indica and in slender quills of H. brachyura. With extensive exploration of the anatomical structures of the quills by ESEM from both the species of Hystrix, we could not find ‘osmetrichia’ in any forms of quill. In contrast, we hypothesized that the channels and network of medulla are serving the purpose for transportation of pheromonal signalling molecules in old world porcupine.     

The effect of isolation,fragmentation, and population bottlenecks on song structure of a Hawaiian honeycreeper

Little is known about how important social behaviors such as song vary within and among populations for any of the endemic Hawaiian honeycreepers. Habitat loss and non‐native diseases (e.g., avian malaria) have resulted in isolation and fragmentation of Hawaiian honeycreepers within primarily high elevation forests. In this study, we examined how isolation of Hawai'i ‘amakihi (Chlorodrepanis virens) populations within a fragmented landscape influences acoustic variability in song. In the last decade, small, isolated populations of disease tolerant ‘amakihi have been found within low elevation forests, allowing us to record ‘amakihi songs across a large elevational gradient (10–1800 m) that parallels disease susceptibility on Hawai'i island. To understand underlying differences among populations, we examined the role of geographic distance, elevation, and habitat structure on acoustic characteristics of ‘amakihi songs. We found that the acoustic characteristics of ‘amakihi songs and song‐type repertoires varied most strongly across an elevational gradient. Differences in ‘amakihi song types were primarily driven by less complex songs (e.g., fewer frequency changes, shorter songs) of individuals recorded at low elevation sites compared to mid and high elevation populations. The reduced complexity of ‘amakihi songs at low elevation sites is most likely shaped by the effects of habitat fragmentation and a disease‐driven population bottleneck associated with avian malaria, and maintained through isolation, localized song learning and sharing, and cultural drift. These results highlight how a non‐native disease through its influence on population demographics may have also indirectly played a role in shaping the acoustic characteristics of a species.     

Twin boundary spacing-dependent deformation behaviours of twinned silver nanowires

Twin boundary spacing (TBS) plays a significant role in the yield behaviour of twinned nanowires (NWs). However, few studies have shown an overall view of the effects on the mechanical response of twinned silver NWs under tensile loading. In this article, the mechanical properties of 〈111〉-oriented NWs with different TBSs are studied using molecular dynamics simulations. In elastic region, it is found that the addition of twin boundaries (TBs) to crystalline NWs can not only cause strengthening but also softening effect, which depending on the S_T/S_F (the ratio of the total area of TBs to the area of lateral free surfaces). Furthermore, our simulation results show that the evolution of reduced number of different types of atoms in twinned Ag NWs has a strong dependence on TBS. For twinned NWs with larger TBSs, the dislocation–TB interaction dominates the plastic deformation process. While for twinned NWs with smaller TBSs, shear banding is activated as the incipient plastic deformation, leading to the atoms clustering into disorder near the surfaces. The study will be helpful to the further understanding of TB-related mechanical properties of nanomaterials.     

Fine structure of the chelicera in the spider Nephila clavata

The fine structural characteristics of the biting apparatus in the orb‐web spider Nephila clavata were studied using scanning electron microscopy. The main biting apparatuses of spiders are the chelicerae and cheliceral fangs in the cephalothorax. The chelicera of N. clavata is that of the jack‐knife (folding knife) type, which is composed of two segments, and has a labidognathous form that moves at right angles to the body axis. Each chelicera bears a hinged fang that folds into a cheliceral groove. The tips of the fangs are quite sharp, and the spider's body is well adapted to driving the fangs into prey. Just below the fang, each side of the cheliceral groove is covered with a total of seven cuticular teeth (four promarginal teeth and three retromarginal teeth) in two rows. The cheliceral fang has a single aperture at the tip of the posterior surface, and the lower margin of the fang which meets the promarginal teeth is a saw‐like groove. Fine structural observation reveals that each fang has a single venom pore, and each cuticular depressive area on the cheliceral groove has two different types of surface pit. Approximately 40 to 50 spiky protrusions were counted at the cheliceral groove, to hold prey tightly.     

冲积平原区高程因子对土壤剖面质地构型的影响--以封丘县为例

河流冲积平原区土壤剖面质地构型对土壤水肥保持、供给能力以及水盐运动产生极为重要的影响。区域土壤的六大成土因素中,地形的影响最为突出。分析土壤剖面质地构型的地形影响,对于指导农业生产具有重要的理论与现实意义。本研究应用模糊c-均值算法模型,基于土壤剖面特征质地层厚度数据,得到研究区9种土壤剖面质地构型。对比分析典型区和研究区土壤剖面质地构型的地形影响结果表明：隶属于土壤剖面质地构型砂-砂-砂的隶属度值与高程之间始终存在正相关,说明地形较高部位发育的土壤质地偏砂的规律性始终存在,而从典型区到研究区,其它土壤剖面质地构型、0-60cm土层质地类型、以及表土层、心土层和底土层质地类型受地形影响的规律性减弱。地形较低部位发育的土壤剖面质地构型相对复杂,而地形较高处,发育的土壤剖面质地构型相对简单。土壤剖面质地构型复杂的地区可能更多地受到人为因素的干扰,从而表现出受地形影响的规律性不明显。     

Syntaxonomy and biogeography of dry grasslands on calcareous substrates in the central and southern Balkans

Questions

Which major syntaxa of dry grasslands supported by carbonate bedrock occur in the central and southern Balkans? What is their position along major ecological gradients and in the context of phytogeographic patterns of the region?

Location

Central and southern Balkans, including western Bulgaria, northern Greece, Kosovo, Macedonia (FYROM) and Serbia.

Methods

We compiled a matrix of 660 relevés of dry grasslands over lime‐rich bedrock, previously classified in the Festuco‐Brometea. We applied clustering techniques to classify separately synoptic and relevé data, and applied NMDS with passive projection of indicator values, climatic data and biogeographic geo‐elements onto ordination diagrams to assist interpretation of the syntaxonomic patterns. We constructed elevation distribution profiles for alliances and classes of grasslands of several grassland classes from a broader study area to elucidate the relationship of the elevational sorting of the syntaxa in relation to latitude.

Results

The analysis revealed six major vegetation types, classified into four orders: (1) Stipo pulcherrimae‐Festucetalia pallentis, incl. (sub)montane rocky steppic grasslands of the Saturejion montanae of central Balkans, and the Koelerio‐Festucion dalmaticae – submontane rocky grasslands of southern Serbia and Kosovo; (2) Astragalo onobrychidis‐Potentilletalia represented by the Saturejo‐Thymion (low‐elevation steppic grasslands of southern Balkans); (3) Festucetalia valesiacae represented by grasslands on deep soil and low elevation of northern Greece, and finally (4) high‐elevation rocky grasslands of southern Balkans, classified as a new alliance – Diantho haematocalycis‐Festucion hirtovaginatae, that might belong to a new, yet undescribed, syntaxonomic order. Ordination suggests that the major differentiation of the high‐rank syntaxa follows north–south geographic and low–high elevation gradients.

Conclusions

Because of the transitional biogeographic position of the studied region, as well as considerable large elevation span across latitudes, the diversity of vegetation types is high. The indication a putative new dry grassland order, the mid‐high altitudes of the southern Balkans points to a need to re‐assess the Balkan vegetation occupying the community niche between the low‐elevation dry grasslands (Festuco‐Brometea) and those typical of high elevations (Elyno‐Seslerietea and Daphno‐Festucetea), seeking parallels to patterns described from the western Alps, Pyrenees, and Apennines. This syntaxonomic unit is poised to expand the concept of the Festuco hystricis‐Ononidetea striatae to the Balkans.

     

Enantioseparation of Tröger's Base Derivatives by Capillary Electrophoresis Using Cyclodextrins as Chiral Selectors

The enantioseparation of seven Tröger's base derivatives (TBs) was carried out by capillary electrophoresis using α‐, β‐, and γ‐cyclodextrins as chiral selectors and phosphate at 20 mmol/l concentration, pH 2.5, as background electrolyte. The method was optimized with respect to the concentration of chosen chiral selectors (0–50 mmol/l) and the amount of organic solvent (acetonitrile, 0–25 % (v/v)) in the electrolyte. The results indicate that all the studied variables, i.e., type of chiral selector, its concentration, and the amount of the added organic solvent, have a significant impact on the enantioseparation of the studied TBs. The best results for the majority of the separated TBs were obtained utilizing β‐cyclodextrin at 5 mmol/l concentration and with various amounts of acetonitrile added ranging from 5 to 15% (v/v) in the background electrolyte. For the two smallest studied TBs, γ‐cyclodextrin with 10% (v/v) acetonitrile also provided good resolution. Chirality 25:379–383, 2013. © 2013 Wiley Periodicals, Inc.     

The claw closer muscle of two estuarine crab species,Cyrtograpsus angulatus and Neohelice granulata (Grapsoidea,Varunidae): histochemical fibre type composition

Longo, M.V. and Díaz, A.O. (2011). The claw closer muscle of two estuarine crab species, Cyrtograpsus angulatus and Neohelice granulata (Grapsoidea, Varunidae): histochemical fibre type composition. —Acta Zoologica (Stockholm) 00 : 1–7. This study permitted the characterization of four types of muscle fibres in the claw closer muscles of Cyrtograpsus angulatus and Neohelice granulata. Succinic dehydrogenase (SDH) for mitochondria, periodic acid Schiff (PAS) for glycogen, Sudan Black B for lipids and myosin‐adenosine triphosphatase (m‐ATPase) preincubated at alkaline and acid pHs were used for that purpose. The mean fibre diameters, the relative areas and frequencies of each muscle fibre type were calculated. Types I and IV would be considered ‘extreme’ groups with type I fibres large, weak and acid/alkaline‐labile m‐ATPase, weak SDH, PAS and Sudan, and type IV fibres small, very strong and acid/alkaline‐resistant m‐ATPase, strong SDH and PAS, and moderate Sudan. Types II and III would belong to a predominant ‘intermediate’ group. Type IV fibres were scarce in C. angulatus but represented 25% of the total fibre population in N. granulata. In C. angulatus, the relative area occupied by type I fibres was bigger than its relative proportion, whereas in N. granulata, types I and II had similar patterns. Concluding, variations in fibre type composition in the claw closer muscles of C. angulatus and N. granulata would be linked to different habitats and feeding behaviours.     

Amplicon‐pyrosequencing‐based detection of compositional shifts in bryophyte‐associated fungal communities along an elevation gradient

Although bryophytes are a dominant vegetation component of boreal and alpine ecosystems, little is known about their associated fungal communities. HPLC assays of ergosterol (fungal biomass) and amplicon pyrosequencing of the ITS2 region of rDNA were used to investigate how the fungal communities associated with four bryophyte species changed across an elevational gradient transitioning from conifer forest to the low‐alpine. Fungal biomass and OTU richness associated with the four moss hosts did not vary significantly across the gradient (P > 0.05), and both were more strongly affected by host and tissue type. Despite largely constant levels of fungal biomass, distinct shifts in community composition of fungi associated with Hylocomium, Pleurozium and Polytrichum occurred between the elevation zones of the gradient. This likely is a result of influence on fungal communities by major environmental factors such as temperature, directly or indirectly mediated by, or interacting with, the response of other components of the vegetation (i.e. the dominant trees). Fungal communities associated with Dicranum were an exception, exhibiting spatial autocorrelation between plots, and no significant structuring by elevation. Nevertheless, the detection of distinct fungal assemblages associated with a single host growing in different elevation zones along an elevational gradient is of particular relevance in the light of the ongoing changes in vegetation patterns in boreal and alpine systems due to global climate warming.     

Dental anomalies within extant members of the mammalian Order Pilosa

Recent discovery of a supernumerary dental anomaly in two‐toed sloths led to an extensive review of extant sloth specimens to look for additional anomalies. In total, 881 museum specimens were examined. These revealed two primary types of anomalies, hyperdontia (extra teeth) and anodontia (loss of teeth), occurring at a rate of 2.4% (n = 21). Two‐toed sloths, Choloepus, were more likely to have hyperdontia in the anterior dentition, whereas three‐toed sloths, Bradypus, experienced anodontia more frequently with the upper caniniforms. Both genera experienced both anomalies. The majority affected the upper dentition, with only three specimens exhibiting mandibular anomalies. Beyond the patterns of tooth positioning, all anomalies were random with respect to age, sex and geography. A few specimens not counted in the initial assessment expressed incomplete anodontia, indicating that the loss occurred postnatally and was not an embryological anomaly. For Bradypus, the findings provide new support for the hypothesis that the taxon represents a neotenic lineage and opens new possibilities about its relationship to the extinct ground sloths with a suggested rooting above that of the basal position it typically occupies for Folivora.     

Lectin histochemistry on mucous substances of the taste buds and adjacent epithelia of different vertebrates

Summary In the present study carbohydrate residues in taste buds (TBs) and adjacent epithelial formations of a teleostean fish, a frog and the rabbit were detected by means of lectin histochemistry. Biotinylated lectins fromPisum sativum (PSA),Arachis hypogaea (PNA),Dolichos biflorus (DBA),Triticum vulgaris (WGA and succinylated WGA),Glycine max (SBA) andUlex europaeus (UEA I) have been applied. The lectins were bound to an avidin-biotin-peroxidase-complex (ABC) and visualized by diaminobenzidine/ H₂O₂. Most intensive reactivity was observed at the taste dise cells of the frog with DBA, S-WGA and SBA. PNA did not bind to the TBs of any of the animals tested. As shown in SBA preparations, sialic acid is present in a nonacylated and an acylated form in the mucosa of the frog's tongue. The TBs of the fish possess all the sugars we looked for except for the disaccharided-galactose-(1–3)--d-N-acetyl-galactosamine (Gal/GalNAc) and sialic acid. The TBs of the rabbit contain GalNAc, as detected with DBA, but not with SBA; and fucose (Fuc), mannose (Man) andN-acetyl-glucosamine (GlcNAc). As revealed by preincubation of the tissue sections with neuraminidase in TB cells of the rabbit, sialic acid masks Gal/GalNAc and GalNAc. These lectin-binding characteristics show that in the TBs of some selected representatives which belong to different vertebrate classes exist different mucous substances. These substances possess different binding characteristics to specific sugars, and this is possibly of particular interest to chemoreception phenomena.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday.Parts of this investigation were presented at the 81. Versammlung der Anatomischen Gesellschaft, March 9–14, 1986 at Lübeck (Witt and Reutter 1986), and at the VII th Congress of the Europaen Chemoreception Research Organization, September 22–26, 1986, at Davos (Reutter and Witt 1987).Supported by the Deutsche Forschungsgemeinschaft (Re 225/9-1)     

Prognostic role of the CDNK1B V109G polymorphism in multiple endocrine neoplasia type 1

CDKN1B encodes the cyclin‐dependent kinase inhibitor p27/Kip1. CDKN1B mutations and polymorphisms are involved in tumorigenesis; specifically, the V109G single nucleotide polymorphism has been linked to different tumours with controversial results. Multiple endocrine neoplasia type 1 (MEN1) is a rare autosomal dominant syndrome, characterized by the development of different types of neuroendocrine tumours and increased incidence of other malignancies. A clear genotype–phenotype correlation in MEN1 has not been established yet. In this study, we assessed whether the CDKN1B V109G polymorphism was associated with the development of aggressive tumours in 55 consecutive patients affected by MEN1. The polymorphism was investigated by PCR amplification of germline DNA followed by direct sequencing. Baseline and follow‐up data of tumour types and their severity were collected and associated with the genetic data. MEN1‐related aggressive and other malignant tumours of any origin were detected in 16.1% of wild‐type and 33.3% of polymorphism allele‐bearing patients (P = NS). The time interval between birth and the first aggressive tumour was significantly shorter in patients with the CDKN1B V109G polymorphism (median 46 years) than in those without (median not reached; P = 0.03). Similarly, shorter was the time interval between MEN1 diagnosis and age of the first aggressive tumour (P = 0.02). Overall survival could not be estimated as 96% patients were still alive at the time of the study. In conclusion, CDKN1B V109G polymorphism seems to play a role in the development of aggressive tumours in MEN1.     

A comparison of the mandibular gnathal edges in branchiopod crustaceans: implications for the phylogenetic position of the Laevicaudata

Two significantly different types of mandibular gnathal edges present in extant Branchiopoda are documented by using SEM. The Anostraca, Spinicaudata, Cyclestherida, and certain Cladocera have a pars molaris that forms the entire gnathal edge. In these taxa, the pars molaris consists of comb-like projections originating from the primary surface of the gnathal edge. The comb teeth form the grinding surface at a second, more distal level. The central area of the molar surface is formed as a smooth plate, perforated by numerous small pores. These corresponding features are interpreted as homologous and indicate the homology of this type of gnathal edge. In comparison with the mandibular gnathal edges of other mandibulate taxa, the ellipsoid pars molaris forming the entire gnathal edge can be interpreted as an apomorphy of the Branchiopoda. Another type of gnathal edge is found in the Notostraca and Laevicaudata. It is characterized by several parallel-oriented teeth. Each of these teeth possesses a dorsal and a ventral cusp, both connected by a concave ridge. In addition, a smaller tooth-like structure, but showing more differences to the other teeth, is present anteriorly, and an incisor or canine-like tooth posteriorly. These similarities between laevicaudatan and notostracan gnathal edges are detailed enough to accept primary homology also of the second type of gnathal edge. Differences between the gnathal edges concern the distinct asymmetry of the mandibles in Notostraca and their symmetry in Laevicaudata. In comparison with the other type of gnathal edge, this type has to be interpreted as a synapomorphy of Notostraca and Laevicaudata. This is in conflict with other characters supporting a monophyletic Diplostraca, with the Laevicaudata as sister group to Spinicaudata + Cladoceromorpha.     

秦巴山区近15年植被NPP时空演变特征及自然与人为因子解析

植被NPP作为衡量陆地生态系统的关键指标和地表碳循环的重要组成部分,能够合理地评价生态系统变化及其可持续性。基于MOD17A3数据,借助GIS空间分析、相关性分析及地理探测器模型等方法,探讨了2000—2014年秦巴山区NPP时空格局及演变特征,并对影响NPP的自然和人为因子进行量化研究。结果表明:(1)秦巴山区近15年NPP总量整体呈波动增加趋势,增速0.65TgC a~(-1),单位面积NPP均值为493.09gC m~(-2) a~(-1),呈"西高东低"空间特征,地域差异明显;(2)不同植被类型的NPP总量存在差异,阔叶林和栽培植被是对秦巴山区生态系统最具贡献的植被类型;(3)NPP随高程、坡度均呈阶段性变化特征,其中坡度影响NPP变化的幅度弱于高程,NPP与降雨、气温、实际蒸散量均呈显著正相关关系;(4)自然因子对NPP贡献率存在显著差异(P0.01),依次排序为:实际蒸散量降雨气温高程坡度,且研究区NPP受多种自然因子的交互影响;(5)人为因子对NPP的影响表现为土地利用类型变化造成NPP总量的损益,可分为还林还草的积极效应及城市发展和人类破坏等的消极效应。     

Long‐term stasis and short‐term divergence in the phenotypes of microsnails on oceanic islands

Phenotypic divergence is often unrelated to genotypic divergence. An extreme example is rapid phenotypic differentiation despite genetic similarity. Another extreme is morphological stasis despite substantial genetic divergence. These opposite patterns have been viewed as reflecting opposite properties of the lineages. In this study, phenotypic radiation accompanied by both rapid divergence and long‐term conservatism is documented in the inferred molecular phylogeny of the micro land snails Cavernacmella (Assimineidae) on the Ogasawara Islands. The populations of Cavernacmella on the Sekimon limestone outcrop of Hahajima Island showed marked divergence in shell morphology. Within this area, one lineage diversified into types with elongated turret shells, conical shells and flat disc‐like shells without substantial genetic differentiation. Additionally, a co‐occurring species with these types developed a much larger shell size. Moreover, a lineage adapted to live inside caves in this area. In contrast, populations in the other areas exhibited no morphological differences despite high genetic divergence among populations. Accordingly, the phenotypic evolution of Cavernacmella in Ogasawara is characterized by a pattern of long‐term stasis and periodic bursts of change. This pattern suggests that even lineages with phenotypic conservatism could shift to an alternative state allowing rapid phenotypic divergence.