Evolution of C isotopes in the Cambrian of China: implications for Cambrian subdivision and trilobite mass extinctions

Carbon and oxygen isotopes were studied in fossiliferous Cambrian carbonates in northwestern Hunan Province (South China) and in northern Anhui and southern Shandong provinces (North China). Two major C isotope excursions related to biological events occur in the Wangcun section (Yongshun County, northwestern Hunan), which consists of a slope carbonate sequence (510 m thick) containing abundant trilobites. The first C isotope excursion (δ¹³C value shifts from -2.3‰ to 2‰) occurs near the boundary between the Qingxudong and Aoxi formations, close to the traditional Lower-Middle Cambrian boundary. The second excursion (δ¹³C value shifts from 0‰ to 3‰) occurs in the interval between the Linguagnostus reconditus Zone and the Glyptagnostus reticulatus Zone. The base of the G. reticulatus Zone define the base of the Paibi Stage and Furongian Series. Similar C isotope excursions also occur in shallow - water carbonate sections in North China. In Jiagou section near Huainan (Anhui Province), recently considered an important interval for defining the lower-middle Cambrian boundary because of dramatic changes in the trilobite fauna (extinction of redlichiids and appearances of ptychopariids), a negative C isotope excursion (δ¹³C value shifts from +1.21‰ to -1.93‰) occurs at the top of the lower member of the Mantou Formation. In the Gushan section (Changqing County, Shandong Province), a C isotope excursion (δ¹³C value shifts from -0.04‰ to 2.23‰) occurs at the base of the Changshan Formation and is coincident with the base of the Chuangia Zone. This excursion can be correlated with the excursion in the lower part of Glyptagnostus reticulatus Zone in the Wangcun section. The above two distinct C isotope excursions, which occur both in slope carbonates in South China and in shallow - water carbonates in North China, have also been recognized in Cambrian sections on other continents, and they coincide with global mass extinctions of trilobites. The two excursions evidently reflect global changes of Cambrian sea level, and they have utility for Cambrian subdivisions and for both regional and global stratigraphic correlation. In addition, a negative carbon excursion below the base of the Ptychagnostus atavus Zone in the Wangcun section supports previous suggestions that the FAD of P. atavus can be considered as a global correlatable horizon within the middle Cambrian.     

Rectus femoris and vastus intermedius fiber excursions predicted by three-dimensional muscle models

Computer models of the musculoskeletal system frequently represent the force-length behavior of muscle with a lumped-parameter model. Lumped-parameter models use simple geometric shapes to characterize the arrangement of muscle fibers and tendon; this may inaccurately represent changes in fiber length and the resulting force-length behavior, especially for muscles with complex architecture. The purpose of this study was to determine the extent to which the complex features of the rectus femoris and vastus intermedius architectures affect the fiber changes in length ("fiber excursions"). We created three-dimensional finite-element models of the rectus femoris and vastus intermedius muscles based on magnetic resonance (MR) images, and compared the fiber excursions predicted by the finite-element models with fiber excursions predicted by lumped-parameter models of these muscles. The finite-element models predicted rectus femoris fiber excursions (over a 100 degrees range of knee flexion) that varied from 55% to 70% of the excursion of the muscle-tendon unit and vastus intermedius fiber excursions that varied from 55% to 98% of the excursion muscle-tendon unit. In contrast, the lumped-parameter model of the rectus femoris predicted fiber excursions that were 86% of the excursion of the muscle-tendon unit and vastus intermedius fiber excursions that were 97% of the excursion of the muscle-tendon unit. These results suggest that fiber excursions of many fibers are overestimated in lumped-parameter models of these muscles. These new representations of muscle architecture can improve the accuracy of computer simulations of movement and provide insight into muscle design.     

The effect of shortening history on isometric and dynamic muscle function

Despite numerous reports on isometric force depression, few reports have quantified force depression during active muscle shortening (dynamic force depression). The purpose of this investigation was to determine the influence of shortening history on isometric force following active shortening, force during isokinetic shortening, and velocity during isotonic shortening. The soleus muscles of four cats were subjected to a series of isokinetic contractions at three shortening velocities and isotonic contractions under three loads. Muscle excursions initiated from three different muscle lengths but terminated at a constant length. Isometric force produced subsequent to active shortening, and force or shortening velocity produced at a specific muscle length during shortening, were compared across all three conditions. Results indicated that shortening history altered isometric force by up to 5%, force during isokinetic shortening up to 30% and shortening velocity during isotonic contractions by up to 63%. Furthermore, there was a load by excursion interaction during isotonic contractions such that excursion had the most influence on shortening velocity when the loads were the greatest. There was not a velocity by excursion interaction during isokinetic contractions. Isokinetic and isotonic power–velocity relationships displayed a downward shift in power as excursions increased. Thus, to discuss force depression based on differences in isometric force subsequent to active shortening may underestimate its importance during dynamic contractions. The presence of dynamic force depression should be realized in sport performance, motor control modeling and when controlling paralyzed limbs through artificial stimulation.     

Late Ordovician (Turinian–Chatfieldian) carbon isotope excursions and their stratigraphic and paleoceanographic significance

Five positive carbon isotope excursions are reported from Platteville–Decorah strata in the Upper Mississippi Valley. All occur in subtidal carbonate strata, and are recognized in the Mifflin, Grand Detour, Quimbys Mill, Spechts Ferry, and Guttenberg intervals. The positive carbon isotope excursions are developed in a Platteville–Decorah succession in which background δ¹³C values increase upward from about −2‰ at the base to about 0‰ Vienna Pee Dee belemnite (VPDB) at the top. A regional north–south δ¹³C gradient, with lighter values to the north and heavier values to the south is also noted. Peak excursion δ¹³C values of up to +2.75 are reported from the Quimbys Mill excursion, and up to +2.6 from the Guttenberg excursion, although there are considerable local changes in the magnitudes of these events. The Quimbys Mill, Spechts Ferry, and Guttenberg carbon isotope excursions occur in units that are bounded by submarine disconformities, and completely starve out in deeper, more offshore areas. Closely spaced chemostratigraphic profiles of these sculpted, pyrite-impregnated hardground surfaces show that they are associated with very abrupt centimeter-scale negative δ¹³C shifts of up to several per mil, possibly resulting from the local diagenetic effects of incursions of euxinic bottom waters during marine flooding events.     

A one night stand? Reproductive excursions of female roe deer as a breeding dispersal tactic

Breeding dispersal, defined as the net movement between successive breeding sites, remains a poorly understood and seldom reported phenomenon in mammals, despite its importance for population dynamics and genetics. In large herbivores, females may be more mobile during the breeding season, undertaking short-term trips (excursions) outside their normal home range. If fertilisation occurs, leading to gene flow of the male genome, this behaviour could be considered a form of breeding dispersal from a genetic point of view. Here, we investigated ranging behaviour of 235 adult roe deer using intensive GPS monitoring in six populations across Europe within the EURODEER initiative. We show that excursions are common from June to August among females, with 41.8 % (vs. 18.1 % of males) making at least one excursion. Most individuals performed only one excursion per season and departure dates for females were concentrated in time, centred on the rutting period, suggesting a link with reproduction. The distance females travelled during excursions was significantly greater than the site-specific average diameter of a male home range, while travel speed decreased once they progressed beyond this diameter, indicating search behaviour or interaction with other male(s) outside the resident male’s territory. Because adults are normally highly sedentary, the potential for mating with relatives is substantial; hence, we conclude that rut excursions could be an alternative tactic enabling females to avoid mating with a closely related male. To understand better the ultimate drivers at play, it will be crucial to explore the genetic causes and consequences of this behaviour.     

In vivo human tendinous tissue stretch upon maximum muscle force generation

In the present study, we examined the hypothesis that stretch of tendinous tissue in the human tibialis anterior (TA) muscle-tendon unit upon isometric dorsiflexion maximum voluntary contraction (MVC) varies along the entire tendinous component length. Ultrasound-based measurements of the excursions of the TA tendon origin and proximal end of the TA central aponeurosis were taken in the transition from rest to MVC in six men. Subtracting the TA tendon origin excursion from the excursion of the aponeurosis proximal end, the aponeurosis excursion was estimated. Estimation of the aponeurosis proximal region excursion was obtained subtracting the excursion of the insertion point of a central region fascicle on the aponeurosis from the whole aponeurosis excursion. Subtracting tendon excursion from the excursion of the central fascicle insertion point, the aponeurosis distal region excursion was estimated. Strain values were calculated dividing the excursions obtained by the original resting lengths. All excursions and lengths were measured in the mid-longitudinal axis of the TA muscle-tendon unit at the neutral anatomical ankle position. Tendon excursion and strain were 0.5+/-0. 08 cm (mean+/-SE) and 3.1+/-0.2%, respectively. Aponeurosis excursion and strain were 1.1+/-0.15 cm and 6.5+/-0.6%, respectively. Aponeurosis distal region excursion and strain were 0.3+/-0.05 cm and 3.5+/-0.3%, respectively. Aponeurosis proximal region excursion and strain were 0.8+/-0.12 cm and 9.2+/-1%, respectively. Aponeurosis excursion and strain were larger by 110-120% (P<0.05) compared with tendon. Aponeurosis proximal region excursion and strain were larger by 165-170% (P<0.05) compared with aponeurosis distal region. These findings are in line with results from in vitro animal material testing and have important implications for theoretical models of muscle function.     

Local paleoenvironmental controls on the carbon‐isotope record defining the Bitter Springs Anomaly

Large magnitude (>10‰) carbon‐isotope (δ¹³C) excursions recorded in carbonate‐bearing sediments are increasingly used to monitor environmental change and constrain the chronology of the critical interval in the Neoproterozoic stratigraphic record that is timed with the first appearance and radiation of metazoan life. The ~10‰ Bitter Springs Anomaly preserved in Tonian‐aged (1000–720 Ma) carbonate rocks in the Amadeus Basin of central Australia has been offered as one of the best preserved examples of a primary marine δ¹³C excursion because it is regionally reproducible and δ¹³C values covary in organic and carbonate carbon arguing against diagenetic exchange. However, here we show that δ¹³C values defining the excursion coincide with abrupt lithofacies changes between regularly cyclic grainstone and microbial carbonates, and desiccated red bed mudstones with interbedded evaporite and dolomite deposits, recording local environmental shifts from restricted marine conditions to alkaline lacustrine and playa settings that preserve negative (?4‰) and positive (+6‰) δ¹³C values, respectively. The stratigraphic δ¹³C pattern in both organic and carbonate carbon recurs within the basin in a similar way to associated sedimentary facies, reflecting the linkage of local paleoenvironmental conditions and δ¹³C values. These local excursions may be time transgressive or record a relative sea‐level influence manifest through exposure of sub‐basins isolated by sea‐level fall below shallow sills, but are independent of secular seawater variation. As the shallow intracratonic setting of the Bitter Springs Formation is typical of other Neoproterozoic carbonate successions used to construct the present δ¹³C seawater record, it identifies the potential for local influences on δ¹³C excursions that are neither diagenetic nor representative of the global exogenic cycle.     

Preparation for flight: pre‐fledging exercise time is correlated with growth and fledging age in burrow‐nesting seabirds

Chicks of many burrow‐nesting seabirds are known to repeatedly emerge from their nests (these trips being termed ‘excursions’) and exercise their wings prior to fledging, but this behavior is poorly documented in the literature, and thus the relationship between growth and exercise remains unclear. Here, we used infrared video cameras placed in front of streaked shearwater Calonectris leucomelas nests during the chick‐emergence period to examine correlations between chick excursions and parameters known to be important for juvenile survival after fledging. In addition, we also attached acceleration‐temperature loggers to several chicks in order to evaluate the relationship between excursion time and time spent exercising the wing muscles (i.e. flapping). Chicks that undertook longer excursions exhibited more rapid increases in wing length and larger body masses at fledging, and also fledged earlier. Correlations between fitness‐related parameters and excursion time indicate that excursions during the emergence period might offer insights into the various relationships between growth and behavior and/or the mechanisms underlying offspring survival following fledging.     

Advances in Cambrian stratigraphy and paleontology: Integrating correlation techniques, paleobiology, taphonomy and paleoenvironmental reconstruction

Papers resulting from the Fourth International Symposium on the Cambrian System, held in Nanjing, China, in 2005 cover three major aspects of geology and paleontology: (1) the developing global standard for Cambrian chronostratigraphy or regional correlation schemes; (2) regional lithostratigraphy, sedimentology and paleoenvironments; (3) organismal paleobiology, phylogenetic affinities and taphonomy.A generalized curve of carbon isotopes (δ¹³C) through the Cambrian suggests a relationship between major biotic events, sea level history and the development of deposits of exceptional preservation (Lagerstätten). Recognition of this relationship increases the importance of the δ¹³C profile as a tool for intercontinental and intracontinental correlation. Significant δ¹³C excursions in the Cambrian are: BACE (negative excursion at the base of the Cambrian System); ZHUCE (positive excursion in the lower part of Stage 2); SHICE (negative excursion in the middle part of Stage 2); CARE (positive excursion near the base of Stage 3); MICE (positive excursion in the lower part of Stage 4); AECE (negative excursion in the middle part of Stage 4); ROECE (negative excursion near the base of Stage 5); DICE (negative excursion beginning near the base of the Drumian Stage); SPICE (positive excursion beginning at the base of the Paibian Stage); TOCE (negative excursion near the top of Stage 10). All acronyms other than SPICE are newly proposed.     

Research on nitrogen-oxygen saturation diving with repetitive excursions

For some tasks of underwater operation the need for longer dive duration and more working divers necessitates the use of saturation diving techniques with excursions. Saturation diving with excursion has high working efficiency. A collaborative experiment with Chinese Underwater Technology Institute, American National Office of Research Undersea Program and Hamilton Research Ltd. was conducted at our Institute in Shanghai. The main experiment objectives were to assess the longer, deeper repetitive excursions during nitrogen-oxygen saturation situation, oxygen exposure management, nitrox saturation decompression after excursions and performance aspects. Four Chinese professional experienced divers were saturated at 25 msw for 5 days at the hyperbaric facility, where they did 15 air excursions to depths between 50 and 75 msw, for duration up to 240 min. Decompression from excursions to the storage were mostly no-stops, but 5 required stops for 3 to 116 min. Saturation decompression began with the "precursory" ascent following a brief return to 25 msw. Doppler bubble detection showed some bubbles of Spencer Grade II and occasionally III, following excursions and during saturation decompression, especially after muscle flexing. No symptoms of decompression sickness were reported: one diver was more of fatigued on one occasion than other times. Oxygen exposure reached its peak of 3103 Oxygen Toxicity Units on Day 6. The only subjective symptom of oxygen toxicity was mild and transient numb fingertips. No significant change was seen in vital capacity.     

Going Out to Mate: Excursion Behaviour of Female Roe Deer

Among mammals, female searching behaviour for a mate has been poorly investigated in behavioural studies on sexual selection. The social organization of roe deer and its physiological constraints suggest the existence of searching strategies by females. Using radiotracking and direct observation we studied the spatial behaviour and intersexual interactions of 32 roe does during the rut in two areas of Tuscany, central Italy. Respectively, 55% and 33% of females performed excursions outside their usual home ranges during the peak of the rut (15 Jul.–15 Aug.). Excursions ranged from 0.6 to 3.0 km, if measured in a straight line, and lasted 30–52 h. During excursions, females (1) moved quickly in one direction; (2) met and were courted by a male; (3) copulated with a male and (4) returned to their home ranges after mating. Before starting an excursion, roaming females were observed to approach unsuccessfully males already courting other females. Most likely excursions represent a condition dependent mating tactic adopted by a variable proportion of females and involving active searching behaviour.     

Stamen development in the Ericaceae. I. Anther wall, microsporogenesis, inversion, and appendages

Development of the introrse, tetrasporangiate, and normally dorsifixed and poricidal stamens has been studied at the gross morphological and cellular level in ten species of Ericaceae. Microsporogenesis, followed in four species, is normal, with cytokinesis simultaneous, forming tetrahedral tetrads. The tricolp(or)ate pollen is shed as permanent tetrads with each segment two-celled except in Enkianthus in which pollen grains are three-celled monads. Anther-wall development is similar in all four species initially, but no regular pattern of wall development could be recognized thereafter. The tapetum, of parietal origin, is binucleate, glandular, and mainly uniseriate. Viscin threads occur with the tetrads in the three rhododendroid species. A well-developed endothecium appears only in Enkianthus.Soon after stamen initiation, anthers of nine species invert at the eventual filament-anther junction to become introrse; in Enkianthus inversion occurs close to anthesis. Microsporogenesis starts during early inversion; greater cell elongation on the abaxial side of the young anther completes inversion by the late sporogenous-tissue stage. In Erica and, to a lesser extent Calluna, inversion results from greater abaxial than adaxial increase in cell number and length just above the filament-anther junction. The single vascular strand reflects the degree of inversion. Stamens of six species are appendaged; three have only awns, two only spurs, while one has both. Appendages arise from residual meristems after inversion is completed (or almost so) in all except Enkianthus. Awns develop at what will be the apex at maturity of each anther half. Their length and orientation vary among species. Only in Vaccinium do the awns become hollow (tubules). Spurs, varying in length, shape, and size, arise on the abaxial side from the filament, connective, or thecae.     

Upper Katian (Upper Ordovician) trans-Atlantic δ13C chemostratigraphy: the geochronological equivalence of the ELKHORN and PAROVEJA excursions and its implications

Since 2010 when the North American ELKHORN and Baltoscandic PAROVEJA isotope excursions were first described and named, their mutual age relations have remained uncertain, if not controversial. This was at least partly due to the incompleteness of the ELKHORN excursion in its reference section in western Ohio. The unexpected discovery of an apparently complete ELKHORN excursion in a drill core from St Marys in western Ohio has led to the conclusion that in terms of stratigraphical position and δ¹³C curve correspondence, the ELKHORN and PAROVEJA excursions are so similar that they apparently represent the same isotopic curve perturbation. The ELKHORN/PAROVEJA excursion occurs in the D. pacificus Graptolite Zone and uppermost A. ordovicicus Conodont Zone in the uppermost Katian Stage (Stage Slice Ka4 of Bergström et al. Lethaia 42, 97–197, 2009). Because the designation PAROVEJA was published two months before that of ELKHORN, it has priority as excursion designation. This excursion is particularly well represented in the carbonate successions in the Great Basin of western United States. Chemostratigraphy and biostratigraphy in that region show that the Richmondian transgression was contemporaneous with the beginning of the middle Katian WHITEWATER/MOE excursion. The onset of the Richmondian transgression has long been controversial but now available evidence suggests that it is of essentially the same age across large regions of the southern, western and central United States.     

Wrist and digital joint motion produce unique flexor tendon force and excursion in the canine forelimb

The force and excursion within the canine digital flexor tendons were measured during passive joint manipulations that simulate those used during rehabilitation after flexor tendon repair and during active muscle contraction, simulating the active rehabilitation protocol. Tendon force was measured using a small buckle placed upon the tendon while excursion was measured using a suture marker and video analysis method. Passive finger motion imposed with the wrist flexed resulted in dramatically lower tendon force (approximately 5 N) compared to passive motion imposed with the wrist extended (approximately 17 N). Lower excursions were seen at the level of the proximal interphalangeal joint with the wrist flexed (approximately 1.5 mm) while high excursion was observed when the wrist was extended or when synergistic finger and wrist motion were imposed (approximately 3.5 mm). Bivariate discriminant analysis of both force and excursion data revealed a natural clustering of the data into three general mechanical paradigms. With the wrist extended and with either one finger or four fingers manipulated, tendons experienced high loads of approximately 1500 g and high excursions of approximately 3.5 mm. In contrast, the same manipulations performed with the wrist flexed resulted in low tendon forces (4-8 N) and low tendon excursions of approximately 1.5 mm. Synergistic wrist and finger manipulation provided the third paradigm where tendon force was relatively low (approximately 4 N) but excursion was as high as those seen in the groups which were manipulated with the wrist extended. Active muscle contraction produced a modest tendon excursion (approximately 1 mm) and high or low tendon force with the wrist extended or flexed, respectively. These data provide the basis for experimentally testable hypotheses with regard to the factors that most significantly affect functional recovery after digital flexor tendon injury and define the normal mechanical operating characteristics of these tendons.     

TEMPORAL VARIATION IN FORAGING BEHAVIOUR OF PATELLA GRANULARIS (PATELLOGASTROPODA) AND SIPHONARIA CONCINNA (BASOMMATOPHORA) ON A SOUTH AFRICAN SHORE

Foraging activity of two mid- to low- shore species of limpet,Patella granulans (Prosobranchia) and Siphonaria concinna (Pulmonata)from an exposed shore on the Eastern Cape coast of South Africawas monitored. In both species, activity was compared duringspring and neap tides and, in P. granularis between summer andwinter. Rhythms of activity of the two species were similar,with foraging excursions being mainly associated with nocturnallow tide times, although some P. granularis foraged during daytimelow tides. It is suggested that foraging excursions in P. granularisare triggered by wave action. Both species foraged further onspring tides than on neap tides and this is suggested to bea result of the limited time limpets have to forage. P. granulariswas also found to forage further during summer when comparedto winter and the possibility that seasonal micro-algal productivityinfluences foraging distances in limpets is discussed. The foraging activity of both species could be divided into3 distinct phases, a relatively rapid outward phase, a muchslower foraging phase and a rapid homeward phase. Whether ornot these limpets graze throughout an excursion is not known.S. concinna was found to home to a fixed scar, although duringthe experiment some scar-swapping occurred. P. granularis didnot home to a fixed scar but possessed a ‘home range’(approx. 5 cm²) to which it returned after each excursion. Patella granularis was found to move randomly during foraging,whilst S. concinna foraged in a non-random direction -whichtook individuals upshore. No tidal-influence is thought to bepresent in this case and the possibility of a learning componentin the foraging behaviour of certain limpet species in relationto the return to optimal feeding patches is discussed. (Received 18 May 1996; accepted 2 September 1996)     

Age does not influence muscle fiber length adaptation to increased excursion.

Muscle fiber length adaptation to static stretch or shortening depends on age, with sarcomere addition in young muscle being dependent on mobility. Series sarcomere number can also increase in young animals in response to increased muscle excursion, but it is not clear whether adult muscles respond similarly. The ankle flexor retinaculum was transected in neonatal and adult rats to increase tibialis anterior muscle excursion. Sarcomere number in tibialis anterior was determined after 8 wk of adaptation. Muscle moment arm and excursion were increased 30% (P < 0.01) in both age groups. Muscle cross-sectional area was reduced by 12% (P < 0.01) in response to the increased mechanical advantage, and this reduction was unaffected by age. Fiber length change was also unaffected by age, with both groups showing a trend (P < 0.10) for slightly (6%) increased fiber length. Retinaculum transection results in shorter muscle length in all joint configurations, so this trend opposes the fiber length decrease predicted by an adaptation to muscle length and indicates that fiber length is influenced by dynamic mechanical signals in addition to static length.     

Chromosomal analyses in vinyl chloride-exposed workers

Chromosomal morphology from cultured peripheral lymphocytes was studied in 81 men; 57 of the men were employed on plants manufacturing vinyl chloride or polyvinylchloride, 19 were on-site controls and 5 were off-site controls. There was a significant increase in chromosomal abnormalities in the exposed workers when compared with the controls. The greatest statistically significant increase in total B and total C cells occurred in autoclave operators, with smaller increases in other job categories. The increase in chromosomal aberrations was correlated with the length of exposure and with a history during the year prior to sampling (1973–1974) of exposure to excursion levels of vinyl chloride. Information on smoking habits was obtained 18 months after blood sampling and a positive correlation between these and total C cell abnormalities was found. There was no positive correlation with various other parameters (bilirubin, platelets, γ-glutamyltranspeptidase, alkaline phosphatase, alanine transaminase and aspartate transaminase). It was not possible to estimate which of the three parameters (smoking history, length of employment or exposure to excursion levels) was the most important.     

Chromosomal analyses in vinyl chloride-exposed workers

Chromosomal morphology from cultured peripheral lymphocytes was studied in 81 men; 57 of the men were employed on plants manufacturing vinyl chloride or polyvinylchloride, 19 were on-site controls and 5 were off-site controls. There was a significant increase in chromosomal abnormalities in the exposed workers when compared with the controls. The greatest statistically significant increase in total B and total C cells occurred in autoclave operators, with smaller increases in other job categories. The increase in chromosomal aberrations was correlated with the length of exposure and with a history during the year prior to sampling (1973–1974) of exposure to excursion levels of vinyl chloride. Information on smoking habits was obtained 18 months after blood sampling and a positive correlation between these and total C cell abnormalities was found. There was no positive correlation with various other parameters (bilirubin, platelets, γ-glutamyltranspeptidase, alkaline phosphatase, alanine transaminase and aspartate transaminase). It was not possible to estimate which of the three parameters (smoking history, length of employment or exposure to excursion levels) was the most important.     

The functional correlates of jaw‐muscle fiber architecture in tree‐gouging and nongouging callitrichid monkeys

Common (Callithrix jacchus) and pygmy (Cebuella pygmaea) marmosets and cotton‐top tamarins (Saguinus oedipus) share broadly similar diets of fruits, insects, and tree exudates. Marmosets, however, differ from tamarins in actively gouging trees with their anterior dentition to elicit tree exudates flow. Tree gouging in common marmosets involves the generation of relatively wide jaw gapes, but not necessarily relatively large bite forces. We compared fiber architecture of the masseter and temporalis muscles in C. jacchus (N = 18), C. pygmaea (N = 5), and S. oedipus (N = 13). We tested the hypothesis that tree‐gouging marmosets would exhibit relatively longer fibers and other architectural variables that facilitate muscle stretch. As an architectural trade‐off between maximizing muscle excursion/contraction velocity and muscle force, we also tested the hypothesis that marmosets would exhibit relatively less pinnate fibers, smaller physiologic cross‐sectional areas (PCSA), and lower priority indices (I) for force. As predicted, marmosets display relatively longer‐fibered muscles, a higher ratio of fiber length to muscle mass, and a relatively greater potential excursion of the distal tendon attachments, all of which favor muscle stretch. Marmosets further display relatively smaller PCSAs and other features that reflect a reduced capacity for force generation. The longer fibers and attendant higher contraction velocities likely facilitate the production of relatively wide jaw gapes and the capacity to generate more power from their jaw muscles during gouging. The observed functional trade‐off between muscle excursion/contraction velocity and muscle force suggests that primate jaw‐muscle architecture reflects evolutionary changes related to jaw movements as one of a number of functional demands imposed on the masticatory apparatus. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Age, growth and feeding in the ballan wrasse Labrus bergylta Ascanius 1767

A study of the age, growth and feeding of the protogynous wrasse Labrus bergylta (Teleostei: Labridae) was made on 25 male and 316 female specimens taken from the southern coasts of the Isle of Man from October 1972 to October 1974. Age determination and back-calculations for length were made from the opercular bones. The oldest male and female specimens were 29 and 25 years old respectively. The growth curves showed only a slight increase in growth rate after sexual inversion, and a pattern of slow irregular increase, with no pronounced levelling off in old fish. The time of sexual inversion varied widely: intersexual specimens of 5 and 14 years were found. The youngest functional male was 6 years old. The weight/length relationships of males and females were very similar and the following equation, derived from all individuals, was used to calculate weights for age utilizing the back-calculated lengths:
The mouth, pharyngeal teeth and gut length to fish length ratio (0.622) suggested an omnivorous diet. Analysis of gut contents confirmed this, with decapod Crustacea, isopods and molluscs the dominant food items. There were seasonal changes in feeding intensity and composition of the diet, related to temperature changes, onshore-offshore migration patterns, availability of food items, and changes in habitat associated with maturation.