Monthly Archives: May 2014

Photo of the day (155): Drymaeus

This time the “Photo of the day” is another video link. Bill Frank caught these specimens of Drymaeus dormani (W.G. Binney, 1857) crawling around. Or perhaps better: in a race to the bottom…

Ddormani1

https://www.youtube.com/watch?v=8HmSbUYbS9o

And another one:

Ddormani2

https://www.youtube.com/watch?v=lyZ77JiF4Ns

Many thanks Bill for sharing these! And perhaps I should consider to rename this series…

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(In)visible shells

Under this heading I like to pay some attention to a paper published last year by Savazzi & Sasaki.

The abstract reads: “The shells of a broad range of land snails were digitally imaged in the near-ultraviolet (NUV), visible range (VIS) and near infrared (NIR). NIR images were recorded in both incident and trans- mitted illumination. In most cases, shell and periostracal pigmentation observed in the VIS was com- pletely translucent in the NIR, while its contrast was enhanced in the NUV. Exceptions to the above rule fit into four main categories. (1) Snails with green or tan shells or periostraca, presumably func- tional as camouflage among vegetation, were often highly absorbing in the NUV, thus matching the optical characteristics of green vegetation in this range. (2) Pigmented spiral stripes in the shells of several Camaenidae and Helicidae were adjacent to nonpigmented areas that display a heightened reflectivity and reduced translucence in the VIS and NIR. This enhanced the contrast of the colour pattern in the VIS, but appeared to lack functions in the NIR. (3) Snails from arid or desert envir- onments exposed to high levels of sunlight often have largely white shells, highly reflective throughout the studied range of wavelengths. This is likely an adaptation to reduce the thermal effects of solar irradiation, and may also be a form of masquerading camouflage. (4) Among numerous Bradybaenidae and a few Camaenidae, Helicidae, Orthalicidae and Enidae, reflective patches or stripes, white in the VIS, were present in the periostracum or outermost shell layer. These structures were highly reflective (and highly opaque to transmitted radiation) across the NUV, VIS and NIR. They may have a dual function as disruptive camouflage in the NUV and VIS, and as reflectors to reduce the thermal effects of solar irradiation in the VIS and NIR”.

Neotropical species dealt with in this paper were Liguus virgineus (L., 1758) from Dominican Republic, Bostryx sp. from Chile, Otala lactea (Müller, 1774) from Bermuda, and O. punctata (Müller, 1774) from Uruguay. The majority of the species studied were from S.E. Asia.

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Liguus virgineus (L., 1758) as seen under NUV, VIS, incident NIR, and transmitted NIR respectively.

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Bostryx sp., seen under NUV, VIS, incident NIR, and transmitted NIR respectively.

SS_3

Otala punctata (Müller, 1774) seen under NUV and transmitted NIR respectively.

This study reveals not only that the colour pattern observed in visible light may appear different at wavelengths invisible to the human eye, and may serve as yet unknown function in camouflage to specific predators. At the same time it makes me wonder if the techniques used to obtain these results might be productive in obtaining additional characteristics in taxonomic studies. Although the methods used don’t seem to be too complicated, a set-up for regular use may be prohibitive for the average taxonomist. Still an interesting paper and food for thought…

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Reference:
Savazzi, E. & Sasaki, T. (2013). Observations on land-snail shells in near-ultraviolet, visible and near-infrared radiation. — Journal of Molluscan Studies 79: 95-111.

Photo of the day (154): predating

Actually this is not a photo post, but linking to a video. And moreover, strictly speaking not about Neotropical snails; consider it one of my “malacological tidbits”.

154_Predating

The link is here, and shows research done in Singapore how a predatory flatworm ingests land snails. In contrast to some other predators this worm succeed in leaving no signs. An intact shell is all he leaves, so one has to be lucky to catch the two in their act (although I definitely have the impression this movie was made under controlled circumstances).

It might be interesting to observe in the field on predation of Neotropical snails too, since such ecological details are very scarce and data are scanty.

Many thanks to Liew Thor Seng for distributing this among colleagues.

Revision of Bostryx stelzneri complex

Miranda & Cuezzo have now published a long awaited paper, presenting a revision of a species group from northern Argentina, the Bostryx stelzneri complex. This paper partly resulted from Miranda’s Ph.D. thesis work.

The abstract reads: “The Bostryx stelzneri species complex is taxonomically reviewed with the description of a new species. This complex is formed by Bostryx stelzneri (Dohrn, 1875), B. peristomatus (Doering, 1879), B. scaber (Parodiz, 1948) and Bostryx roselleus n. sp., all distributed in Argentina. Bostryx peristomatus and B. scaber are elevated to specific status on the basis of morphological characters. This complex has the spire less than half the total shell height and the aperture higher in relation to total shell height than in any other species of the genus. Traditional shell morphometry and a geometric morphometric analysis were used to document shell variation in size and shape among species. Radula, jaw and shell morphology were examined with SEM. All species in the complex are described or redescribed using new morphological information. In this species complex, pallial organs are very similar among species and vary only in the degree of opening of the secondary ureter. The genitalia differ in the relative proportion of organs, such as length of vagina relative to free oviduct and penis or epiphallus length relative to penis length. Sculpture of the inner wall of the flagellum and epiphallus is similar in all species studied, whereas sculpture of the inner wall of the penis is variable. Geometric morphometric analysis allows an objective interpretation of shell shape variation detecting differences in shape components irrespective of the differences in size between Bostryx Troschel, 1847 species of the stelzneri group.”

MC2014f2

In the introduction (p. 74) I saw a sentence that shows a misinterpretation of my 1979 thesis. “Breure (1979) listed 23 species of Bostryx in Argentina, while Miquel (1993, 1995) recognised only 13 valid species using shell morphology similarities to justify his synonymic actions.” The misinterpretation lies within the suggestion that in my thesis the species lists under each genus were lists of valid species. There were not; my thesis was a revision of the genera within the subfamily (now regarded as family Bulimulidae), the lists of ‘species’ under each genus were actually a list of taxon names from literature that had been placed in the genus. Nothing less, nothing more. The later work of Miquel was a more detailed taxonomic revision of the species from Argentina; of the available taxa he considered 10 as junior subjective synonyms, and thus ended up with 13 species.
Finally, in the discussion (p. 89), the authors state “he [Breure 1979] did not describe the inner penial anatomy which is unknown in all Bostryx species”. Possibly the authors had the Argentinean species in mind? In Breure 1979: fig. 63-64 schematic reconstructions of two (Peruvian) Bostryx species are given, while in a previous paper the histology is described of the inner genitalia from nine Bostryx species, among which B. stelzneri (Breure 1978: 127-128). But indeed, “the reproductive system is very simple in comparison to other genera of Bulimulidae” as the authors state (p. 89).

In this paper Miranda & Cuezzo have thoroughly studied all available material at hand, and propose a new classification. The 13 species have been reduced to four, with additionally a number of “morphological or population variations” within Bostryx stelzneri.

MC2014f10

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References:

Breure, A. S. H. 1978. Notes on and descriptions of Bulimulidae (Mollusca, Gastropoda). — Zoologische Verhandelingen 164: 1–255.
Breure, A. S. H. 1979. Systematics, Phylogeny and Zoogeography of Bulimulinae (Mollusca). — Zoologische Verhandelingen 216: 1–98.
Miquel, S. E. 1993. Las especies del género Bostryx Troschel, 1847 en la República Argentina (1ra. parte) (Gastropoda Stylom- matophora: Bulimulidae). — Archiv für Molluskenkunde 121: 157–171.
Miquel, S. E. 1995. Las especies del género Bostryx Troschel, 1847 en la República Argentina (2da. y última parte) (Gastropoda Sty- lommatophora: Bulimulidae). —Archiv für Molluskenkunde 124: 119–127.
Miranda, M.J. & Cuezzo, M.G. (2014). Taxonomic revision of the Bostryx stelzneri species complex, with description of a new species (Gastropoda: Orthalicoidea: Bulimulidae). — American Malacological Bulletin 32: 74-93.

GAS in Brazil (MSc. thesis)

The Giant African Snail (Lissachatina fulica) is around in Brazil for more than 30 years. Aquino (2013) has made his Master thesis on this subject within the framework of biology and health policy. Since this kind of theses is often difficult to grasp (no formal publication, unless the author takes the effort to write also a paper summarising the data), it is mentioned here. As an exception, the full text (in Portuguese) is added after the reference.

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The abstract reads: “Since it had been introduced in Brazil dating back to the 80s, the Great African Snail Achatina fulica has spread all over the country. Some researchers associate its incredibly good adaptation success to the dermal mucous of this species. With the objective and the aim of better knowing and understanding the dermal mucous of the Great African Snail and also suggesting new forms of taking advantage of it with a view to controlling this invading and exotic snail, this study work carried out the chemical characterization of the shell, of the snail without the shell and of the dermal mucous of the Great African Snail in the State of Alagoas, Brazil, and also evaluated and assessed the scarring/healing action of a solution from the mucous, already confirmed for skin tissue, in corneal ulcers surgically produced in rabbits. The wild snails were kept in a laboratory utilizing a new methodology specially developed for keeping arboreal snails in laboratory, with sensibly improved hygienic conditions, reduction of the time spent for the daily treatment and reduction of animal stress. This methodology has been described in details at the XXII EBRAM in 2011, in Fortaleza, State of Ceará, Brazil, and published in the form of a scientific article under the name “new breeding management for snails (molusca: gastropoda: pulmonata) in plastic boxes (recipients/containers)”. The following analyses were carried out: the mineral composition of the snail without its shell, of the shell and of the mucous; the centesimal composition of the lyophilized mucous and the anti oxidizing capacity evaluated through the seizing activity of the free radical 2,2-diphenyl- 1-picryl-hydrazyl (DPPH). With regards to the results, the macro and micro minerals composition present in the snail without a shell, in the shell and in the dermal mucous of the A. fulica was determined for 23 nutrients, 5 macro-nutrients (Ca, P, Na, K and Mg) and 18 micro-nutrients (Al, As, Ba, Cd, Cr, Cu, Fe, Li, Mn, Mo, Ni, Si, Sr, V, Zn, Co, Sb and Se). With regards to the centesimal composition, the following data was obtained: dried matter (91.72 ± 1.85), humidity (8.28 ± 0.97), ashes (31.1 ± 0.35), crude protein (49.97 ± 3.21), carbohydrates (8.15 ± 1.43), total calories (242.48 ± 53.23), lipids in 100 g (2.5 ± 0.44), cholesterol (50.2 ± 0.3). The mucous did not show anti oxidizing capacity in any of the analysed samples. For the experiment in vivo, the evolution of the corneal lesions on the 18 rabbits, divided in three groups of 6 animals: the control group, the mucous group and the group treated with the ophthalmic solution Epitegel, was accompanied and monitored by the percentage measurement of scarring/healing of the 36 areas of scarring through 144 macro photographs taken along the experiment at 0, 24, 48 and 72 hours. To carry out the experiment, duly approved by the Ethical Committee of UFAL (The Federal University of Alagoas), process no. 010190/2011-85, a scalpel blade to remove the corneal epithelium previously circumscribed by a circular scalpel (punch no. 5) and the anaesthetic protocol utilized comprised 3 steps: tranquilizing with acepromazine (0,05 mg / kgPV/IM), anaesthetizing with cetamine chlorydrate (12mg/IM/kgPV) and local anesthetizing with proxymethacaine chlorydrate 0,5%. For the orientation regarding the ideal choice for mucous concentration for the treatment of the lesions on the experiment in vivo, solutions were tested in the following concentrations: 0.01 mg mL-1, 0.03 mg mL-1, 0.06 mg mL-1 and 0.125 mg mL-1. The cellular viability was verified through the MTT and Tripan Blue methods. No statistical differences were observed between the tested concentrations; therefore, the chosen concentration to be the base for the preparation of the ophthalmic solution was the one that gratifyingly better stimulated the cellular proliferation (0,125 mg mL-1). With regards to the results, there were no statistical differences between the mucous group and the Epitegel; the ophthalmic solution based on the mucous (0,125 mg 25 μL) had a similar performance to the ophthalmic solution Epitegel 10g (Ophthalmological Gel Dexpantenol 50 mg g-1, positive control), one of the best available medicines in the market for the treatment of corneal ulcers/lesions. Nevertheless, both presented some significance regarding the result of the control group, which presented a longer scarring/healing time. With 72 hours, of the 12 lesions of the control group, only 2 (16,66%) were scarred/healed; of the Epitegel group, only 8 (66,66%) were scarred/healed and of the mucous groups, all (100%) were scarred/healed. It has been thus demonstrated the scarring/healing capacity of the A. fulica’s mucous also for the treatment of corneal ulcers and its specific action, furthermore than merely accelerating the recovery of lesions in animals and it also did not produce, in any of them, a single visible scar. It is yet to be exactly known its action mechanism in conjunction with the set of steps of the corneal scarring/healing, especially if it detains a stimulating action over the reproduction of trunk cells, which are responsible for the regeneration of this epithelium”.

Reference:
Aquino, M. C. (2013): Caracterizaçao química do caracol africano (Achatina (Lissachatina) fulica (Bowdich, 1822) e avaliação dos efeitos do muco cutâneo em úlceras de córnea em coelhos (Oryctolagus cuniculus). MSc. thesis, Instituto de Ciências Biológicas e da Saúde, Universidade Federal de Alagoas, 94 pp.

Aquino 2013