Paleoecology of the Zoophycos producers

Kotake, Nobuhiro 1989 07 15: Paleoecology of the Zoophycos producers. Lethaia , Vol. 22. pp. 327–341. Oslo. ISSN 0024–1164.
Well-preserved Zoophycos and Spirophyton- like burrows occur in the Upper Pliocene deep-sea sediments exposed along the southern coast of Boso Peninsula, central Japan. They consist of an axial tunnel and helically coiled spreite with fecal pellets. In most cases the two kinds of trace fossil are found separately. In several complete specimens, however, the upper and lower portions represent a Spirophyton- like burrow and Zoophycos , respectively. The downward increase in size of the spreite and fecal pellets in a single burrow suggests that the complete Zoophycos was built successively as the producing animal grew. The occurrence of incomplete Zoophycos may have resulted from post-mortem destruction by echinoid locomotion and turbidity currents. In some cases, the uppermost portion of the axial tunnel is covered with a thin tuff layer. Fecal pellets in such burrows consist of the same tuffaceous material which must have originated from the overlying tuff layer. This fact indicates that the burrow producer did not feed on organic matter within the sediments but foraged detritus on the sea floor. The animal could probably stretch a part of the body from the top of the axial tunnel for feeding and systematically pack the fecal pellets into the sediments. Such segregation between the feeding place and the excretory space is interpreted as an efficient feeding strategy for the detritus-feeding burrowers in the deep sea. D Zoophycos, Spirophyton-like burrow, paleoecology, feeding and excretory behavior, Boso Peninsula, Japan .     

Deep-sea echiurans: possible producers of Zoophycos

Kotake, N. 1992 07 15: Deep-sea echiurans: possible producers of Zoophycos.
The trace fossil Zoophycos in the upper Pliocene deep-sea deposits (Shiramazu Formation) distributed in the southernmost part of Boso Peninsula, central Japan, appears to be a product of feeding and excretory behavior by surface deposit-feeders inhabiting middle bathyal depths. Ecology and anatomy of modern deep-sea echiurans are consistent with those of the Zoophycos producers based on the Pliocene examples. Consequently, deep-sea echiurans may be producers of Zoophycos . Systematic lamellae structures of the spreite reflect excretory behavior in sediment resulting from deposit-feeding on the sea-floor. Z oophycos , deep-sea echiurans, Pliocene, Boso Peninsula, Japan .     

Geochemical composition of faecal pellets as an indicator of deposit‐feeding strategies in the trace fossil Phymatoderma

Phymatoderma is a branching burrow system consisting of tunnels filled with faecal pellets, and it has been interpreted as a product of a surface deposit‐feeding animal. Elemental analyses of Phymatoderma were conducted to reveal the specific feeding mode of its tracemaker, using samples from the Lower Jurassic epicontinental shelf deposits in the Dotternhausen section, southern Germany and from the Upper Pliocene continental slope deposits in the Shioura section, central Japan. Elemental compositions of the pelletal infill of Phymatoderma and its overlying mudstone from the Dotternhausen section show no significant difference, suggesting that the tracemaker was a non‐selective deposit feeder. In contrast, elemental compositions of the tuffaceous pellets of Phymatoderma from the Shioura section and its overlying volcanic ash show a difference in trends: CaO is significantly concentrated in the pellets. Because microfossils such as foraminifera and coccoliths are occasionally found in the tuffaceous pellets, CaO accumulation in the pelletal infill indicates the Phymatoderma‐producer that lived in the Pliocene slope setting selectively ingested particles with higher biomass of such microorganisms (or ingested microorganisms themselves) when feeding the surface sediments. Although two types of feeding modes of the tracemaker were recognized in Phymatoderma between different bathymetrical settings, each feeding mode seems to be an effective strategy to intake nutrients from the surface sediments and to reflect an adaptation of the tracemaker to the food contents in the surrounding substrate. This study suggests that geochemical composition of faecal pellets of trace fossils can be a useful indicator of grain‐selective/non‐selective deposit‐feeding strategies of ancient animals.     

贵州独山中泥盆世动藻迹生态习性探讨

贵州独山中泥盆统产有丰富的遗迹化石Zoopkycos,现从其产出的特征和古生态等方面对其生活习性进行探讨。认为分布于静水、贫氧、有机质丰富环境的Zoopkycos为螺旋向上的内生觅食构造;边缘管一端通过中央通道与海水相通,呈“J”形;蹼状构造系造迹生物觅食区域的扩大、边缘管增大而形成;同一个体的Zoopkycos可以分出许多的与蹼状构造变化规律相近的、具同一边缘管的觅食序列(food-system),每一觅食序列的边缘管具有一端向上与中央通道相通,另一端向下与相邻觅食序列的边缘管相联;螺旋的疏密、大小与相对沉积速度有关。产于独山地区中泥盆统的Zoopkycos的造迹生物可能是星虫类(sipunculids)。     

Analysis of Mineral Segregation in Euzonus mucronata Burrow Structures: One Possible Method Used in the Construction of Ancient Macaronichnus segregates

Mineralogical segregation of sand grains distinguishes the trace fossil Macaronichnus segregatis, which is composed of a felsic burrow infill with a mafic-and mica-rich burrow mantle. This study focuses on determining the mechanism by which M. segregatis trace-makers segregated mineral grains during deposit feeding. A modern opheliid polychaete, Euzonus mucronata, from Pachena Bay, Vancouver Island (Canada), was examined to explain the activities of their ancient counterparts. Microscopic videotaping of deposit feeding allowed for collection of data on ingestion and excretion through visual grain counts of felsic, mafic, and shell components. Normalization of these grain counts to the composition of the host sediment illustrates preferential ingestion of felsic grains over mafic. Shell fragments were generally avoided and visually mantled the burrows, obscuring the paucity of mafic grains in burrow infills. The avoidance of shell fragments is potentially a function of the large grain size, angular shape, surface texture, and/or associated low nutritive value. The preferential ingestion of felsic grains is attributed to en masse feeding in felsic-rich locales identified through sediment probing. This form of mineral segregation likely reflects the specific nature of the sediment and worm population. Accordingly, en mass deposit feeding in selected felsic-rich localities is one possible mechanism used in the construction of Macaronichnus segregatis and M. segregatis-like structures.     

Complex behavioural pattern as an aid to identify the producer of Zoophycos from the Middle Permian of Oman

The trace fossil Zoophycos is abundant in transgressive, shallow marine carbonates in the Middle Permian (Wordian) Khuff Formation of the Huqf-Haushi Uplift of Interior Oman. It often occurs as part of a complex (compound) trace fossil that comprises two integrated elements: (i) irregular galleries with straight to gently curved tunnels and interconnected shafts, and (ii) simple planar to complex spreiten structures with a marginal tube ( Zoophycos ). The galleries are characterized by irregularly winding, dichotomous branching, large variation in shape and size and circular to elliptical vertical cross-sections. Zoophycos consists of spreiten with a marginal tube, either originating as a simple lobe from the convex segment of a curved tunnel, or forming more complex, subcircular, spreiten systems parallel to bedding. The spreiten were formed by simple strip mining, where the animal defecated without producing faecal pellets. U-shaped marginal tubes indicate that the burrows were well aerated. The complex trace fossil points to combined dwelling and deposit-feeding behaviour, with irregular galleries in the firm substrate and Zoophycos spreiten in the softground below it. It can be assumed that the animal used the open tunnel system mainly for dwelling (domichnion) and possibly suspension feeding, but occasionally changed to deposit feeding while creating the spreiten (fodinichnion). The integration of the irregular galleries (tunnels and interconnected shafts) with the marginal tubes of Zoophycos suggests the same producer for this compound trace fossil. Many modern polychaetes produce very similar galleries within firm and soft substrates, and polychaetes are therefore interpreted as the most likely producers. Similarities between Permian and Triassic Zoophycos suggest comparable trace making behaviour before and after the end-Permian mass extinction.     

The response of meiofauna and microphytobenthos to engineering effects of fiddler crabs on a subtropical intertidal sandflat

Fiddler crabs are key bioturbators on tidal flats. During their intense bioturbation process, they manipulate large amounts of sediment, altering the physical state of existing materials. We investigated whether different types of sediment bioturbation produced by fiddler crabs modulate meiofaunal assemblages and microphytobenthic content. We hypothesized that sedimentary structures produced by burrowing (the burrow itself and the excavation pellets) and feeding (feeding pellets) generate different microenvironments compared with areas without apparent signs of fiddler crab disturbance, affecting both meiofauna and microphytobenthos, independent of the sampling period. Our results indicate that the engineering effects of burrow construction and maintenance and the engineering effects of fiddler crab foraging modulate meiofaunal assemblages in different ways. Overall, meiofauna from burrows and excavation pellets was more abundant and diverse than at control sites, whereas feeding pellets contained poor meiofaunal assemblages. By contrast, only foraging effects were detected on microphytobenthos; independent of the sampling period, Chl a and phaeopigment content were higher in the feeding pellets, but similar among burrows, excavation pellets and control sites. The present study demonstrates that the different engineering effects of fiddler crabs are an important source of habitat heterogeneity and a structuring agent of meiofaunal assemblages on subtropical tidal flats.     

Adaptive strategy of the Porcellanasterid sea stars

Morphological–functional analysis suggests that the adaptations of sea stars of the family Porcellanasteridae to burrowing and deposit feeding are related to morphological simplification. This simplification led to reduction of the morphological structures responsible for respiration (papulae and paxillae), decrease in the number of cribriform organs, reduction of body size, and retention of juvenile characters by adults. The forced-circulation water system inside the burrow also changes. The water generated by the cribriform organs becomes upwardly directed. The adaptive strategy in the family is characterized by intensification of nonselective deposit feeding by means of active moving within the muddy sediment and removal of fecal materials from the burrow.     

Rosselia socialis: a dwelling structure of a probable terebellid polychaete

The trace fossil Rosselia socialis Dahmer 1937 is a funnel-shaped structure characterized by a concentrically laminated wall having a narrow cylindrical shaft at the central portion. In association with well-preserved funnel-shaped R. socialis , many spindle-shaped R. socialis -like specimens are abundant in the Middle Pleistocene Kongochi Formation in central Japan. While the former always occur just below an erosional bedding plane or outcrop surface parallel to the bedding, the latter are found in sediment showing no breaks in sedimentation. This suggests that the funnel-shaped 'R. socialis' is actually the truncated lower part of the spindle-shaped structure. In one specimen, deformation of laminae appears to have formed synchronously with construction of the wall. Morphology of the structure strongly suggests that the wall of R. socialis was formed through outward expansion caused by accretion of muddy material at the inner surface of the wall by the trace-maker inhabiting the central burrow. A specimen that was covered by a volcanic ash has the wall made up of the ash. This indicates that the maker of the burrow utilized surface sediment to construct the wall; that is, the trace-maker was possibly a detritus feeder. The terebellid polychaetes are reasonable candidates for the trace-makers. □ R osselia socialis , Japan, Middle Pleistocene, trace fossil, trace-making process, trace-maker.     

Zoophycos size may indicate environmental gradients

Detailed examination through a continuous stratigraphic interval representing nearly the entire Lower Devonian Onesquethawan Stage shows that the presence and size of the trace fossil Zoophycos varies systematically throughout the unit. The lithofacies of this sequence are interpreted to represent a double offshore-nshore cycle. Both maximum and mean diameters of the Zoophycos web (=spreite) are relatively large within a more offshore setting and become progressively smaller towards both margins of this geographic (= stratigraphic) zone. Close inspection of Zoophycos morphology reveals a nearly perfect correlation (r = 0.96) between Zoophycos web diameter and meniscus height. Meniscus height bears a constant relationship to the maximum body diameter of the animal creating the burrow, consequently, size of the web is directly proportional to body size. Thus the animal is largest near the center of its environmental range and smallest near the margins. Other ichnofossils in the section ( Scalarituba, Phycodes, Chondrites ), measured on a more limited scale, show similar size variations with smaller forms at the margins of their respective ranges. Therefore, trace fossil size may be a sensitive indicator of paleoenvironmental gradients.     

Phylogenetic relationships and phylogeography of Hynobius tokyoensis (Amphibia: Caudata) using complete sequences of cytochrome b and control region genes of mitochondrial DNA

Using complete sequences of cytochrome b (cyt b) and control region (CR; D-loop) genes of mitochondrial DNA, we investigated the phylogenetic relationships and phylogeography among populations of the salamander Hynobius tokyoensis in northern Japan. Inclusion of populations from Aichi, Chubu region within Hynobius nebulosus by previous results was confirmed because they formed a clade with H. nebulosus. Monophyly of H. tokyoensis was supported in all trees analyzed, and two clades consistently emerged: clade A from northeastern Kanto (Ibaraki) to southern Tohoku (Fukushima), and clade B from the remaining area south of northern Kanto (Tochigi). These two clades are estimated to have an old history of divergence during the late Pliocene, when the present-day Kanto Plain was under the sea. Within clade B, three haplotypes groups (I-III) are hypothesized to have diverged more recently, i.e., between the early and mid-Pleistocene, probably in relation to glacial events. The ancestral groups I and II were separated at the present-day western Kanto and Boso Peninsula areas, respectively, and subsequently, group II invaded northward to the present-day northern Kanto area and gave rise to group III. Populations of the Miura Peninsula are thought to have multiple origins, one directly from Boso and another from a more recent southward invasion from the northern Kanto area. Cytochrome b appears to have evolved more quickly than CR genes in H. tokyoensis, and thus will be more useful for phylogenetic analyses and formulating conservation measures.     

Orientation during short-range feeding in the crab Dotilla wichmanni

The ocypodid crab Dotilla wichmanni is a common inhabitant of tropical sandy shores, where it feeds at low tide by sorting the material deposited by the ebbing tide. Feeding occurs in the immediate vicinity of the burrow by means of systematically sampling the sand surface. While feeding, the crabs move along trenches radiating from the burrow and produce pseudofaecal pellets which are amassed over the already excavated area. When disturbed, the crabs rapidly vanish into the burrow, where they remain hidden for a while. Upon re-emerging, they recommence feeding moving along the same trench as before retreat. The crabs, however, were found to assume the same feeding direction held before retreating even if any sign that could be derived from their previous activity was removed experimentally. To uncover the orientation cues used in this behaviour, the area near the burrow was manipulated in particular ways. The crabs were found to rely mainly on the skylight polarization pattern, while visual landmarks near the feeding area may play a role when astronomic cues provide no useful information, such as under overcast skies. Both cues were used by the crabs as references to assume the same feeding direction as that used before retreat. Accepted: 9 June 1997     

Rapid,gregarious settlement of the larvae of the marine echiuran Urechis caupo Fisher & MacGinitie 1928

Larvae of Urechis caupo Fisher & MacGinitie, reared in the laboratory, were exposed to potential settlement stimuli, including natural sediment from adult burrows, and “scent” obtained from the skin of adult animals. Competent larvae settled rapidly and specifically in response to adult burrow sediment when compared with their responses to other natural and abiotic sediments. Larvae also responded specifically to chemical “scent” from adult animals when the “scent” of another echiuran worm, Listriolobus pelodes Fisher served as a control. Larval responses to chemical “scent” were as great as their responses to natural burrow sediment. Hence, it is likely that larvae settle gregariously in nature in response to “scent” on sediment grains of adult burrows. The chemical “scent” had a molecular weight between ≈3500 and 14000 daltons, as determined by dialysis. It quickly lost its effectiveness in promoting settlement after it was heated to 80 °C, but was relatively stable at ambient ocean temperatures, retaining its effectiveness for several days. It was soluble in sea water. However, larvae did not respond to the chemical “scent”, unless it was adsorbed onto a surface. Purely tactile stimuli, such as the shape, texture, and size-distribution of particles, were not important settlement cues during these experiments.     

湖北三峡地区埃迪卡拉系灯影组“蝌蚪状”遗迹化石*

遗迹化石是埃迪卡拉纪存在两侧对称动物最有力的证据。但多数埃迪卡拉纪遗迹化石为简单、水平的表面爬迹或潜穴。在湖北三峡地区灯影组石板滩段含典型埃迪卡拉软躯体化石的地层中新发现一类形态特别的化石,呈蝌蚪状,一端膨大,一端细管状。通过对化石形态、同位素分析以及沉积学特征的研究,说明该化石为遗迹化石,而不是实体化石。蝌蚪状化石为一种复合迹,垂向活动形成球状的膨大端,平行藻席层活动形成近于水平的潜穴,反映了造迹生物垂向切穿藻席层并沿藻席层进行觅食的行为。该发现说明了在埃迪卡拉纪晚期已有两侧对称动物开始形成较为复杂的潜穴。     

Trusheimichnus New Ichnogenus From the Middle Triassic of the Germanic Basin,Southern Germany

The study of Jurassic Zoophycos from south‐eastern France has led us to some original results concerning its morphological organization and paleoenvironmental significance. Zoophycos represents a spreite constituted by a coiling lamina, constructed upwards in sediments, with only one opening at the sediment‐water interface. Zoophycos, produced by a deep sediment feeder, is emplaced late in an almost coherent substrate, intermediate between soft and firm ground. This suggests periods of very low or no sedimentation during which time the trace was constructed.

The Zoophycos studied developed on slope areas, characterized by a particular style of sedimentation: periods of nutrient supplies coming from proximal areas, alternating with periods of sedimentary breaks. Other paleoecologic and paleoethologic characteristics of the Zoophycos‐producer are discussed here: working activity, competition behavior, substrate modification, growing pattern and burrow oxygenation are the most interesting.     

Role of fiddler crabs of a subtropical intertidal flat on the fate of sedimentary fatty acids

Fatty acid compositions of three ocypodid crabs, Uca vocans, U. lactea and Scopimera globosa, collected on a subtropical intertidal flat (Okinawa, Japan), were analysed as well as the surrounding surface sediment of their burrows, their food pellets and their faeces. U. vocans and U. lactea exhibited a higher concentration of fatty acids than S. globosa. Food pellets revealed a higher relative contribution of saturated fatty acids and lower amounts of polyunsaturated and branched fatty acids than in the surface sediment samples. These differences of fatty acid compositions suggest an initial selection of food before the particle sorting in the buccal region. This result, and also because of the relatively high fatty acid content of faeces, indicate that fiddler crabs play a significant role in the fate of these lipids in the subtropical intertidal flats. Comparative analysis of the fatty acid compositions of the different samples indicates that these fiddler crabs actively sorted bacteria in order to ingest them. Diatoms seem to be used in larger amount by U. vocans may be because of its higher mobility while looking for food. Other primary producers present in the environment, mangrove leaves and algae, have been sorted but contributed weakly to the organic matter pool of the surface sediment and therefore to the diet of the crabs.     

Burrow morphology and utilization of the goby (Parapocryptes serperaster) in the Mekong Delta,Vietnam

Some fish species living in mudflats construct burrows for dwelling and hiding. The goby Parapocryptes serperaster is a burrowing fish in mudflats of many estuaries in South East Asia. This study was carried out in the Mekong Delta, Vietnam, to examine burrow morphology and usage by this species. Morphology of the burrows constructed by P. serperaster was investigated by resin castings in situ to obtain the physical structure and configuration of each burrow. Fish from the burrows were caught and measured before burrow casts were made. Fish burrows comprised several openings, a few branching tunnels and multi-bulbous chambers. The surface openings were circular, and the shapes of branching tunnels were nearly round. The burrows had interconnected tunnels and various short cul-de-sac side branches. The burrow structure differed between fish sizes, but burrow dimensions were positively correlated with fish size, indicating that larger fish can make larger and more sophisticated burrow. The burrow structure and dimensions were not different between the dry and wet seasons. Laboratory observations showed that P. serperaster used body movements to dig burrows in the sediment. Burrows could provide a low-tide retreat and protection from predators, but were not used for spawning and feeding for this goby species. This study indicates that the burrowing activity of gobies is an important adaptation for living in shallow and muddy habitats.     

Late Pliocene grassland from Olduvai Gorge,Tanzania

The Olduvai fossil plants documented by us in this paper are the first direct evidence for open grassland in the late Neogene of Africa based on macroplant remains. Silicified remains of herbaceous ground cover are exceptionally well preserved in situ within Late Pliocene sediments below the initial pyroclastic ash surge unit of Tuff IF in the uppermost part of Bed I, Olduvai Gorge, northern Tanzania. Published radiometric and palaeomagnetic dates place this grass layer between 1.839 + 0.005 Ma and 1.785 + 0.01 Ma. Exposed at localities on the south side of the Gorge this herbaceous ground cover grew on a floodplain developed on a dried out lake bed, following pronounced lake retreat of saline–alkaline palaeo-Lake Olduvai during a developing dry climatic phase. Sheathed basal culms, rhizomes and roots are interpreted as those of one or more small mat-forming grasses or less likely, sedges. Small dicotyledonous herbs were probably also present. The proximity of adjacent plants indicates a relatively dense ground cover. Roots extended at least 8 cm below the ground surface. Aerial parts of the plants were absent or were not preserved when the weathered basal culms were covered by a thin layer of brown waxy clay, followed by fallout of pyroclastic ash. Both units were mostly eroded away prior to emplacement of a wet, cool pyroclastic surge which then buried and preserved in situ remnants of the herbaceous ground cover. Preservation of the semi-woody rhizomes implies well-drained soils, otherwise the plant material would have quickly rotted. Collections from discontinuous exposures indicate the grassland covered an area of at least a few hectares. This open grassland would have provided grazing for the Late Pliocene fauna.     

Feeding Responses of Hatchery-Reared Gilthead Sea Bream (Sparus aurata L.) to a Commercial Diet and Natural Prey Items

Many fish species have evolved feeding mechanisms and behaviours enabling them to feed on specific prey. However, such mechanisms may not be optimal for feeding on commercial-pelleted diets in aquaculture. Gilthead sea bream chew and occasionally eject pellets or parts of pellets from the mouth when feeding on commercial diets. This may result in an increase in nutritional waste from the intensive culture of this species. In this study we examined the prevalence of this food processing behaviour in two sizes of sea bream, feeding on three types of natural prey items in comparison to a commercial pellet, to give an insight into the circumstances in which excess chewing and ejection of food items from the mouth occurred. These included two hard-textured food items (commercial pellet and hard-shelled prey) and two soft-textured food items (larvae and small crustacean). Both sizes of sea bream frequently consumed the soft-textured food types, however large sea bream also frequently consumed hard-textured pellets. Hard-textured food required longer handling times and elicited more chewing and the ejection of food items from the mouth. These results suggest that future investigations on the food processing behaviour and consequent waste when fed commercial diets differing in texture could give an insight into improving diets and feeding efficiency for intensively cultivated gilthead sea bream.     

Feeding Responses of Hatchery-Reared Gilthead Sea Bream (Sparus aurata L.) to a Commercial Diet and Natural Prey Items

Many fish species have evolved feeding mechanisms and behaviours enabling them to feed on specific prey. However, such mechanisms may not be optimal for feeding on commercial-pelleted diets in aquaculture. Gilthead sea bream chew and occasionally eject pellets or parts of pellets from the mouth when feeding on commercial diets. This may result in an increase in nutritional waste from the intensive culture of this species. In this study we examined the prevalence of this food processing behaviour in two sizes of sea bream, feeding on three types of natural prey items in comparison to a commercial pellet, to give an insight into the circumstances in which excess chewing and ejection of food items from the mouth occurred. These included two hard-textured food items (commercial pellet and hard-shelled prey) and two soft-textured food items (larvae and small crustacean). Both sizes of sea bream frequently consumed the soft-textured food types, however large sea bream also frequently consumed hard-textured pellets. Hard-textured food required longer handling times and elicited more chewing and the ejection of food items from the mouth. These results suggest that future investigations on the food processing behaviour and consequent waste when fed commercial diets differing in texture could give an insight into improving diets and feeding efficiency for intensively cultivated gilthead sea bream.