Monogamy in a new species of wild guinea pigs (Galea sp.)

A new species of wild guinea pigs from Bolivia was recently discovered: Galea sp. So far no data are available concerning its social and mating systems. We therefore investigated behavioural compatibility, sexual dimorphism, paternity in a male-competing situation, testicular and epididymal size, and sperm morphology and motility. The results showed a complete intrasexual and moderate intersexual behavioural incompatibility between unfamiliar animals, a reversed sexual dimorphism with females larger than males, and litters always fathered by single males. Furthermore, both the reproductive organ weights and the percentage of motile sperm and sperm with intact acrosomes were significantly lower compared with the promiscuous congeneric Galea musteloides. In summary, these data strongly suggest a monogamous social and mating system for the recently discovered Galea sp.     

Maturation,epitoky and regeneration in the polychaete Eunice siciliensis under field and laboratory conditions

In the gonochoric polychaetous annelid Eunice siciliensis Grube, germ cells only develop in the posterior segments of the worm; these segments subsequently differentiate into an epitokous portion separating at maturity from the infertile body part. As in the Pacific and Atlantic palolo worms, the epitokous portions die some hours after spawning. Laboratory investigations revealed that the anterior parts of spawned worms survive and regenerate genital segments. After a period of at least 8 months, paired gonads are developed in these segments. Gonia proliferating later from the germinal tissue are released from gonadal sacs into the coelomal cavities, where gamete development occurs. A reproductive epitokous portion does not mature and separate until the second year of cultivation; it is followed by caudal regeneration. These facts and the observation that only about 50% of the individuals obtained from samples of coralligène were sexually differentiated, led to the conclusion that E. siciliensis probably has a bi-annual reproductive cycle. Caudal regeneration does not depend on the presence of a prostomia hormone. The ability to form posterior regenerates is inherent to the parapodial segments of all body regions, except for mature genital segments. This is also valid for the formation of morphologically different secondary prostomia. However, for initiation and further promotion of gametogenesis and epitokous development, at least one gonadotropic factor originating from the prostomium is required. Neurosecretory cells within the brain suggest this factor(s) to be of neuro-endocrine nature. Specimens developing secondary prostomia were found both under field and laboratory conditions. In several cases, sexual development took place, and even epitokous portions were separated from such individuals. From this it appears that the gonadotropic functions are re-established by the regenerated prostomia in order to ensure reproduction in individuals accidentally deprived of the anterior end. The possible rôle of temperature and light as environmental factors involved in the control of normal and regenerative growth, of sexual development and reproduction is discussed.     

Concentrations and vertical fluxes of zooplankton fecal pellets on a continental shelf

The contribution of fecal pellets to the benthos of the southeastern shelf of the USA is investigated through an analytic model which considers pellet production by different stage groups of the genus Paracalanus. Model results indicate that the concentration and vertical flux of pellets is a function of producer size and consumer size and abundance. Nauplii and adults, respectively, produce daily on the average 50 and 13% of total pellet mass, yet contribute 4 and 63%, respectively, to the daily pellet flux. Most of the pellets produced are consumed or degraded in the water column, with only 0.2% of the average daily primary production reaching the seafloor (35 m) as fecal pellets. This contributes to an impoverished benthos, such as that found on the southeastern continental shelf.     

Nachweis der epitokie als fortpflanzungsmodus des polychaeten Eunice siciliensis (Polychaeta: Annelida)

Eunice siciliensis (Grube)¹ is a sedentary polychaete with separate sexes; its germ cells develop only in the posterior part of the body. In March and April, females with whitish or even dark-green oocytes, males with only few spermatogonia, and individuals with no germ cells at all were discovered in the “coralligène” of the Banyuls region (European Mediterranean Sea). In august, besides immature and sexually non-differentiated worms, mature individuals of both sexes were captured: females with dark bluish-green oocytes of diameters up to 250μm, and males with milky genital segments containing spermatozoa. Soon after isolation from the substrate, these individuals performed characteristic movements with their posterior body parts, which then autotomized, and released ova and spermatozoa. Evidence is given that the anterior, atokous body parts survive in their tubes in the “coralligène” after separation from the epitokous portions, and regenerate new genetal segments. The development of gametes observed in these regenerated segments indicates the ability of E. siciliensis to reproduce more than once during its lifetime. Not only caudal, but also prostomial regeneration was observed; the formation of a (morphologically different) secondary prostomium appears to be essential for any development of germ cells in worm fragments. E. siciliensis exhibits surprising similarities in habits and in formation of an epitokous form with Eunice viridis (Gray), the “palolo” worm of the South Pacific Ocean, but nevertheless, lacks the prominent criteria of this famous species: the ventral eye spots on each genital segment in males and females, and the paired areas with brown pigmentation on the ventral side of each epitokous segment in the males.     

Carbon metabolism and strobilation in Cassiopea andromedea (Cnidaria: Scyphozoa): Significance of endosymbiotic dinoflagellates

Scyphopolyps and scyphomedusae of Cassiopea andromeda Forskål (Cnidaria, Scyphozoa) containing dinoflagellate endosymbionts (zooxanthellae) were investigated for rates and pathways of carbon fixation. Photosynthesis by the algae, accounting for 80 and 15 mol C h^-1 on a dry weight basis in medusae and polyps, respectively, by far exceeds dark incorporation of inorganic carbon by the intact association. Photosynthetic carbon fixation is operated via C₃ pathway of carbon reduction. DCMU-treatment (1×10^-6 M and 1×10^-5 M) completely inhibits light-dependent carbon assimilation. Major photosynthates presumably involved in a metabolite flow from algal symbionts to animal tissue are glycerol and glucose. A total of 5–10% net algal photosynthate appears to be seleased in vivo to the host. This is probably less than the energy supply ultimately required for the nutrition of the polyps and medusae. The presence of zooxanthellae proved to be indispensable for strobilation in the scyphopolyps. However, photosynthesis by algal symbionts as well as photosynthate release is obviously not essential for the initiation of ephyrae as is shown by DCMU-treatment, culture in continous darkness, and aposymbiotic controls. It is therefore concluded that strobilation is supported, but not triggered by algal photosynthetic activity. The induction of strobilation thus seems to depend on a more complex system of regulation.     

How <Emphasis Type="Italic">Doratomyces stemonitis</Emphasis> copes with Benzoxazolin-2(3<Emphasis Type="Italic">H</Emphasis>)-one (BOA), its derivatives and detoxification products

Summary. Doratomyces stemonitis (Hyphomycetales, Dematiaceae) is a saprotrophic fungus belonging to the mycobiota of the cereal rhizosphere. The fungus is able to metabolize benzoxazolin-2-(3H)-one and a variety of its derivatives including higher plant detoxification products, microbial degradation products and the chemically rather stable 2-amino-(3H)-phenoxazin-3-one. D. stemonitis can use all of these compounds as sole C-sources but their utilization, especially that of microbial degradation products and 2-amino-(3H)-phenoxazin-3-one, seems to be highly energy consuming, resulting in slow mycelium growth and a change of colony morphology. Benzoxazolin-2-(3H)-one derived compounds induce the synthesis of different isoforms of a glycosylated protein with sequence homologies to the endo-1,3-β-glucanase Asp f2, an allergen from Aspergillus fumigatus and other Asp f2-like proteins e.g., from Verticillium dahliae or PRA1 antigen from Candida albicans. The induction of the protein is regarded as a stress response.     

Female-specific colouration, carotenoids and reproductive investment in a dichromatic species, the upland goose Chloephaga picta leucoptera

Although studies on the evolution and function of female ornaments have become more numerous in the last years, the majority of these studies were carried out in cases where female ornaments were a smaller and duller version of the ornaments found in males. There are substantially fewer studies on species with female-specific ornaments. However, no study so far investigated the potential of female-specific colouration as a quality signal in birds with conventional sex roles. We studied female-specific ornamentation in a strongly sexually dichromatic species, the upland goose Chloephaga picta leucoptera, in two consecutive years. Male upland geese have white head and breast feathers and black legs, whereas females have reddish-brown head and breast feathers and conspicuous yellow-orange legs. We found that female-specific colouration in upland geese can reliably indicate different aspects of female phenotypic quality. Females with more orange coloured legs and more red-like head colours had higher clutch and egg volumes than females with a paler leg and head colouration, and a more reddish plumage colouration was related to a higher body condition. These relationships provide the theoretic possibility for males to assess female phenotypic quality on the basis of colouration. Furthermore, the females with a more orange-like tarsus colouration had higher plasma carotenoid levels. Both tarsus colouration and carotenoid concentrations of individual females were highly correlated across years, indicating that tarsus colour is a stable signal. Despite this correlation, small individual differences in plasma carotenoid concentrations between the two study years were related to differences in tarsus colouration. We thus show for the first time in a wild bird and under natural conditions that carotenoid-based integument colouration remains consistent between individuals in consecutive years and is also a dynamic trait reflecting individual changes in carotenoid levels. In this species, where pairs form life-long bonds, the honesty of the carotenoid-based integument colouration suggests that it may be a sexually selected female ornament that has evolved through male mate choice.