Worldwide observations of remarkable deep-sea squids.

Abstract

The bathypelagic realm of the ocean encompasses >90% of the nonsubterranean biosphere, comprising the largest, yet least explored, ecosystem. Recent interest has focused on biodiversity in the deep ocean ([1][1],[2][2]). Here, we report observations from submersibles of large unknown squids at bathypelagic depths in four ocean basins (Table 1). Sample frames from videotapes of some of the observations are presented in [Fig. 1][3]. Videotaped records of these encounters lasted up to 10 min. View this table: Table Table 1. Summary of submersible observations on unusual bathypelagic squids. ![Figure 1][4] Figure 1 Video frames of bathypelagic squids observed from submersibles. ( A ) Squid 2 (see Table 1); ( B ) squid 4; ( C ) squid 5; ( D ) squid 7; and ( E ) squid 8. Representative digitized video clips are available on Science Online ([3][5]). In most cases, the squids were first encountered within a few meters of the sea floor with their extremely large, terminal fins undulating slowly and with arms and tentacles typically held in a unique position: spread outward from the body axis, then abruptly bent anteriorly ([Fig. 1][3], A and B). None of these squids were collected, but all share the following morphology: The arms cannot be distinguished from the tentacles (modified ventrolateral arms of decapod cephalopods), appearing as 10 identical brachial appendages, all of about equal thicknesses and lengths. The relative length of these appendages is far greater than the arm length in any known squid, although all appendages are highly contractile. The filamentous distal portions of the brachial appendages appeared lighter in color than the rest of the animal in some videos. During extreme close-ups of squids 7 and 8, suckers could be seen along the oral surfaces of the proximal arms but not on the filamentous segments distal to the elbowlike bends. Most of the squids did not appear initially to react to the approach of the submersibles. In one case (squid 4), no escape response was noted even when the brachial appendages brushed the sample basket. After a few minutes, one animal (squid 7) moved slowly away, flapping its fins but with the arm crown still spread ([Fig. 1][3]D). However, when most squids either touched a submersible or encountered its turbulence, the escape reaction consisted of strongly flapping the fins and towing the retracted brachial crown (e.g., [Fig. 1][3]C). When squid 7 changed from hovering to rapid swimming, the first pulse included a contraction of the mantle, but no jetting was observed subsequently. One squid (squid 5) became entangled in the submersible and seemed to have difficulty releasing its arms and tentacles; during its attempts to swim away, multiple appendages stretched greatly. We cannot be certain of the identity of these squids until specimens are captured; the morphology is very different from any known family. They are, however, most similar to the family Magnapinnidae. This family was recently described from two juveniles and a paralarva, all captured in epipelagic waters in the central and eastern Pacific Ocean ([4][6]). The Magnapinnidae is characterized by tentacles and arms with slender elongate tips and very large terminal fins. The squids reported here could be the unknown adults of this family. The sharp bend of the arms, which appears to coincide with a change in sucker distribution, could mark the junction between the arms and the terminal filaments seen on juvenile magnapinnids. The inference from eight sightings within a few years of a completely unknown deep-sea animal at similar depths in the Gulf of Mexico and the Atlantic, Indian, and Pacific oceans is that these squids are comparatively common worldwide in the bathypelagic realm. That such a substantial animal is common in the world's largest ecosystem, yet has not previously been captured or observed, is an indication of how little is known about life in the deep ocean. 1. [↵][7]1. J. Asubel , Oceanography 12, 4 (1999). [OpenUrl][8] 2. [↵][9]1. C. R. Smith, 2. L. A. Levin, 3. L. S. Mullineaux , Deep Sea Res. 45, 1 (1998). [OpenUrl][10][Web of Science][11] 3. [↵][12]Videos and acknowledgements are available at [www.sciencemag.org/cgi/content/full/294/5551/2505/DC1][13]. 4. [↵][14]1. M. Vecchione, 2. R. E. Young , S. Afr. J. Mar. Sci. 20, 429 (1998). 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