Descripción de la morfología externa e interna del langostino con algunas aplicaciones de indole taxonómica y biológica

In the present paper the external and internal morphology of the shrimp Pleoticus muelleri (Bate), is described in detail. Special attention is given to those features which are of diagnostic value or which are significant for a fuller understanding of the biology of this species. The major portion of the paper deals with the description of the cephalopereion, pleon and telson and its appendages, as well as the nervous, respiratory, circulatory, digestive, excretory and reproductive systems. Special attention is given to the digestive system, the stomodaeal apparatus and sexual dimorphism. The relations between form and function of several organs and systems are pointed out. A study is made of the development of the gonads, the sexual cycle in males and females; the variations found in relative weight and size are described. The phylogenetical jposition of the Penaeidae, the genera of the subfamily Solenoceridae and of P. muelleri are discussed. (PDF contains 72 pages)

Reproduction in Gammarus (Crustacea, Amphipoda): basic processes

Research on the basic reproduction processes of Gammarus is summarized and reviewed, reproductive strategies in males and females being left to two later papers. The author describes the reproductive systems, the development of eggs (oocytes) in the ovaries, courtship and precopulatory amplexus, mating and the production of sperms, egg laying, mortality and diapause.

Environmental oestrogens and sexual development in fish

This brief paper discusses the assumption that watercourses might be harbouring a chemical(s) affecting the sexual development in fish. Male fish was found with the oestrogen-dependent blood protein, vitellogenin, usually found only in maturing females. The author examines a number of man-made chemicals present in the environment have been found to be oestrogenic. The paper concludes that rivers contain environmental oestrogens that are capable of causing disruptions in the sexual development of fish. Whether or not these environmental oestrogens are causing a widespread disruption in reproduction in wild fish, however, has yet to be determined.

A seven year study of the life cycle of the Mayfly Ephemera danica

Ephemera danica Müller, 1764 (Ephemeroptera) is one of the largest mayflies found in the British Isles with some females reaching over 30 mm. It is a common and widespread species found in rivers, lakes and streams throughout Europe and is particularly abundant in many of the lowland rivers of the British Isles. The larvae are burrowers – mainly found where silt accumulates below macrophytes. This article gives a general overview of research work on the factors affecting the life cycle of Ephemera danica over a seven year period (1995–2002) on two rivers, the River Test at Leckford in Hampshire and the North Wey at Tilford in Surrey.

Reproductive biology of Rastrineobola argentea (Pellegrin) in the northern waters of Lake Victoria

Size at first maturity, breeding periods and condition factor were determined for the small pelagic cyprinid Rastrineobola argentea (Pellegrin) in the Jinja waters of Lake Victoria in 1996-1997. Females showed a reduced size at maturity compared to ten years earlier when exploitation of the species was minimal. The males, however, have changed little. Although the species breeds throughout the year, two breeding peaks were observed during the drier months of August and December-January. Minimal breeding was observed in the rainy months of April-May and October-November. Fish from the open water station at Bugaia showed a higher proportion of breeding individuals than those from inshore areas. The mean monthly condition factor of fish from Napoleon Gulf confirmed breeding peaks obtained from examination of gonad development.

Reproductive biology of Oreochromis niloticus (L.) in the Nyanza Gulf of Lake Victoria

The reproduction of Nile tilapia, Oreochromis niloticus (L.), in the Nyanza Gulf of Lake Victoria was studied from June 1998 to May 1999. Length at maturity ranged from 28-30 cm TL for females and from 32-34 cm TL for males. Males were more abundant in all length classes longer than 36 cm TL. Relative condition factor was above unity, except in August, October and May for males, and October for females. Gonadosomatic index (GSI) was low during the post spawning period (July to October) and high during the protracted breeding period (December-June).

Distribution of Oreochromis niloticus (L.) in the Ugandan waters of Lake Victoria

The Lake Victoria fish fauna was dominated by cichlids before the establishment of the exotic species Oreochromis niloticus (L.) and Latus niloticus (L.). With the alterations in the ecology of Lake Victoria, changes may be expected to occur in the population dynamics of the fish species. In two zones of Lake Victoria, the size structure, distribution and abundance, condition factors, length-weight relationship and sex ratios of O. niloticus were determined. Larger fish were found in zone II than in zone III, where very few larger fish were recorded. More O. niloticus were caught in zone III, especially in Itome Bay, than in zone II but catch by weight was greater in zone II. More males than females were encountered in both zones. Oreochromis niloticus had similar condition factors in both zones.

From the individual to the community and beyond: water quality, stress indicators and key species in coastal waters

This review examines water quality and stress indicators at levels of organisation from the individual to the community and beyond by means of three case studies concentrating on rocky shores within the north-east Atlantic. Responses of dogwhelks (Nucella) to tributyltin pollution from antifouling paints is examined as the main case study. There are effects at the individual level (development of male sexual characteristics in the female leading to effective sterility) and population level (reduction in juveniles, few females and eventual population disappearance of dogwhelks in badly contaminated areas) but information on community level effects of dogwhelk demise is sparse. Such effects were simulated by dogwhelk removal experiments on well studied, moderately exposed ledges on shores on the Isle of Man. The removal of dogwhelks reduced the size and longevity of newly established Fucus clumps that had escaped grazing. Removal of dogwhelks also increased the likelihood of algal escapes. In a factorial experiment dogwhelks were shown to be less important than limpets \{Patella) in structuring communities but still had a significant modifying effect by increasing the probability of algal escapes. Community level responses to stress on rocky shores are then explored by reference to catastrophic impacts such as oil spills, using the Torrey Canyon as a case study. Recovery of the system in response to this major perturbation took between 10-15 years through a series of damped oscillations. The final case study is that of indicators of ecosystem level change in response to climate fluctuations, using ratios of northern \{Semibalanus balanoides) and southern (Chthamalus spp.) barnacles. Indices derived from counts on the shore show good correlations with inshore sea-water temperatures after a 2-year lag phase. The use of barnacles to measure offshore changes is reviewed. The discussion considers the use of bioindicators at various levels of organisation.

Contribución al conocimiento de la biología del surel (Trachurus picturatus australis) del área de Mar del Plata (Pisces, Carangidae)

The individuals studied came from commercial catches on the coastal area off Mar del Plata. The monthly distribution of sizes shows that the juvenile stay in coastal waters, while the adult individuals leave those waters during winter season to return there in the spring during the season of sexual maturation and spawning, when the water reaches temperature of 10-11°C. The jack mackerel is a relatively small fish, compared with other species of its genus, and has a total length of scarcely 25 cm. The comparison of indexes and mesurements does not reveal any marked difference between sexes, except for the total length, which is greater in the females. Sexually nature individuals at a lenth of 13 cm have been found. Spawning takes place in coastal waters. A great part of the population spawns from December to January. There are oscillations ranging from November to March. On this latter month mature individuals of smaller size have veen found. The jack mackerel feeds usually on copepods and other planktonic organims, but it can feed also on juveniles of other fishes. This fish is caught throghout the whole year. The catches show their greater peak during winter; one other non-constant peak occurs during the spring (October-November) and declines shoraply during the summer months. It follows from this that the time of greates catch does not coincide with spawning season, or with the appearence of the greatest mean sizes. This happens because the interests of the fishermen are attracted during those months by others species of greater commercial value.

Size composition of the catches of the pink shrimp Penaeus duorarum notialis in the shrimp fishery of Sierra Leone

Measurements were taken of size distribution of P. d. notialis collected off Sierra Leone over a period of six months from October 1977 to March 1978. From the frequency distribution curves it is observed that the curves for male shrimps show only one or two major modes, which show prominence between 12.5 and 14.1 cm of total length. Females mostly exhibited size groups with three or four different length ranges and occasional occurrence of 1 to 5 modes. These size groups were observed to show continuous changes. No one group could be said to be permanent. The point of entry into the fishery of male shrimps was found to be at an average total length of 10.5 cm, while females did so at 11 cm. Sex ratios in the different samples were usually 1:1 but in one case the males were more numerous by 2:1 and in four other samples females were significantly preponderent. These departures from the 1:1 ratio may have been artificially created by sorting of the catches on board the ships.

Social structure and underwater behavior of harbor seals in southern Monterey Bay, California

To understand harbor seal social and mating strategies, I examined site fidelity, seasonal abundance and distribution, herd integrity, and underwater behavior of individual harbor seals in southern Monterey Bay. Individual harbor seals (n = 444) were identified by natural markings and represented greater than 80% of an estimated 520 seals within this community. Year to year fidelity of individual harbor seals to southern Monterey Bay coastline was 84% (n = 388), and long-term associations (>2 yrs) among individuals were common (>40%). Consistent with these long-term associations, harbor seals were highly social underwater throughout the year. Underwater social behavior included three primary types: (1) visual and acoustic displays, such as vocalizing, surface splashing, and bubble-blowing; (2) playful or agonistic social behavior such as rolling, mounting, attending, and biting; and (3) signal gestures such as head-thrusting, fore-flipper scratch~ng, and growling. Frequency of these types of behavior was related to seal age, gender, season, and resource availability. Underwater behavior had a variety of functions, including promotion of learning and social development, reduction of aggression and preservation of social bonds by maintaining social hierarchy, and facilitation of mate selection during breeding season. Social behavior among adult males was significantly correlated with vocalization characteristics (r = 0.99, X2 = 37.7, p = 0.00087), indicating that seals may assess their competition based on underwater vocalization displays and adopt individual strategies for attracting females during breeding season based on social status. Individual mating strategies may include defending underwater territories, using scramble tactics, and developing social alliances. (PDF contains 105 pages)

The abiotic ecology of breeding ground of Palaemonid prawns in the Ilaje Estuary, Ondo State, Nigeria

In situ ecological assessment of the breeding grounds of palaemonid prawns was conducted in some selected locations around Ondo state coastal area between the months of April and September. Data obtained were subjected to both descriptive and inferential statistics. Three species of Palaemonid prawns were identified in four different locations within the study area with relative abundance ratio of 4:3:1. Macrobrachium macrobrachion, Nematopalaemon hastatus and Palaemon maculatus respectively. Sex ratio of 1 male to 5 females for M. macrobrachion, and 1 male to 2 females for N. hastatus and P. maculatus were observed with result showing significant relationships (P < 0.05) in distribution patterns across collection sites. Population distribution within the water column showed that palaemons are sub-lithoral prawns inhabiting maximum mean depth of 0.67m ± 0.025. Surface macro-phytes such as Eichhornia crassipies, Paspalum vaginatum, and Pistia stratiotes are common providing hiding spots for the prawn at the breeding ground. The mean soil pH across the sites stands at 6.67± 0.399 with the soil textural class that range from silty-loam to silty-clay. Also, the water quality parameters of study areas suggest that captive culture and rearing of Palaemons may be feasible outside the breeding areas.

Étude du crabe rouge profond Geryon quinquedens en Côte d'Ivoire. 2 - Éléments de biologie et d'écologie avec références aux résultats obtenus au Congo

Geryon quinquedens is present along the West African continental slope at depths from 300 to 1000 m, on silt-clay sediments. Geryon is a cold and rather poorly oxygenated water loving species. It is easily caught by traps as it is a scavenger and predatory crustacea. In a given area its distribution does not appear to be homogeneous: for example, densities of red crabs are higher in the eastern and western region of Côte d'Ivoire than in the central zone. Similar observations can be made off Congo, Angola and United States. It can be assumed that there is a relation between the abundance of Geryon and the productivity level of the area. Geographical variations of sex ratio are suspected to be correlated with the density distribution. Males and females have not the same bathymetric distribution: females are only common in the shallower waters (300-500 m) whereas males are present in the whole biotope. Seasonal migrations occur down and up the slope in both the sexes and are certainly related to the reproductive biology. Knowledge of the reproductive biology is also necessary to understand fishing-trap catch rate: egg maturation extends over several months and ovigerous females are exceptionally caught by traps; males also are less available during the same period (March to August) when migrations are less important; in this period, mean size increases and probably this happens at the end of a moult. From September to February the catch-rates increase. Growth is slow compared with other littoral Guinean Crustacea (Peneides). Females become sexually mature at a size of 80 mm (carapace width): modification in the allometric relations of abdomen and carapace are then conspicuous.

Arctic charr from Ennerdale Water: a pilot study

There are three fish species in the north west of England, Arctic charr (Salvelinus alpinus, L.), schelly (Coreqonus lavaretus. L.), and vendace (C. albula, L.), which have been reported as rare and vulnerable and have been identified as requiring the preparation and implementation of a conservation management plan. The presence of Arctic charr in Ennerdale Water has resulted in it being designated as a Site of Special Scientific Interest. These fish and one race of the species in Lake Windermere are the only English populations of charr known to spawn in running water. Associated with Ennerdale charr is the copepod parasite Salmincola edwardsii which has not been recorded from any other charr inhabited waters of the Lake District. However, it has been recorded on charr from four Scottish Lochs (Stack, Lee, Tay and Doon). The unique nature of Ennerdale is further highlighted by the presence of two crustaceans, Mysis relicta and Limnocalanus macrurus. The former has been recorded in Ireland while the latter is not known to exist anywhere else in the British Isles. The aim of this pilot study was to obtain baseline data on charr that spawn in Smithy Beck and the River Liza. This would indicate the current status of the population and help identify areas requiring further investigation. A total of 161 fish (95 males and 66 females) was caught and tagged over the 3 day period, 141 from Smithy Beck and 20 from the Liza. The raw data of the findings is presented in two appendices.

Croissance et détermination de l'âge par lecture d'écailles d'un poisson plat de Côte d'Ivoire, Cynoglossus canariensis (Steind. 1882)

Cynoglossus canariensis has a very rapid growth. The rate of the males is 0,36 and the female one is 0,32. The asymptotic size is 55,0cm for the females and 50,5cm for the males. Females and males younger than three years (40cm), which represent 90 per cent of the Côte d'Ivoire stock have a similar growth, so the average equation: Lt=53,5 (1-e -0,34(t+1)) will be used.