Storage and absorption in the digestive system of carnivorous and herbivorous prickleback fishes (Teleostei: Stichaeidae): ontogenetic, dietary, and phylogenetic effects

The effects of ontogeny, diet, and phylogeny on glycogen storage levels and esterase and alkaline phosphatase activities in four related prickleback fishes were determined in situ using quantitative histochemistry. Of these species, Cebidichthys violaceus and Xiphister mucosus shift from carnivory to herbivory at approximately 45 mm standard length (SL), whereas Xiphister atropurpureus and Anoplarchus purpurescens remain carnivores. Comparisons between small (30-40 mm SL) and larger (60-75 mm SL) wild-caught juveniles showed that glycogen storage levels and alkaline phosphatase activity were unchanged with ontogeny. Comparisons between the larger wild-caught juveniles and juveniles of the same size that had been raised on a high-protein animal diet revealed that glycogen storage level and alkaline phosphatase activity increased in all species in response to this diet. Esterase activity also increased in response to the high-protein animal diet in all four species but increased with ontogeny only in C. violaceus, X. mucosus, and X. atropurpureus, in the xiphisterine clade, and not in A. purpurescens, in the adjacent alectriine clade. Xiphister mucosus and X. atropurpureus showed indistinguishable responses in esterase activity to ontogeny and diet despite their divergent natural diets. Overall, glycogen storage level and alkaline phosphatase activity responded primarily to diet, whereas esterase activity was also influenced by ontogeny and phylogeny and differed between intestinal regions among the species.     

Digestive enzyme activities in herbivorous and carnivorous prickleback fishes (Teleostei: Stichaeidae): ontogenetic, dietary, and phylogenetic effects

We measured the activities of eight digestive enzymes in four species of herbivorous and carnivorous prickleback fishes and determined the effects of ontogeny, diet, and phylogeny on these enzyme activities. Of the four species, Cebidichthys violaceus and Xiphister mucosus shift to a more herbivorous diet as they grow (> or =45 mm SL [standard length]), whereas Xiphister atropurpureus and Anoplarchus purpurescens remain carnivores throughout life. Digestive enzyme activities of small (30-40 mm SL) carnivorous juveniles were compared with those of larger (60-75 mm SL) wild-caught juveniles that had consumed a natural diet and larger (60-75 mm SL) juveniles raised on a high-protein animal diet. Cebidichthys violaceus and both species of Xiphister showed ontogenetic changes in digestive enzyme activities, whereas A. purpurescens did not. Despite dietary differences between X. atropurpureus and X. mucosus, these sister taxa displayed the most similar digestive enzyme activities from ontogenetic and dietary perspectives (high alpha-amylase and lipase and low trypsin and aminopeptidase activities), and both were more similar to C. violaceus, a member of the same largely herbivorous clade, than either was to A. purpurescens, a member of an adjacent, carnivorous clade. The results support the hypothesis that phylogeny influences digestive enzyme activities in these fishes. Anoplarchus purpurescens, a carnivore with a diverse diet, showed great plasticity in enzyme activity, especially trypsin and aminopeptidase, which were elevated in this species to the highest level among the four species after consuming the high-protein diet. These results support the hypothesis that fishes with relatively broad diets can modulate digestive enzyme activities in response to changes in dietary composition.     

Digestive enzyme activities in carnivores and herbivores: comparisons among four closely related prickleback fishes (Teleostei: Stichaeidae) from a California rocky intertidal habitat

Three digestive enzymes in four species of closely related prickleback fishes (family Stichaeidae: Cebidichthys violaceus, Xiphister mucosus , Xiphister atropurpureus and Anoplarchus purpurescens ) were analysed to assess whether diet or phylogeny played a larger role in influencing digestive enzyme activity. Cebidichthys violaceus and X. mucosus are primarily herbivorous, whereas X. atropurpureus and A. purpurescens are mainly carnivorous. The two Xiphister species are sister taxa, and A. purpurescens is in a clade adjacent to that of the three other species. Pepsin and trypsin specific activities did not differ significantly among the four species, but α‐amylase activity was significantly higher in the two Xiphister species, followed by C. violaceus , and then A. purpurescens . The wide disparity between the two carnivores, the striking similarity between the two sister taxa, and the significant difference between the two herbivores indicate that activity of α‐amylase follows a pattern influenced more by phylogeny than by diet in these fishes.     

Sequence and expression of an α-amylase gene in four related species of prickleback fishes (Teleostei: Stichaeidae): ontogenetic,dietary, and species-level effects

Partial α-amylase gene sequences were determined and α-amylase gene expression was quantified in four species of carnivorous, omnivorous, and herbivorous prickleback fishes (family Stichaeidae) to assess the effects of ontogeny, diet, and species on expression of this gene. Pairwise comparison of α-amylase nucleotide sequences revealed 96–98 % identity, and comparison of amino acid portions revealed 93–95 % similarity among the four prickleback species. Expression was determined using in situ hybridization and intensity of expression quantified using image analysis. Alpha-amylase expression level was compared in three feeding categories of the four species: (1) small, wild-caught carnivorous juveniles; (2) larger, wild-caught juveniles of the carnivorous species and the three that had shifted to herbivory or omnivory; and (3) larger, juveniles produced by feeding a low-starch artificial diet to small juveniles until they reached the size of the larger wild-caught juveniles. The results showed no dietary effect in any species but significant ontogenetic and species-level effects in Cebidichthys violaceus, as well as in the sister species Xiphister mucosus and X. atropurpureus. Based on a phylogeny for the Stichaeidae produced for this study using two mtDNA genes and one nuclear gene, the ontogenetic dietary shifts to herbivory/omnivory evolved independently in C. violaceus and in the clade containing the two species of Xiphister. All three of these species increased α-amylase gene expression with increase in size and had higher expression than Anoplarchus purpurescens, which is a member of a third, stichaeid clade comprising carnivores. These results show the importance of α-amylase in the herbivores and omnivores.     

Contrasting quaternary histories in an ecologically divergent sister pair of low-dispersing intertidal fish (Xiphister) revealed by multilocus DNA analysis

Recurrent glacial advances have shaped community histories across the planet. While biogeographic responses to glaciations likely varied with latitude, the consequences for temperate marine communities histories are less clear. By coalescent analyses of multiloci DNA sequence data (mitochondrial DNA control region, alpha-enolase intron, and alpha-tropomyosin intron) collected from a low-dispersing sister pair of rocky intertidal fishes commonly found from southeastern Alaska to California (Xiphister atropurpureus and X. mucosus), we uncover two very different responses to historical glaciations. A variety of methods that include a simulation analysis, coestimates of migration and divergence times, and estimates of minimum ages of populations sampled up and down the North American Pacific coast all strongly revealed a history of range persistence in X. atropurpureus and extreme range contraction and expansion from a southern refugium in X. mucosus. Furthermore, these conclusions are not sensitive to the independent estimates of the DNA substitution rates we obtain. While gene flow and dispersal are low in both species, the widely different histories are rather likely to have arisen from ecological differences such as diet breadth, generation time, and habitat specificity.     

The ‘Expansion–Contraction’ model of Pleistocene biogeography: rocky shores suffer a sea change?

Approximately 20 000 years ago the last glacial maximum (LGM) radically altered the distributions of many Northern Hemisphere terrestrial organisms. Fewer studies describing the biogeographic responses of marine species to the LGM have been conducted, but existing genetic data from coastal marine species indicate that fewer taxa show clear signatures of post-LGM recolonization. We have assembled a mitochondrial DNA (mtDNA) data set for 14 co-distributed northeastern Pacific rocky-shore species from four phyla by combining new sequences from ten species with previously published sequences from eight species. Nuclear sequences from four species were retrieved from GenBank, plus we gathered new elongation factor 1-α sequences from the barnacle Balanus glandula . Results from demographic analyses of mtDNA for five (36%) species ( Evasterias troschelii, Pisaster ochraceus, Littorina sitkana, L. scutulata, Xiphister mucosus ) were consistent with large population expansions occurring near the LGM, a pattern expected if these species recently recolonized the region. However, seven (50%) species ( Mytilus trossulus, M. californianus, B. glandula, S. cariosus, Patiria miniata, Katharina tunicata , X. atropurpureus ) exhibited histories consistent with long-term stability in effective population size, a pattern indicative of regional persistence during the LGM. Two species of Nucella with significant mtDNA genetic structure showed spatially variable demographic histories. Multilocus analyses for five species were largely consistent with mtDNA: the majority of multilocus interpopulation divergence times significantly exceeded the LGM. Our results indicate that the LGM did not extirpate the majority of species in the northeastern Pacific; instead, regional persistence during the LGM appears a common biogeographic history for rocky-shore organisms in this region.     

A histological study of the organogenesis of the digestive system in bay snook Petenia splendida Günther, 1862 from hatching to the juvenile stage

In bay snook (Petenia splendida) larvae the histological development of the digestive system and swim bladder, and their relative timing of differentiation were studied from hatching to 45 days post‐hatch (dph) at 29°C. Newly hatched larvae showed a simple digestive tract, which appeared as a straight undifferentiated tube lined by a single layer of columnar epithelial cells (future enterocytes). The anatomical and histological differentiation of the digestive tract and accessory glands was a very intense, asynchronous process, proceeding from the distal to the anterior part. The intestine was the first region to differentiate (9 days post‐hatch – dph, 6.5 mm SL), and the oesophagus the last (21 dph, 8.4 mm SL). At the onset of feeding, the digestive system was organized into different functional and histologically differentiated sections, such as the buccopharynx, oesophagus, glandular stomach, and anterior and posterior intestine. This organization resembled that of the juveniles, with the exception of pharyngeal teeth and buccopharyngeal as well as oesophageal goblet cells, which proliferated later during the mixed feeding period. Histological observations revealed that bay snook larvae retained endogenous yolk reserves until 24 dph (8.9 ± 0.4 mm SL), which might be helpful for weaning this species onto a compound diet. The important lipidic accumulation observed in the intestinal mucosa, liver, and pancreas in fish fed a compound trout diet indicated that although fish were able to digest and absorb lipids, the diet formulation did not fit the nutritional requirements of early juveniles of this species. The ontogeny of the digestive system followed the same general pattern as in most cichlid species described to date. However, we detected species‐specific differences in the timing of differentiation that were related to their reproductive guild. According to the histological results, some recommendations regarding the intensive culture of this species are also provided.     

Characterization of the Mamestra configurata (Lepidoptera: Noctuidae) larval midgut protease complement and adaptation to feeding on artificial diet,Brassica species,and protease inhibitor

The midgut protease profiles from 5th instar Mamestra configurata larvae fed various diets (standard artificial diet, low protein diet, low protein diet with soybean trypsin inhibitor [SBTI], or Brassica napus) were characterized by one‐dimensional enzymography in gelatin gels. The gut protease profile of larvae fed B. napus possessed protease activities of molecular masses of approximately 33 and 55 kDa, which were not present in the guts of larvae fed artificial diet. Similarly, larvae fed artificial diet had protease activities of molecular masses of approximately 21, 30, and 100 kDa that were absent in larvae fed B. napus. Protease profiles changed within 12 to 24 h after switching larvae from artificial diet to plant diet and vice versa. The gut protease profiles from larvae fed various other brassicaceous species and lines having different secondary metabolite profiles did not differ despite significant differences in larval growth rates on the different host plants. Genes encoding putative digestive proteolytic enzymes, including four carboxypeptidases, five aminopeptidases, and 48 serine proteases, were identified in cDNA libraries from 4th instar M. configurata midgut tissue. Many of the protease‐encoding genes were expressed at similar levels on all diets; however, three chymoptrypsin‐like genes (McSP23, McSP27, and McSP37) were expressed at much higher levels on standard artificial diet and diet containing SBTI as was the trypsin‐like gene McSP34. The expression of the trypsin‐like gene McSP50 was highest on B. napus. The adaptation of M. configurata digestive biochemistry to different diets is discussed in the context of the flexibility of polyphagous insects to changing diet sources. Published 2010 Wiley Periodicals, Inc.     

The feeding ecology of juvenile mullet (Mugilidae) in south-east African estuaries

Changes in the feeding ecology of juveniles (10–59 mm standard length) of eleven species of Mugilidae were investigated in south-east African estuaries. Adults of all species spawn in the sea and juveniles enter estuaries at a length of about 10 mm. In estuaries they change their feeding habits in the following sequence: zooplankton to zooplankton in the benthos (10–15 mm), zooplankton in the benthos to meiobenthos (10–20 mm), and meiobenthos to sand particles and associated microbenthos (15–25 mm). All species show a similar pattern of change but interspecific competition is probably prevented by the rapid switch to the adult diet of microbenthos and sand particles and because species enter estuaries at different times according to spawning periods. The juveniles seek shallow quiet water areas of estuaries and it is suggested that the change from being planktonic macrophagous carnivores to benthic microphagous omnivores can only take place in the estuaries of the region. Conditions in the inshore waters of the Indian Ocean in south-east Africa are probably too rough for substrate feeding by juvenile mullet.     

Mismatch between shape changes and ecological shifts during the post-settlement growth of the surgeonfish, Acanthurus triostegus

Background

Many coral reef fishes undergo habitat and diet shifts during ontogeny. However, studies focusing on the physiological and morphological adaptations that may prepare them for these transitions are relatively scarce. Here, we explored the body shape variation related to ontogenetic shifts in the ecology of the surgeonfish Acanthurus triostegus (Acanthuridae) from new settler to adult stages at Moorea Island (French Polynesia). Specifically, we tested the relationship between diet and habitat shifts and changes in overall body shape during the ontogeny of A. triostegus using a combination of geometric morphometric methods, stomach contents and stable isotope analysis.

Results

After reef settlement, stable isotope composition of carbon and nitrogen revealed a change from a zooplanktivorous to a benthic algae diet. The large amount of algae (> 75% of stomach contents) found in the digestive tract of small juveniles (25?C30 mm SL) suggested the diet shift is rapid. The post-settlement growth of A. triostegus is highly allometric. The allometric shape changes mainly concern cephalic and pectoral regions. The head becomes shorter and more ventrally oriented during growth. Morphological changes are directly related to the diet shift given that a small mouth ventrally oriented is particularly suited for grazing activities at the adult stage. The pectoral fin is more anteriorely and vertically positioned and its basis is larger in adults than in juveniles. This shape variation had implications for swimming performance, manoeuvrability, turning ability and is related to habitat shift. Acanthurus triostegus achieves its main transformation of body shape to an adult-like form at size of 35?C40 mm SL.

Conclusion

Most of the shape changes occurred after the reef colonization but before the transition between juvenile habitat (fringing reef) and adult habitat (barrier reef). A large amount of allometric variation was observed after diet shift from zooplankton to benthic algae. Diet shift could act as an environmental factor favouring or inducing morphological changes. On the other hand, the main shape changes have to be achieved before the recruitment to adult populations and start negotiating the biophysical challenges of locomotion and feeding in wave- and current-swept outer reef habitat.     

Prey use of wetland benthivorous sunfishes: ontogenetic, interspecific and seasonal variation

The intensity of competitive interactions between fishes is partly determined by prey use and ontogenetic niche shifts. In a wetland where distinct habitat shifts are missing we compared prey use of three generalist benthivorous sunfishes to look for evidence of ontogenetic, interspecific, and “seasonal” variation in prey composition. Diet analysis revealed evidence of diet ontogeny in warmouth (Lepomis gulosus, 30–152 mm standard length, SL), but not in bluespotted sunfish (Enneacanthus gloriosus, 30–47 mm SL) or dollar sunfish (Lepomis marginatus, 30–60 mm SL). Bluespotted and dollar sunfishes consumed small dipteran and amphipod prey and had similar diets in both seasons suggesting a potential for strong interspecific competition. In the dry season, warmouth shifted from using smaller insect prey to larger decapod and fish prey with increasing size. This shift to prey types that were little used by the other species reduced dietary niche overlap with the other sunfishes. After drought and re-flooding (in the wet season), decapods and small fish were less abundant in the wetland and the warmouth ontogenetic shift was less distinct. When matched for gape width, prey composition differed between warmouth and both dollar and bluespotted sunfishes in the wet season, suggesting differences in sunfish foraging modes, but prey use differences were less clear in the dry season when prey were abundant. Both warmouth ontogenetic diet shifts and seasonal variation in prey use (probably mediated by prey abundance) had strong influences on diet overlap and therefore the potential for intra- and interspecific competition between sunfishes in this wetland ecosystem.     

Redescription of Ammodytoides gilli, the tropical eastern Pacific sand lance (Perciformes: Ammodytidae)

Ammodytoides gilli (Bean, 1895) is the correct name for the tropical eastern Pacific sand lance. Its range is extended from Cabo San Lucas, Baja California south to Panama, Ecuador, and the Galapagos Islands. Ammodytes lucasanus Beebe and Tee-Van, 1938 is a junior synonym. Types of both nominal species were re-examined. The species is redescribed based on 50 specimens (42.3-115 mm SL) from 12 lots and is compared with other known species of Ammodytoides. Changes in ontogeny from the smallest known specimen (42.3 mm SL, illustrated) are detailed including reduction in the posterior dorsal fin lobe and development of branched dorsal and anal fin rays.     

Transitional ecological requirements for early juveniles of two sympatric stichaeid fishes,Cebidichthys violaceus andXiphister mucosus

Synopsis The distribution patterns, diets, and substratum (refuge) requirements of early juveniles of two sympatric stichaeid fishesCebidichthys violaceus andXiphister mucosus, were investigated in a rocky intertidal habitat at Diablo Canyon, California. Monthly investigations were conducted at low tide for four consecutive months, to assess ontogenetic differences in distribution, diet, and refuge requirements within and between the two species. Distinct differences in vertical zonation were exhibited by both stichaeids throughout the study. Interspecific zonation patterns were similar to those recorded for adults of both species. Diet analyses showed that early juveniles of both stichaeids were zooplanktivorous, differing markedly from the primarily herbivorous diets of adults. Changes in diet were largely due to the selection of larger prey taxa as both fishes, and their mouth size, grew over the study period. Predation by both fishes on water-column planktors (calanoid copepods, zoea and polychaete larvae) was greatest following initial intertidal settlement and habitat establishment by early juvenile fishes. Greater dependence on substrate-oriented and/or benthic prey (harpacticoid copepods, gammarid amphipods and mysid shrimp) was exhibited by both fishes as they grew in size. Affinities for sand, gravel, and pebbles during monthly field surveys were similar for both species throughout the study. As the fishes grew, their substratum preferences changed in relation to the substrata which provided the best refuge. Results from laboratory experiments indicated that young stichaeids select very specific substrata based on fish age (size) and substratum suitability (i.e. adequate refuge). Similarities in diet and substratum preferences, and changes in those preferences over time, appear to be the result of morphological similarities (body size and shape and mouth gape) for both species at a given age.     

Ontogenetic shift in buoyancy and habitat in the Antarctic toothfish, <Emphasis Type="Italic">Dissostichus mawsoni</Emphasis> (Perciformes: Nototheniidae)

Buoyancy measurements and depth of capture were taken on 70 individuals of Dissostichus mawsoni collected from the Southern Scotia Arc and McMurdo Sound, Antarctica, to examine the effect of age on buoyancy and habitat use. Standard lengths (SL) ranged from 10.4 to 138.0 cm. Juveniles were not buoyant (heavy in water), whereas adults were neutrally buoyant. The slope of the relationship between buoyancy and SL was significantly negative for juveniles (individuals less than 81 cm SL), but there was no significant relationship for adults (individuals greater than 81 cm SL). These results demonstrate an ontogenetic shift in buoyancy. For juveniles, depth of capture and SL had a significantly positive relationship. As individuals reach adulthood they achieve neutral buoyancy and appear to use deeper water habitats. This interpretation is supported by a significant positive correlation between buoyancy and depth of capture for juveniles. Changes in buoyancy with maturation of juveniles may also be associated with a shift in habitat use. Juveniles appear to exploit benthic habitats, whereas adults use the entire water column over deeper water. Given the differences in prey species available in these habitats and based on our results, we predict that diets of juveniles and adults should differ significantly. We also hypothesize that accumulation of lipid deposits from the diet during maturation of juveniles may account for the ontogenetic shift in buoyancy and allow neutral buoyancy to be achieved in adulthood.     

Ontogeny of auditory saccular sensitivity in the plainfin midshipman fish, <Emphasis Type="Italic">Porichthys notatus</Emphasis>

The auditory system of the plainfin midshipman fish, Porichthys notatus, is an important sensory receiver system used to encode intraspecific social communication signals in adults, but the response properties and function of this receiver system in pre-adult stages are less known. In this study we examined the response properties of auditory-evoked potentials from the midshipman saccule, the main organ of hearing in this species, to determine whether the frequency response and auditory threshold of saccular hair cells to behaviorally relevant single tone stimuli change during ontogeny. Saccular potentials were recorded from three relative sizes of midshipman fish: small juveniles [1.9–3.1 cm standard length (SL), large juveniles (6.8–8.0 cm SL) and non-reproductive adults (9.0–22.6 cm SL)]. The auditory evoked potentials were recorded from the rostral, middle and caudal regions of the saccule while single tone stimuli (75–1,025 Hz) were presented via an underwater speaker. We show that the frequency response and auditory threshold of the midshipman saccule is established early in development and retained throughout ontogeny. We also show that saccular sensitivity to frequencies greater than 385 Hz increases with age/size and that the midshipman saccule of small and large juveniles, like that of non-reproductive adults, is best suited to detect low frequency sounds (<105 Hz) in their natural acoustic environment.     

The Reproductive Biology and Early Ontogeny of the Mouthbrooding Banggai Cardinalfish, Pterapogon Kauderni (Perciformes, Apogonidae)

Pterapogon kauderni differs from most apogonids in several aspects of its reproductive biology. A breeding pair often allows a secondary male to intervene during mating. Each clutch consists of about 40 eggs 3 mm in diameter, held together by chorionic filaments and is incubated in the buccal pouch of the male for approximately 19 days. P. kauderni is the first apogonid in which direct development is described. Embryos hatch at post-flexion stages measuring about 6 mm SL and remain in the male's oral cavity for another ten days. When released as juveniles they measure 8 mm SL, their large yolksac is almost entirely consumed, and they do not pass through a planktonic interval. After release, juveniles do not return to the male's mouth for refuge, and any association between the male and newly released juveniles ceases. Juveniles reach 30 mm TL after four months and mature in another five to seven months. The embryo and juvenile development is presented.     

Assessing the diversity and abundances of larvae and juveniles of coral reef fish: a synthesis of six sampling techniques

Due to an increasing emphasis for fish population survey and regulation, efficient tools for evaluating the abundance and diversity of fish from various life stages are needed, especially for coral reef species that present a high taxonomic diversity. The characteristics of six different techniques used for sampling pelagic larvae (a plankton-net and two light-traps), newly settled juveniles (one type of artificial reef), and older juveniles (an underwater seine net in seagrass and macroalgal beds, and rotenone poisoning in coral patches) are described in this study. Larvae belonging to 70 families and juveniles belonging to 34 families were collected. An analysis of similarity (ANOSIM) showed that the taxonomic composition of assemblages collected with the plankton-net and the two light-traps were overlapping but clearly different, due to the higher occurrence of Gobiidae in the plankton-net and of Pomacentridae in both light-traps. Larvae being 2–4 mm standard length (SL) dominated in the plankton-net, whereas larvae being 9–11 mm SL dominated in both light-traps. Pomacentridae juveniles were more abundant in rotenone samples, whereas Labridae dominated in the underwater seine. Juvenile fish collected with the artificial reefs, the underwater seine, and rotenone poisoning largely overlapped in size, with mean sizes of 22, 38, and 33 mm SL, respectively. Seven families were caught by the six sampling techniques, but with unequal success. This study provides ecologists and managers with a unique review of six techniques for sampling a wide range of developmental stages of young fish in different habitats of a coral reef lagoon.

Insectivore to frugivore: ontogenetic changes in gut morphology and digestive enzyme activity in the characid fish Brycon guatemalensis from Costa Rican rain forest streams

Brycon guatemalensis , a Neotropical characid fish, consumes an entirely terrestrial diet, shifting from eating insects as juveniles to fruits and leaves as adults. Juvenile and larger‐sized fish collected in the Rio Puerto Viejo at the La Selva Biological Station in Costa Rica were studied to test the hypotheses that, with ontogeny, (1) relative gut length increases, (2) pyloric caeca arrangement and number remain unchanged and (3) pepsin, trypsin and lipase activities decrease, while α‐amylase activity increases. These hypotheses were mainly supported in that larger fish had longer guts, unchanged pyloric caeca arrangement but fewer caeca, and, at both environmental and standard temperatures for the enzyme assays, lower pepsin and trypsin activities but higher α‐amylase activities than the juveniles. Only lipase, among the digestive enzymes, exhibited the unexpected outcome of either not differing significantly in activity (per g of tissue) between juveniles and larger fish or being significantly higher (per mg of protein) in larger fish. The overall results support the view that B. guatemalensis is specialized morphologically and biochemically to function first as a carnivore and then as a herbivore during its life history.     

The early life history of kurosoi,Sebastes schlegeli (Scorpaenidae), in the Sea of Japan

Larval and juvenile stages of kurosoi,Sebastes schlegeli, are described and illustrated from wild specimens. Some ecological aspects of larvae and juveniles are also described. Notochord flexion occurred between 5.6–7.5 mm SL. Transformation occurred between 13–20 mm SL. Preflexion and flexion larvae ofS. schlegeli can be distinguished from similar larvae by the pigmentation of the dorsal and ventral midlines of the tail and absence of pigmentation on the ventral portion of the rectum. After notochord flexion, the dorsal and lateral regions in both larvae and pelagic juveniles were heavily pigmented, suggesting adaptation for neustonic life style. Larvae and juveniles were caught at many coastal stations, but did not occur in cooler offshore waters. Larvae smaller than 20 mm SL inhabited surface waters. Until ca. 40 mm SL, juveniles inhabited mainly surface waters (without drifting seaweed), but also used other habitats, such as the drifting seaweed, and near the sea bed. Small larvae (<7 mm SL) fed mainly on copepod nauplii. Larger larvae fed on calanoid copepodites andEvadne nordmanni. Pelagic juveniles fed mainly on fish eggs, with fish larvae also being important food items for some individuals. Most food items taken by juveniles that were associated with drifting seaweed were eggs with attaching filaments (Cololabis saira andHyporhamphus sajori), suggesting that the high density of such food items both attracts and keeps juveniles around drifting seaweed.     

Optimization of diet and culture environment for larvae and juvenile freshwater pearl mussels,Hyriopsis (Limnoscapha) myersiana Lea, 1856

Summary

Culture of the freshwater pearl mussel, Hyriopsis (Limnoscapha) myersiana, was carried out in three consecutive steps: (1) culture of glochidia larvae in artificial media, (2) rearing the early juveniles (0–120 days old) in a nursery, and (3) rearing the juveniles (120–360 days old) in an earthen pond. The percentage survival of glochidia in standard tissue culture medium (M199) supplemented with common carp plasma was 95±2.5. All surviving larvae (100%) transformed to juveniles, the duration of transformation being 8 days. The early juveniles (0–60 days old) were fed with a mixture of four selected phytoplankton species (Chlorella sp., Kirchneriella incurvata, Navicula sp. and Coccomyxa sp.). The survival rate of juveniles was 8±0.2%. The average length of these juveniles increased from 0.13±0.01 mm to 1.41±0.16 mm and the average height from 0.16±0.01 mm to 0.98±0.09 mm. Subsequently, 60–120-day juveniles were fed with one of the same four phytoplankton species or a combination of the four. Feeding the juveniles with K. incurvata resulted in the highest survival rate (65±8.32%), with an average length of 3.46±0.04 mm and an average height of 1.94±0.04 mm. Finally, the 120–360-day juveniles were cultured in an earthen pond. There were progressive changes in average weight (0.0037±0.002 g to 11.24±5.02 g), length (3.48±0.39 mm to 54.08±6.21 mm), height (1.97±0.24 mm to 25.09±2.48 mm) and width (0.98±0.06 mm to 12.28±3.21 mm) from 120 to 360 days. The average growth rates per day of these parameters were 0.0497±0.01 g, 0.2414±0.15 mm, 0.0975±0.08 mm and 0.0493±0.03 mm, respectively. H. (L.) myersiana juveniles developed the complete structural composition of the adult by 160 days, and at 360 days, gametogenesis was complete.