Evidence for matrotrophy in the viviparous sea cucumber Leptosynapta clarki: A role for the genital haemal sinus?

Summary

Viviparity, where the embryos develop in the female reproductive system, is a rare form of reproduction in marine invertebrates, being described in only 14 species of echinoderm. In the intraovarian brooding sea cucumber, Leptosynapta clarki Heding 1928 (cf., Sewell et al. 1995), we used direct evidence (changes in energetic content) to show that significant additional nutrients are provided to the embryos during viviparous development (matrotrophy). In the transition from a structure used to produce gametes to a long-term brooding structure there are visual, histological and transmission electron microscopy (TEM) changes in the structure of the ovarian wall. Changes occur primarily in the cells of the visceral peritoneum and involve an increase in size of the connective tissue/genital haemal sinus (CT/GHS). In the latter part of the brooding period the visceral peritoneum returns to a flattened form, and new oocytes develop along the tubule wall. Similar changes in the intraovarian brooding sea cucumber Oneirophanta mutabilis affinis lead us to suggest that there is a role for the genital haemal sinus in providing nutrition during the brooding period in viviparous echinoderms. Future research is suggested to focus on changes in the ovarian wall structure during the different phases of reproduction (gamete production/brooding) in these species.     

FOOD-INDUCED BODY PIGMENTATION QUESTIONS THE TAXONOMIC VALUE OF COLOUR IN THE SELF-FERTILIZING SLUG CARINARION SPP

Body pigmentation is a popular taxonomic marker in slugs to discriminateclosely related species. However, the genetic background ofbody pigmentation is known only for a few species, while inmany others body pigmentation is influenced by age, food and/orclimate. In this study, we investigated the effects of differentfood items on body pigmentation expression in two selfing pulmonategastropods, Arion (Carinarion) silvaticus and Arion (Carinarion) fasciatus.Both species mainly differ in the distribution of yellow-orangegranules on the body, which in A. fasciatus are concentratedin lateral bands, and in A. silvaticus are evenly scattered.Animals were raised individually under the same conditions, whilethey laid eggs as a consequence of selfing. This F₁ generation wasafterwards divided into two groups, which were fed with different fooditems. A diet of carrot, lettuce or paper had no effect on the distributionof the yellow-orange granules in A. silvaticus, but provokeda loss of the yellow-orange lateral bands in A. fasciatusso that externally these F₁ specimens became similar to A. silvaticus.In both species, a diet of nettle resulted in a strong yellow-orangepigmentation, which often formed yellow-orange lateral bands.These results indicate that food can probably influence the'species-specific' body pigmentation in Carinarion, and thusquestion the reliability of colour traits to distinguish A.silvaticus and A. fasciatus. (Received 5 May 2000; accepted 29 September 2000)     

A clinally varying promoter polymorphism associated with adaptive variation in wing size in Drosophila

Body size often shows adaptive clines in many ectotherms across altitude and latitude, but little is known about the genetic basis of these adaptive clines. Here we identify a polymorphism in the Dca (Drosophila cold acclimation) gene in Drosophila melanogaster that influences wing size, affects wing:thorax allometry and also controls a substantial proportion of the clinal wing‐size variation. A polymorphism in the promoter region of Dca had two common alleles showing strong reciprocal clinal variation in frequency with latitude along the east coast of Australia. The Dca‐237 allele increased towards the tropics where wing size is smaller. A within‐population association study highlighted that an increase in the frequency of this allele decreased wing size but did not influence thorax size. A manipulated increase in the level of expression of Dca achieved through UAS‐GAL4 was associated with a decrease in wing size but had no effect on thorax size. This was consistent with higher Dca expression levels in family lines with higher frequency of the Dca‐237 allele. Genetic variation in the promoter region of the Dca gene appears to influence adaptive size variation in the eastern Australian cline of Drosophila melanogaster and accounts for more than 10% of the genetic variation in size within and between populations.     

Feeding Ecology of Ring-Necked Pheasant and Northern Bobwhite Chicks in Conservation Reserve Program Fields

ABSTRACT Gamebird chick survival is dependent on invertebrate availability, and the ability to access insect prey is an important characteristic defining brood habitat quality. Different mixes of warm-season grasses and forbs were established to improve the habitat quality of fields enrolled in the Conservation Reserve Program (CRP) for gamebirds in the Southern Plains. We analyzed the feeding ecology of human-imprinted, 4- to 10-day-old ring-necked pheasant (Phasianus colchicus) and northern bobwhite (Colinus virginianus) chicks in wheat fields and 4 types of conservation practices (CP) fields enrolled in CRP (CP10, improved CP10, CP2, and CP25) in western Kansas, USA, during June and July, 2004 and 2005. Foraging rates were greatest for bobwhite chicks in improved CP10 and CP25 fields and greatest for pheasant chicks in CP10 and CP25 fields. Vegetation characteristics such as bare ground cover appear to have a significant impact on insect selection, because the diet was more diverse for both species in fields with more bare ground. The CP25 fields provided the best combination of mobility and diet breadth for both species. Although herbicide-treated wheat fields had low feeding rates, we determined non-herbicide-treated fields (i.e., weedy wheat) provided easy mobility and feeding rates similar to CRP fields. We suggest that management of vegetation to benefit gamebirds does not affect species equally. Feeding rates of bobwhite chicks were sensitive to vegetation-influenced mobility. Management of CRP fields for both pheasant and bobwhite chicks can be reconciled by practices that permit more open space at ground level, such as light disking or burning, to permit easier movement for chicks.     

Stand selection by birds in Scots pinewoods in Scotland: the need for more old-growth pinewood

A study at Abernethy Forest, Scotland, examined stand selection by some of the birds of conservation concern that inhabit pinewoods. Abernethy Forest was ideally suited for the study because all four main stand types of forest development (stand initiation, stem exclusion, understorey reinitiation and old-growth) were represented. Capercaillies Tetrao urogallus (both males and females) and crossbills Loxia spp. preferred old-growth pinewood in winter, and Redstarts Phoenicurus phoenicurus and Tree Pipits Anthus trivialis preferred old-growth in summer. Great Spotted Woodpecker Dendrocopos major selected snags in old-growth to excavate nest and roost sites. In winter, Crested Tits Parus cristatus had a weak selection for old-growth stands and Bullfinches Pyrrhula pyrrhula preferred stands at initiation. Possible reasons for these preferences are put forward. Although the area of conifer woodland in Scotland is 888 000 ha, it largely comprises North American species destined to be cut before reaching old-growth. Old-growth pinewood in Scotland is largely confined to the fragments of ancient native pinewood, amounting to only 16 000 ha. To conserve some pinewood birds of conservation concern, a mechanism to allow more Scots Pine Pinus sylvestris woods to reach and remain in an old-growth state needs to be pursued.