Hermaphroditic Shrimp Research Articles

Male mating opportunities affect sex allocation in a protrandric-simultaneous hermaphroditic shrimp

Sex allocation theory predicts phenotypic adjustments by individuals in their investments into the male and female reproductive function in response to environmental conditions. I tested for phenotypically plastic shifts in sex allocation in a protandric simultaneous hermaphrodite, in which individuals mature and reproduce as males first, and later in life, as simultaneous hermaphrodites. I predicted that initially maturing males should adjust the timing of maturation as hermaphrodites according to male mating opportunities mediated by population size of hermaphrodites. In a first experiment, males maintained with only one hermaphrodite reduced the time they spent as males in comparison to males maintained with no conspecifics, presumably because total reproductive output is maximized by two individuals being simultaneous hermaphrodites when the mating system is a pair. Conversely, males maintained in groups with two or more hermaphrodites increased the time they spent as males in comparison to single males. This delay in maturation was not an effect of resource depletion with increasing shrimp density because the growth rate of males did not differ among most of the experimental treatments. One hypothesis to explain this social mediation of sex allocation is that the smaller males are more successful in mating as males than are the larger hermaphrodites: it will pay reproductively for males to delay maturation as hermaphrodites in large but not in small groups. In agreement with this notion, a second experiment demonstrated that smaller males were four times more successful than were larger hermaphrodites in inseminating shrimps reproducing as females. The informative cue that males may use to perceive different group sizes deserves further attention.

Effects of density and simulated recruitment and mortality on sex change in a protandric simultaneous hermaphroditic shrimp, Lysmata wurdemanni

Sex change in many hermaphrodite animals has been suggested to be environmentally determined, especially socially. To investigate whether sex change in the protandric simultaneous hermaphrodite shrimp Lysmata wurdemanni (Gibbes 1850) is socially mediated, two experiments were conducted in the laboratory between September 2002 and April 2004 using laboratory-cultured shrimp that originated from Port Aransas, Texas, USA. The size at sex change (from male to simultaneous hermaphrodite) in this shrimp is variable, with the minimum around 2.4 cm in total length (TL). Large shrimp (2.4–4.5 cm TL) still in the male-phase (MP) have been found in the wild and laboratory environments. This study tested the hypothesis that large MP shrimp delay changing to the euhermaphrodite-phase (EP) due to social control. In the first experiment, ten shrimp were raised in large (110-l) and small (20-l) containers to test the effect of habitat size/density on sex change. The percentage of shrimp changing to EP was significantly higher in the large container (low density) than in the small container after 60 and 120 days. But after 570 days sex ratios were the same, 2 MP:8 EP. In the second experiment, group composition was changed over time to simulate population recruitment and mortality. MP shrimp delayed sex change when EP shrimp were present. However, if group structure is stable, some MP shrimp may not change sex during their lifetime. Under certain demographic conditions, such as when postlarvae (PL) were added to (simulating recruitment) or EP shrimp were removed from (simulating mortality) a group, all old MP (from original PL) shrimp changed to EP. The response of old MP shrimp to simulated recruitment is faster than to simulated mortality. The present study confirms that social control affects the size and timing of sex change in L. wurdemanni. However, some MP shrimp never change sex suggesting that genetics might also play a role in the sex ratios of L. wurdemanni populations.

Comparative mating success of smaller male-phase and larger male-role euhermaphrodite-phase shrimp, Lysmata wurdemanni (Caridea: Hippolytidae)

The protandric simultaneous hermaphrodite shrimp Lysmata wurdemanni (Gibbes 1850) has a pure searching mating system, i.e., males are continually searching for receptive females and copulation is brief. To examine whether size-based advantage in male–male competition occurs and whether the mating ability of male-phase (M) shrimp equals that of euhermaphrodite-phase shrimp serving as males (Em), mating performance, including mating frequency and precopulatory behavior, of M and Em shrimp was compared using two M:Em ratios. Two experiments were carried out from March 2004 to August 2004 at Florida Institute of Technology’s Vero Beach Marine Laboratory using laboratory-cultured shrimp that originated from Port Aransas, TX, USA. In the two experiments, one parturial euhermaphrodite-phase shrimp acting as a female (Ef) was maintained with one M and two Em shrimp (one with and one without an egg mass), and two M and two Em shrimp, respectively. The M shrimp used were always smaller than the Em shrimp. Experiment 1 showed that there was no significant difference in mating ability between Em with and without egg mass. In both experiments, the M shrimp gained mating partners more frequently than the Em shrimp did. In the experiment with two M and two Em shrimp, mating frequencies of the small M and large M shrimp were similar. Precopulatory behaviors of the M shrimp were more active than those of the Em shrimp. Mating between the small M and larger Ef shrimp was sometimes successful even when the size difference was 20.0 mm total length (TL). Mating between a larger M shrimp and smaller Ef shrimp sometimes failed when the size difference was only 13.0 mm TL. Mating frequency of M shrimp over that of Em shrimp with Ef shrimp increased significantly with increasing density and operational sex ratio. The advantage of M over Em shrimp in obtaining mating partners is probably a result of sexual selection and adaptation, and may partially explain the observed delayed sex change in some L. wurdemanni, i.e., some male-phase shrimp grow very large and never become hermaphrodites.

Short report on the effect of a parasitic isopod on the reproductive performance of a shrimp

The present work studied the degree of inhibition caused by the bopyrid isopod Eophryxus lysmatae ( Caroli, 1930 [Caroli, E., 1930. Notizia di tre specie nuove ed una poco nota di Bopiridi addominali, parassiti di Caridei del golfo di Napoli. (Contributo alla conoscenza del genere Phrixus Rathke). Boll. Soc. Nat. Napoli 41, 258–269]), an abdominal parasite, on the reproductive performance of its host, the protandric simultaneous hermaphrodite shrimp Lysmata seticaudata (Risso, 1816). Parasitized shrimp (PS) was not able to produce embryos, although they could successfully fertilise the eggs of unparasitized shrimp (US). All US paired with PS were able to fertilise eggs when paired with other US. The average number of larvae (±S.D.) produced by US shrimp paired with US and PS (344±27 and 346±23, respectively) was not significantly different ( p=0.73). The average intermolt period duration (±S.D.) for US and PS (10±1.2 and 11±0.8 days, respectively) was not significantly different ( p=0.82), with bopyrid parasites molting synchronously with their host. No PS lost its parasite during ecdysis. Although only three parasitized shrimp were used in the present work, parasitic castration induced by E. lysmatae seems to only affect the female sexual system of the simultaneous hermaphrodite L. seticaudata, and therefore parasite-induced “reproductive death” does not occur in this species as in other gonochoric and sequencial hermaphroditic caridean shrimp. Nutritional drain and disruption of endocrine mechanisms possibly caused by the bopyrid parasite are discussed.

Amino and fatty acid dynamics of Lysmata seticaudata (Decapoda: Hippolytidae) embryos during early and late reproductive season

The present study investigates amino and fatty acid dynamics of embryos of different-sized simultaneous hermaphrodite shrimp (SH) (Lysmata seticaudata) during early (ERS) and late reproductive seasons (LRS). A significant relative decrease in total amino acids and essential amino acids (EAA) was recorded (P<0.05) during the development of embryos produced by shrimp collected during ERS and LRS. The content of non-essential amino acids (NEAA) showed a smaller variation, without a marked decrease. During the last embryonic stage, the major EAAs of embryos were, in decreasing magnitude, lysine and arginine, while the major NEAAs were glutamic acid and valine. A substantial decrease in lipid content (P<0.05) was observed, and the quantitatively more important fatty acids were the saturates 16:0 and 18:0, the monounsaturates 18:1n-9 and 18:1n-7 and the polyunsaturates 20:4n-6 (arachidonic acid, ARA), 20:5n-3 (eicosapentaenoic acid, EPA) and 22:6n-3 (docosahexaenoic acid, DHA). Monounsaturates were used at a higher rate, and embryos produced by SH shrimp displayed similar consumption rates of saturated and polyunsaturated fatty acids. Considering individual fatty acids, no clear utilization pattern between different-sized SH shrimp in ERS and LRS was recorded. The inexistence of consistent differences between amino and fatty acid utilization during embryogenesis among different-sized SH shrimp in ERS and LRS emphasizes the variability affecting offspring in decapod crustaceans.

Development of sexual morphs in two simultaneous hermaphroditic shrimp, Lysmata wurdemanni and Lysmata rathbunae

Summary Development of secondary sexual morphs from post-larva to maturation was described for two simultaneous hermaphroditic shrimp, Lysmata wurdemanni and L. rathbunae. In post-larval stage and male-phase (MP) individuals, both endopods of the first pleopods and appendix interna (AI) of pleopod 2 increase as shrimp grow. The morph change from MP to the euhermaphrodite phase (EP) is a gradual process involving five molts. A reliable and simple criterion for identifying MP, transitional-phase, and EP shrimp is presented.

Mating Without Anterior Pleopods in a Simultaneous hermaphroditic shrimp, Lysmata Wurdemanni (Decapoda, Caridea)

The effects of copulatory rami removal of male-role shrimp (male-phase (MP) or euhermaphrodi te-phase (EP)) on mating behavior of a simultaneous hermaphroditic shrimp, Lysmata wurdemanni, were investigated in the laboratory. There was no difference in general mating behavior between male-role shrimp with or without ablation of copulatory pleopods. However, ablation highly significantly (P < 0.001) affected copulation frequency. The influence was also sex dependent (P < 0.001). In general, copulation frequency in ablated EP shrimp was significantly higher (P < 0.05) than in ablated MP of the same treatment. Ablation of either pleopod 1 or pleopod 2 in MP shrimp did not affect mating behavior or spermatophore transfer. The success of spermatophore transfer was negatively correlated with the mean copulation frequency (R = ?0.9707, P < 0.001). Normally, spermatophores were deposited on the base of the last two pairs of pereiopods. Ablation of the pleopods may lead to failure of emission or improper deposition of a spermatophore. Some new mating behaviors are described and a possible mating mechanism for the shrimp is proposed.

Fertilization Success without Anterior Pleopods in Lysmata Wurdemanni (Decapoda: Caridea), a Protandric Simultaneous Hermaphrodite

Abstract The modifications of the first two pleopods in male shrimp have long been considered to serve in insemination of the female. The role of pleopods 1 and 2 in mating in a protandric simultaneous hermaphroditic shrimp, Lysmata wurdemanni, were investigated. Results indicate that the modified endopod of pleopod 1 is not needed to transfer sperm in both male-phase (MP) and euhermaphrodite-phase (EP) shrimp. Absence of pleopod 2 does not affect the sperm-transfer success in both MP and EP shrimp. Removal of pleopod 1 also has no impact on fertilization in the MP shrimp; however, sperm transfer is affected by removal of pleopod 1 in some EP shrimp. Even when both pleopods 1 and 2 are completely ablated, about 20% of the shrimp can still fertilize successfully and another 20% partially successfully.

Sex Change and Population Fluctuations in Pandalid Shrimp

Sex Change and Population Fluctuations in Pandalid Shrimp

Hermaphroditic White Shrimp, Penaeus setiferus, Parasitized by Thelohania sp.

Abstract Two white shrimp, Penaeus setiferus, with external and histological characteristics of both male and female, are considered hermaphrodites. Both were infected with protozoan microsporidial parasites, Thelohania sp., probably Thelohania penaei.