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Research Journal of Fisheries and Hydrobiology, 5(2): 76-80, 2010 © 2010, INSInet Publication Affectation of Swimming Capacity in Callinectes Rathbunae (Crustacea: Brachyura) Caused by Loxothylacus Texanus (Crustacea: Rhizocephala) Horacio Vázquez-López Laboratorio de Ecología, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Avenida de los Barrios, Número 1, Los Reyes Iztacala, Tlalnepantla, Estado de México, C. P. 54090, México. Abstract: Dark crabs Callinectes rathbunae Contreras, 1930 parasitized with the sacculinid rhizocephalan Loxothylacus texanus Boschma, 1933, were collected from lagoon-estuarine subsystem of Alvarado, Veracruz, México, in regular samplings. A total of 298 crabs parasitized with the rhizocephalan L. texanus was captured. In all, we observed 190 females and 108 males; 90 showed no movement in swimming legs, 49 were females and 41 males. Crabs with virgin externa (62.4%) kept the capacity to move the natatory legs and the ability to swim; 21.5% of the crabs with immature externa lost the capacity to move the natatory legs, so their displacement was limited only to walking; the rest of the crabs in the same category (5.4%) kept the capacity to move the natatory legs and the ability to swim. 8.7% of the hosts (both sexes) with mature externa lost the capacity to move the natatory legs and, consequently, the capacity to swim. It was concluded that there is a relationship between the grade of development of the externa and the loss of movement in the natatory legs. This is the first report that has been carried out on the affectation of the natatory legs in a brachyuran crab parasitized by a rhizocephalan. Key words: Parasitism; Loxothylacus texanus; crustaceans; behavior; externa, barnacle INTRODUCTION Robles et al.[25], have concluded that the presence of mature parasites of L. texanus represents an extra The parasites are an extraordinarily important metabolic load for C. rathbunae. Same authors have group of organisms[4] which include protozoa, observed that C. rathbunae parasitized with mature L. helminthes, insects and crustaceans, among others[7, 23, texanus lost the osmoregulation capacity. Vázquez- 4, 3, 16, 30, 11]. Within the group of crustaceans, common López et al.[33] have reported that C. rathbunae parasites are copepods, tantulocarids, isopods, parasitized with mature L. texanus are less aggressive amphipods and some cirripedes[12,20,6,13,16]. The than those that present immature parasites, crabs with Rhizocephala have become singularly specialized to mature parasites increase their appetite because the parasitism within other Crustacea; they influence the parasites represents a great metabolic load, same morphology and biology of their hosts to a remarkable authors affirm that the degree of aggressiveness of the degree[27, 29, 14]. All species parasitize marine and a few parasitized crabs is related with the degree of freshwater Crustacea, and have a complicated life cycle development of the parasite; in addition, they also have with both endo-and ectoparasitic stages[15]. observed loss of vision and the presence of paralysis in Their hosts are decapods or, exceptionally, isopods, the pair of swimming legs of crabs with mature cumaceans, stomatopoda, or even balanomorph parasites. barnacles[13]. Rhizocephala affect the host´s The objective of present work was to establish the development, transform the morphology, change rate of parasitized L. texanus with paralysis in legs secondary sex characters of the host too[21, 34, 15] and (without movement in swimming legs) in the captured manipulate host behavior[15, 17, 18]; the hosts gonads do individuals. Should be noted that this research was not mature, and thus parasitized female hosts do not generated as part of a general study focused to produce eggs, parasitized male hosts are feminized, characterize L. texanus life cycle (published data apart). parasitized males will have the smaller chelae and wider abdomen (in Brachyura) characteristic of females, MATERIALS AND METHODS while allometric characteristics of parasitized females remain relatively unchanged[21,20,1,2,8,31]. Dark crabs C. rathbunae (known in Mexico as Corresponding Author: Horacio Vázquez-López, Laboratorio de Ecología, Facultad de Estudios Superiores Iztacala, UNAM, Av. De Los Barrios, No. 1, Los Reyes Iztacala, Tlalnepantla, Estado de México, México. C. P. 54090, A. P. 314. Tel: (+52)5556231173 E-mail: [email protected] 76 Res. J. Fish. & Hydrobiol., 5(2): 76-80, 2010 jaiba prieta), both sexes parasitized with the sacculinid It was observed that crabs (both sexes) with virgin rhizocephalan L. texanus, were collected from lagoon- externa (62.4%) had the capacity to move the natatory estuarine subsystem of Alvarado, Veracruz, México. legs (pereiopods natatory) and the ability to swim; Crabs were captured using handmade fishing net 21.5% of the crabs (both sexes) with immature externa which is locally called aro jaibero (crab hoop)[19]. lost the capacity to move the natatory legs, so their Crabs were transported to the laboratory of the displacement was limited only to walking; the rest of National Collection of Crustaceans in the National the crabs in the same category (5.4%) had the capacity Autonomous University of Mexico, in México City. In to move the natatory legs and the ability to swim. the laboratory all crabs (5.8-12.3 cm) were measured 8.7% of the hosts (both sexes) with mature externa lost with 0.1 mm precision Vernier caliper and classified [34] the capacity to move the natatory legs and, following the Wardle and Tirpak criteria . Organisms consequently, the capacity to swim. The rest of the were maintained in recirculation systems for their crabs in the same category (2%) kept the capacity to acclimatization. Then the crabs were placed move the natatory legs; however, these organisms did individually in 20-liter aquaria to begin main not swim like the organisms with virgin externa did. It experiment. The salinity was maintained in 15 PSU was observed that the crabs that lost the movement (practical salinity units) and the temperature in 250C. capacity of the natatory legs, folded over the shell and The crabs were feeding daily in the morning ad libitum near the lateral spines. with fresh fish and/or with chicken liver. During a two-year period, behavior of 298 In order to know if there was a relationship between the extent of development in the parasites and parasitized crabs captured in different samplings was 2 recorded for 11 hours daily (from 9:00 to 20:00). At the loss of movement in the natatory pereiopods, a X test was carried out (test of independence) (α = 0.05 the same time that the aquaria were reviewed in search 20.05,2 of eggs and / or larvae (to complete larval development and degrees of freedom (3-1)(2-1)= 2, X = 5.9 for of L. texanus in laboratory conditions), were observed females and males). When the null hypothesis was 20 20.05,2 the movement of crabs in the aquaria. All movement rejected (reject null hypothesis if X > X , how 20.05,2 20 20.05,2 of crabs were recorded and later analyzed. Data X = 5.9 < X = 136.6 for females and X = 5.9 20 considered in this study were those related to the type < X = 77.6 for males, then we rejected null of movement of organisms. The hosts were recorded hypothesis) it was concluded that there is a relationship first by development degree of parasite (type of between the extent of development of the externa and externa) following the Wardle and Tirpak criteria[34]. the loss of movement. When the null hypothesis was Then, the crabs were counted in one of two accepted, ANOVA test showed a relationship between possible categories without movement in swimming the extent of development of externa and loss of pereyopods (crabs that can’t swim) or with movement movement in the natatory pereiopods (reject null in swimming pereyopods (crabs that can swim) (see hypothesis if Fo > F0.053,6 = 4.7, how Fo = 0.4 < F = Vázquez-López et al.[33]. Crabs included hosts with 4.7, then Fo is accepted) it was concluded that there virgin externa (externa that have not been fecundated is a relationship between the extent of development of and presented a milky white color), immature externa the externa and the loss of movement. (which presented a yellow color and are about to expel larvae) and mature externa (externae dark brown color, Discussion: It is known that the rhizocephalans take which are the ones that expel larvae periodically) (see absolute control of their hosts, provoking in them [34] [33] Wardle and Tirpak ; Vázquez-López et al. Data morphologic and physiologic effects[21, 22, 24, 15], such as were analyzed with X2 test (independence test) and [28] abnormal abdominal widening, known as feminization variance analysis (ANOVA) . regarding the males and hyperfeminization regarding the females. Results: Were captured 298 crabs parasitized with the What was observed in this work agrees with the rhizocephalan L. texanus, with carapace width interval consulted literature. For example, Høeg[14] mentions that 5.8-9.6 cm., the mean was 8.5 cm. Were observed 190 establishing host control is pivotal to parasite success. females and 108 males. From these parasitized crabs, It is therefore significant that the root system 90 showed no movement in swimming legs, 49 were invades the neuroendocrine organs of the host during females and 41 males. Of the 128 (42.9%) females with virgin externa, all could swim, of the 48 females the early stage of the interna’s growth and before it starts to infiltrate the digestive system. Høeg and with immature externa, only 9 (3.0%) could swim and [12] of 14 females with mature externa, only 4 (1.3%) could Lützen mention that in the establishment stage of swim.