<I>Moringua Edwardsi</I>
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BULLETIN OF MARINE SCIENCE, 29(1): 1-18, 1979 EARLY LIFE-HISTORY OF THE EEL MORINGUA EDWARDSI (PISCES, MORINGUIDAE) IN THE WESTERN NORTH ATLANTIC P. H. J. Castle ABSTRACT The eel Morillgua edwardsi (Jordan and Bollman, 1889) is known principally from immature specimens in the western North Atlantic from Bermuda southwards to Atlantic Panama and Colombia. Its distinctive larva, earlier recognized as Leptocephalus diptychus Eigenmann, 1900, has about seven alternating, midlateral melanophores and also one in front of the anus. Larvae have 110-124 myomeres, hatch at about 5 mm TL and reach full growth at 50 mm TL, a process which takes 3-5 months, before metamorphosis begins. They live in the upper 35 ill and occur over a broad area of the western North Atlantic encompassing 1O°-40oN and 40o_88°W but those of about 10 mm TL occur only near the Caribbean Islands. Spawning is suggested to occur in the Caribbean the year round but principally at monthly intervals from November to April. Some larvae are dispersed out into the Atlantic by the Gulf Stream. This pattern of distribution and dispersal is similar to that of the only other Atlantic moringuid Neoconger mucronatus Girard, 1859. At a time when the classification of the 1968) to clarify the nomenclature of the eels is undergoing critical scrutiny, major Moringuidae pointed out that at least one difficulties are still being presented by the character (number of vertebrae) would family Moringuidae. Moringuid eels are need to be considered in any re-appraisal readily captured with piscicides in many of moringuid classification. However, it be- shallow areas of the tropical Indo-Pacific came clear from the previous study that and western Atlantic Oceans and are con- vertebral numbers were, alone, insufficient sequently abundant in museum collections to distinguish the species. around the world. However, it is still not While it is now reasonably certain that possible confidently to identify the Indo- the Moringuidae contains but two genera: Pacific species. Furthermore, little is known Moringua Gray, 1831 and Neoconger about the life-history and biology of these Girard, 1858 (Smith and Castle, 1972) eels, including the complex changes which this was not always considered to be so. they appear to undergo prior to maturation Species of Moringua have at times been (Gosline and Strasburg, 1956). described in six families, the Ratabouridae, The most substantial key to members of Ptyobranchidae, Moringuidae, Stilbiscidae, the family, based essentially on body pro- Echelidae, and Anguillichthyidae and under portions and other external characters ten other generic names: Rataboura Gray, (Schultz, et aI., 1953) was seriously ques- 1831, Pterurus Swainson, 1839; Pachyurus, tioned by Gosline and Strasburg (1956) Swainson, 1839; Ptyobranchus McClelland, who demonstrated marked sexual dimorph- 1844; Aphthalmichthys Kaup, 1856; Pseu- ism in Hawaiian moringuids which they domoringua Bleeker, 1865; Stilbiscus Jor- referred to Moringua macrochir Bleeker, dan and Bollman, 1889; Mayerina Silvester, 1855. This observation was foreshadowed 1915; A nguillichthys Mowbray, 1927 and by the brief studies of Parr (1930) and Merinthichthys Howell Rivero, 1935. The Gordon (1954) on Moringua edwardsi distinctions between these nominal genera (Jordan and Bollman, 1889) in the tropical were drawn essentially on the basis of what West Atlantic. My own attempt (Castle, most probably are morphological changes 2 BULLET]N OF MARINE SCIENCE, VOL. 21, NO. ], ]979 during maturation of males and females, i.e., distinctive for them to have been readily those shown for Hawaiian moringuids and separated 'rom leptocephali of Neoconger known also to occur in other species. These mucronatu;', the only other moringuid spe- changes are indeed as marked as any seen cies in the western North Atlantic. More- in fishes as a group and are certainly more over, the .arvae of M. edwardsi are very than occur in any other genus of eels. It is well represented in the DANA Oceano- now widely accepted that immature morin- graphical Collections as some 1200 speci- guids pass through an "Aphthalmichthys" mens frorr. various Danish expeditions in phase with reduced eyes and fins and that the Atlantc, but mainly from the DANA the "Stilbiscus-Anguillichthys" form with cruises 1920-22. The material included larger eyes and fins is not adopted until specimens of 7.5 mm to 49 mm total maturity of both males and females. How- lengths, as well as metamorphic larvae. From ever, the precise relationship between stage such a L1rge number, wide size and of gonad development, as established geographic 11 range, it is now possible to histologically, and body form has yet to be describe tl e larval life of M. edwardsi as fully studied and described. has already been done for Neoconger It has recently been shown (Castle and mucronatu.: in the western Atlantic (Smith Bohlke, 1976) that the very considerable and Castlt:, 1972) and also to compare variation in body form and particularly these two moringuid species. body size attained at maturity in M. A furth~r 280 moringuid larvae were edwardsi is correlated with sex: mature also collected by the DANA in the Indo- males are only 115-155 mm in length while Pacific OCf an during the Round-the-World females with clearly recognizable ova attain Expedition 1928-30. Some 34 species of 245-360 mm. Furthermore, males have Moringua have been described from this 109-117 vertebrae and females 116-125, ocean (Ca,tle, 1968) but there are almost there being a significant difference in the certainly many fewer valid species. Schultz mean vertebral number in the sexes (112.6 et al. (19.53) recognize 14. My previous and 119.4 in males and females respec- review (Clstle, 1968) suggests that there tively). This discovery at last resolves the are probably about 10 species with a major long-standing problem of the wide variation group ha\ ing vertebral numbers in the in morphology of M. edwardsi and also range 105-130, but with others at about anticipates similar findings in the Indo- 150 and 160. The Indo-Pacific larvae Pacific complex of species. collected JY the DANA have myomeres The present contribution to knowledge ranging fom 98-180 with most between of these eels does not seek to describe or 105-130 arid other groupings at 150, 160, explain these changes in body form, nor and 170. The larval counts therefore to determine the significance of this poly- broadly conform with vertebral numbers of morphism in their life. A clarification of adults. However, adults of Indo-Pacific these phenomena and of specific distinctions moringuidE have not been studied on a and nomenclature in the Indo-Pacific spe- comprehensive basis and as yet it is difficult cies must await a comprehensive systematic to assign most of the larvae from this study including a familiarity with morin- ocean to their adult species. guids in the field. The sekction of Moringua edwardsi en- The purpose of this report is simply to ables a stujy to be made of larval variation, described that part of the life-history prior growth, d.spersal, and distribution in a to metamorphosis of the leptocephalus of single mo 'inguid species without encum- the single Atlantic species Moringua ed- brance of the problems of specific distinc- wardsi. This species lends itself well to tion and :lomenclature that would be in- such a study since the larvae are sufficiently volved in H similar study of the Indo-Pacific CASTLE: LIFE-HISTORY OF EEL MOR/NGVA EDWARDSI 3 species. Knowledge of these aspects of lar- moringuid AphthalmichtllYs caribbeus, a name that val biology of a single, well-characterized was to be later overlooked. In the same year Eigenmann (1900) described Leptocephalus dip- species will perhaps serve as a basis for tye/IIIS, a larval form which was not identified dealing with the Indo-Pacific complex in until many years later. Other families, genera, and due course. species were from time to time admitted to this The larval form of M. edwardsi has been group with the description of Mayerina mayeri known for many years but it has only Silvester, A ngllillichtllYs bahamellsis Mowbray (Anguillichthyidae), Moringlla boekei Metzelaar recently been recognized as such (Eldred, and the Stilbiscidae (Parr). 1968; Castle, 1968; 1969). Eigenmann As more information became available on these (1900) described Leptocephalus diptychus forms the taxa were progressively reduced in num- from two western Atlantic specimens but ber. It became generally accepted, though not definitely proven, that there is but the single spe- Castle ( 1965) showed that leptocephali cies present in the western North Atlantic which with the characters of this species were necessarily must take the name Morillglla edwardsi referable to Moringua. Eldred (1968) de- (Jordan and Bollman, 1889). Castle and Bohlke scribed a further four leptocephali. Thus, (1976), in a study of mainly U.S. material, includ- ing several hundred immature and 40 mature speci- M. edwardsi larval has hitherto been re- mens, as well as some of the DANAlarvae described ported from only six specimens and nothing in this report, finally confirmed this suggestion. further has been known of the early life history of this species. Moringua edwardsi (Jordan and Bollman) Figures 1-13 MATERIAL Stilbiscils edwardsi Jordan and Bollman, 1889: The material for this study came from the fol- 549 (original description, holotype USNM lowing sources, with abbreviations used for them 41735, 337 mm, Green Turtle Cay, Bahamas). in the synonymy and the station list appended: Jordan and Davis, 1892: 645 (description). Jor- ZMUC-DANA Oceanographical Collections, Zoo- dan and Evermann, 1896: 363 (description, based logical Museum, University of Copenhagen, Cop- on original). Jordan, Evermann and Clark, 1930: 89 (listed). Parr, 1930: 15 (description, 1 speci- enhagen; UMML-Rosenstiel School of Marine men BOC 2562, Crooked Island, Bahamas). and Atmospheric Science, University of Miami; Gordon, 1954: 11 (7 specimens, AMNH, 137- URI-University of Rhode Island; FSBC-Florida 368 mOl, Bimini, Bahamas).