Microscopic anatomy and ultrastructure of the digestive system of three Antarctic shrimps (Crustacea: Decapoda: Caridea)

Mandibles and stomachs of three Antarctic shrimp species (Nematocarcinus lanceopes, Notocrangon antarcticus, and Chorismus antarcticus) were investigated by means of scanning electron microscopy. Transmission electron microscopy of the midgut glands was applied to find out the nutritional status of the animals, which contained a broad variety of food items in their stomachs. In contrast to the Antarctic krill, the three carideans possess a dual filter system; primary filters in the cardia and secondary filters in the pyloric chamber. Morphologically, the mandibles and stomachs of the three species vary considerably; however, their food items are similar. We conclude that stomach contents do not really reflect the different modes of life or habitat preferences of the investigated species.     

Effects of a rapidly receding ice edge on the abundance,age structure and feeding of three dominant calanoid copepods in the Weddell Sea,Antarctica

Open-water, marginal-ice and in-ice zones were sampled in the Weddell Sea during November and December, 1993 in an effort to examine the influence of the early spring bloom on the diet and population structure of the three biomass dominant copepods: Metridia gerlachei, Calanus propinquus, and Calanoides acutus. The abundance of all three species in the upper 200 m was highest at stations in the open water, but individually, each species displayed a unique trend. M. gerlachei, which showed the least variability, was significantly more abundant in open water than in the marginal-ice zone. The abundance of Calanus propinquus was higher in open water than in the marginal-ice zone or in the ice. Calanoides acutus displayed the highest variability, with significant differences between all three ice-cover zones. Diet analysis revealed no significant differences in the number of food items within each ice-cover zone and diatoms were the most numerous item identified in the guts of all three species. However, M. gerlachei and Calanus propinquus also contained metazoan material, while Calanoides acutus did not. There were dramatic differences in the age composition of the species between the zones. Early copepodite stages of all three species predominated at the ice edge and in open water. Numbers of M. gerlachei adult females were roughly equivalent in all three zones while Calanoides acutus and Calanus propinquus adult females composed a higher fraction of the total population within the ice. These results compare well with life-history data compiled by other authors and reinforce the importance of the ice edge to bloom-dependent Antarctic zooplankton. Accepted: 5 April 1999     

Reproductive activity of two dominant Antarctic copepod species, Metridia gerlachei and Ctenocalanus citer, in late autumn in the eastern Bellingshausen Sea

The main reproductive period of herbivorous Antarctic copepods is coupled to the phytoplankton bloom in spring, while omnivorous or carnivorous species apparently reproduce year round. However, our knowledge of the reproduction during autumn and winter is limited. Therefore this study during a cruise with RV "Polarstern" aimed to measure reproductive activity in two dominant copepod species, Metridia gerlachei and Ctenocalanus citer, in late autumn (April/May). For this purpose, gonad development stages were determined from both species, taken with Bongo net in the eastern Bellingshausen Sea (Antarctic Peninsula region), and related to the ambient feeding conditions represented as chlorophyll a concentration. In addition, experiments were conducted with M. gerlachei to study the influence of feeding and starvation on gonad development. Gonad maturity of M. gerlachei differed considerably between stations and decreased over time. The correlation of chlorophyll a and the proportion of mature females, though significant, was weak and highly variable. In experiments, the gonads of feeding females were in better condition than those of their starving counterparts, showing that reproductive activity in M. gerlachei was related to ambient feeding conditions. Mature females of C. citer were found at each station (17-67%). The gonad stage composition was rather similar at all stations, showing no clear temporal and spatial trend. In this species, the proportion of mature females was not related to the chlorophyll a concentration, indicating either that the ambient phytoplankton stock was sufficient to fuel maturation or that other food sources were used. Our study shows that both species are reproducing during the austral autumn, indicating that their reproduction is partially decoupled from the spring phytoplankton bloom.     

On the nutrition of two Antarctic acanthonotozomatidae (Crustacea: Amphipoda)

Summary Two species of Antarctic acanthonotozomatid amphipods (Echiniphimedia hodgsoni and Maxilliphimedia longipes) have been investigated in regard to their food preference. Examinations of food remains in foreguts and midguts indicate that Echiniphimedia hodgsoni feeds on sponges and Maxilliphimedia longipes ingests Cnidaria. These foregut analyses are supported by a study of the functional morphology of the mouthparts. The structure of the mandibles in particular can be interpreted as an adaptation to the presumed food source. The right mandible of Echiniphimedia hodgsoni bears a lacinia mobilis which works as an additional cutting edge. By means of this cutting mechanism Echiniphimedia hodgsoni should be able to bite out tough sponge material. The mandibular endites of Maxilliphimedia longipes are medially excavated, the incisors are regulary toothed and the molars vestigial. Such kinds of mandibles are adapted to cut large fragments of soft food, i.e. the mucous tissue of Cnidaria.     

Feeding patterns of dominant Antarctic copepods: an interplay of diapause,selectivity, and availability of food

Gut contents and feeding activity of five dominant Antarctic copepods (Calanus propinquus, Calanoides acutus, Rhincalanus gigas, Metridia gerlachei and Microcalanus pygmaeus) were studied from samples collected during several cruises of the RV Polarstern to the eastern Weddell Sea. In summer, feeding activity, estimated as percentage of copepods with food in the guts, was high in all the species, and diatoms dominated all gut contents. In winter, C. acutus was trophically inactive, and C. propinquus and R. gigas considerably decreased their feeding activity, while a decrease in feeding of M. gerlachei and M. pygmaeus was less pronounced. Unidentified mass dominated gut contents in winter, supplemented by phytoplankton and protozoans. Prior to the spring bloom, feeding activity of C. acutus was low, with unidentified food predominating, while carnivory was important in actively feeding C. propinquus. Rhincalanus gigas tended to be more carnivorous than C. acutus, however with less feeding activity than C. propinquus. Seasonal changes in feeding patterns are discussed.     

Vernal abundance,structure and development of epipelagic copepod populations of the eastern Weddell Sea (Antarctica)

Summary Pelagic copepod populations under the pack ice of the Antarctic Weddell Sea were sampled with a 50 m net between October 2 and December 7, 1986, to study their abundance and developmental stage composition before and at the onset of the vernal phytoplankton bloom. Subadult stages and adult females were incubated to estimate rates of development and egg production. Copepod densities in the upper 200 m were highest for the small-sized species Oithona similis, Oncaea curvata and Ctenocalanus citer. About 95% of the copedite stages belonged to these species, dominated by Oithona. The copepodids were outnumbered by the nauplii in all species, except in Oncaea. The stage distribution in the small-sized species was bimodal with peaks in N3 and C4. The larger species Calanus propinquus and Metridia gerlachei showed peaks in nauplii only. Eggs were relatively abundant in all small and large species. Animals smaller than 1 mm not only were more abundant than the larger ones, but also had a higher total potential respiration. Eggs were produced by incubated females in sea water virtually without food at 0°C. Eggs hatched, and Oithona nauplii developed at a rate of about 7 days per stage. Copepodite stages did not develop significantly. Reproduction in the most abundant species commonly occurred before the algal spring increase when food levels were very low. Maintenance of a stable stage distribution at the expense of a high juvenile mortality seemed to be characteristic for the overwintering strategy of Antarctic copepods.     

Adaptations for the maintenance of water balance by three species of Antarctic mites

Three species of Antarctic mites, Alaskozetes antarcticus, Hydrogamasellus antarcticus and Rhagidia gerlachei, are abundant in the vicinity of Palmer Station, Antarctica. No single mechanism for reducing water stress was shared by all three species. A. antarcticus and R. gerlachei (both ca. 200 μg) are over twice as large as H. antarcticus (ca. 90 μg), but all had similar body water content (67%) and tolerated a loss of up to 35% of their body water before succumbing to dehydration. All imbibed free water and had the capacity to reduce water loss behaviorally by forming clusters. Alaskozetes antarcticus was distinct in that it relied heavily on water conservation (xerophilic classification) that was largely achieved by its thick cuticular armor, a feature shared by all members of this suborder (Oribatida), and abundant cuticular hydrocarbons. In comparison to the other two species, A. antarcticus was coated with 2–3× the amount of cuticular hydrocarbons, had a 20-fold reduction in net transpiration rate, and had a critical transition temperature (CTT) that indicates a pronounced suppression in activation energy (E _a) at temperatures below 25°C. In contrast, H. antarcticus and R. gerlachei lack a CTT, have lower amounts of cuticular hydrocarbons and have low E _as and high net transpiration rates, classifying them as hydrophilic. Only H. antarcticus was capable of utilizing water vapor to replenish its water stores, but it could do so only at relative humidities close to saturation (95–98 %RH). Thus, H. antarcticus and R. gerlachei require wet habitats and low temperature to counter water loss, and replace lost water behaviorally through predation. Compared to mites from the temperate zone, all three Antarctic species had a lower water content, a feature that commonly enhances cold tolerance.     

Egg and faecal pellet production rates of the marine copepod Metridia gerlachei northwest of the Antarctic Peninsula

Egg and faecal pellet production rates, and their functional response to food and temperature, were measured for the Antarctic copepod Metridia gerlachei during January 1996. The study area comprised the Gerlache and Bransfield Straits and Drake Passage. The highest rates of “in situ” egg and faecal pellet production were observed in Gerlache stations, coinciding with chlorophyll a concentrations approaching food saturation levels. In the Bransfield and Drake stations, with very low chlorophyll concentrations, the rates of egg production were either very low, or no eggs were produced. Egg production rates, although well correlated with “in situ” chlorophyll values, appeared to be independent of food concentration on a short time-scale (24-h incubations), while the production of faecal pellets was closely related to food abundance in the same experiments. In general, the rates of egg production were low, even at food saturation, with a very high individual variability. Although in the majority of Gerlache stations about 50% of total chlorophyll a corresponded to the phytoplankton size-fraction >10 μm, M. gerlachei feeds preferentially on the <10-μm fraction. Temperature had no clear effects on egg production rate but had a significant effect on pellet production rates, with maximum values at 2.5°C. These features appear to agree with the reproductive strategy attributed to the species, based on a relatively low rate of egg production extended over a long reproductive period. Received: 18 November 1996 / Accepted: 24 March 1997     

Life cycle strategies and seasonal variations in distribution and population structure of four dominant calanoid copepod species in the eastern Weddell Sea, Antarctica

The dominant Antarctic copepod species Calanoides acutus, Calanuspropinquus, Rhincalanus gigas and Metridia gerlachei were investigatedwith respect to their abundance, vertical distribution, developmentalstage composition, dry weight and lipid content. The specimenswere sampled during three expeditions to the eastern WeddellSea in summer (January/February 1985), late winter/early spring(October/November 1986) and autumn (April/May 1992) between0 and 1000 m depth to follow the seasonal development of thepopulations. Three species were most abundant in April, onlyC.propinquus reached highest concentrations in February. A seasonalmigration pattern was evident in all four species, but was mostpronounced in C.acutus. In October/November, they inhabiteddeeper water layers, their ascent started by mid-November andin mid-February the species concentrated in the upper 50 m,except for M.gerlachei (50–100 m). Their descent was observedin April/May. The stage composition changed dramatically withseason, the older developmental stages (CIII–CVI) dominatedthe populations in late winter/early spring, whereas youngerstages (CI and CII) prevailed during summer (C.acutus, C.propinquus)or autumn (R.gigas, M.gerlachei). Only C.acutus ceased feedingin autumn and diapaused at depth. Strong differences betweenseasons were also detected in dry weight and lipid levels, withminima in late winter/early spring and maxima in summer (C.acutus,R.gigas) or autumn (C.propinquus, M.gerlachei). Lipid reservesseem to be most important for the older stages of C.acutus andC.propinquus. Based on these seasonal data, different life cyclestrategies are suggested for the four species.     

Aspects of the study of the life cycles of Antarctic copepods

Different approaches to the study of life cycle strategies of Antarctic copepods are described in an attempt to shed new light on our present knowledge. To date, most studies were carried out on abundance, horizontal and vertical distribution and stage composition during different seasons and in various regions. Hence, the seasonal pictures had to be compiled from different years and sampling regions. The physiological method includes measurements on e.g. egg production, feeding, respiration and excretion rates, C:N and O:N ratios, lipid and protein contents. However, both physiological and biochemical data are still rare. Results of field observations are given in this paper for investigations conducted within the last 15 years in the eastern Weddell Sea, while data of physiological parameters are based on a broader geographical region. In the eastern Weddell Sea, eight copepod species account for about 95% of copepod abundance and for more than 80% of copepod biomass. Within the calanoids, the small species Microcalanus pygmaeus dominates by numbers with 66%, while the large species Calanoides acutus and Calanus propinquus comprise together 52% of the biomass. Species abundance is lowest in winter and highest in summer/autumn, however, seasonal changes in the abundance of M. pygmaeus are small and this species occurs in similar quantities throughout the year. All copepod species show a distinct seasonal vertical distribution pattern and they occur in upper water layers in summer, in contrast to the other seasons. However, the depth layers of maximum concentration differ between species. The ontogenetic vertical migration is most pronounced in C. acutus and relatively weak in C. propinquus. The age structure also shows seasonal differences with the youngest population observed in summer for C. acutus, C. propinquus, Ctenocalanus citer or autumn for Metridia gerlachei, whereas the M. pygmaeus population is oldest during summer. The youngest copepodite stage and the males are not always present in C. acutus and C. propinquus. In contrast, all developmental stages and both sexes occur throughout the year in M. gerlachei, M. pygmaeus and C. citer. Gonad maturation in the dominant calanoid species proceeds well before the onset of phytoplankton production in the eastern Weddell Sea. However, the highest portion of females with ripe gonads and hence highest egg production rates coincide with the productive period in spring and summer. In autumn, ovaries of the three larger species C. acutus, C. propinquus and M. gerlacheiare all spent. In contrast, the percentage of ripe females of the two smaller species, C. citer and M. pygmaeus, stays high in autumn. Egg production rates are highly variable within one region and species. Many copepods accumulate large depots of lipid, mainly wax esters. In contrast, five species (C. propinquus, C. simillimus, Euchirella rostromagna, Stephos longipes and Paralabidocera antarctica) almost exclusively synthesise triacylglycerols and not wax esters. The lipid content exhibits distinct seasonal patterns, and is highest in autumn. A seasonal difference is also obvious in metabolic activities with lowest rates during the dark season. The adaptation to the pronounced seasonality in the Southern Ocean differs greatly between copepod species, and most Antarctic copepods stay active during the dark season. Calanoides acutus seems to be the only true diapause species. Calculations of summer developmental rates and winter mortality rates of the large species C. acutus and C. propinquus suggest that both species have a 1-year life cycle with few females overwintering and probably spawning a second time. In contrast, a 2-year life cycle is more likely in R. gigas. However, life cycle durations of all species studied are still uncertain and regional differences are very probable.     

Ultrastructure and Molecular Phylogeny of Mesodinium coatsi sp. nov., a Benthic Marine Ciliate

Mesodinium is a globally distributed ciliate genus forming frequent and recurrent blooms in diverse marine habitats. Here, we describe a new marine species, Mesodinium coatsi n. sp., originally isolated from interstitial water of surface sand samples collected at Mohang Beach, Korea. The species was maintained under a mixotrophic growth condition for longer than 1 yr by providing a cryptomonad, Chroomonas sp., as the sole prey. Cell morphology and subcellular structure were examined by light microscopy, scanning, and transmission electron microscopy, and molecular phylogeny was inferred from nuclear‐encoded 18S rDNA sequence data. Like other Mesodinium species, M. coatsi consisted of two hemispheres separated by two types of kinetids, and had tentacles located at the oral end of the cell. Several food vacuoles were observed in the cytoplasm, and partially digested prey cells sometimes existed in food vacuoles. Kinetids and the associated accessory structures were quite similar to those previously reported, but M. coatsi was differentiated from other marine Mesodinium species by ultrastructural characters of the dikinetids, polykinetids, and tentacles. We also provided a detailed illustration of infraciliature. Molecular phylogeny revealed that M. coatsi and Mesodinium chamaeleon were closely related to each other.     

Gut contents and diel feeding rhythm in dominant copepods in the ice-covered Weddell Sea,March 1992

Zooplankton was sampled at a diurnal station during the drift of the Ice Station Weddell-1 in the western Weddell Sea in March 1992. Gut contents of Metridia gerlachei, Calanoides acutus, Calanus propinquus and Rhincalanus gigas were studied. Calanoides acutus was trophically inactive, but 18%, 33% and 45% of Calanus propinquus, R. gigas and M. gerlachei, respectively, contained food in their guts. Diel changes in gut levels and percentage of individuals with full guts with maximum during the dark period were observed in M. gerlachei copepodite stage V and females. The possible reasons for observed differences in foraging patterns of the four copepod species are discussed.     

CYTOMORPHOLOGICAL CHARACTERIZATION OF THE PLANKTONIC DIAZOTROPHIC CYANOBACTERIA TRICHODESMIUM SPP. FROM THE INDIAN OCEAN AND CARIBBEAN AND SARGASSO SEAS1

Trichodesmium Ehrenberg species were collected in the Caribbean Sea, Sargasso Sea, and coastal areas of Tanzania (Indian Ocean). The specimens were divided into five species on the basis of morphometric characters such as cell dimensions and colony formation: T. tenue Wille, T. erythraeum Ehrenberg, T. thiebautii Gomont, T. hildebrandtii Gomont, and T. contortum Wille. In addition, Trichodesmium sp., a spherical colony of uncertain taxonomic position was examined. The cell structure of each species was investigated by means of light, scanning electron, and transvnission electron microscopy. Particular attention was paid to the presence and ultrastructural arrangement of gas vacuoles and glycogen fiber clusters (GFCs). This resulted in identification of two major groups of species: 1) T. tenue, Trichodesmium sp. with spherical-shaped colonies, and T. erythraeum with GFCs and more or less localized gas vacuoles; and 2) T. thiebautii, T. hildebrandtii, and T. contortum lacking GFCs and with gas vacuoles spread at random. The species within each group were further characterized with respect to the dimension of the gas vesicles, cylindrical bodies, scroll bodies, and a new cellular inclusion body, Differences in colony formation and cell dimensions correlated with specific ultrastructural characters in five of the six forms. This is the first ultrastructural study comparing different forms of Trichodesmium sampled at geographically remote areas and shows that one species appears identical regardless of the sampling site. Some of the species had not been investigated earlier, and probably more species are to be identified and analyzed.     

Morphological diversity of the resting eggs in the anostracan genus Chirocephalus (Crustacea, Branchiopoda)

Resting egg morphology of the species groups in Chirocephalus defined by Brtek (1995) on the basis of classical characters was examined by scanning electron microscopy (SEM) in order to verify this taxonomically useful character. The results are complex: some species groups show well delineated cyst morphology, but often not. Some species show rather constant morphologies, while in others, cyst ornamentation varies widely with and between populations.     

Epizoic bacteria on the foot of the Antarctic bivalve, Lissarca notorcadensis Melville and Standen, 1907 (Filibranchia: Philobryidae)

Specimens of the epizoic bivalve Lissarca notorcadensis Melville and Standen, 1907 (Philobryidae) were collected from the spines of cidaroid sea-urchins in the Weddell Sea during austral summer 1991. Soft tissues were investigated by means of transmission electron microscopy. Epizoic bacteria were discovered on the foot in 14 out of 15 specimens of the bivalve, and in juveniles as well as in adults. The presence of bacteria was restricted to a certain area of the foot's surface, where they were populating the brushborder of the epidermal epithelium. This is the first time that epizoic bacteria have been described, either from an Antarctic bivalve or from the foot epithelium of any bivalve species. Aspects of the fine structure were studied with regard to future work on this symbiosis. The bacteria undergo a full life-cycle in the brushborder. Whereas young or dividing bacteria are found more distally between the microvilli, senescent stages seem to disintegrate and be absorbed between their bases. The bacteria could contribute to the nutrition of their host by breaking down macromolecular or particulate organic matter, which would facilitate parenteral absorption by the bivalve, as well as eventual digestion. The ultrastructural findings suggest that the bacteria are neither sulphidotrophic nor methylotrophic. Based on their appearance, they are classified as sub-cuticular bacteria, which have been recently described from the surface epithelia in various marine invertebrate species. The phenomenon is discussed in respect to seasonal food limitation for Antarctic suspension feeders and the brooding behaviour of the host species and its ecological success. Received: 26 April 1996 / Accepted: 8 September 1996     

Feeding plasticity of Trematomus newnesi (Pisces, Nototheniidae) in Terra Nova Bay, Ross Sea, in relation to environmental conditions

Forty-three and 49 specimens of the Antarctic fish Trematomus newnesi were collected in the coastal waters of Terra Nova Bay, Ross Sea, during December 1994 and February 1998, respectively. The dietary composition of the two fish samples was determined by means of stomach content analysis and then compared. In general, as reported in most of the previous studies, planktivory appeared to be the main feeding habit of T. newnesi. However, the different environmental conditions occurring in the study area in the two periods investigated, such as the degree of the sea-ice coverage and the related amount of light available below the ice, influenced the food composition of T. newnesi. In December 1994, the whole area investigated was covered by a thick layer of sea ice and the diet of T. newnesi consisted of few prey taxa. Some species that characterize the so-called “cryopelagic habitat”, such as the euphausiid Euphausia crystallorophias and the copepod Metridia gerlachei, were by far the most important prey, followed by amphipods and the pteropod Limacina helicina. Conversely, the ostracod Alacia belgicae and larval stages of fish (Pleuragramma antarcticum) were consumed occasionally. In late summer (February 1998), the lack of sea-ice coverage and changes in the associated fauna influenced the feeding habit of T. newnesi. In this period the food spectrum appeared to be more diverse, revealing an active feeding search in the water column. The bulk of food was composed of several prey groups, such as E. crystallorophias, hyperiid amphipods (Hyperiella dilatata), copepods, L. helicina and several species of fish larvae. Present data provide evidence of a marked feeding plasticity of T. newnesi, in response to diverse environmental conditions that characterize the High-Antarctic Zone. Accepted: 17 July 1999     

Micromorphological and chemical characterisation of Stachys recta L. subsp. serpentini (Fiori) Arrigoni in comparison to Stachys recta L. subsp. recta (Lamiaceae)

Stachys recta L. is a very polymorphous species in which numerous subspecies were recognised. S. recta L. subsp. serpentini (Fiori) Arrigoni is a typical endemism growing on serpentine soils in northern Apennines and particularly in Tuscany (Italy). In order to contribute to a better knowledge of this plant and to its differentiation with respect to S. recta L. subsp. recta, the micromorphological characters (non-glandular and glandular trichomes) and the essential oil composition of the two subspecies were investigated. Micromorphological characters were studied using scanning and transmission electron microscopy, while light microscopy was used for histochemical observations. Essential oil analysis was carried out by gas chromatography and mass spectrometry.In the two examined taxa, the morphology and distribution of glandular and non-glandular trichomes, and the different essential oil composition, may be considered distinctive characters at subspecies level. This is consistent with the taxonomic classification considering S. recta subsp. serpentini a subordinate taxon of S. recta.     

Ultrastructural observations of the protonephridia of Polymerurus nodicaudus (Gastrotricha: Paucitubulatina)

Kieneke, A. and Hochberg, R. 2012. Ultrastructural observations of the protonephridia of Polymerurus nodicaudus (Gastrotricha: Paucitubulatina). —Acta Zoologica (Stockholm) 93 : 115–124. We studied different regions of the protonephridia of the limnic gastrotrich Polymerurus nodicaudus by means of light and electron microscopy to determine how freshwater species might differ from their marine relatives. Microscopic and ultrastructural characters are in accordance with another limnic species of Paucitubulatina, Chaetonotus maximus, whose protonephridial system has been previously reconstructed. Shared protonephridial characters of both species include the presence of highly elongate terminal organ cilia, microvilli, and the canal cell lumen as well as the presence of a conspicuous anterior loop of the protonephridial lumen. These features are not present in representatives of earlier, marine, paucitubulatan lineages (i.e., Xenotrichulidae) and so are assessed as evolutionary novelties that were likely important for the successful colonization of the freshwater environment.     

A new species of Myriochele (Polychaeta, Oweniidae) from Antarctica, with considerations on the Antarctic oweniids

A new species of Oweniidae from the Ross Sea (Antarctica) is described and compared with the remaining species of the genus Myriochele from the Antarctic seas. The authors also discuss the difficulty of detecting the shape of uncini (considered as an important diagnostic character) by optical microscopy; they propose a key to Antarctic Oweniidae based on characters easier to observe than uncini. Received: 14 October 1997 / Accepted: 16 December 1997     

Gastric teeth of some thoracotreme crabs and their contribution to the brachyuran phylogeny

The gastric teeth of three ocypodoid species were investigated using scanning electron microscopy, and the morphological results were discussed with respect to the known food preferences. The species were chosen in particular because of contrasting ideas about their relationships within the Thoracotremata. For the genera Heloecius, Dotilla, Mictyris, and “Uca” (s. str.), we find a specific correlation of the gastric teeth with the suspension feeding. The lateral gastric teeth of Uca have no prominent lateral teeth cusps, and most of their teeth surface consists of transverse comb‐like lamellae. However, this possible food adaptation does not exclude the usability of specific teeth characters to distinguish species of suspension feeders. The closer relationship of the Dotillidae to grapsoid lines of gecarcinid or sesarmid crabs suggested by molecular data is not supported by the gastric teeth. For the genus Ucides, we found several characters that distinguish Ucides from the remaining ocypodoid genera Heloecius, Dotilla, Mictyris, and “Uca.” In particular, the structures of the lateral and the dorsomedian teeth show some similarities to genera of the Gecarcinidae and Sesarmidae. Our results suggest that foregut characters can be used for phylogenetic analyses. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.