FAU Institutional Repository http://purl.fcla.edu/fau/fauir This paper was submitted by the faculty of FAU’s Harbor Branch Oceanographic Institute. Notice: ©1980 The Ichthyological Society of Japan. This article may be cited as: Mok, H.-K. (1980). Notes on the classification of Actinopterygian intestinal patterns. Japanese Journal of Ichthyology, 27(1), 29-40. Japanese Journal of Ichthyology Vol. V. No. I 1980 Notes on the Classification of Actinopterygian Intestinal Patterns Hin-Kiu Mok (Received February 19, 1979) Abstract A classification of actinopterygian intestinal patterns represented by 596 species is presented. Individual and developmental variations, distribution, and interrelationships of intestinal patterns were studied. The low conspecific variation, non-random pattern vari­ ation in groups with complex patterns, and resemblance of intestinal patterns among mem­ bers of monophyletic groups suggest that intestinal pattern provides valuable information regarding phylogenetic interrelationships. Suyehiro's (1942) study of a variety of tele­ patterns which can be significant to phylo­ ostean digestive systems is the only system­ genetic studies. After the generalized acti­ atic survey of the digestive system within this nopterygian patterns were recognized, patterns group. His objective was to understand fish that differ from these generalized types may feeding habits by studying the digestive organs. be treated as apomorphic or derived char­ He discovered various types of intestinal pat­ acters at various taxonomic levels (Hennig, terns (within the peritoneal cavity the positions 1966). of the various gastrointestinal segments form the fish intestinal pattern; the elements of the Materials and methods pattern are the relative positions of the seg­ Specimens of 596 actinopterygian species ments). In contrast to this ecological-anatom­ examined were on loan from the American ical study, Harder (1960) used superficial gut Museum of Natural History, Academy of morphology (the stomach and pneumatic duct) Natural Sciences of Philadelphia, Australian as a basis for interpreting the phylogeny of Museum in Sidney, Bernice P. Bishop Museum, the clupeoids. Greenwood (1968) described California Academy of Sciences, South Austra­ the gut and other viscera in Denticeps clupeoides lian Museum, Scripps Institution of Oceanog­ in an attempt to resolve its systematic posi­ raphy, Institute of Animal Resource Ecology, tion among clupeiforms. Nelson (1972) found University of British Columbia, Western Aus­ evidence for monophyly of osteoglossomorphs tralian Museum, Zoology Museum, National (including hiodontids) from the intestinal Taiwan University, and Zoology Museum, pattern. A similar systematic survey of the University of Michigan. Data from examined digestive system, swimbladder, and related specimens are not listed herein, but are tissues (e.g., the gas-gland) of tetraodontiforms available in Mok ([978). was conducted by Mok (1975). Results of Dissections were made on one or more in­ that study suggested that the intestinal pattern dividuals of each species studied. The fish might be applicable to the reconstruction of were cut on the right side of the body cavity. phylogenetic relationships among other fishes. Intestinal pattern was recorded by tracing the Accordingly, the major objectives of the pres­ coiling pathway with a continuous line. ent study are 1) to classify the types of intestinal patterns that generally appear in Results actinopterygians, 2) to survey the distribution Loop f and loop a of these types, and 3) to understand individual In most actinopterygians, the anterior part and developmental variations of intestinal of the intestine proceeds anteriorly and then patterns. This study will provide baseline displaces to the right of the stomach, which information about actinopterygian intestinal is, in most cases, either U-, V-, or T-shaped - 29 Japan. J. Ichthyo!. 27(1), 1980 A TYPE B B TYPE 01 c TYPE 02 '~ 1J~~~ ~c ('),-~\.~\'- '" '-----~:~.:.:~ ~:'~'."....;:.:. ~.,. ~. D TYPE SP E TYPE S F TYPE Z G TYPE HZ H TYPE LA TYPE T TYPE:~ J K Fig. I. Left side-view of eleven basic types of actinopterygian intestinal patterns. A: Type B. B: Type Dl. C: Type D2. D: Type SP. E: Type S. F: Type Z. G: Type HZ. H: Type LA. I: Type T. J: Type LF. K: Type ST. i, intestine; r, rectum; s, stomach. Arrows, coiling (or folding) directions of loop a; fine stippled areas, loop f; heavy stippled areas, loop a; heavy lines, specific sections of the patterns (see text for explanation);-(-, junction of stomach and intestine. (Suyehiro, 1942; Greenwood, 1968; Nelson, of the intestine between its beginning and 1972). The loop formed by the anterior the tip of the loop, and the length from the section of the intestine at the front of the tip of the loop to the anus, are about the peritoneal cavity I designate loop f (first loop; same. With this mid-intestinal position as a Fig. 1, fine stippling). By definition, this loop basic criterion, mistakes in recognizing this can be found in species in which the stomach loop will be few. Sometimes, however, the is not straight or l-shaped. The intestine in intestine is long and the pattern too complex the rear of the peritoneal cavity commonly to recognize loop a. In such cases, com­ forms another loop, which I designate loop a parisons may be limited to the overall winding (Fig. I, heavy stippling). Loop a may be tendencies of the intestine, not the exact recognized in most cases, because the length numbers and shapes of loops. - 30- Mok : Intestinal Patterns A Fig. 2. Left side-view of the intestinal pattern of Mene annocarolina (A) and Lumpenus lumpretaeformis (B). Arrows, the downward bending of the anterior section of the intestine (heavy line); stippling, loop a; -(-, junction of stomach and intestine. A B c o E F Fig. 3. Left side-view of the intestinal patterns of six atherinoids. A: Allanetta harringtonensis. B: Atherinops affinis. C: Membras vagrans. D: Menidia menidia. E: Chilatherina sp. F: Melanotaenia nigrans. Fine stippling, loop f; heavy stippling, loop a; heavy line, esophagus. Types of intestinal patterns Type B: Loop f is to the right of the esoph­ Actinopterygian patterns can be classified agus, and loop a extends horizontally to the into eleven basic types with reference to the posterior part of the peritoneal cavity (Fig. variations of loop f and loop a. They are IA). This is the basic and most widely dis­ types B, Dl, D2, SP, S, Z, HZ, LA, T, LF, tributed pattern in acanthopterygians, although and ST (Fig. I A~K). it occurs also in some pre-acanthopterygian - 31 Japan. J. Ichthyol. 27(1), 1980 d7 ?Pr- '------ A B s . i:? ... c - Fig. 4.. Left side-view of the intestinal pattern of A: Bostockia porosa. B: Astrapogon stellatus. C: Cheilodipterus macrodon. D: Glossamia aprion. Stippling, loop a; -(-, junction of stomach and intestine. teleosts. Nelson (1972) reported the same mach. I have not yet examined the patterns pattern in primitive actinopterygians, Acipenser of Isonidae, Neostethidae, and Phallosteth­ oxyrhynehus (Acipenseridae) and Lepisosteus idae. A survey of these groups would be platyrhineus. Among the perciforms I have helpful in understanding the generalized (or studied, the vast majority (more than 80%,) primitive) pattern of this suborder. have this pattern (Mok, 1978). It is, there­ Loop a of Type B generally does not bend. fore, a generalized or primitive character Exceptions occur in loop a of Bostockia porosa state for acanthopterygians as a whole. (Serranidae), Glossamia aprion, Cheilodipterus There are some perciforms with patterns macrodon, Astrapogon stellatus (Apogonidae), that seem to be variants of Type B. In Mene and Doratonotus megalepis (Labridae) which annoearolina (Menidae) and Lumpenus lumpre­ distinctively tilt upward at a very steep angle taeformis (Stichaeidae) (Fig. 2A and B, re­ (Fig. 4). spectively) the patterns are similar in that Type Dl: Loop a winds dextrally to the the anterior section of the intestine bends right of the rectum (Fig. IB). Type ni has downward (arrows in these illustrations show a broad distribution among perciforms. Some the bending direction of that section of the examples are Scomberoides toloo, Vomer de­ intestine). clivifrons (Carangldae), Cirrhitichthys falco In osteoglossiforms and some atherinoids (Cirrhitidae), Kuhlia taeniura, K. malo (but loop f occurs left of the esophagus and stom­ not in K. marginata and Nantherina balstoni, ach (Suyehiro, 1942; Nelson, 1972). Nelson Kuhliidae), Gnathodentex aurolineatus, Mono­ considered the left position of loop f as an taxis grandoeulis (Lethrinidae), Monodaetylus apornorphic character of osteoglossomorphs [alciforrnis (Monodactylidae), Oplegnathus sp. (including hiodontids). Interestingly, loop (Oplegnathidae), Pseudopriaeanthus atlus f of atherinoids, Allanetta harringtonensis, (Priacanthidae), Dampieria eyclophthalma, Atherinops aJlinis, Membras vagrans, and Gramma sp. (Pseudochromidae), Stellifer ras­ Menidia menida (Atherinidae), Chilatherina sp., trifer (Sciaenidae), Amniataba percoides (Ter­ and Melanotaenia nigrans (Melanotaeniidae) aponidae), and Triehodon triehodon (Trich­ (Fig. 3) all occur left of the esophagus and sto- odontidae). This type does not characterize a - 32- Mok : Intestinal Patterns c~ ~.~~ A B c D Fig. 5. Left side-view of the intestinal pattern of A: Archosargus probatocephalus. B: Bryostemma nigator. C: Holocentrus rufus. D: Hexagrammos decagramma. Stippling, loop a; -(-, junction of stomach and intestine. genus or family as a whole,