Significant extension in northern Australia of the known geographic range of the Shield Shrimp Triops australiensis (Crustacea: Notostraca)

The program BIOCLIM predicts the total geographic distribution of species, based upon the biogeoclimatic characteristics common to the localities at which they are known to occur. Field studies in the Northern Territory have located the Shield Shrimp Triops australiensis at localities substantially north of its known and predicted geographic distribution.     

中华鲎虫外部形态结构的初步观察

中华鲎虫体由头、躯干和尾3部分组成.头部具1对复眼和1个无节幼体眼,复眼后有1个颈感器.第1触角细小、棒状,第2触角退化.口器由上唇、大颚和2对小颚组成,上唇为头部的突起物,大颚和2对小颚为附肢,第2小颚的皮肤皱褶延长扩大形成头胸甲.雌体躯干部由36个体节组成,雄体39个体节,前30节具附肢,共57对.雌体躯干部后6个体节无附肢,雄体躯干部后9个体节无附肢.尾节分叉,细长多节,具刚毛,左右两根尾鞭的分节不对称.     

Population genetics and reproductive strategies of two Notostraca (Crustacea) species from winter ponds in Israel

Fluorescent-amplified fragment length polymorphism (FAFLP) fingerprinting assay was used to compare the genetic diversity within and between tadpole shrimps (Notostraca) populations of Lepidurus apus (n=7) and Triops cancriformis (n=2) from rain pools in Israel. Each ephemeral water body has revealed a unique fingerprint pattern with an entailed genetic drift between nearby ponds. High similarity of genotypic diversity within each geographic area led to three clusters of water bodies, north, south and center of Israel. FAFLP assays on several newly hatched individuals of T. cancriformis revealed high identity amongst kin, as compared to L. apus where newly hatched from the same maternal source showed high diversity. Results indicate that T. cancriformis populations from Israel are probably parthenogenetic as indicated by clonal structures. The higher genetic variability in the L. apus populations and in laboratory-hatched specimens indicates the existence of sexual reproduction.     

Limb development in a primitive crustacean,Triops longicaudatus: subdivision of the early limb bud gives rise to multibranched limbs

 Recent advances in developmental genetics of Drosophila have uncovered some of the key molecules involved in the positioning and outgrowth of the leg primordia. Although expression patterns of these molecules have been analyzed in several arthropod species, broad comparisons of mechanisms of limb development among arthropods remain somewhat speculative since no detailed studies of limb development exist for crustaceans, the postulated sister group of insects. As a basis for such comparisons, we analysed limb development in a primitive branchiopod crustacean, Triops longicaudatus. Adults have a series of similar limbs with eight branches or lobes that project from the main shaft. Phalloidin staining of developing limbs buds shows the distal epithelial ridge of the early limb bud exhibits eight folds that extend in a dorsal ventral (D/V) arc across the body. These initial folds subsequently form the eight lobes of the adult limb. This study demonstrates that, in a primitive crustacean, branched limbs do not arise via sequential splitting. Current models of limb development based on Drosophila do not provide a mechanism for establishing eight branches along the D/V axis of a segment. Although the events that position limbs on a body segment appear to be conserved between insects and crustaceans, mechanisms of limb branching may not. Received: 28 February 1996/Accepted: 24 June 1996     

Tadpole shrimp structure macroinvertebrate communities in playa lake microcosms

Laboratory microcosms were used to assess whether tadpole shrimp, Triops sp., affect community structure of other native macroinvertebrates in playa lakes of the Southern High Plains of Texas. Removal of tadpole shrimp shortly after hatching reduced abundances of many taxa, and decreased subsequent taxonomic richness and diversity. For many invertebrates, the presence of tadpole shrimp in low numbers had a positive effect on mean abundance. Direct effects of tadpole shrimp include the reduction of prey species abundance, which in turn may alter biotic interactions among other taxa. Indirect effects include physical modification of the environment during foraging through surface sediments. Results suggest that tadpole shrimp may be a key species controlling structure of macroinvertebrate communities in playa lakes.     

Population dynamics of Triops cancriformis (Crustacea: Branchiopoda: Notostraca) of the Espolla temporary pond in the northeastern Iberian peninsula

The population dynamics of Triops cancriformis in Espolla temporary pond (NE Iberian peninsula) were studied during 1996 and 1997, which encompassed six flooded periods. Data were collected on each individual's size, sex, and, if female, on number of eggs in the oostegopodes. Male-biased sex ratios were found only in the drying-out phase and variations in fecundity were strongly related to hydroperiod duration. Sex ratio variation during the drying-out phase can be attributed to female mortality because the very low recruitment observed does not support the hypothesis of an increase of males. Two hypotheses are advanced to account for female mortality: (1) differential reproductive effort, and (2) size selective predation by herons. This population is characterised by low values of maximum densities compared with other notostracan populations, and by higher densities in the spring–summer hydroperiods than in the winter ones.     

The formation of the nervous system during larval development in Triops cancriformis (Bosc) (crustacea,Branchiopoda): An immunohistochemical survey

We provide data of the development of thenervous system during the first five larval stages of Triops cancriformis. We use immunohistochemical labeling (against acetylated α‐tubulin, serotonin, histamine, and FMRFamide), confocal laser scanning microscopy analysis, and 3D‐reconstruction. The development of the nervous system corresponds with the general anamorphic development in T. cancriformis. In larval stage I (L I), all brain parts (proto‐, deuto‐, and tritocerebrum), the circumoral connectives, and the mandibular neuromere are already present. Also, the frontal filaments and the developing nauplius eye are already present. However, until stage L III, the nauplius eye only consists of three cups. Throughout larval development, the protocerebral network differentiates into distinct subdivisions. In the postnaupliar region, additional neuromeres and their commissures emerge in an anteroposterior gradient. The larval nervous system in L V consists of a differentiated protocerebrum including a central body, a nauplius eye comprising four cups, a circumoral nerve ring, mandibular‐ and postnaupliar neuromeres up to the seventh thoracic segment, each featuring an anterior and a posterior commissure, and two parallel connectives. The presence of a protocerebral bridge is questionable. The distribution of neurotransmitters in L I is restricted to the naupliar nervous system. Over the course of the five stages of development, neurotransmitter distribution also follows an anteroposterior gradient. Each neuromere is equipped with two ganglia innervating the locomotional appendages and possesses a specific neurotransmitter distribution pattern. We suggest a correlation between neurotransmitter expression and locomotion. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Analysis of the diet of the tadpole shrimp, Triops sinensis, in paddy fields of Shouchang River watershed

The tadpole shrimp, Triops sinensis, was discovered in the paddy fields of the Shouchang River watershed. The gut contents of the shrimp from these field populations were analyzed in order to quantify their dietary patterns. Some species of tadpole shrimps were found to prey on mosquito larvae as well as uproot weeds. Mosquito larvae and weeds were seldom found in the paddy fields which the tadpole shrimp inhabited in the Shouchang River watershed. The results further showed that the larvae of these tadpole shrimp mainly feed on algae and rice lamina. The tadpole shrimp could feed on animal food including protozoa, nematodes, rotifers, crustaceans, and aquatic insect larvae, though the animal food was subsidiary.     

Toxicity and effects of mosquito larvicides methoprene and surface film (Agnique® MMF) on the development and fecundity of the tadpole shrimp Triops newberryi (Packard) (Notostraca: Triopsidae)

We investigated the interactions of tadpole shrimp, a mosquito biological control agent, with the juvenile hormone analog methoprene and a monomolecular surface film. In laboratory assays, the tadpole shrimp (TPS) Triops newberryi (Packard) was able to tolerate high concentrations of methoprene without negative impacts on its growth, longevity, and fecundity when exposed to 1 to 10 mg/liter, or 90–900 fold, of the IE₉₀ levels against a laboratory colony of Culex quinquefasciatus Say. The same held true in field trials when the habitats were treated with Altosid® Liquid Larvicide (Altosid® LL, 5% methoprene) at 0.3–1.2 liters/ha. or 1–4 fold of the label rates for mosquito control. However, some significant impacts on the TPS occurred when they were exposed to Agnique® Monomolecular Film (Agnique® MMF) at the label rates for mosquito control ranging from 1.89–9.45 liters/ha. under laboratory and field conditions. To avoid the negative impact of Agnique MMF on tadpole shrimp, it appears that 1.89 liters/ha. would be the maximum rate when Agnique MMF is used to control mosquitoes in the habitats where the TPS is employed as a biological control agent, or prevailing in the aquatic habitats with potential for suppressing mosquito larval populations.     

Ultrastructural observations on the oogenesis of Triops cancriformis (Crustacea,Notostraca)

Summary The first stages of the oogenesis of Triops cancriformis have been studied. At the outset the oocyte is smaller than the nurse cells. Meiosis begins with typical synaptonemal complexes. The significance of these complexes and of some other peculiar structures of germ cells, i.e., pore complexes and annuli within the nucleus, and annulate lamellae within the cytoplasm are discussed. The morphofunctional uniformity of some cytoplasmic structures (annulate lamellae, concentrically arranged ER, and yolk globules) in the oocyte as well as its nurse cells is also discussed.