ABNORMAL ROSTRUM AND TELSON IN TWO SPECIES OF PENAEID SHRIMP (DECAPODA, DENDROBRANCHIATA, PENAEIDAE) FROM THE PACIFIC COAST OF MEXICO

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1 ABNORMAL ROSTRUM AND TELSON IN TWO SPECIES OF PENAEID SHRIMP (DECAPODA, DENDROBRANCHIATA, PENAEIDAE) FROM THE PACIFIC COAST OF MEXICO BY HUGO AGUIRRE 1 ) and MICHEL E. HENDRICKX 2,3 ) 1 ) Instituto Nacional de la Pesca, Centro Regional de Investigación Pesquera, P.O. Box 1177, Mazatlán, Sinaloa 82000, Mexico 2 ) Laboratorio de Invertebrados Bentónicos, Unidad Académica Mazatlán, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, P.O. Box 811, Mazatlán, Sinaloa 82000, Mexico ABSTRACT Morphological abnormalities were observed in two specimens of penaeid shrimp collected along the east coast of the Gulf of California, Mexico. A bifid rostrum was observed in the brown shrimp, Farfantepenaeus californiensis and a bifid telson in the white shrimp, Litopenaeus vannamei. RÉSUMÉ Des anomalies morphologiques ont été observées chez deux spécimens de crevettes Pénéides recoltées le long de la côte est du golfe de Californie, Mexique. La crevette brune, Farfantepenaeus californiensis, présente un rostre bifide et la crevette blanche, Litopenaeus vannamei, un telson bifide. INTRODUCTION AND MATERIAL Morphological abnormalities have long been noticed among decapod crustaceans. These include malformations in appendages or body segments (Lucas, 1844; Le Senechal, 1888; Richard, 1893; Fauvel, 1900; Santana et al., 1990), duplication of structures (Carvacho, 1988; Williams, 1988; Rudolph, 1996; Nakatani et al., 1997) or lack of such structures (Kulkarni et al., 1980), and reversal of asymmetry (Nouvel, 1944; Lemaitre et al., 1982; Stevens & Munk, 1991). Some deformities are related to bilateral gynandromorphy (Micheli, 1991). Malformations of 3 ) michel@ola.icmyl.unam.mx Koninklijke Brill NV, Leiden, 2005 Crustaceana 78 (1): Also available online:

2 114 HUGO AGUIRRE & MICHEL E. HENDRICKX sexual appendages have also been noted among decapod crustaceans (Ivanov & Sokolov, 1997; Rodriguez & Campos, 2000). Among shrimps, abnormalities of the rostrum have often been reported and most deal with a significant increase in size or in rostral teeth number (see Santana et al., 1990; Ayub & Ahmed, 1991; De Grave, 1999). In Penaeidae, variations in shrimp rostra have been noticed on several species fished in the Indian Ocean. Fenneropenaeus penicillatus (Alcock, 1905) (1.9% of examined individuals), F. merguiensis (De Man, 1888) (2.9%), and Metapenaeus affinis (H. Milne Edwards, 1837) (0.3%) were found to possess abnormal rostra, either for number of rostral teeth or for rostral length (Ayub & Ahmed, 1991). However, no abnormalities in the shape of the rostrum or telson of Penaeidae have been reported before. During two recent Pacific shrimp sampling programmes of the National Fisheries Institute (Instituto Nacional de la Pesca) of Mexico, shrimps of the genus Farfantepenaeus and Litopenaeus were collected by trawl along the coast of Sinaloa by the R/V BIP XII and smaller boats. During routine analysis of the catch, specimens of the brown shrimp, Farfantepenaeus californiensis (Holmes,1900) and of the white shrimp, Litopenaeus vannamei (Boone, 1931) were recognized and separated for closer examination. Among these, one specimen of F. californiensis and one specimen of L. vannamei presented abnormalities that have apparently never been documented for this group of shrimp before. RESULTS Farfantepenaeus californiensis (Holmes, 1900) (fig. 1A-D) Material examined. One female (carapace length 64 mm), off La Tonina, Altata Bay ( N W), Sinaloa, Mexico, 21/Aug/1996, muddy bottom, depth 10 m (5.5 fathoms). Remarks. The length of the rostrum is 18 mm, with a bifurcation starting at about mid-length; the length of each prong is ca. 12 mm, and the fork forms an angle of ca. 50 (fig. 1A, B). The proximal portion of the rostrum bears five dorsal teeth, while the distal, bifurcate portions are smooth (fig. 1C, D). There is one ventral tooth on the left prong (fig. 1A, D). Two short, stout, fixed spines are present between the two prongs (fig. 1B). In normal specimens of F. californiensis, the rostrum bears 8-11 dorsal teeth. The absence of dorsal teeth on the bifurcated part of the rostrum accounts for the decrease in number of teeth in the abnormal specimen, although the two stout spines at the inner base of the prongs might correspond to two of the missing dorsal teeth. There is only one ventral tooth (in lateroventral position) on the left prong

3 Fig. 1. A-D, Abnormalities in the rostrum of the brown shrimp, Farfantepenaeus californiensis (Holmes, 1900); and, E, an abnormality in the telson of the white shrimp, Litopenaeus vannamei (Boone, 1931). A, Tip of rostrum, showing two spines on proximal, inner margin of prong (arrow) as well as ventro-lateral tooth (arrow); B, dorsal overview of carapace with bifurcate rostrum; C, lateral view of rostrum, right prong; D, lateral view of distal part of rostrum, left prong; E, dorsal view of bifurcate tip of telson. Scale bars: A, E, 5 mm; B, 1 cm. ABNORMAL ROSTRUM, TELSON IN PENAEID SHRIMP 115

4 116 HUGO AGUIRRE & MICHEL E. HENDRICKX instead of the two ventral teeth normally found in this species. The rostrum is also much more elevated than in normal specimens, and the dorsal teeth are more erect. Litopenaeus vannamei (Boone, 1931) (fig. 1E) Material examined. One female (carapace length 59 mm), entrance of El Colorado Bay ( N W), Sinaloa, Mexico, 10/Aug/2001, muddy bottom, depth 5.5 m (3 fathoms). Remarks. The telson length is 20 mm, with a bifurcation starting at ¾ from the proximal margin, the right prong is ca. 5 mm long, the left prong is slightly shorter, the inner margin of the prongs is densely setose throughout. The prongs form an angle of ca. 55 (fig. 1E). DISCUSSION Variation in rostral dentition and size, and variation in telson setation, have been reported for several species of Caridea. Some species also present significant morphological changes in rostral structure and size during growth (Yaldwyn, 1957; Hendrickx et al., 1998; De Grave, 1999). In penaeid shrimp, however, rostrum size and dentition appear to be much more stable than in caridean shrimps, both in regard to shape and relative length. The closest case of a bifid rostrum was reported by Fauvel (1900), who described it in a specimen of Palaemon serratus (Pennant, 1777) collected in Cherbourg, France. In that specimen, however, the normal rostrum was conserved and a second, accessory rostrum emerged at its left base at an angle of 45. The dorsal teeth of the accessory rostrum were of somewhat abnormal size, and also spaced, like in Farfantepenaeus californiensis. Malformations in decapod crustaceans have been attributed to parasitic infections (e.g., dinoflagellates, bopyrid isopods), but most are related to reproduction or secondary sexual characters (see Shields, 1994; Ivanov & Sokolov, 1997; Trilles, 1999) and there is suspicion that, at least in some cases (particularly with freshwater or coastal species), pollution might induce malformations (see O Connor & Huggett, 1988; Weiss et al., 1988). A few studies, however, indicate that some morphological abnormalities might be the result of wounds failing to heal, resulting in regeneration of appendages with mirror-image symmetry (Shelton et al., 1981; Shelton, 1982). In the present case, no information was obtained on contamination levels in the ecosystems where the shrimps were caught. The coastal area of Sinaloa is subject to heavy runoff of agricultural pesticides and local pollution by heavy metals (Paez-Osuna, 2001). These factors are known to affect hatching, development, and

5 ABNORMAL ROSTRUM, TELSON IN PENAEID SHRIMP 117 even adult moulting or regeneration processes in crustaceans (Amin et al., 1998; Weis et al., 1992; Zapata et al., 2001; Lavolpe et al., 2004), and environmentally induced abnormalities might be at issue in the present cases. There is an intensive shrimp fishery in the region, particularly in shallow water (continental shelf, bays, and coastal lagoons). Although species of the genera Farfantepenaeus and Litopenaeus represent the target-species of the local shrimp fishery and are retained by fisherman, some specimens might be injured during trawling activities and yet escape from the fishing gear. Wounds might, therefore, represent a source of abnormal regenerative growth, although in this case there is no mirror-image symmetry in the abnormal rostrum due to the presence of a ventral tooth on the left prong. The specimens examined showed no signs of parasitic infections, so the possibility of a parasite interaction is not retained. ACKNOWLEDGEMENTS We wish to give special thanks to J. A. Virgen who collected the specimens and generously gave access to this material. The authors thanks P. Y. Noël and Ph. Bearez (Muséum national d Histoire naturelle, Paris, France), M. Girardin (CEMAGREF, Cestas, France), and C. McLay (University of Canterbury, New Zealand) for providing useful information related to abnormalities in Crustacea. We thank M. Cordero R. for reviewing literature and preparing the final version of the manuscript. REFERENCES AMIN, O. A., E. M. RODRIGUEZ, M. HERNANDO, L. I. COMOGLIO & L. S. LOPEZ, Effects of lead and cadmium on hatching of the southern king crab Lithodes santolla (Decapoda, Anomura). Invert. Reprod. Dev., 33 (1): AYUB, Z.& M. AHMED, Rostral variations in the shrimps Penaeus penicillatus, P. merguiensis and Metapenaeus affinis from Pakistan. Pakistan Journ. Zool., 23 (2): CARVACHO, A., On some abnormalities in the chelae of commercial crabs (genus Cancer) from Baja California, Mexico. California Fish Game, 74 (3): DE GRAVE, S Variation in rostral dentition and telson setation in a saltmarsh population of Palaemonetes varians (Leach) (Crustacea: Decapoda: Palaemonidae). Hydrobiologia, 397: FAUVEL, P., Palaemon serratus Penn. à rostre monstrueux. Feuille Jeunes Nat. Paris, (3) 359, 2 pp. HENDRICKX, M. E., F. OSUNA-PÁEZ & H. M. ZAZUETA-PADILLA, Biology and biochemical composition of the deep water shrimp Heterocarpus vicarius (Crustacea: Decapoda: Caridea: Pandalidae) from the southeastern Gulf of California, Mexico. Bull. mar. Sci., 63 (2): IVANOV, B. G.& V. I. SOKOLOV, Abnormalities in the development of secondary sexual characters in the deepwater prawn Pandalus borealis (Crustacea, Decapoda, Pandalidae). Zool. Zhurn., 76 (2):

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