Selectivity Parameters and Size at First Maturity in Deep-Water Shrimps, Aristaeomorpha foliacea (Risso, 1827) and Aristeus antennatus (Risso, 1816), from the North-Western Ionian Sea (Mediterranean Sea)

Selectivity experiments were carried out during trawling targeting deep-water shrimps Aristaeomorpha foliacea (Risso, 1827) and Aristeus antennatus (Risso, 1816) (Crustacea, Decapoda, Aristeidae) in the North-Western Ionian Sea (Eastern-Central Mediterranean). Different criteria were employed to analyse maturity; however, the proportion at 50% of retained, mated and mature specimens was always used to indicate the size, expressed as Carapace Length (CL, mm), at first capture (CL_c), mating (CL_sp) and at first maturity (CL_m), respectively. In order to estimate the size at 50% maturity (CL_m) for females of both species, three criteria were adopted. In particular, CL_m was computed for the mature females not considering the presence of spermatophores, for the mature females with spermatophores and for the mature females intersected by the decreasing proportion with size of females without spermatophores. Three diamond stretched mesh codends of 40, 50 and 60 mm were tested using a cover of 20 mm. The 40-mm stretched mesh size (European Union legal size in the Mediterranean) was not selective for the sampled population of each species. The size at first capture (CL_c), calculated in both species for the two sexes combined, increased significantly with mesh size. Even for the mesh size of 60 mm, the size at first capture was still smaller than the sizes at 50% maturity, whatever the criterion adopted. Since the differences between the size at first maturity and the sizes at first capture are greater in A. foliacea than A. antennatus, the former species appears in this respect to be more vulnerable to trawling than the latter.     

Catch Composition on Red Shrimps’ (Aristaeomorpha foliacea and Aristeus antennatus) Grounds in the Eastern Ionian Sea

In the present study, the catch composition and the catch per unit effort (CPUE) by weight and numbers in red shrimps’ (Aristaeomorpha foliacea and Aristeus antennatus) grounds was examined in the southern part of the eastern Ionian Sea, in order to collect important information for the Greek waters, where no deep-water fishery exists. In the depth stratum 500–700 m, the catch of the commercial species represented a high proportion (>70%) of the total catch. Red shrimps and several other commercial species were found in important quantities. The present results suggest the possibility of developing a deep-water fishery in Greece. In such a case, attention should be paid because of the high vulnerability of A. foliacea – the main deep-water fishing resource in the area – to the fishing pressure.     

狭胸天牛成虫和幼虫的消化道研究

研究了狭胸天牛成虫和幼虫消化道形态。成虫消化道细长,嗉囊长囊状,中肠前段具极少的稀疏瘤状小突起。幼虫消化道相当长,前肠细短,中肠很长,前中肠粗短而膨大,中肠表面无小盲囊。     

Isolation and characterization of 14 polymorphic microsatellite markers for the blue and red shrimp, Aristeus antennatus (Crustacea, Decapoda)

Eighteen microsatellite loci were isolated and characterized from the blue and red shrimp, Aristeus antennatus Risso 1816, a commercially exploited marine crustacean widely distributed throughout the Mediterranean Sea and in the eastern Atlantic. Polymorphism was assessed in a population (n = 20) from the southwestern Sardinian seas; 14 loci resulted polymorphic and showed from three to 13 alleles. The observed heterozygosity ranged from 0.2 to 0.85. These microsatellites will be potentially useful for the study of A. antennatus population genetic structure.     

Comparative fecundity and oocyte size of Aristaeomorpha foliacea and Aristeus antennatus in the Greek Ionian Sea (E. Mediterranean) (Decapoda: Aristeidae)

Absolute and relative fecundity of 49 ripe gonads (from the cephalic and the abdominal sections of the same specimen) of Aristaeomorpha foliacea and 71 ripe gonads of Aristeus antennatus caught in the Ionian Sea (E. Mediterranean) and their oocyte size were studied. Both average absolute and relative fecundities estimated for A. antennatus were statistically higher than those estimated for A. foliacea; the average absolute fecundity of A. foliacea was 151 936 oocytes/female and that of A. antennatus was 200 472 oocytes/female and the average relative fecundity of A. foliacea was 5477 oocytes/g and that of A. antennatus was 9386 oocytes/g. Fecundity in both red shrimp species is linearly related to carapace length, body and gonad weight, although, the most precise estimation is provided by the relationship of body weight and fecundity. In the present study, the oocyte size (diameter, volume) of both species could be considered very large. In conclusion, A. foliacea shows lower fecundity than A. antennatus, having a lower ovogenetic activity, but it produces larger oocytes. This is in accordance with the highest value of the gonad weight and gonad volume of A. foliacea exhibited in relation to A. antennatus.     

Ultrastructure of the spermatozoa of Aristaeopsis edwardsiana and Aristeus varidens (Crustacea, Dendrobranchiata, Aristeidae)

The acrosome-less spermatozoon of Aristaeopsis edwardsiana (Crustacea, Aristeidae), which consists of a central non-membrane bound nuclear region surrounded by a thin peripheral cytoplasm, much resembles that of the previously studied aristeid Aristaeomorpha foliacea. The marked spermatozoal similarities between these two species appear to indicate a close phylogenetic proximity. A considerably different spermatozoal pattern is observed in aristeids from the genus Aristeus (A. varidens and A. antennatus), whose spermatozoa possess an anterior spherical acrosome, lacking a spike, and partially embedded in (instead of capping) the main sperm body. The two distinct sperm types found in the Aristeidae differ significantly from the spiked sperm typically found in most penaeoids (Penaeidae, Solenoceridae and Sicyoniidae), thus suggesting a phylogenetic separation of the Aristeidae from the remaining Penaeoidea.     

Characterization of antioxidant systems, oxidation status and lipids in brain of wild-caught size-class distributed Aristeus antennatus (Risso, 1816) Crustacea, Decapoda

The objectives of the study were to characterize the enzymic antioxidant system (free radical scavenging enzymes such as catalase, superoxide dismutase, glutathione peroxidases, glutathione transferase and glutathione reductase), dietary antioxidants (vitamin E), the oxidation status (malondialdehyde (MDA) levels and the fluorescence intensity of lipid-soluble fluorescent products (LSFP)) and lipid composition (lipid classes and polyunsaturated fatty acids (PUFA) as pro-oxidants) in neural tissues from males and females of wild-caught size-class distributed blue and red marine shrimp Aristeus antennatus (Risso, 1816), trawled off the south coast of Spain. Moreover, the mechanisms that may result in the deposition of age-pigments in relation to the physiological age of this species in its natural environment were investigated. Three different size classes were defined for males and four for females, and differences were observed for the different variables measured between sexes. The proportion of polar lipids (primarily phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine) predominated over that of neutral lipids, increasing significantly in males but decreasing in females. However, cerebrosides increased significantly from size–age class I to III in males but no significant differences were observed in females. The fatty acid composition showed increases in monounsaturated fatty acids (particularly 18:1 and 24:1 isomers) and dimethyl acetals, but decreases in PUFA (primarily 22:6(n-3)) with increasing size–age in both sexes. The concentration of MDA (nmol g⁻¹ brain) did not present any marked trend with size–age in both sexes. In contrast, fluorescence intensity showed increasing trends in both sexes with increasing size–age, when expressed as % fluorescence brain⁻¹ (λ_ex/em 350–445 nm and λ_ex/em 400–455). However, when expressed as % fluorescence mg⁻¹ brain total lipid, only males presented an upward trend with size–age (λ_ex/em 400–455). The concentration of vitamin E (ng mg⁻¹ brain) did not show significant differences between different size–age classes within the same sex and showed a molar ratio of one molecule of vitamin E per approximately 200 molecules of PUFA in brain membranes. The antioxidant enzyme activities showed clearer patterns with increasing size–age in males than in females, with catalase and glutathione transferase presenting downward trends and superoxide dismutase and total glutathione peroxidase showing upward trends. The fluorescence analysis of brain LSFP was not a useful tool to separate the population into different size–age classes, although the different patterns encountered between sexes for the variables measured points to males as better subjects for this type of study.